Category Archives: Health

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:  https://wageningenbeasts.com/2016/12/04/optimizing-your-sleep-and-biological-rhythm/). 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.

Conclusion
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.

References
[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.

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What is health?     

By Wietse In het Panhuis

health_1

“What is healthy?”

You have probably heard this question, asked this question, or answered this question very often. It is a topic that everyone has an opinion about, and therefore a topic of discussion. People often tend to disagree, and argumentation between persons differs frequently. There are countless so called ‘experts’ who have written a book about nutrition, and countless subdivisions of groups of people, all with their own visions and way of living healthy. Nutrition and health can almost be called a religion. With so much diversity in opinion and belief, how do we know what is healthy? And what does ‘healthy’ even mean?

Definition

Let’s start with some definitions of health.

According to the World Health Organization (WHO), health can be defined as: “a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity”[1]. This definition has been established in 1948. A more recent definition states: “Health is the ability of individuals or communities to adapt and self-manage when facing physical, mental or social changes”[2].

Health has a lot of different meanings. It can say something about the physical and mental status of a person, but also about the lifestyle in which nutrition, physical activity and habits are included. In this article I will mainly talk about health in relation to nutrition, as nutrition can have a great impact on both good and bad health.

From an economical perspective, a population is healthy if health care costs and unemployment due to disease will be low. So in other words, health would be defined as merely the absence of disease. From an environmental point of view, health would be defined as having a dietary pattern that is good for the body, which mainly includes sustainable and environmentally friendly foods. From a cultural perspective, health is simply eating the foods of your own culture. You are healthy if you eat the foods of your (eating) culture. Your own culture’s foods would contribute to a good physical and mental well-being. These three examples show that the meaning of health is determined by perspective, and there are many more perspectives than just these three; to each his own perspective towards life. There is not a single truth.

What if health is defined as happiness? That in turn raises the question: What is happiness? Happiness could be defined as living the way you want to live, not worrying about what you can and can’t eat for example. You can eat only healthy foods, but you may still be unhappy. Being unhappy can be physically unhealthy for you. Just doing whatever you want might make you happy (and therefore healthy), but it might have consequences for the duration of your life. For some people this is a trade-off. Happiness can also be defined as the absence of disease: being sick can decrease your quality of life significantly. Therefore, the absence of disease might be a prerequisite to being happy and healthy.

In conclusion, the definition of health is different for everyone.

Why do these definitions matter?             

Why would it matter to have different definitions of health? Isn’t living a lifestyle that is supposed to be healthy beneficial for everyone in general? Of course, exercising, eating healthy, not smoking, not drinking, etcetera can be beneficial for everyone. However, as there are so many definitions of health, there is not a lifestyle that fits all of these definitions. Everyone has their own definition of health, and therefore there might be different ways to approach this. What can be seen as healthy, could not be as healthy or important for another person. Some examples below will illustrate this.

Think of a person suffering from anorexia nervosa (an eating disorder). This person has a mental problem that is causing the inability to eat. When such a person eats, this provokes feelings of fear. For this person it is extremely important to tackle this mental issue and learning to eat again, while proper nutrition and exercise are less important.

Another example: the elderly. It is well-known that muscle mass and functionality decrease with aging[3]. This often results in immobility, such as not being able to rise from a chair, walk the stairs, do groceries, etcetera. Eventually, this will lead to a loss of independence, meaning that elderly can’t take care of themselves anymore. So for elderly the focus could be on maintaining their muscle mass and functionality. This goal requires different dietary factors than what is generally considered to contribute to health. To optimize muscle mass and functionality, one should engage in physical activity (partly cardio, partly strength training) and have sufficient protein intake and total energy intake. A high protein and energy intake are not considered to be good for general health outcomes, such as good organ functionality, healthy aging, absence of disease, etc. Eating vegetables for example is not important for the goal of optimizing muscle mass and functionality.

As was mentioned earlier, happiness and thereby healthiness can be determined by living a lifestyle where you just do what you want to do. There is scientific consensus on the fact that it is best to not drink alcohol, and limit red meat intake[4,5]. For persons who value unhealthy habits this might seem irrelevant, because alcohol and red meat might be important contributors to their happiness.

Conclusion

Everyone has their own definition of health, based on what would be best for their situation or on their view on life. This can depend on age, mental well-being, physical well-being, the presence or absence of disease, the differences in risk people have of getting a disease, and so on. Therefore, health should be seen as a relative concept, and thereby there should also be different ways to approach it. There is not a ‘one-size-fits-all-solution’.

Should you give the same lifestyle recommendations to an anorexic girl of 14 years old and a frail man aged 85? Or to a young woman suffering from depression, a man with terminal cancer who has 1 year to live, or a grandmother with dementia that doesn’t even recognize her own husband anymore? No! They all have different priorities in live. The anorexic girl needs to survive: she has to prevent starving to death by working on her mental issues. The frail man needs to improve his mobility, by exercising and having a high energy high protein diet. The young woman with depression might eat healthy in order to keep her body healthy, but when you suffer from depression this can also make you physically unhealthy, let alone the fact that she is not happy. Mental health is much more important for this woman than physical health. The man with terminal cancer should try to make most of his life that he has left. Should he eat his fruits and vegetables every day in order to be healthy? He is going to die anyway, why not eat the foods he likes and spend time with his family on the couch? Also, why would you keep the grandmother with dementia alive? She does not recognize her family anymore, she doesn’t know where she is, her quality of life has tremendously decreased. Would you want her to eat fruits and vegetables in order to be physically healthy when mentally she is already long gone? In these cases it might seem more humane if death comes soon naturally after years of suffering…

This article might have had a bit of a philosophical approach instead of some clear answers on what is healthy, which is probably what you hoped for when you started reading this article. However, this article might set you thinking about what is important for you. What do you need in your life that makes you happy? What should you emphasize in your life? After all, being happy is more important than being healthy. It is just nice if these two can fit together in your life.

Find your priorities in life, live accordingly and pursue happiness.

References

[1] Preamble to the Constitution of the World Health Organization as adopted by the International Health Conference, New York, 19-22 June, 1946; signed on 22 July 1946 by the representatives of 61 States (Official Records of the World Health Organization, no. 2, p. 100) and entered into force on 7 April 1948.

[2] Huber, M., Knottnerus, J. A., Green, L., van der Horst, H., Jadad, A. R., Kromhout, D., … & Schnabel, P. (2011). How should we define health?. Bmj, 343.

[3] Aoyagi, Y., & Shephard, R. J. (1992). Aging and muscle function. Sports Medicine, 14(6), 376-396.
[4] International Agency for Research on Cancer. (2015). IARC Monographs evaluate consumption of red meat and processed meat. press release, (240).
[5] Alcohol. World Health Organization. Retrieved January 29, 2017, from http://www.who.int/topics/alcohol_drinking/en/

Optimizing your sleep and biological rhythm

 By Wietse In het Panhuis

Do you have trouble falling asleep? Are you sleeping long, but are you still feeling tired? Do you have a disturbed sleep rhythm and do you want to change it? I addressed these questions and many others in my recent lecture on sleep and rest. For members there is an opportunity to watch the lecture online (it is posted in our Facebook group under videos) in case you missed the lecture. Nonetheless, I will summarize my lecture in this article. First, I will provide some background information on sleep and rest, and afterwards I will give some tips on how to change sleep rhythm and improve sleep.

sleep

Biological clock
The biological clock is a ‘system’ in the brain that regulates the daily rhythm of +/- 24 hours. As most of you might know, the biological clock plays an important role in the sleep rhythm. In humans (and many other animals), this rhythm is not exactly 24 hours. This system, also called the suprachiasmatic nucleus (SCN), which is located in the hypothalamus of the brain, is set like a stopwatch: every day it counts down 24.2 hours. This would mean that after one month of such a rhythm, your rhythm dgfdgwill have shifted 6 hours (30 times 0.2 hours per day). Luckily, this system (or stopwatch) is able to adapt in such a way that this clock becomes 24 hours exactly. This adaption (or entrainment) can happen because the body is able to register signals from the surrounding environment. These signals (or stimuli) tell us something about the time of the day, and are therefore also referred to as ‘zeitgebers’ (=time-givers). The most important zeitgeber is light. The SCN is able to register light, which will result in a signal of ‘day’. In the absence of light, the SCN will interpret this as ‘night’[1]. This adaptation of the biological clock, also called the pathway of light entrainment, is displayed simplistically on the picture on the right (retrieved from: https://www.nigms.nih.gov/education/pages/factsheet_circadianrhythms.aspx). Here you see that light travels to the SCN through the eyes, which will result in a message of ‘day’ in the brain.

Most of you probably have also heard of melatonin. This hormone is released in the brain (in the pineal gland (hypofyse in Dutch)) during the evening, and levels peak during the middle of the night (and are low to zero during the day). Melatonin makes you feel tired and stimulates the body to fall asleep. Therefore, melatonin plays an important role in the sleep rhythm. Melatonin is also involved in the pathway of light entrainment (which was described above). During the day, the light will tell the SCN that it is ‘day’. The SCN in turn will inhibit or block the pineal gland, which will prevent the pineal gland from releasing melatonin. During the evening, the absence of light will allow this inhibition to stop: melatonin will be slowly released, and you will become tired[2].

The eyes are especially sensitive to blue light, which means that of all colors of the light spectrum, blue light has the greatest impact on the SCN. This means that blue light gives the strongest signal to the brain that it is day[3]. Blue light is highly present in televisions, laptops, smartphones, etcetera. You might imagine, that when the eyes are exposed to a lot of blue light during the evening, this will inhibit melatonin to be released, and will result in problems falling asleep. So if you use these devices a lot during the evening, this can lead to sleeping problems.

Sleep and training         
The main function of sleep Is cognitive recovery; to give the brain rest, and to store the memories that are made during the day[1]. Of course the body also rests and recovers during sleep, but recovery from training also occurs during the day (when you are sitting or lying down)[4]. In addition, sleep duration does not seem to be associated to heavy exercise: top athletes do not need more sleep than non-athletes[5,6]. Thus, sleeping more is not essential in recovering from training. However: sleep deprivation can hamper recovery[7]. Thus, make sure to get your hours of sleep, but you do not need more than that. This will probably raise the question: how many hours do we need?

How many hours of sleep do we need, and how is this determined? 
Age is the most important determinant of how much sleep one needs. Newborns need most sleep, and elderly least. However, within the same age groups, there are large differences in how much one sleeps. How much sleep you (as an average adult) need is determined by mainly two factors: genetics and habit. It is not exactly known how important the genetic factor is, in other words: how great the difference in required hours of sleep is between persons solely due to genetic differences. However, it is known that habit can cause great differences and that the role of genetics in sleep duration is probably small[8]. All in all, no clear conclusions can be drawn on how much sleep an individual actually needs. So… now you still don’t have an answer to the question: how much sleep do you need?

Even though differences in individual sleep requirements are not known yet, one study looked at the average hours of sleep and the corresponding mortality ratio in a group of over 1.000.000 people[9]. The mortality ratio tells something about the relative chance of death, compared between groups (if you do not understand it: it can be interpreted as an indication of how healthy someone is). These mortality ratios can be seen in the figures below (retrieved from Youngstedth et al 2004[9]).

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The first thing that can be concluded from these graphs is that there are hardly any differences between women and men in the mortality ratios of each group with different sleep durations. The figure also shows that people who sleep between 6.5 and 7.5 hours per night have the lowest mortality ratio and can therefore be seen as most healthy. The figure also shows that the mortality ratio increases with less than 6.5 hours of sleep, but what’s striking, is that the mortality ratio increases even more if people sleep longer than 7.5 hours of sleep. Also, on average, sleeping more than 9.5 hours a night is worse than sleeping 2.5-3.5 hours a night. Of course this is only one study, but it gives a good indication for the general population (side note: the study did adjust for lifestyle, physical activity and dietary factors).

Now there are some people who sleep 9 or even more hours a night, and if they sleep less, they are tired and not functioning. As you read before, genetics play a small role in differences in sleep duration, so this is a good example of habit. The body gets used to the amount of hours you sleep (Small intermezzo to illustrate this. Polyphasic sleep regimens are sleeping patterns during which you sleep (the most extreme example) only 2 hours per 24 hours. Every 4 hours you sleep 20 minutes. Within these 2 hours you rest as much as during a normal 8-hour night, since this sleep solely consists of deep sleep which has a higher restorative capacity. Anyone can get used to such a sleep pattern, but it takes a very long time to get used to. These polyphasic sleep regimens are a perfect example that shows that sleep is mainly determined by habit). If one would sleep 6 hours every night for many(!) nights in a row, the body will adjust the restorative capacity of sleep: one would have more restful sleep (more deep sleep, as deep sleep is most important in recovery). If one would sleep 9 or 10 hours for many nights in a row, the sleep rhythm will adjust to that: one would have relatively more light sleep (light sleep is not very important in recovery). In conclusion, even though there might be some genetic differences in how much sleep one needs, habit probably explains the large differences in sleep duration between people. Therefore, one can also change their habits and thus change their total sleep duration, which will result in more (productive) hours during the day.

How to change the sleep rhythm?           
Now, how can one change his sleep rhythm? You might want to change your rhythm in case you go to bed late and wake up late, and you want to advance these times, or when you want to reduce your sleep duration in case you are sleeping 9-10 hours a night, as mentioned in the last paragraph. To help you with this, I have some tips:

  1. Be consistent! The biological clock is a complex mechanism, which is why it adapts very slowly to changes in your daily rhythm[1]. Thus, be consistent in the time you go to bed and when you wake up. Sleeping late during the weekend with the intention to catch up sleep actually disturbs your rhythm, as this is a sudden, large change for your rhythm. Also, when you want to change (advance) your sleep rhythm, try to go to bed and wake up 5-15 minutes earlier every single day.
  2. When step 1 does not really work for you, since you are having problems with falling asleep earlier than usual, you might cold turkey your rhythm. Just set your alarm clock 1-2 hours earlier than you are used to and stick to it: wake up every day at this time. Your biological clock will have a harder time to adapt and will be disturbed due to the large change, but your body and brain will be more tired during the evening, which will aid in falling asleep. Doing this is more exhausting than option 1, as you will experience tiredness until your biological clock has adapted. Adapting completely might even take a few weeks! One important side note: when doing this, you will probably be more prone to fall asleep during the day. However, it is important you do not take daytime naps, as this will hinder sleep onset at night!
  3. A third option that might help is melatonin. As mentioned before, melatonin is a hormone that is produced by the pineal gland in the brain and is released (secreted) during the evening. Melatonin causes the typical feeling of being tired when it is getting darker outside. This hormone is also available in supplement-form. Taking low dosages of melatonin supplements a few hours before going to sleep can stimulate and advance the melatonin production of the body[10]. This helps you fall asleep earlier and thus advance your sleeping rhythm. One important side note: do not use this chronically, and do not use high dosages. Chronic use or high dosages of melatonin can hamper the melatonin production of the body, and will result in melatonin-resistance: your body needs more melatonin to experience the same effects (due to receptor insensitivity, which basically happens when you administer any kind of drug)[1]. 

How to improve sleep? 
If you want to improve sleep (e.g. when you have trouble falling asleep or in case you are experiencing restless sleep such as frequent awakenings during the night) I also have some tips for you. Do mind, that not all of these tips are practical or feasible, but from a theoretical point of view to optimize sleep.

  1. Increasing zeitgeber strength can make the biological rhythm stronger and the sleep cycle better[11]. This means, that when differences between day and night are greater, the body will have a stronger perception of day and night (zeitgebers). This can be done by:
  • Decreasing the amount of light during the evening (dim the lights of the lamps and the television).
  • Downloading a blue light filter on laptops and smartphones. As mentioned before, blue light exposure during the evening can inhibit melatonin release. This application filters most of the blue light from the screen, which will diminish inhibition of melatonin release.
  • Limiting light from entering the room during the night, by having good curtains, and switching off all the lights.
  • Spending the day in the light. Sunlight exposure can help, but also switching on lights inside the house when it is cloudy outside, will keep the light signals (zeitgeber strength) high.
  1. Avoid drugs (or psychostimulants). Pretty obvious, but that doesn’t make it less important. Avoiding substances such as hard drugs (MDMA, speed, etc.)[12], but also limitation or elimination of smoking (nicotine)[13], caffeine[14,15] and alcohol[16] will help in order to optimize the nights rest. Consumption of these substances are all related to a decrease in sleep quality. A little side note for caffeine: there are large differences between persons in their sensitivity to caffeine (due to genetics and habit). This explains why some people can drink coffee during the evening without having difficulties falling asleep, while others have these difficulties when they drink coffee at 3 pm. Therefore, there are no clear conclusions about this yet, but as a general rule of thumb it is wise to avoid caffeine consumption (coffee, energy drinks) 6 hours prior to bedtime, and limit consumption of tea and soft drinks throughout the day[14,15].
  2. Limit stress. Stress can have a great impact on sleep: falling asleep is more difficult, sleep quality is less, and it will cause feelings of fatigue during the day[17]. Limiting stress is therefore essential for optimizing sleep. However, this is easier said than done. Terminating stress from daily life can be achieved by looking at the stressor: what causes the stress? Are you able to eliminate this from your life? If it is not possible to change this stressor, it is better to change your attitude and how you perceive this stressor. Now this is quite an extensive topic, which is why we will discuss it more thoroughly in another article. For now, I can recommend meditation or yoga. A lot of people are not into this, but before dismissing it, you could give it a try. It takes some practice, but then it can be really beneficial and enjoyable. If you don’t want to try this, you might try a quick, easy tip: 4-7-8 breathing. This can be done when lying in bed when attempting to fall asleep. It is a special way of breathing that allows your mind and body to fully relax. With this technique you breathe in for 4 seconds, hold this for 7 seconds, and breathe out for 8 seconds. Do this very slowly, breathe deep into your belly and not your ribcage, and try to relax all your (facial) muscles. Doing this lowers the heart rate, relaxes the muscles, and lets the mind focus on the body instead of thoughts and will thereby help you to fall asleep more easily (this actually is the basic principle of meditation). You can look up 4-7-8 breathing on YouTube or Google for a more detailed explanation.
  3. My last and most important tip, is to think positively. The mind and body are closely connected. People who suffer from depression are feeling physically sick and people who are happy are physically healthier than when they wouldn’t be happy. Besides this, the mind also plays a crucial role in sleep. When you think you had a good night of sleep, you will feel energetic. When you think you had a bad night of sleep, you will feel tired. Your perception of sleep influences how tired or energetic you are. A good illustration of this, is a study that looked at elderly insomniacs: elderly people who suffer from chronic sleeping problems. From all possible non-pharmacological interventions that improve sleep, Cognitive Behavioral Treatment (CBT) seemed most effective in improving sleep in these insomniacs[18,19,20]. This treatment is normally applied for patients suffering from depression, as it helps to change unhelpful thinking and behavior. Thus, CBT, which helps in thinking more positively, seems to be most effective in improving sleep and energy levels during the day. This example shows how important mindset is in sleep. My message to you: don’t worry if you have one bad night of sleep. You will be fine! Your body is well able to deal with a little less sleep every now and then. Don’t let this influence how you feel! The same goes for those people who sleep 9-10 hours a night: you don’t need this, 8 hours will be fine. It is just a matter of mindset and habituation.

I hope these tips will help you, they sure have helped me improve my sleep. Good night all!

References

[1] Breedlove, S.M.W., N.V. , Biological Psychology: An Introduction to Behavioral, Cognitive, and Clinical Neuroscience. 7th ed. 2013, Sunderland, Massachusetts: Sinauer Associates Inc. 633.
[2] Reiter, R.J., Melatonin: the chemical expression of darkness. Molecular and cellular endocrinology, 1991. 79(1): p. C153-C158.
[3] Gooley, J.J., et al., Spectral responses of the human circadian system depend on the irradiance and duration of exposure to light. Science translational medicine, 2010. 2(31): p. 31ra33-31ra33.
[4] Phillips, S. M., Tipton, K. D., Aarsland, A. S. L. E., Wolf, S. E., & Wolfe, R. R. (1997). Mixed muscle protein synthesis and breakdown after resistance exercise in humans. American Journal of Physiology-Endocrinology And Metabolism, 273(1), E99-E107.
[5] Brand, S., Gerber, M., Beck, J., Hatzinger, M., Pühse, U., & Holsboer-Trachsler, E. (2010). High exercise levels are related to favorable sleep patterns and psychological functioning in adolescents: a comparison of athletes and controls. Journal of Adolescent Health, 46(2), 133-141.
[6] Leeder, J., Glaister, M., Pizzoferro, K., Dawson, J., & Pedlar, C. (2012). Sleep duration and quality in elite athletes measured using wristwatch actigraphy. Journal of sports sciences, 30(6), 541-545.
[7] Reilly, T., & Piercy, M. (1994). The effect of partial sleep deprivation on weight-lifting performance. Ergonomics, 37(1), 107-115.
[8] Barclay, N. L., Eley, T. C., Buysse, D. J., Rijsdijk, F. V., & Gregory, A. M. (2010). Genetic and environmental influences on different components of the Pittsburgh Sleep Quality Index and their overlap. Sleep, 33(5), 659-668.
[9] Youngstedth, S.D., & Kripke, D.F. (2004). Long sleep and mortality: rationale for sleep restriction. Sleep medicine reviews, 8(3), 159-174.
[10] Sánchez-Barceló, E. J., Mediavilla, M. D., & Reiter, R. J. (2011). Clinical uses of melatonin in pediatrics. International journal of pediatrics, 2011.
[11] Kramer, A., Merrow, M., Circadian Clocks. Handbook of Experimental Pharmacology. Vol. 217. 2013, Berlin Heidelberg: Springer-Verlag 417.
[12] McCann, U. D., & Ricaurte, G. A. (2007). Effects of (±) 3, 4-methylenedioxymethamphetamine (MDMA) on sleep and circadian rhythms. The Scientific World Journal, 7, 231-238.
[13] Sabanayagam, C. and A. Shankar, The association between active smoking, smokeless tobacco, second-hand smoke exposure and insufficient sleep. Sleep Medicine, 2011. 12(1): p. 7-11.
[14] Clark, I. and H.P. Landolt, Coffee, caffeine, and sleep: A systematic review of epidemiological studies and randomized controlled trials. Sleep Medicine Reviews, 2016.
[15] Drake, C., et al., Caffeine effects on sleep taken 0, 3, or 6 hours before going to bed. J Clin Sleep Med, 2013. 9(11): p. 1195-1200.
[16] Kamel, N.S. and J.K. Gammack, Insomnia in the Elderly: Cause, Approach, and Treatment. The American Journal of Medicine. 119(6): p. 463-469.
[17] Âkerstedt, T. (2006). Psychosocial stress and impaired sleep. Scandinavian journal of work, environment & health, 493-501.
[18] Irwin, M.R., J.C. Cole, and P.M. Nicassio, Comparative meta-analysis of behavioral interventions for insomnia and their efficacy in middle-aged adults and in older adults 55+ years of age. Health Psychology, 2006. 25(1): p. 3.
[19] Okajima, I., Y. Komada, and Y. Inoue, A meta‐analysis on the treatment effectiveness of cognitive behavioral therapy for primary insomnia. Sleep and Biological Rhythms, 2011. 9(1): p. 24-34.
[20] Trauer, J.M., et al., Cognitive behavioral therapy for chronic insomnia: a systematic review and meta-analysis. Annals of internal medicine, 2015. 163(3): p. 191-204.

Nutrition and cancer prevention

By Wietse In het Panhuis

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Everyone probably knows someone who has or has had the terrible disease called “cancer”.  Cancer has not only affected their life tremendously, but also the life of their parents, their children, their brothers and sisters, their partners, their friends, their acquaintances, and you. Cancer is a scary disease because it silently develops over decades until at some moment you find out that you have cancer, and by then it may be already too late. But what can we do to  prevent this? What is in our own hands?

Ask yourself: Which dietary or lifestyle factors will increase the risk of getting cancer? And which factors will decrease that risk?

What factors could you come up with? The answer of an average consumer would be: “E-numbers, coloring agents, sweeteners, hormones, sugar, and dairy products increase your risk of getting cancer and superfoods decrease your risk of getting cancer”. Read the rest of this entry