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Do women naturally have less muscle building potential than men?

By Fleur van Griensven

When a girl tells people she just started lifting, they often think that she will wake up as a Hulk the next day. They think that lifting makes women look bulky, so they shouldn’t train like men. Another thing you often hear, is that women can never get as big as men, but is that true? Do women naturally have less muscular potential than men? Or can we finally acknowledge the fact that women should train heavy too and that a lot of girls are not living up to their potential by lifting 2 kg pink dumbbells?


The natural muscular potential of women.

Popular opinion is that men have more muscular potential than women and thus can gain more muscle. However, some research indicates that women naturally have roughly the same muscle building potential. A prospective intervention study examined the influences of gender on muscle size responses to strength training. The results were that women can gain the same percentage of muscle mass compared to men during strength training [1].

Studies on protein synthesis came also to the same conclusion. Women have similar muscle protein synthesis rates and thus seem to build the same amount of muscle protein after training compared to men [2]. This is however the conclusion of only a few studies, so more research is definitely needed to be 100% clear that women do naturally have the same muscle building potential. However, this is difficult because these studies take a long time and need to be well-controlled.

When women start training they do have a different body composition. Most of the times, women have less muscle mass and more fat mass compared to men. Women have +/- 12% essential body fat compared to just +/- 3% fat in men [3]. Essential body fat is all the fat which we can not lose without it negatively affecting our physiological functions. It surrounds our organs and nerve tissues. Men and women do have a different starting point when it comes to muscle mass, but they seem to be gaining muscle mass at the same rate. Keep in mind that for the rest of this article I always compare men with a starting point to women with the same starting point, so a same body composition.

How about testosterone?

Testosterone is the most important male sex hormone. Women however do also produce testosterone, even though they have 15 times less active testosterone than men, under normal circumstances [4]. Besides the known functions of testosterone in our body, like development of primary/secondary sexual characteristics and production of sperm, it also plays a positive role in muscle building. Testosterone is an anabolic hormone, which means that it stimulates muscle protein synthesis and thus muscle growth.

Is it then true, because women have less testosterone they also have less potential to build muscle mass? No, this is probably not the case. The testosterone functions are different in men and women. What comes next might be a bit of a complicated story with terms you never heard about, but do not worry about that and try to see the big picture in why having less testosterone as a woman is not that bad at all.

It seems that testosterone is not needed for muscle development in women because growth factors like IGF-1 and growth hormone take over the anabolic role that testosterone plays in men [5]. This has been found in an animal study done with mice, so more studies are necessary to test if this is the case in humans too. However since women can gain muscle with lower testosterone levels, it can be safely assumed that other hormones besides testosterone are involved in this muscle building process.

Women have just as much IGF-1 and produce +/- 3 times as much growth hormone as men [6]. This study shows that despite the fact that women have lower testosterone levels than men, they do have higher growth hormone levels. It could be possible that in women growth hormone partly takes over the role of testosterone. This explains why having less testosterone does probably not limit how much muscle women can build. People think that testosterone is the most important hormone, but there are more hormones that play a role in muscle growth.

The other (sex)hormones combined with the advantages/disadvantages women have.


Where testosterone is the most important male sex hormone, estrogen is the most important female sex hormone. Estrogen is commonly seen as the hormone that makes you fat and frail. However, its positive effects should not be disregarded. Some of these positive physiological effects are:

  • It is anti-catabolic, which means that it prevents muscle loss [7].
  • It aids in muscle repair [8].
  • It is good for connective tissue (bones, ligaments etc.).

The bad reputation of estrogen is based on nothing more than the assumption that if testosterone is anabolic, estrogen must be catabolic. There is a lot of ongoing research and there are indications that it plays a role in muscle growth and the well-being of skeletal muscle. However, more research is needed in the future.


One big disadvantage for a lot of women these days is the use of the anti-contraceptive pill. This holds especially true for the ones containing a lot of progesterone. They do have a negative effect on muscle growth compared to not using an anti-contraceptive pill, because progesterone competes with testosterone for the androgen receptor. Basically, this comes down to less active testosterone when you take in an anti-contraceptive pill with a lot of progesterone [9]. How much of a negative effect occurs is hard to tell, because it is very difficult to study.

Here is a practical tip which you can use to take advantage of the benefit we have being a woman. Hopefully this and more research in the future about some other topics relating the effects of hormones on muscle growth will help you get the most out of your training sessions!

  • We can use a higher rep range.

There are two types of muscle fibres: Type I&II. Type I muscle fibers are known as slow-twitch muscle fibers, which makes them able to contract for a long period of time and more resistant to fatigue. Being able to contract for a long period of time could mean that women can benefit from a higher rep range. This could mean that for women to grow to their full potential, more reps per set need to be done to benefit from the type I fibres which are more  resistant to fatigue and can contract longer. One study came to the conclusion that during exercise in women, a potential conversion to type I muscle fibers or no conversion at all takes place [10]. This study looked at the muscle fibre adaptations during execution of a knee-extension exercise in both young men and women. They found a significant increase in percentage of type I fibres in young women. The study has its limitations: if the muscle fibres had been splitted into type Ia, IIa, IIb etcetera, no significant result would have been found. This also is anecdotal evidence and more research needs to be done.

Conclusion, do women naturally have less muscle building potential than men?

There is some research which indicates that women can gain the same percentage of muscle mass compared to men during strength training [1,2]. However more research is needed.

Why you see more men with a significant amount of muscle mass compared to women and why women aren’t 100% living up to their potential can be contributed to a lot of factors:

  • Mostly social-cultural. There are not as many women compared to men training with weights. If they do train, some of them just do not want to build as much mass as possible. Everyone has their own goal and idea of how they want to look. That is okay, as long as you do what makes you happy and never have someone telling you what you shouldn’t or can’t achieve.
  • If women go to the gym, they spend countless hours on the treadmill or playing around with pink dumbbells, that is for sure not 100% optimal if you want to build as much muscle mass as possible.
  • Oral-contraceptives, which have a negative effect on muscle growth. Part of the anabolic role of testosterone will be taken over by other hormones in women, so testosterone production probably does not limit how much muscle women can build.

More information about this topic for sure will come available in the future as more and more studies are being done on this interesting topic. When that time comes we will update this article and bring you the latest conclusions.

One take home message for all the women out there busting their ass off (or on) in the gym: you probably are not less capable of putting on muscle mass than men, and the only limitations you have are the ones you put on yourself!


[1] Roth, SM (2001). Muscle size responses to strength training in young and older men and women. Journal of the American Geriatrics Society, 49(11), 1428-33.

[2] O’Hagan, FT (1995). Response to resistance training in young women and men. International journal of sports medicine, 16(5), 314-21.

[3] Vehrs, P (2013). Assessment and interpretation of body composition in physical education. Journal of Physical Education, Recreation & Dance, 46-51

[4] Wisse, B (2016, 2 March). Testosterone. Retrieved from

[5] MacLean, HE (2008). Impaired skeletal muscle development and function in male, but not female, genomic androgen receptor knockout mice. FASEB journal, 22(8), 2676-89.

[6] Van den Berg, G (1996). An amplitude-specific divergence in the pulsatile mode of growth hormone (GH) secretion underlies the gender difference in mean GH concentrations in men and premenopausal women. Journal Clinical endocrinal Metab, 81(7), 2460-2467

[7] Hansen, Mette (2014). Influence of Sex and Estrogen on Musculotendinous Protein Turnover at Rest and after exercise. Exercise & Sport Sciences Reviews, 42(4), 183-192.

[8] Velders, M (2013). How Sex hormones promote skeletal muscle regeneration. Sports Medicine, 43(11), 1089-1100.

[9] Woock, C (2009). Oral Contraceptive use impairs muscle gains in young women. The FASEB Journal, 23(1).

[10] Martel, G (2006). Age and sex affect human muscle fibre adaptations to heavy resistance strength training. Experimental Physiology, 91(2), 457-464


BCAA’s: a smart marketing trick?

By Fleur van Griensven

BCAA’s are thought to put you in an anabolic state. Some people claim that you should use them before training when you are in a fasted state to prevent muscle loss. Is this true and should we all run to the nearest shop to spare our gains? Or is it just a smart marketing strategy from producing companies?


What are BCAA’s?

BCAA’s are branched-chain amino acids. These amino acids are branched (in Dutch vertakt), which in comparison to other amino acids makes it easier for enzymes to digest. Amino acids are the building blocks of proteins. When we consume protein our body uses specific enzymes which breaks these down into smaller units, the amino acids. There are 20 amino acids which can be converted into one another. At least, that’s true for the non-essential ones. The essential amino acids need to be present in our food because the body can’t synthesize them itself. There are 8 essential amino acids: Lysine, Tryptophan, Phenylalanine, Leucine, Isoleucine, Threonine, Methionine and Valine.

The three BCAA’s are Leucine, Isoleucine and Valine. During intensive activity, muscles will convert these quickly into energy. BCAA’s are supplemented just before or during training. The reason for supplementation is to stop muscle breakdown, recover quicker and in the long run build more muscle mass and strength. [1]

Are BCAA’s useful?

Many studies have been done on BCAA’s. A lot of people claim that you should take them before training fasted or during training. Some studies do find an effect of supplementation, whilst others don’t. There are many promising abstracts, but they are almost always hampered by lack of dietary control and/or a low protein intake. Making real conclusions based on these studies is hard.

The effectiveness of BCAA supplementation to reduce exercise-induced muscle soreness is mixed. One randomized placebo controlled study compared a BCAA’s + carbohydrate versus a carbohydrate sports drink following 3 days of intense weight training. BCAA + carbohydrate supplementation did not improve markers of muscle damage/soreness compared to carbohydrates only. [2]

A randomized, double-blind, placebo controlled study concluded the opposite. Participants received a BCAA supplement or a placebo. Before and after the damaging exercise (100 drop-jumps) they measured different muscle damage variables. They concluded that BCAA administered before and following damaging resistance exercise reduces markers of muscle damage and accelerates recovery in resistance-trained males. This might be due to greater bioavailability of substrate to improve protein synthesis. [3]

Research which shows a net anabolic effect of BCAA supplementation before, during or after training is often used to sell these powders [4]. Supplementing BCAA’s would eventually increase build-up of muscle. No evidence supports that ingestion of BCAA supplements is more effective than consuming a proper amount of food (protein) with respect to building muscle. In fact, there’s research to the contrary: food, and whey protein specifically, may be even more effective than a BCAA drink [5]. This is why you can consume a whey shake before training to get into a net anabolic state. It’s cheaper than BCAA powders, comes in many delicious flavours and is more effective.

What are the costs of BCAA’s?

BCAA’s can be bought in shops and online. The prices differ per brand and they sell both powders as tablets. For example, BCAA’s from Body & Fitshop will cost you €14,90 for 500 grams. The recommended daily serving is 20 grams before or during training, so a package lasts for about 25 days. Thus, quite expensive.

The amino acids shown in the picture above (Amino X from BSN) are even more expensive. You pay €19,90 for 435 grams. The daily serving is 29 grams, so you would pay €1,33 on a daily. Are these any better than Body & Fitshop own label? They both contain the three amino acids L-leucine, L-isoleucine and L-valine but probably in a bit different ratio. The Amino X also contains L-alanine, Taurine and L-arginine and vit D3 + vit B6. Will this add any effect to the product itself? Not sure, but you will just pay for something extra next to the BCAA’s you actually want to buy.

Selling BCAA’s on the market is a smart marketing strategy, because you basically pay for only three amino acids with a bit of a nice flavour added to it. Companies make good use of this by slogans as: ‘Amino X BSN, next level technology!’ or ‘BCAA Sensation V2 only contains the perfect ratio amino acids’. Yeah right if this would all be true, would just not one product with everything be enough? Companies try to come up with new things to make us consumers think that we just have to buy the new product. Smart marketing strategy it is!

Conclusion, BCAA’s: a smart marketing strategy?

Concluded can be so far:

  • The studies find a mixed effect of supplementation, but if they do find an effect are lacking in many aspects.
  • They are a smart marketing strategy.
  • They are expensive.
  • You can get your BCAA’s from food instead which is cheaper and more satisfying.BCAAs_2In general, there are studies that seem to show promising effects of supplementation. These however are hampered when taking a closer look. A whey shake just before training has shown to be even more effective in provoking a net anabolic response.

    If you think that you need to take a serving of BCAA’s before training fasted, first ask yourself the following. Is training fasted going to be any better in losing fat than having a meal and smash the hell out of your cardio session? An article about fasted morning cardio might follow, but at the end of the day it still comes down to being in a negative energy balance. If you enjoy doing cardio first thing in the morning go ahead, but don’t get deceived by this BCAA marketing strategy, drink a whey shake and save yourself money!


    [1] BCAA. Retreived from:

    [2] Wesley C. Kephart et all (2016). Post-exercise branched chain amino acid supplementation does not affect recovery markers following three consecutive high intensity resistance training bouts compared to carbohydrate supplementation. Journal of the International Society of Sports Nutrition.

    [3] Glyn Howatson et all (2012). Exercise-induced muscle damage is reduced in resistance-trained males by branched chain amino acids: a randomized, double-blind, placebo controlled study. Journal of the International Society of Sports Nutrition

    [4] Sharp CP, Pearson DR (2010). Amino acid supplements and recovery from high-intensity resistance training. Journal Strength Conditioning Research.

    [5] Hulmi JJ et all (2010). Effect of protein/essential amino acids and resistance training on skeletal muscle hypertrophy: A case for whey protein. Nutrition & Metabolism.


The optimal way of cardio for burning fat

By Wietse In het Panhuis

We probably all know the struggle of cutting. Sometimes it is difficult to lose fat, even though you are in a caloric deficit. Cardio is a helpful tool to cut down on body fat. Some speculation exists about the cardio intensity that would be optimal to burn fat. Is it better to do cardio with a low intensity for a long time, or a high intensity for a short time?

Energy systems in the body       
Before explaining what the ideal form of cardio is for burning fat, you should have a basic understanding of metabolism in the human body.

The body needs energy for a lot of different processes: basic functions to stay alive, repair and growth of tissue, and physical activity[1]. In this situation we are mainly interested in the latter one. The body gets its energy from the conversion of ATP to ADP (I am sure you know what that is by now). To create ATP, several forms of fuel are used, such as carbohydrates (sugars), fats (fatty acids), and ketone bodies (which are only formed and used when being in a fasted state). These fuels are present in blood and stored in the body. After a meal, food is digested and taken up in the blood via the intestines. However, only small amounts of nutrients are present in the blood, because the blood has a strict range of concentrations of nutrients and other compounds. If these concentrations would be much lower or higher, the body cannot function properly. For example, in total only a few grams of sugar are present in the blood, providing the body with about 20-30 kilo calories (kcal). When you cycle for 2 minutes, all of this sugar will be used up. Therefore, the body needs strict regulations of the nutrients: an excess of nutrients will be quickly stored, and a nutrient shortage will be compensated for by releasing nutrients from the body stores into the blood.

Carbohydrates and sugars are stored in glycogen in the muscle and liver. Fat is mostly stored in adipose (fat) tissue, and some of it in the muscles and around the organs. Proteins can also be used as energy fuel, for which they first have to be converted to sugars (and urea). Protein is present in lots of different tissue, but its main storage location is in the muscles.

When the body needs energy (for example during exercise), it does not exclusively use one type of fuel, instead it will use different forms of fuel at the same time[1]. The situation determines how much of a fuel is used. For instance, when you have not eaten for more than 24 hours, your glycogen stores will be low. Your body will then switch to more fat oxidation (the burning of fat to get energy), and the breakdown of protein (and thus muscle) will be increased in order to supply the body with enough glucose. The latter is important, because the brain can only use glucose as energy fuel, and not fat. If there would be no glucose, the brain would stop functioning. When you have just eaten a big meal, your body will switch to predominantly carbohydrates, and will thus burn less fat or breakdown less muscle for protein.

During exercise, the intensity determines how much carbohydrates and fats will be burned. In general, when exercise intensity increases, carbohydrate oxidation increases[1,2]. Also, fat oxidation will increase when exercise intensity increases, but at some point it will decrease again. Therefore, there is an optimal intensity to burn fat. Implementing this knowledge in your (cardio) workout, could help with optimizing fat loss.

Studies tried to investigate which exercise intensity is ideal for fat loss. This optimal fat burning point, or the exercise intensity at which the maximal fat oxidation rate occurs, has been named Fatmax[3]. Exercise intensity in cardio can be expressed in Wmax: The maximal amount of Watt produced before hitting failure. Wmax is closely related to VO2max, which is the maximal volume of oxygen the body is able to use. Wmax and VO2max therefore reflect pulmonary (lung) and cardiac (heart) functioning. Wmax and VO2max are therefore higher in trained athletes. A Wmax of 100% means maximal intensity of (cardio) exercise. At that point, the body simply cannot work harder because it cannot use more oxygen than it already does.

One study tried to investigate the amount of fat oxidation during different exercise intensities[2]. The exercise intensities in cardio were expressed in Wmax. This study compared the amount of carbohydrates and fats that are burned during rest and at a Wmax of 40%, 55% and 75%. As can be seen in Figure 1, at Wmax 40%, the body will have a fat oxidation of about 50% (muscle and plasma TG + plasma FFA is about 25 KJ/min which is half of the total energy that is burned(50 KJ/min)). At a Wmax of 55%, fat oxidation is about 46% (30 KJ/min fat oxidation, 35 KJ/min glucose oxidation, total 65 kJ/min), so at this point in absolute numbers more fat is burned, but since glucose oxidation increases more, relatively less fat is burned. At a Wmax of 75%, fat oxidation is about 20% (20 KJ/min of total 80 KJ/min), which is both lower in absolute and relative numbers. Thus, exercising at 40% of max Watt has the highest relative fat oxidation.

Figure 1. Quantification of glucose and fat oxidation during different exercise intensities. Muscle glycogen and plasma glucose are part of glucose oxidation, muscle and plasma TG and plasma FFA are part of fat oxidation. %Wmax= percentage of the maximal exercise intensity displayed in Watt. Copied from van Loon et al (2001)[2].

This does not mean that exercising at a Wmax of 40% is best for fat loss. Once again, it depends on the situation:

  1. When you have a lot of muscle mass and you are trying to lose some body fat to get to a low body fat percentage, it is important to minimize muscle loss. When the body is low on carbohydrates (during a cut), it will break down proteins and thus muscle mass to produce sugars. Loss of muscle muss is therefore minimized when fat oxidation is relatively high, and glucose oxidation relatively low. This is the case for a Wmax of 40%: less fat is burned than at a Wmax of 55%, but also much less glucose is burned. In this situation a Wmax of 40% might be ideal.
  2. When you don’t have a lot of muscle mass, and/or when you just want to lose a lot of fat, minimizing muscle mass loss is less important than losing fat. In this case, a Wmax of 55% might be more ideal. In this situation, energy balance is much more important: you just have to burn more than you eat. Therefore, you might also exercise at an intensity of 75% Wmax. You burn less fat and much more glucose in this case, but this will indirectly result in greater fat loss because fat stores will be burned to supply the body with enough energy. However, when having little carbohydrates/glycogen in the system, exercising at a high intensity is very heavy, and it might therefore be a better option to exercise at an intensity of 55% Wmax.

According to literature, the optimal fat burning point could be different for persons, as gender, age, training status, diet and body composition might play a role[3]. An explanation for this could be that the bodies of trained athletes and people who consume low carb diets (either by fasting or high fat diets in the absence of carbs) are more efficient by being better able to switch to fat oxidation. Furthermore, there is some variation in Wmax, as these might differ per day. This variation is estimated to be around 3 to 7%[4]. It is therefore difficult to implement the Fatmax concept with 100% accuracy in your training strategy. It might be that you need a slightly higher or lower intensity than what is recommended to have optimal fat oxidation. However, it might still be a good approach for cutting.

How to implement Fatmax in your training        
To start exercising at a certain intensity, you should know what your Wmax is. To determine Wmax, the following (simplified) protocol on a cycle ergometer could be used[4]:

  1. Warm up for 5 minutes at 100W for males or 75W for females. Maintain at least 60 rotations per minute during the whole test.
  2. Increase the intensity with 35W every 2 minutes, until exhaustion.

Exhaustion =  the point at which you cannot maintain 60 rotations per minute for more than 20 seconds

  1. Write down the maximal work load (W) at exhaustion.

Now you know your Wmax, you can implement the concept of Fatmax into your cardio workout schedule to optimize fat loss.

The concept of Fatmax might be useful with regard to weight loss programs. The concept is however based on assumptions of physiology. I could not find any randomized controlled trials that investigated the validity of Fatmax for weight loss in comparison to another exercise regime. Therefore, it is not sure if optimal fat oxidation results in significantly greater weight loss compared to other fat burning strategies. I would therefore recommend to primarily stick to the key concept in weight loss, which is a negative energy balance. If you are able to implement Fatmax in your weight loss schedule, you might give it a try.

In short, Fatmax can be implemented in your training by:

  1. Finding your Wmax with a cycling test.
  2. Exercise at 40% of Wmax if you want to minimize muscle loss during a cut.
  3. Exercise at 55% of Wmax if you want to maximize fat loss during a cut.
  4. Look at your total exercise energy expenditure. A lower %Wmax also means that the exercise duration should be longer in order to burn the same amount of calories.

[1] Jeukendrup, A., & Gleeson, M. (2010). Sport nutrition: an introduction to energy production and performance (No. Ed. 2). Human Kinetics.
[2] van Loon, L. J., Greenhaff, P. L., Constantin‐Teodosiu, D., Saris, W. H., & Wagenmakers, A. J. (2001). The effects of increasing exercise intensity on muscle fuel utilisation in humans. The Journal of physiology536(1), 295-304.
[3] Ghanbari-Niaki, A., & Zare-Kookandeh, N. (2016). Maximal Lipid Oxidation (Fatmax) in Physical Exercise and Training: A review and Update. Annals of Applied Sport Science4(3), 0-0.
[4] Kuipers, H., Verstappen, F. T. J., Keizer, H. A., Geurten, P., & Van Kranenburg, G. (1985). Variability of aerobic performance in the laboratory and its physiologic correlates. International journal of sports medicine6(04), 197-201.

Is sleeping in during the weekend beneficial?

By Wietse In het Panhuis

Probably everyone recognizes this situation: You have had a busy work week, waking up early at 7 am every morning, and going to bed at 11 pm. On Friday, you feel tired and you have the feeling that you should catch up on sleep, but you also want to go to bed later, since it’s weekend. Therefore, you decide not to set your alarm clock on Saturday and Sunday. You stay up late on Friday and Saturday, and you wake up at 11 am on Saturday and Sunday morning. Is this a good idea? Does sleeping in really help to catch up on sleep, rest and recover?

Sleep deprivation          
As mentioned before in my other article on sleep and rest, there is not an optimal sleep duration that works for all people (if you missed the previous article, you can read it here: Some people need much sleep, others need less. The reason for this is differences in habit, but also differences in genetics (and of course differences in age, but this can be neglected since the readers of this article are probably all students). Therefore, no solid recommendations can be done on how long you should sleep.

If you get less sleep than you need, sleep deprivation (the need for sleep) will accumulate. Often when you have one bad night of sleep, you will still feel fine the next day, but when this happens for a few nights in a row you will start to notice the effects of sleep deprivation. Of course I don’t have to explain to you that (chronic) sleep deprivation is bad for you and can have serious health consequences. That is probably also the reason you want to sleep late during the weekends, to get some more rest. In theory, it is true that the body needs to catch up on sleep when it is sleep deprived, so in that respect you are right. There are however other factors that play a role.

The biological clock       
Like mentioned before in my previous article, the biological clock is a mechanism that (a.o.) informs the body about time: the sensation of day and night. The biological clock is a complex system, because it can be influenced by many factors (think of light, psychological factors, activity, food intake). The complexity is also the reason why the biological clock does not adapt easily to changes in the daily routine. A jet-lag is a perfect example for this. After traveling it takes some time to adjust the sleep rhythm to the new time zone. However, it takes even longer before you are fully adapted to the new time (e.g. when you don’t need an alarm clock to wake up at a certain time). A rule of thumb is: don’t mess with your biological clock! It is best for the biological clock to have a regular pattern in sleep (most important), but also in things like food intake. Big changes in these patterns disturb the clock, which could result in sleeping problems, fatigue, changes in mood, concentration, study performance and metabolism, and in more severe cases (like chronic shift-work) in diseases like diabetes, cardiovascular disease and obesity, and even mortality[1-6]. A stable clock is therefore a healthy clock.

When you wake up early during the week and late in the weekend, this is confusing for the biological clock, especially when there is a great difference between the times of waking up. For each day you go to bed and wake up at a different time, the biological clock has to adapt. When sleeping in during the weekend and waking up early on Monday again, the biological clock keeps adapting back and forth. In this way, the body does not fully get used to waking up early during the week. This could possibly be the explanation why you are feeling tired during the week.

What I personally notice, is when I am not used to waking up early, and I wake up early even though I get my hours of sleep, I am still tired. This is because the biological clock is not used to waking up at a different hour, and not because the body did not get enough sleep. When sleeping in during the weekend, the body is not well-adapted to waking up early during the week, and this can cause the sensation of fatigue.

Thus, when you are tired after waking up early for a week, the likely cause of this is that your rhythm during the weekend is different, and not because you don’t get enough sleep. The latter is of course still a possibility, and in that case you could try to go to bed earlier to see if that helps. The answer to the question: ‘Is sleeping in during the weekend beneficial?’ is therefore: No, the benefits of some extra sleep do not outweigh the disadvantage of a disturbed biological clock. If you still want some extra sleep during the weekend, the best thing to do is to go to bed earlier.

Of course this is not a very attractive message. When it is Friday, we want to enjoy our weekend by staying up late and do fun things. This message discourages that. You might accept and implement this message by enjoying your weekend in the morning instead of late in the evening, but I can imagine that you don’t want to give up your nights out. Alternatively, when you go out partying, it might be better to still wake up early (maybe one hour later than on a weekday). In this way, you will have some sleep deprivation, but you can solve this by taking a power nap during the day or by going to sleep earlier in the evening. The upside of this, is that your biological rhythm will be more stable, which will be more beneficial in the long run.

[1] Åkerstedt, T., Kecklund, G., & Johansson, S. E. (2004). Shift work and mortality. Chronobiology international21(6), 1055-1061.
[2] Ramin, C., Devore, E. E., Wang, W., Pierre-Paul, J., Wegrzyn, L. R., & Schernhammer, E. S. (2015). Night shift work at specific age ranges and chronic disease risk factors. Occup Environ Med72(2), 100-107.
[3] Antunes, L. C., Levandovski, R., Dantas, G., Caumo, W., & Hidalgo, M. P. (2010). Obesity and shift work: chronobiological aspects. Nutrition research reviews23(01), 155-168.
[4] Li, Y., Sato, Y., & Yamaguchi, N. (2011). Shift work and the risk of metabolic syndrome: a nested case-control study. International journal of occupational and environmental health17(2), 154-160.
[5] Trockel, M. T., Barnes, M. D., & Egget, D. L. (2000). Health-related variables and academic performance among first-year college students: implications for sleep and other behaviors. Journal of American college health49(3), 125-131.
[6] Wolfson, A. R., & Carskadon, M. A. (1998). Sleep schedules and daytime functioning in adolescents. Child development69(4), 875-887.

Carb cycling: the secret to get shredded?

By Fleur van Griensven


You might have heard the saying: ‘Carbs are bad for you’ or ‘eating after 8 pm makes you fat’. A lot of people claim that this will result in fat gain. Are carbs really the enemy or are these two examples just one of the thousand misconceptions in the fitness industry? Can we actually benefit from cycling our carb intake whilst cutting? Is carb cycling the secret to get shredded?

What is Carb cycling?
Carb cycling is just what the name implies: Cycling the carbohydrate intake during the week, which translates into higher carb days and days with fewer/no carbohydrates. This is also called a non-linear dieting approach. A linear dieting approach means that the amount of calories and ratio of carbs/protein/fats remains the same every day. Thus, the non-linear dieting approach includes differences in the amount of calories, carbs, protein and fats between different days. I will try to make this clearer with an example.

If you would eat 200 g carbs, 150 g protein and 60 g fat 7 days a week you’d be following a linear dieting approach

If you would eat 250 g carbs, 150 g protein and 60 g fat on your 5 training days and 150 g carbs, 150 g protein and 60 g fat on your 2 rest days, you would be following a non-linear/carb-cycling diet.

With a carb-cycling diet, you basically manipulate your carbohydrate intake on different days of the week. Figuring out how much carbs to eat on these days is not that simple, but we will get back to that later on. In addition, I will give some tips on how to incorporate carb cycling in a diet yourself.

When can it be used and what are the benefits?
Carb cycling can be used both during a cutting (caloric deficit) and bulking period (caloric surplus). In this article, we will not cover carb cycling during a bulk. Carb cycling can be used from the start of a cut or when you go deeper into a caloric deficit. Most people will choose the second option. They do this because as calories are decreased a lot, it’s harder to stay motivated. Having different amounts of calories on different days might give you something to look forward to.

Carb cycling may have some potential benefits. Firstly, for some it gives a psychological boost and motivation to keep going. Implementing higher carb days gives you something to look forward to when dieting gets tough. The prospect of a day filled with pasta, bread or whatever carb source you’re craving can just be enough to keep on track with dieting.

Menno Henselmans, the founder of Bayesian Bodybuilding, has been talking about carb cycling in one of his interviews. Bayesian Bodybuilding uses an evidence and scientific-based approach to bodybuilding, so everything is based on scientific data. In this interview, Menno Henselmans says that there are almost no studies done on the carb cycling approach and the physiological benefits. The science about carb cycling is lacking, which I also encountered when digging deeper into this topic. Menno Henselmans believes that the few days during which the carb intake is increased, or higher carb days in general, do not have any practical physiological effect. A few days of increased carb consumption after several days lower in carbs is not enough to bring hormones related to hunger and appetite back to normal. [1]

There are however some studies that looked at the effect of an increased carbs intake for one or more days on a hormone that are related to hunger and appetite.

One of these hormones is leptin. Leptin is a hormone secreted (produced) by fat cells and controls both long-term energy balance and appetite. When body fat is going down during a cut, leptin production is decreased over time. This results in more and more hunger when you are deeper into a cut. Here the fun part of shoving your face with carbs comes in. Higher carb days, also called refeed days, are thought to bring the lowered leptin concentration back to a normal level. This will reduce the increased sensation of hunger (for a while), which might help you to stick to your diet.

However, recent studies did not show that a refeed or just one-high carb day can bring leptin levels back up. Yes, refeeding does give a rise in serum leptin levels, but leptin levels return to baseline (the starting point) after 24h. This means that leptin levels are not restored long-term. Switching between higher and lower carbs days is not going to do much for an improvement in leptin and thus those hunger feelings will still be there. [2]

Carbs are the main energy source during physical activity, because they provide the glucose that is required for energy. What most people experience is that eating more carbs will result in more energy during their training session. This results in them being able to train harder and lift more. That’s why it is recommended to have higher carbs on the heaviest training days.

How to set up your carb cycling plan? [3]
The most crucial thing in setting up macros for a carb cycling diet is to still have the same weekly total carb intake as you would have in a linear dieting approach. We leave aside protein and fat for the moment as they remain the same and we are only going to manipulate our carb intake on different days. Let’s go back to the example used earlier to show how you can set it up yourself.

On a linear diet, we would have 200 g carbs x 7 days = 1400 g of carbs per week.

For example, on a carb cycling diet it could look like this:

  • 190 g 6 days per week and 260 g 1 day per week.
  • 184 g 5 days per week and 240 g 2 days per week.
  • 185 g 4 days per week and 220 g 3 days per week.

How you choose to set up your carb cycling plan is all personal preference. A few factors you can take into account are:

  • How often do you train? If you only train two or three days a week, bigger carb load days might be more beneficial for you. If you instead train five or even six days a week, a more moderate spreading of carbs might be better.

  • What are your heaviest training days? If adding more calories on these days gives performance a huge boost, go ahead and train the house down.

  • What suits my lifestyle? Can you be a bit strict during the week and have more carbs to spend for burgers with friends during the weekend? Or would you rather have a more moderate carb intake?

Conclusion, Carb cycling: The secret to get shredded?
NO carb cycling is not the secret to get shredded. The secret to get lean is maintaining a caloric deficit for as long as needed to achieve the physique or shape you’re after. If cycling your carb intake (in whatever way you choose to do so) makes it easier to stick to your diet, carb cycling might be a good strategy. Alternatively, if you enjoy doing it and get results from it, then do it. However, keep in mind that it won’t give you better results than a linear-dieting approach with a daily constant caloric deficit. Whether you use a linear or non-linear dieting approach like for example carb cycling does not matter as long as your weekly caloric averages come out the same.

Take home message: Don’t overcomplicate the whole fat loss thing, it’s not rocket science. Stick to a caloric deficit, choose a strategy you can do consistent and rock the beach this summer!

[1] Henselmans, M. (Bayesian Bodybuilding). (2015, 24 February). Refeeds, Body Recomposition &
Non-Linear Diets. [Radio Podcast]. In Danny Lennon. Sigma Nutrition& Performance.

[2] Kolaczynski J, (1996). Responses of leptin to short-term fasting and refeeding in humans: a link with ketogenesis but not ketones themselves. Diabetes. 45(11):1511-5.

[3] Cheadle, N (2015, 13 November). Carb cycling for fat loss. Retrieved from on April 26th 2017

Beta-alanine for strength training: yay or nay?

By Wietse In het Panhuis

If you have been training for some time, you have probably heard about it before. If you ever used pre-workout, you probably felt its effects before. I am talking about beta-alanine. Beta-alanine has been shown to be effective for some sports. The question is: Can beta-alanine supplementation be beneficial for strength training?Beta_alanine_1

What is beta-alanine?
Beta-alanine is a non-essential amino acid, which means that it is naturally present in the body. Even though it is already present in the body, supplementation with the intention to increase its levels could be beneficial (just like creatine). Beta-alanine is often used in sports that involve high intensity exercises, such as rowing and short-distance ice-skating. It is believed to combat muscle fatigue, and thereby has a positive effect on muscle endurance. Science has shown that beta-alanine is especially interesting for endurance during high intensity sports, and not for endurance (e.g. long distance running) and explosive (e.g. shot-put) sports[1].

How does beta-alanine improve endurance?    
Endurance is improved when fatigue is inhibited. There are many processes during exercise that could lead to fatigue. One of those processes is acidification of the muscles due to buildup of H+-ions (hydrogen ions) and lactate. Of course, the body has many mechanisms to prevent and counteract acidification, to make the pH (a measure of acidity) neutral again. Such mechanisms are called buffer mechanisms. In one of those mechanisms, a protein called carnosine plays a role[1]. During the production of ATP (energy production from food), H+-ions are formed. During exercise, a lot of energy is produced, and therefore also a lot of H+-ions. This will lead to a drop in pH (and will thus be more acidified). Carnosine works as a buffer by reacting with H+-ions. In that way, acidification and thereby fatigue of the muscles will be inhibited, which results in increased endurance.

Now beta-alanine comes in the picture. Beta-alanine supplementation results in increased carnosine levels[2]. Greater carnosine levels have been shown to increase endurance during high intensity exercise with a short duration, such as rowing and sprinting, like mentioned before. This raises the question: why not just supplement carnosine? This will not be effective, since muscle cells cannot take up carnosine from the blood stream[3]. The only way to increase carnosine inside the muscle cells, is if carnosine is produced (synthesized) in the cells themselves. Carnosine can be synthesized from beta-alanine and L-histidine (an amino acid), which in turn cannot be produced by muscle cells, but they can be taken up from the blood by muscle cells[4]. There is more L-histidine than beta-alanine in the blood, and the enzyme that combines these two to form carnosine, binds more easily to L-histidine than to beta-alanine[5-7]. For these two reasons, enough L-histidine is present while beta-alanine is often in shortage when carnosine is being produced (in other words: beta-alanine is the limiting factor). This means, that only beta-alanine is necessary to increase carnosine levels.

Thus, beta-alanine supplementation increases carnosine levels in the muscles. In turn, carnosine  works as a buffer to stabilize the pH and thereby endurance is increased. This is illustrated in Figure 1.


Figure 1. Beta-alanine’s mode of action. Retrieved from

How much beta-alanine do you need to use to see results?       
Increasing carnosine levels in the muscle cannot by achieved by taking beta-alanine once. According to scientific studies, supplementing 6,4 grams for 4 weeks is the most effective strategy to increase the carnosine levels in the muscle (by 65%)[8]. When supplementing for longer than 4 weeks, this will be equally effective and thus gives the same results. It just implies that supplementing beta-alanine for a short time period (less than 4 weeks) is not very effective.

The supplement is safe, but you may get a tingling, itching feeling on your skin (paresthesia) when you take more than 10 mg/kg body weight at once (around 800 mg). To prevent this, you can take eight daily dosages of 800 mg. Alternatively, four doses of 1600 mg of slow-release capsules also works to get the same effect without experiencing paresthesia[8]. Beta-alanine is commercially available in powder or slow release capsules. Powder costs about €16,- per 500 grams or ~€5,-/month. Slow-release capsules are about €15,- for 90 capsules or ~€20,-/month, making slow-release capsules four times as expensive as powder.

Fun fact: Beta-alanine is often present in pre-workout, but since intramuscular carnosine levels cannot be increased by taking beta-alanine once (like you do with pre-workout), this beta alanine has no added benefit to the pre-workout. Since beta-alanine dosages are often above 800 mg in pre-workout, this often results in paresthesia. Concluding: beta-alanine in pre-workout is useless and only gives you itches.

Can beta-alanine improve workouts for strength training?         
Unfortunately, in order to draw clear conclusions on this topic, more scientific research should be done. There are however a few studies that investigated this. One study looked at the effect of beta-alanine during a 10 week training program[9]. This study showed that total working volume increases due to beta-alanine. This effect only occurs during high-repetition sessions (8-12 repetitions) with little rest (30-90 seconds) and not in low-repetition sessions (±5 repetitions) with long rest (2-5 minutes)[9,11]. This makes sense, as during bodybuilding, muscles will get acidified which quickly can result in fatigue. Since beta-alanine improves the buffer capacity of the muscle by increasing carnosine levels, more repetitions can be done before reaching failure. In general, a greater training volume results in increased muscle mass. However, so far it has not yet been proven that the usage of beta-alanine supplements improves the gaining of muscle mass[10-12]. This might be due to the fact that in the performed studies training schedules varied and also included sets with fewer repetitions.

Thus, beta-alanine mainly seems to work for high intensity exercise during which glycolysis plays a major role (exercise durations of 1-6 minutes), since beta-alanine supplementation increases the muscle’s acid buffer capacity. Beta-alanine does not increase strength (like creatine does). Therefore, beta-alanine might be useful for bodybuilders (or for sports like bootcamp), but not for powerlifters or any sport that requires short bursts of energy (such as shot-put). More studies that test long term beta-alanine supplementation during a bodybuilding training schedule should be conducted to get clear answers on how much bodybuilders could benefit from beta-alanine.

Beta-alanine: yay or nay? Yay AND nay!      


It is both yay and nay, because there is not a clear answer.


  • Beta-alanine might improve endurance in bodybuilders, bootcampers and other high-intensity sports.


  • Beta-alanine supplementation does not increase strength.
  • Evidence for increases in muscle mass is lacking (even though it is likely).
  • In addition, supplementation can be either expensive or really inconvenient. Since beta-alanine can have paresthesia as a side effect at high dosages, supplementing about 6.4 grams per day without experiencing paresthesia can be done in three ways[8]:
  1. The cheapest option is to supplement 8 servings of 800 milligrams distributed over the day.
  2. If you do not like regular supplementation, you might consider two daily servings of slow-release capsules (which is however four times as expensive).
  3. Finally, you might just take 5 grams of powder in one or two servings per day, with the disadvantage of itches which may last up to one hour.

In summary, beta-alanine probably has some beneficial effects for bodybuilders by increasing volume and thereby possibly muscle mass. However, more scientific studies should be done to be sure. Please take into account that effects of single supplements are generally relatively small: The greatest improvements come from a good training schedule and good nutrition. Thus, as long as you are on amateur level of training, supplements in general will not make great differences. For professional athletes it can be more useful, since small differences could make the difference between winning or losing a competition. If you are not a pro, but if you want to improve in sports as much as you can, of course that’s fine. If you think it is worthwhile to either regularly supplement, pay a lot of money or experience itches, beta-alanine might be a good contribution to your workout.

[1] Artioli, G. G., Gualano, B., Smith, A., Stout, J., & Lancha Jr, A. H. (2010). Role of beta-alanine supplementation on muscle carnosine and exercise performance. Med Sci Sports Exerc, 42(6), 1162-1173.
[2] Suzuki, Y., Ito, O., Mukai, N., Takahashi, H., & Takamatsu, K. (2002). High level of skeletal muscle carnosine contributes to the latter half of exercise performance during 30-s maximal cycle ergometer sprinting. The Japanese journal of physiology, 52(2), 199-205.
[3] BAUER, K., & SCHULZ, M. (1994). Biosynthesis of carnosine and related peptides by skeletal muscle cells in primary culture. European journal of biochemistry, 219(1‐2), 43-47.
[4] Matthews, M. M., & Traut, T. W. (1987). Regulation of N-carbamoyl-beta-alanine amidohydrolase, the terminal enzyme in pyrimidine catabolism, by ligand-induced change in polymerization. Journal of Biological Chemistry, 262(15), 7232-7237.
[5] Harris, R. C., Tallon, M. J., Dunnett, M., Boobis, L., Coakley, J., Kim, H. J., … & Wise, J. A. (2006). The absorption of orally supplied β-alanine and its effect on muscle carnosine synthesis in human vastus lateralis. Amino acids, 30(3), 279-289.
[6] Horinishi, H., Grillo, M., & Margolis, F. L. (1978). Purification and characterization of carnosine synthetase from mouse olfactory bulbs. Journal of neurochemistry, 31(4), 909-919.
[8] Harris, R. C., Tallon, M. J., Dunnett, M., Boobis, L., Coakley, J., Kim, H. J., … & Wise, J. A. (2006). The absorption of orally supplied β-alanine and its effect on muscle carnosine synthesis in human vastus lateralis. Amino acids, 30(3), 279-289.
[9] Hoffman, J., Ratamess, N., Kang, J., Mangine, G., Faigenbaum, A., & Stout, J. (2006). Effect of creatine and ß-alanine supplementation on performance and endocrine responses in strength/power athletes. International journal of sport nutrition and exercise metabolism, 16(4), 430-446.
[10] Hoffman J, Ratamess NA, Ross R, Kang J, Magrelli J, Neese K, Faigenbaum AD, and Wise JA. Beta-alanine and the hormonal response to exercise. Int J Sports Med 29: 952–958, 2008.
[11] Hoffman JR, Ratamess NA, Faigenbaum AD, Ross R, Kang J, Stout JR, and Wise JA. Short-duration beta-alanine supplementation increases training volume and reduces subjective feelings of fatigue in college football players. Nutr Res 28: 31–35, 2008.
[12] Kendrick, I. P., Harris, R. C., Kim, H. J., Kim, C. K., Dang, V. H., Lam, T. Q., … & Wise, J. A. (2008). The effects of 10 weeks of resistance training combined with β-alanine supplementation on whole body strength, force production, muscular endurance and body composition. Amino acids, 34(4), 547-554.


Superfoods: yay or nay?

By Wietse In het Panhuis

Superfoods are a hot topic. Several people claim superfoods have high amounts of good nutrients and antioxidants, and numerous of beneficial health effects. When you eat a lot of superfoods, you will be healthy. Or will you?


What are superfoods?  
Some well-known examples of superfoods are: Goji berries, cacao beans, chia seed, hemp seed, and coconut oil. According to the definition of the term superfood, a superfood is any food with a beneficial health effect. This term is actually a marketing term instead of a scientific term. There are no nutritionists, dieticians or doctors with an academic background that would promote the use of it.

Are superfoods super healthy? 
Superfoods are claimed to have high levels of healthy nutrients and antioxidants, which in turn would have many health effects. Such effects include: Increases in energy and concentration, improvement of the immune system, even the prevention and curing of diseases (including cancer), anti-aging properties, and last but not least: Increases in life force! Is there any truth in any of these claims?

There is a flaw in the reasoning of articles that claim these things. You probably have seen it more than once: ‘Top 10 reasons to eat –insert superfood-‘. The superfood fights cancer, improves your eyesight, protects from cardiovascular disease, and so on. Here is an example to illustrate the reasoning behind most superfood articles is this: Superfood X contains vitamin A. A shortage of vitamin A has been shown to be bad for your eyes. Thus, when ingesting enough vitamin A by eating plenty of superfood X, these eye problems due to a shortage are prevented (true). Writers of these articles interpret this as: Eating enough vitamin A can prevent eye problems caused by a vitamin A shortage, therefore, Vitamin A is good for your eyes. Since vitamin A is good for the eyes, consuming more vitamin A is even better: You will improve your eyesight (false). Thus, superfood X improves the eyesight. In reality, vitamins (and other compounds) don’t work like that. They have a beneficial effect up to a certain point, and if you ingest more than that, it will not be more beneficial (and possibly even harmful). In superfood articles, the above described reasoning and exaggeration is often used. Hereby, the truth of a very small effect is turned into a miracle, a magic formula: When you eat this food, you will be healthy.

Superfoods are often claimed to have big effect sizes (in other words: a big impact on the body). These claimed effect sizes of superfoods are comparable to those of medicine (drugs), since medicine also has a big effect size on the body. Take anti-diabetic drugs for example: They improve glucose tolerance (an important measure in diabetes) and thereby give a significant ‘improvement’ of the situation. (This doesn’t mean that this is a good solution. It is treating symptoms, not treating the source of the problem.) In reality, single foods in general have a relatively small effect on health. There is not a single food (and thus not a single superfood) that could improve glucose tolerance like anti-diabetic drugs can, and this example goes for all drugs. However, when looking at a whole diet-lifestyle approach, big effects could be reached. It has for instance been shown that a good diet and exercise works just as well as medicine for treating diabetes[1]. (This does not hold true for any disease. Cancer and many other diseases cannot be cured by nutrition, while chance of survival can be improved nonetheless.) So, diet and nutrition should be looked at as a whole, and not at the effects of single foods.

It is for the reason that single foods only have small health effects, that scientific studies on superfoods either find no truth in claims on single superfoods, or they conclude there is not enough evidence to support these claims. So far, there has not been a single (super)food that has miraculous health effects.

Some people swear by superfoods. They say eating a lot of superfoods everyday changed their life. They felt much healthier and energetic. In such cases, these persons often dropped their unhealthy habits, such as overeating and eating unhealthy products, and replaced these with superfoods. Undoubtedly, this is good for your health. However, when you would replace unhealthy foods with vegetables and fruits you would see the same effect. Superfoods are healthy foods in general, but they are not healthier than fruits and vegetables.

One problem that might occur when people depend on superfoods, is that they choose superfoods over vegetables because they think superfoods are healthier. This might result in a diet with little variation, while the key to a healthy diet is a varied diet. Variation in a diet assures that you get all the nutrients you need, since different foods contain different nutrients. In this way, superfoods might work counterproductive.

How expensive are superfoods?             
Prices differ for different superfoods, but superfoods are generally sold in small packages with about 2 weeks worth of a daily serving. As an example, dried Goji berries from Body&Fitshop cost €4,90 for 250 grams. It is recommended to take at least 20 grams of berries per day, so a package lasts for about 12 days. Monthly this will cost you €12,15. When you look at table 1, you can see that a consumption of 20 grams of goji berries does not contribute a lot to the recommended daily intake (RDI), because this portion is small. Thus, goji berries are relatively quite expensive. Additionally, when you would eat greater amounts, this would contribute more to the RDI, but also would result in a high sugar intake.

This is only one of many examples, but in general you pay a lot for little product.

Table 1: Nutritional values of dried goji berries[2].

Nutrient Amount per 100 grams Amount per 20 grams % of ADH
Energy (kcal) 343 68.6
Sugar (g) 45.6 9.1
Fibre (g) 13 2.6 7.4%
Calcium (mg) 190 38 3.8%
Iron (mg) 6.8 1.3 14.4%
Vitamin C (mg) 48 9.6 12.8%

How are superfoods marketed?              
People are often ranting on the pharmaceutical industry, since this industry has the primary purpose of making money, while not caring about the consumer’s health. It is true that a lot of money is being made in this industry and making money is always the driving force behind important decisions. However, I seldom hear people about the superfood industry. They are selling regular healthy foods for high prices, while marketing them as super beneficial for health. What they are doing is like selling tomatoes for three time the original price, and people buy it because of smart marketing. In this respect, there is little difference between the pharmaceutical industry and the superfood industry. When you read about superfoods, there is often a story behind it, like: The famous Li Qing Yuen (born in 1678) ate lots of Goji berries that grow in old protected valleys in Mongolia and Tibet. Li Qing Yuen became 256 years of age. Articles on superfoods often start with such a romantic story and then just give you a top 10 of the superfood’s (claimed) effects. Sometimes these background stories are obviously nonsense, like this example, but sometimes there are more impressive, believable stories. I remember one story about a sheep herder, who had a lot of sheep suffering from cancer. Then the sheep accidentally ate from a certain superfood, and the cancer disappeared. Of course, when common sense is used, you might find this story quite unlikely. There are however a lot of people without a background in biology and these topics. To those people, this can be a trustworthy story. Nearly all superfoods have been given a story like this, which is all part of the marketing trick.

One example of marketing superfoods is kale. As a Dutchman, you all know kale (boerenkool). Apparently, kale has been marketed as a superfood in the US. It has been called an antioxidant superstar with impressive anti-cancer effects. It’s good for this, good for that, etcetera, etcetera… Meanwhile, in the Netherlands we have been eating kale for a very long time. Is it healthy? Sure! Is it super? No. Is it expensive in the Netherlands? No. Is it expensive as a superfood? Take a guess. One funny superfood product called ‘Essential 10 Super Greens Super Food with Kale & Barley Grass’ contains kale and some other regular vegetables. This product costs €14,25 for 21 servings. That will cost you €20,- per month. One serving provides you with 20 to 35% of the RDI of fibres, vitamin C, vitamin K and calcium. This product thus contributes only a small part of the RDI of only four nutrients (there are over 20 vitamins and minerals). That means you still need to eat a lot of other foods to get everything you need. In comparison, when eating 100 grams of broccoli, this will contribute to 100% of the RDI of vitamin C, about 50% of the RDI of vitamin A, 22% of the RDI of copper, about 15% of the RDI of zinc, 14% of the RDI of fosfor, 11% of the RDI of iron, and 10% of the RDI of fibres. Broccoli is roughly said a better source of nutrients when taking portion sizes into account. 100 grams of broccoli costs €0,30 while one serving of the superfood costs €0,68. Thus, even though the above mentioned superfood might be good because of its fibre and vitamin K content (two nutrients that are more difficult to consume plenty of), it is way too expensive in relation to the small contribution to your health. (Of course it is difficult to make a 1 on 1 comparison, since you are not and you should not be eating broccoli every day, but you get the picture.)


People want to believe there are such things at superfoods, because we want to believe that we can dramatically improve our health by simply eating a few new products. The superfood industry exploits this desire by knowingly telling fairytales (such as the sheep story), and the next thing that happens is that some self-proclaimed food expert writes a book about super foods. After that, people start to blog about superfoods and how it changed their lives, and then share it on the internet. Anyone can write anything they want, while it is not checked whether the facts are true. Subsequently, other people will believe the claimed facts because they are uninformed, and have a strong desire to do what is best for their body. More and more people will start buying foods and spreading the word on the amazing effects of superfoods. This is a vicious circle that keeps expanding. It is brilliant marketing from the superfood industry.

Conclusion – superfoods: yay or nay?   
Concluding so far:

  • The term superfood is a term invented as a clever marketing strategy
  • Superfoods are healthy, but they are not healthier than regular foods
  • Superfoods are expensive

Superfoods: yay or nay? NAY!


In general, superfoods are a waste of money if you buy them because you think they are super healthy. Are superfoods bad for you? No, they are healthy products, but you still need variation in your diet. If you like your money, you are better of buying regular fruits and vegetables, because they are equally healthy and much cheaper. Buying regular fruits and vegetables will save you a lot of money. Of course, when you buy superfoods for their taste, that is totally up to you.

If you love eating superfoods and are feeling great by doing it, please feel free to do so. The message of this article is: Just don’t get deceived by this marketing strategy. There are no magical formulas for being healthy.

[1] Gillies, C. L., Abrams, K. R., Lambert, P. C., Cooper, N. J., Sutton, A. J., Hsu, R. T., & Khunti, K. (2007). Pharmacological and lifestyle interventions to prevent or delay type 2 diabetes in people with impaired glucose tolerance: systematic review and meta-analysis. Bmj334(7588), 299.
[2] Bessen goji- gedroogd (NEVO-code 3445), NEVO-online versie 2016/5.0, accessed on 31-03-2017.

Creatine, a beneficial peptide

by Ricky Siebeler

Creatine is a peptide composed of several amino acids. Specifically, the compound contains L-arginine, glycine and methionine. Currently it is one of the most used supplements by strength athletes, as it accelerates the recovery of available energy in the cells. Whether you are currently supplementing with creatine or not, your body already uses this compound on a day to day basis. These days there is even some evidence suggesting that creatine has potential benefits for non-athletes. Everything mentioned above explains why it is one of the most studied supplements available. This article will offer some in-depth information about the supplementation of creatine monohydrate, with some additional myth busting.

How does it work?

Without going too in-depth about the body’s energy systems; the body breaks down nutrients such as carbohydrates, fats and ketones to produce ATP (adenosine triphosphate). ATP is used by the cells as a source of energy. By breaking the bond between one of the phosphates, energy is released. This will convert ATP into ADP (adenosine diphosphate) and AMP (adenosine monophosphate). In order to keep a constant supply of energy in the cells, the precursors (ADP & AMP) need to be converted back into ATP.


The body does so by creating a high energy body between the precursors and phosphate groups. Creatine supplementation aids in the acceleration of this process, but before it is able to do so, it is phosphorylated into phosphocreatine by creatine kinase [1-3]. Phosphocreatine aids in this process by increasing the pool of available phosphate groups [4].


Effects of supplementation

As mentioned before, creatine is one of the most studied supplements available. This results in countless studies, aimed towards different effects. This section will only feature studies of importance to strength athletes.

Creatine supplementation has been proven to increase muscle creatine content by a significant amount, proving the effectiveness of supplementation [5-6]. There is also some evidence suggesting that creatine non-responders do exist, who will not benefit from supplementation [7]. There are currently over 60 studies showing a very significant increase in strength levels, after supplementation with creatine. Meta-analyses show effects ranges upwards to about a 7,5% increase in strength [8-9]. As result from creatine supplementation, some water retention may occur, of which the amount differs greatly from person to person. Contradictory to what most people suggest, creatine could be beneficial for more moderate intensity (such as lifting or exercising in the higher rep ranges) athletes as well [10-11]. So far, some of the studies suggest that creatine may also be significantly beneficial when training outside common strength training repetition ranges, these effects seem to get smaller with each additional decrease in intensity. Example: powerlifters get the most benefits, sprinters some benefits, and endurance runners no benefits.

How to supplement with creatine

In order to benefit the most from creatine supplementation, the muscles need to be fully saturated with creatine. In order to achieve/maintain this saturation, creatine is often supplemented each and every day.  Creatine can be supplemented through a loading protocol, or without one. The reason for using a loading protocol could be to reach a saturated state early on, and benefit from the supplementation as fast as possible [12]. Some downsides of using a loading protocol would be the possible discomfort in the digestive tract, and the additional costs of using a higher dosage. A typical loading protocol would be to supplement with about 0,3g/per kilogram of bodyweight per day, for about one week [13], followed by a maintenance dose of about 0,03g/per kilogram of bodyweight per day for the remainder of the cycle, or indefinitely [12]. When not using the loading protocol, just start with the maintenance dose which will yield the same effect, after a couple of weeks. Maintenance dose calculations will probably result in a much lower dosage than the generally recommended 5g dose. The 5g dosage is usually taken for one of the following reasons: creatine is very cheap, there is some research suggesting a possible minor benefit to higher dosage supplementation, scoop size, and to make the supplement companies more money.

Additional supplementation tip: Digestive tract discomfort may occur when supplementing without sufficient water intake. Some people may even experience diarrhea or nausea. These effects are more present when using a loading protocol. To counteract some of these effects, drink enough water and perhaps spread out the supplementation over several meals.

Creatine myths

  1. Since creatine is produced by the body, supplementation will suppress the body’s ability to produce its own creatine.

Research does suggest that the production of creatine will be inhibited, if the amount of supplemented creatine is able to cover the vital needs. This inhibition may actually be beneficial to general health, mainly because of the costs (such as essential amino acids) associated with the synthesis of creatine by the body. So far, research suggest that creatine production will go up to baseline levels again when the supplementation is discontinued [14-16].

  1. Creatine may be damaging to the body in the long-term.

There have been several studies testing the safety of long-term supplementation with creatine. Examples of these studies would be the supplementation of 5g on older adults and athletes for about one year. These studies found no negative effects of supplementation [14-16]. This suggests there is no need to cycle creatine out of safety reasons. Some people claim that creatine could be damaging to the liver. This claim is based on the fact that creatine will increase the blood creatinine levels, which are often used as a marker of liver damage. When supplementing with creatine, this marker becomes useless.

  1. There are different forms of creatine available, which lead to better results than creatine monohydrate.

There are countless different forms of creatine on the market today, some of the most well know being: buffered creatine, creatine nitrate, creatine ethyl ester, liquid creatine, and creatine HCl. These are generally being marketed as more potent or better digestible than creatine monohydrate. Some of these forms of creatine have been studied fairly well, and show no significant benefit over creatine monohydrate [6,17-18]. Even though some forms of creatine may be better in theory, so far research suggests otherwise. These forms of creatine are often several times more expensive than creatine monohydrate. Keep in mind that most of the countless studies on the efficacy and safety of creatine were conducted on creatine monohydrate.

  1. My daily meat consumption will provide enough creatine, I don’t need to supplement with creatine for the additional benefits.

According to the previously established maintenance dosage an average 85 kg person would need about 2,5g/per day, while an average person (American) only consumes about 0,85g/per day. Some meats have been shown to contain relatively much creatine: beef 5g/kg, chicken 3,4g/kg. Keep in mind that these numbers are for the uncooked meat, cooking them would denature most of the creatine [19]. Unless you are into consuming a lot of medium rare chicken, supplementation would be needed to attain most of the benefits.

  1. I need to take my creatine after my workout, with carbohydrates.

Timing of creatine has not been proven to be of importance. In theory the body could be more susceptible to the uptake of nutrients after a workout, even though the effects would be minor. Carbohydrates may also slightly improve the uptake of creatine [20]. Both of these effects will not make a difference in the effects of creatine. However, they could aid in decreasing the digestive tract discomfort caused by a creatine loading phase, but during the maintenance phase the factors will not make any difference.

  1. alcohol will diminish the effects of creatine.

Currently there is no research on the specific interaction between alcohol and creatine supplementation. Therefore we are not able to draw any conclusions about this topic, however we are able to hypothesize what kind of interaction we can expect. The uptake and storage of creatine requires water, while alcohol has a diuretic effect. This leads us to believe that alcohol does negatively affect the creatine supplementation. The next question would be to what extent this will affect the benefits of supplementation. Well consider the following: once you consumed the required amount alcohol to dehydrate yourself, you will probably not be able to properly train anyway. When consuming alcohol with moderation (which is not that much), creatine levels should not be affected significantly.

Take home messages:

– To get the most benefits from creatine for the least amount of money, use 3-5g of creatine monohydrate per day, timing does not matter.

– Continued usage for over a whole year have been shown to be safe (at normal dosages).

– Creatine ingested from diet alone is not significant in a normal diet (no medium rare chicken).


[1]          Mujika I, Padilla S. Creatine supplementation as an ergogenic aid for sports performance in highly trained athletes: a critical review. Int J Sports Med. 1997;18(7):491-6.

[2]          Terjung RL, Clarkson P, Eichner ER, et al. American College of Sports Medicine roundtable. The physiological and health effects of oral creatine supplementation. Med Sci Sports Exerc. 2000;32(3):706-17.

[3]          Guzun R, Timohhina N, Tepp K, et al. Systems bioenergetics of creatine kinase networks: physiological roles of creatine and phosphocreatine in regulation of cardiac cell function. Amino Acids. 2011;40(5):1333-48.

[4]          Adhihetty PJ, Beal MF. Creatine and its potential therapeutic value for targeting cellular energy impairment in neurodegenerative diseases. Neuromolecular Med. 2008;10(4):275-90.

[5]          Del favero S, Roschel H, Artioli G, et al. Creatine but not betaine supplementation increases muscle phosphorylcreatine content and strength performance. Amino Acids. 2012;42(6):2299-305.

[6]          Spillane M, Schoch R, Cooke M, et al. The effects of creatine ethyl ester supplementation combined with heavy resistance training on body composition, muscle performance, and serum and muscle creatine levels. J Int Soc Sports Nutr. 2009;6:6.

[7]          Syrotuik DG, Bell GJ. Acute creatine monohydrate supplementation: a descriptive physiological profile of responders vs. nonresponders. J Strength Cond Res. 2004;18(3):610-7.

[8]          Branch JD. Effect of creatine supplementation on body composition and performance: a meta-analysis. Int J Sport Nutr Exerc Metab. 2003;13(2):198-226.

[9]          Dempsey RL, Mazzone MF, Meurer LN. Does oral creatine supplementation improve strength? A meta-analysis. J Fam Pract. 2002;51(11):945-51.

[10]       Graef JL, Smith AE, Kendall KL, et al. The effects of four weeks of creatine supplementation and high-intensity interval training on cardiorespiratory fitness: a randomized controlled trial. J Int Soc Sports Nutr. 2009;6:18.

[11]       Mcconell GK, Shinewell J, Stephens TJ, Stathis CG, Canny BJ, Snow RJ. Creatine supplementation reduces muscle inosine monophosphate during endurance exercise in humans. Med Sci Sports Exerc. 2005;37(12):2054-61.

[12]       Kilduff LP, Pitsiladis YP, Tasker L, et al. Effects of creatine on body composition and strength gains after 4 weeks of resistance training in previously nonresistance-trained humans. Int J Sport Nutr Exerc Metab. 2003;13(4):504-20.

[13]       Burke DG, Chilibeck PD, Parise G, Candow DG, Mahoney D, Tarnopolsky M. Effect of creatine and weight training on muscle creatine and performance in vegetarians. Med Sci Sports Exerc. 2003;35(11):1946-55.

[14]       Groeneveld GJ, Beijer C, Veldink JH, Kalmijn S, Wokke JH, Van den berg LH. Few adverse effects of long-term creatine supplementation in a placebo-controlled trial. Int J Sports Med. 2005;26(4):307-13.

[15]       Shao A, Hathcock JN. Risk assessment for creatine monohydrate. Regul Toxicol Pharmacol. 2006;45(3):242-51.

[16]       Bender A, Samtleben W, Elstner M, Klopstock T. Long-term creatine supplementation is safe in aged patients with Parkinson disease. Nutr Res. 2008;28(3):172-8.

[17]       Jagim AR, Oliver JM, Sanchez A, et al. A buffered form of creatine does not promote greater changes in muscle creatine content, body composition, or training adaptations than creatine monohydrate. J Int Soc Sports Nutr. 2012;9(1):43.

[18]       Jäger R, Harris RC, Purpura M, Francaux M. Comparison of new forms of creatine in raising plasma creatine levels. J Int Soc Sports Nutr. 2007;4:17.

[19]       Mora, L., M.A. Sentandreu, and F. Toldra, Effect of cooking conditions on creatinine formation in cooked ham. J Agric Food Chem, 2008. 56(23): p. 11279-84.

[20]       Green AL, Hultman E, Macdonald IA, Sewell DA, Greenhaff PL. Carbohydrate ingestion augments skeletal muscle creatine accumulation during creatine supplementation in humans. Am J Physiol. 1996;271(5 Pt 1):E821-6.

Mythbuster: Can you bake with extra virgin (olive) oil?

By Wietse In het PanhuisOlive_1

A common myth is that you should not use extra virgin (olive) oil for baking. This myth states that this might be bad for you due to trans-fat formation, and that the taste will adversely change. Is there a healthier alternative? Is this myth true or not? Keep on reading to find out!

What are trans fats?       

Trans fats are unsaturated fatty acids, of which the geometric configuration (the way the atoms are ordered in the fat) is different from (cis-)unsaturated fatty acids that we are familiar with. As can be seen in the picture below, both fatty acids have exactly the same atoms in the same order. The only difference is the placement of the hydrogen atoms (H) at the double bond (indicated with the red and blue circle). At the cis-bond, the hydrogen atoms are at the same side of the carbon chain, and at the trans-bond, the hydrogen atoms are at the opposite side. This small structural difference could cause big differences in important factors such as the melting point, and can thereby explain differences in healthiness between trans fats and non-trans fats. Processes such as heating can change the configuration of a bond from cis to trans. In other words: heating of unsaturated fats can result in trans fat formation. This is only possible if fats contain a double bond. Since saturated fats do not have a double bond, trans fat formation can only occur in unsaturated fats.Olive_2

Regulation of trans fats
Since the 1950s, trans fats have been abundantly used in the food industry. Trans fats do not only occur naturally in foods, but are also a byproduct formed by production processes such as hydrogenation of vegetable oils (a process during which liquid oils are converted to solid or semi-solid fats). The latter form is called artificial trans fat. It is generally known that artificial trans fats are bad for health. Consumption increases the risk of multiple cardiovascular risk factors and coronary heart disease events such as heart attack and stroke[1]. It is for that reason that use of artificial trans fats was banned in 2006 by the FDA. Trans fats occurring naturally in animal products are also thought to be unhealthy, but they are probably not as worse as artificial trans fats (and trans fat levels are also much lower compared to food products containing artificial trans fats). Thus, it can be concluded that trans fats are unhealthy.

Oil baking/frying and trans fat formation
Trans fats are also formed by heating of vegetable oils, such as olive oil. Especially during deep-frying, a lot of trans fat formation will occur. However, this trans fat formation predominantly occurs at high temperatures (150-200+ degrees Celsius). Therefore, baking or stir-frying with vegetable oils hardly induces trans fat formation, even not at high temperatures as confirmed by this study[2]. Thus, baking with oil in general will be safe with regard to trans fat formation.


Differences between extra virgin/refined
What is the exact difference between extra virgin olive oil and refined olive oil? Oil is produced by the extraction process of vegetables and seeds, such as olives, sunflowers, rapeseed, and so on.  There are many different names for each oil. There is refined olive oil, virgin olive oil and extra virgin olive oil (and some other examples on which we will not go into detail). The difference between these oils is the degree of processing and thereby the quality of the oil. Extra-virgin olive oil is of the highest quality, followed by virgin olive oil and lastly refined olive oil. The word virgin indicates that the olives were pressed in order to extract the oil. This is the purest form of oil, and thus has the highest quality. This is different from refined oils, which have been produced by chemical or heating processes after the olives are pressed to create virgin oil. Thus, the big difference is the amount of nutrients and the sensory properties (or in other words, the taste).

Both refined and (extra) virgin olive oil are high in poly unsaturated fatty acids (PUFAs), which are healthy compared to saturated fats[3]. Thus, cooking with oil is always better than cooking with butter(based) baking products, as these contain more saturated fats and less PUFAs. Additionally (extra) virgin olive oil contains a lot of polyphenols (e.g. vitamins E and K, phytosterols and polyphenols), which have been proven to have protective health effects with regard to cardiovascular diseases[4,5]. A lot of these compounds function as antioxidants. Thus, extra virgin olive oil is the best choice to consume, as this is the most healthy one.

What happens when extra virgin olive oil is heated?      
It is often said that when extra virgin olive oil is heated during baking, the taste changes and trans fats are formed. This would not be the case for refined oils.

Firstly, like previously stated, heating oils at low temperatures (like temperatures during baking) cannot (or hardly) produce trans fats. The only difference between extra virgin oil and refined oil is quality and nutrients. It would therefore be weird that trans fats would be formed when baking with extra virgin, but not with refined olive oil. Thus, we can safely assume that no trans fats will be formed when baking with extra virgin (olive) oil.

Nonetheless, there are some changes occurring in the extra virgin olive oil during baking, otherwise the taste would not change. Some of the antioxidants in the oil are thought to be degraded during baking. I could not find studies looking exactly into this problem. Most studies are looking at changes in extra virgin olive oil due to deep frying. In addition, the total amount of polyphenols in the oil consists of a lot of different compounds, of which many we did not identify yet. It is therefore difficult to measure all the polyphenols, so answering the question how many polyphenols are degraded due to baking proves to be difficult. From my personal point of view, I don’t believe that all the polyphenols present in the oil will be degraded by baking shortly with oil, as these temperatures are relatively low and heating duration is short. Therefore, even though some of the polyphenols are lost, there are still more polyphenols remaining than when cooking with refined oil in which hardly any polyphenols are present. With this respect, extra virgin olive oil would still be a healthier choice to bake with. A study that investigated the effect of heating on antioxidants and polyphenols in virgin olive oil confirms this hypothesis[6]. This study showed that the antioxidants present in the oil have a protective effect on polyphenols. In other words, heating degrades antioxidants while most of the polyphenols are spared and still intact.

However, it is true that heating extra virgin olive oil changes the taste of the extra virgin olive oil. You have to decide for yourself whether you think this is a problem or not. Extra virgin oils have a more distinctive taste than refined oils. This characteristic taste will change. I myself do not have a sophisticated taste. I therefore do not mind if the distinctive taste of extra virgin oil is changed during the baking. I do not taste much difference between baking with refined oil or extra virgin olive oil. I care more about the health properties. Think of it like this: If you are baking with refined oil, the taste is of less quality than extra virgin olive oil. When baking with extra virgin olive oil, the taste does not get worse than refined oil, so you might as well choose to bake with extra virgin oil since it’s healthier.

Concluding: not baking with extra virgin oils? Myth!     
Let’s summarize what we have found:

  1. Baking with extra virgin oil does not produce trans fats.
  2. When baking with extra virgin oil some antioxidants (polyphenols) are lost, but most of the polyphenols will still be present in the oil.
  3. The taste of extra virgin oil may be affected by heating. You should decide for yourself whether you find this important.

Thus, when approaching this health-wise, the myth that you should not use extra virgin olive oil for baking is not true.

Disclaimer: In this article I only talk about baking and not about deep-frying. When you are deep-frying, olive oil is not a good choice as a lot of trans fats will be formed. In this case more stable oils such as sunflower oil are healthier alternatives.

[1] Mozaffarian, D., Aro, A., & Willett, W. C. (2009). Health effects of trans-fatty acids: experimental and observational evidence. European journal of clinical nutrition, 63, S5-S21.
[2] Przybylski, R., & Aladedunye, F. A. (2012). Formation of Trans fats: during food preparation. Canadian Journal of Dietetic Practice and Research, 73(2), 98-101.
[3] Schwab, U. (2014). 1, Lauritzen L 2, Tholstrup T 2, Haldorssoni T 3, Riserus U 4, Uusitupa M 5, Becker W 6. Effect of the amount and type of dietary fat on cardiometabolic risk factors and risk of developing type 2 diabetes, cardiovascular diseases, and cancer: a systematic review. Food Nutr Res.
[4] Morrison, M. C., Mulder, P., Stavro, P. M., Suárez, M., Arola-Arnal, A., Van Duyvenvoorde, W., … & Kleemann, R. (2015). Replacement of dietary saturated fat by PUFA-rich pumpkin seed oil attenuates non-alcoholic fatty liver disease and atherosclerosis development, with additional health effects of virgin over refined oil. PloS one, 10(9), e0139196.
[5] Khurana S, Venkataraman K, Hollingsworth A, Piche M, Tai TC. Polyphenols: benefits to the cardiovascular system in health and in aging. Nutrients. 2013; 5(10):3779–827. doi: 10.3390/nu5103779 PMID: 24077237
[6] Pellegrini, N., Visioli, F., Buratti, S., & Brighenti, F. (2001). Direct analysis of total antioxidant activity of olive oil and studies on the influence of heating. Journal of Agricultural and Food Chemistry, 49(5), 2532-2538.

Zinc supplementation: Worth the money?

By Fleur van Griensven


According to a recent poll and survey, you guys wanted to know more about zinc supplementation, so here you go! It’s a mineral not spoken much of, but that doesn’t necessary mean we should forget about it. What does this mineral do in the body? Are there any consequences of a low intake? Is zinc supplementation useful? You can read it all in this article: Zinc supplementation: worth the money?

What is Zinc?

Zinc is a mineral which is part of the trace elements in nutrition. Trace elements are minerals that are present in very small quantities in our diet, but are nonetheless essential. Other examples of trace elements are iodine and selenium.

Zinc is an essential element for hundreds of proteins in the body, including numerous enzymes and DNA-binding proteins. A few examples of proteins that contain zinc are the receptors for vitamin A and vitamin D. It also plays a role in immune function, wound healing and cell division. On top of that it also supports normal growth and development during pregnancy, childhood and adolescence[1].

Zinc can be found naturally present in some foods, it can be added to food,  and it can be available as a dietary supplement. A wide variety of foods contain zinc. See table 1 below for an overview of the foods naturally containing zinc. Besides red meat and poultry, oysters are a great zinc source. Other good sources include nuts, beans, seafood, whole grains and dairy products.

Table 1: Food sources of Zinc[2].

Food Milligrams (mg)
per serving
Percent DV*
Oysters, cooked, breaded and fried, 3 ounces 74.0 493
Beef chuck roast, braised, 3 ounces 7.0 47
Crab, Alaska king, cooked, 3 ounces 6.5 43
Beef patty, broiled, 3 ounces 5.3 35
Breakfast cereal, fortified with 25% of the DV for zinc, ¾ cup serving 3.8 25
Lobster, cooked, 3 ounces 3.4 23
Pork chop, loin, cooked, 3 ounces 2.9 19
Baked beans, canned, plain or vegetarian, ½ cup 2.9 19
Chicken, dark meat, cooked, 3 ounces 2.4 16
Yogurt, fruit, low fat, 8 ounces 1.7 11
Cashews, dry roasted, 1 ounce 1.6 11
Chickpeas, cooked, ½ cup 1.3 9
Cheese, Swiss, 1 ounce 1.2 8
Oatmeal, instant, plain, prepared with water, 1 packet 1.1 7
Milk, low-fat or non fat, 1 cup 1.0 7
Almonds, dry roasted, 1 ounce 0.9 6
Kidney beans, cooked, ½ cup 0.9 6
Chicken breast, roasted, skin removed, ½ breast 0.9 6
Cheese, cheddar or mozzarella, 1 ounce 0.9 6
Peas, green, frozen, cooked, ½ cup 0.5 3
Flounder or sole, cooked, 3 ounces 0.3 2

*DV=Daily Value. The Daily Value by the U.S. Food and Drug Administration is 15 mg for adults and children older than 4 year. Note: Food labels do not need to list zinc content unless it is a fortified product.

Phytates, which are compounds presents in whole-grain breads, cereals, legumes (for example spinach) and some other foods, inhibit zinc absorption. This leads to a difference in bioavailability of zinc from plant foods compared to animal foods. Bioavailability is the fraction of the dose which you take that reaches the systemic circulation (blood circulation). This might seem rather complicated but I’ll try to explain it more clearly. When some medication is administered intravenously (directly into a vein) its bioavailability is 100% because it directly reaches the blood circulation. However, when a medication is administered orally its bioavailability is lower, since not all of it is absorbed in the intestine. Take home point: the bioavailability of zinc from plants foods is lower due to the fact that they inhibit zinc absorption, although many plant based foods are still good sources of zinc.

Supplements contain several forms of zinc, for example zinc gluconate, zinc sulfate and zinc acetate. In each of these forms the percentage of elemental zinc varies, but the elemental zinc content always appears on the supplement container. Research has not yet shown and determined whether differences exist among these forms of zinc in absorption and bioavailability.

Recommended intake

Zinc intake recommendations are provided in Recommended Dietary Allowances (‘Aanbevolen Dagelijkse Hoeveelheid’ in Dutch) developed by the Food and Nutrition Board (FNB). This is an average daily level of intake sufficient to meet the requirements of nearly all healthy individuals (97%). To see what the current RDA for zinc is, check table 2 below.

Table 2: RDA for zinc[2].

Age Male Female Pregnancy Lactation
0–6 months 2 mg* 2 mg*
7–12 months 3 mg 3 mg
1–3 years 3 mg 3 mg
4–8 years 5 mg 5 mg
9–13 years 8 mg 8 mg
14–18 years 11 mg 9 mg 12 mg 13 mg
19+ years 11 mg 8 mg 11 mg 12 mg

* Adequate Intake (AI)

What are consequences of a low zinc intake?

A zinc deficiency is characterized by growth retardation, loss of appetite and immune impairment. Especially immune impairment can lead to increased risk of getting infectious diseases. This is the case in developing countries as there is a bigger chance of zinc deficiencies. The prevalence (occurrence) of an inadequate zinc intake is >25% in Sub-Saharan and South Asia[3].  Most people in Western Countries and also the Netherlands have a wide variety of foods in their diet, which under normal circumstances should be enough to meet their RDI of zinc.

One study in 1995 made use of three conventional tests (serum, urine, and hair samples) in groups of Dutch children with symptoms common in zinc deficiency (diarrhea, recurrent infection, or growth retardation). From this study can be concluded that +/- 1% of Dutch children with minor complaints suffer from either acute or subacute zinc deficiency[4]. Thus zinc deficiency is not common among Dutch children.

There are more non-specific symptoms (weight loss, taste abnormalities and mental lethargy) which can result from a severe zinc deficiency, but these are often associated with other health conditions and a medical examination is needed in those cases.

Laboratory diagnosis of a zinc deficiency is difficult because zinc is distributed throughout the body and bound to various proteins. People can have symptoms of a zinc deficiency, but the laboratory tests might not confirm this.

However, there are some groups which may be at risk of zinc deficiency:

  • People with gastrointestinal diseases
  • Vegetarians
  • Pregnant women
  • Alcoholics

How about ZMA?

ZMA is a supplement widely used by bodybuilders these days. The supplement contains 2 minerals (zinc monomethionine aspartate and magnesium aspartate) and vitamin B6.  It’s a supplement which claims to promote recovery and additionally raises strength levels and enhance hormonal profiles. Most labels indicate that it should be taken in 60-90 minutes prior to bedtime on an empty stomach.

Several scientific studies have been done on the effects of ZMA. One study in 2009 gave athletes the daily recommended dose of ZMA and measured androgen levels during the next 56 days. ZMA supplementation showed no effect on androgen levels between the placebo and ZMA group, so ZMA doesn’t elevate androgen levels[5]. In addition, most people don’t benefit from zinc and vitamin B6 supplementation, because they already meet the Recommended Dietary Allowances. Magnesium deficiencies are more common however.

This is just my own experience: I’ve used ZMA for a month or so, when I was cutting back in the days. I always have some problems falling asleep when I go deeper into a cut (because of the hunger, which keeps me awake during the night) and wanted to try out if it was any good. It sure made my muscles relax a bit more, but later I realized that I was better and cheaper off by just buying magnesium Citrate. Magnesium supplementation will be discussed in another article soon.

There are some claimed benefits from taking a zinc supplement. First, it states to accelerate wound healing and therefore zinc is being used to treat skin conditions such as ulcers. Relatively few studies support this. A meta-analysis of 181 participants from six randomized controlled trials of oral zinc sulfate versus placebo for venous or arterial leg ulcers found no significant difference in time between intervention and placebo group[6].

Secondly there is the claimed benefit on growth. A meta-analysis of 33 randomized controlled trials enrolling prepubertal children from North and South America, Europe, Africa, and Asia who were at risk of zinc deficiency showed that zinc supplementation modestly enhanced linear growth and weight gain. Growth responses were greater in children with low initial weight-for-age and in those with low initial height-for-age[7]. This only means that zinc supplementation can prevent a growth retardation. If you aren’t zinc deficient, it won’t make you grow.

Conclusion, zinc supplementation: worth the money?

In the end we can conclude that zinc supplementation isn’t necessarily needed provided you consume a healthy diet with a variety of different food sources. Food sources like red meat, poultry, nuts, dairy and whole grains all contain small quantities of zinc. There are however some risk groups which can benefit from taking a zinc supplement.

If you yourself experience some of the symptoms described above which might indicate a zinc deficiency, go and get your blood levels checked to see if this really is the case. The claimed effects of zinc supplementation are mixed. Most studies did not found a significant effect on wound healing. However on growth we see a modest improvement in children who were at risk of zinc deficiency. Take into account that zinc deficiency is rare in our country. So there is no added benefit of supplementing without actually suffering a zinc deficiency.

It can’t do any harm to eat more of the just mentioned food sources or take a zinc supplement if a deficiency really is the case. If not, you’re better off spending your money on food or other supplements which are in line with your personal situation!


[1] EDX Nutrition and Health part 2: Micronutrients and Malnutrition. Available online:

[2] National Institute of Health: Office of Dietary supplements. Available online:

[3] K. Ryan Wessells and Kenneth H. Brown (2012). Estimating the Global Prevalence of Zinc Deficiency: Results Based on Zinc Availability in National Food Supplies and the Prevalence of Stunting. PLoS One. 7(11)

[4] Van Wouwe JP (1995). Clinical and laboratory assessment of zinc deficiency in Dutch children. A review. Biol Trace Elem Res. 49(2-3): 211-25.

[5] Koehler K, Parr MK, Geyer H, Mester J, Schänzer W (2009). Serum testosterone and urinary excretion of steroid hormone metabolites after administration of a high-dose zinc supplement. European Journal of Clinical Nutrition. 63(1): 65-70

[6] Wilkinson EA1, Hawke CI (1998). Does oral zinc aid the healing of chronic leg ulcers? A systematic literature review. Arch Dermatol. 134(12): 1556-60

[7] Brown KH1, Peerson JM, Rivera J, Allen LH (2002). Effect of supplemental zinc on the growth and serum zinc concentrations of prepubertal children: a meta-analysis of randomized controlled trials. Am J Clin Nutr. 75(6): 1062-71.