Nutrition and cancer prevention
By Wietse In het Panhuis
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”.
If you ask the same question to the average nutritionist or scientist, they will answer: “smoking, overweight, alcohol, red- and processed meat increase your risk of getting cancer, and vegetables, fruits, and physical activity decrease your risk of getting cancer”. Consumers base their answer on what they hear from the media, from their friends, and from the internet: a place where everyone can tell everyone everything, which is why there is so much false information. Nutritionists base their answer on thousands of studies that have been conducted over decades. Complex mechanisms, controlled animal studies, large population studies; all of those studies were carried out, improved, carried out again, and so on. The evidence surrounding these cancer risk factors, is pretty clear.
Figure 1: Summary of strong evidence on diet, nutrition, physical activity and prevention of cancer. Before clear conclusions can be drawn, convincing data is required. If the data is not convincing enough, it is called probable data. This figure shows for each lifestyle, dietary or environmental component (left column) whether it increases or decreases the risk of specific cancers.
People often dislike hearing that most factors that influence the risk of getting cancer are in their own hands, and that these are not things like toxins in their environment which are beyond their control. On the other hand, giving you some sort of control over it can help you take matters into your own hands. Disclaimer: cancer is never completely under your control, and getting cancer is never your fault. Cancer is basically a roulette game: When you are lucky, you are born with a good genetic profile and when luck is not on your side, you are born with a genetic profile that increases your risk of cancer. One may never smoke and get lung cancer, or one may smoke every day of your life without getting lung cancer. That is life. HOWEVER, what you CAN do is influence these risks, to influence our chances at the roulette game.
Example*: when looking at genetic susceptibility, person A has a chance of 10% of getting cancer in his life, and person B a chance of 40%. That doesn’t necessarily mean that person B can’t do anything about it. If person B lives healthy his entire life, this chance might be 30%. If the person lives unhealthy all his life, this chance might be 50%. Saying “Oh, I will get cancer anyway so it doesn’t matter how I live” is a way people justify their behavior, but this is not true. There are always ways in which you can influence your risk of getting cancer, there are just no guarantees.
*These are not real values, just an illustration
“1 in 3 cancers could be prevented if we would all have a healthy lifestyle”
-World Cancer Research Fund (WCRF)
How much of the cancer cases are due to lifestyle?
Lifestyle is one of the factors that contributes to all cancers. It is not the main factor though (this article will not elaborate in detail on all factors that play a role in cancer). The main risk factor for cancer is age. The older you are, the more likely it is you will get cancer. In the Western world the population is becoming older and older, and along with this phenomenon there is an increase in cancer rates. People don’t die from infectious diseases like in developing countries. A shift has taken place, from infectious diseases, to welfare diseases (cancer, diabetes, cardiovascular disease, etc). Although age is a crucial factor in cancer development, lifestyle still plays a big role in cancer incidence. 1 in 3 cancers can be prevented if we would all have a healthy lifestyle. For example, lung cancer is the most common cancer worldwide. A shocking number of 85% of all lung cancer cases can be prevented if everybody would stop smoking.
What is this healthy lifestyle?
There are a few guidelines on what you can do regarding cancer prevention [4,5]. As I mentioned before: there are no guarantees. However, following these guidelines will make you feel better in general and will decrease your quality of life by decreasing your risk catching other diseases that are more in your control, such as high blood pressure or diabetes. The guidelines are:
- Keep your body weight as low as possible within the healthy range (but prevent being underweight): <25 BMI with little abdominal fat.
- Be physically active for at least 30 minutes every day, and sit less.
- Avoid high-calorie foods and sugary drinks.
- Eat more grains, vegetables (>200gr/d), fruits (>2/d) and beans. Try to vary in this as much as possible.
- Limit red meat (such as beef and pork) and avoid processed meat (such as ham, bacon, salami). A maximum 5 times a week a serving of 100 grams of red meat is advised. Per 100 grams of red meat per day the relative risk of colon cancer increases with 17%, and per 50 grams of processed meat the relative risk of colon cancer increases with 18%, which means that your risk of getting colorectal cancer increases from 5% to 5.8%[6,7] (see figure 2 for a visual illustration).
- Don’t drink alcohol. IF you drink, limit this by 1 having glass (women) or 2 glasses (men) per day. However, those 1-2 glasses already increase your risk!
- Eat less salt. Keep in mind that nearly all of your salt intake comes from food products you buy, and not the salt you add to your meal. Especially processed foods contain a lot of salt.
- Don’t rely on supplements: do not use supplement with the intention to prevent cancer. Too high doses of supplements can even increase the risk of cancer, so it is better to have a balanced diet in order to prevent nutrient deficiencies. With a balanced diet supplements are unnecessary (there are a few exceptions for specific groups that are prone to deficiencies, these exceptions will be discussed in another article).
- If possible, breastfeed your baby for six months. This is best for both mother and baby.
- After cancer treatment, the best advice is to follow the Cancer Prevention Recommendations.
- Most important: do not smoke! Smoking increases the risk of lung cancer significantly, but other cancers like bladder cancer are also more common among smokers.
Do you have any questions about this guideline? For more information visit http://www.wcrf.org/int/research-we-fund/our-cancer-prevention-recommendations (English) or http://www.wkof.nl/nl/kanker-voorkomen/verklein-de-kans-op-kanker (Dutch)
Figure 2: Tobacco vs Meat: what’s the risk? There was a lot of fuss in the media about red meat and cancer, and that meat would be as bad for you as smoking. This picture illustrates what the real risks are.
The choice of what you do with your life is in your own hands: you can reduce your cancer risk significantly. However, adhering to all of these guidelines is not easy and only a very small portion of the population actually follows these guidelines. People often try to live healthier and prevent cancer by taking products like superfoods and supplements, but when you tell them that eliminating alcohol and cigarettes from their lifestyle, eating modest, and physical activity can already make a big impact, people are always willing to actually make a change. For instance, if you value having some alcohol in your diet, it might be your weighted consideration to consume alcohol and take the extra risk of getting cancer. If that significantly increases your quality of life then that’s a choice you could make. Or if you decide to have red or processed meat in your diet. The risk of getting cancer from these meats is not that high, but it adds up to all the other possible cancer risking factors. Besides that, eating meat is bad for the environment, processed meat contains a lot of salt, and red and processed meat are also related to stroke and diabetes[9-14].
All in all, it is your life and you are the one who decides how to live it. At a young age, it is hard to imagine what life would be like when you are older: it is not easy to think about the consequences of your actions of today. But keep this message in your head: your future is in your own hands.
Are you interested in what your current cancer risk is? Then you can fill in this questionnaire: https://www.oncolink.org/whatsmyrisk
 WCRF, 2007. Continuous Update Project (CUP) matrix. Retrieved from: http://www.wcrf.org/int/research-we-fund/continuous-update-project-findings-reports/continuous-update-project-cup-matrix
 WCRF, Cancer preventability estimates for diet, nutrition, body fatness, and physical activity. Retrieved from http://www.wcrf.org/int/cancer-facts-figures/preventability-estimates/cancer-preventability-estimates-diet-nutrition
 WCRF, Cancer prevention recommendations. Retrieved from: http://www.wcrf.org/int/research-we-fund/our-cancer-prevention-recommendations
 Chan, D. S., Lau, R., Aune, D., Vieira, R., Greenwood, D. C., Kampman, E., & Norat, T. (2011). Red and processed meat and colorectal cancer incidence: meta-analysis of prospective studies. PloS one, 6(6), e20456.
 Casey Dunlop, Cancer Research UK, October 26, 2015. Processed meat and cancer – what you need to know. Retrieved from: http://scienceblog.cancerresearchuk.org/2015/10/26/processed-meat-and-cancer-what-you-need-to-know/
 Kaluza, J., Wolk, A., & Larsson, S. C. (2012). Red Meat Consumption and Risk of Stroke A Meta-Analysis of Prospective Studies. Stroke, 43(10), 2556-2560.
 Chen, G. C., Lv, D. B., Pang, Z., & Liu, Q. F. (2013). Red and processed meat consumption and risk of stroke: a meta-analysis of prospective cohort studies. European journal of clinical nutrition, 67(1), 91-95.
 Micha R, Wallace SK, Mozaffarian D. Red and processed meat consumption and risk of incident coronary heart disease, stroke, and diabetes mellitus: a systematic review and meta-analysis. Circulation 2010; 121: 2271–2283.
 Aune D, Ursin G, Veierod MB. Meat consumption and the risk of type 2 diabetes: a systematic review and meta-analysis of cohort studies.Diabetologia 2009; 52: 2277–2287.
 Pan A, Sun Q, Bernstein AM, Schulze MB, Manson JE, Willett WC et al. Red meat consumption and risk of type 2 diabetes: 3 cohorts of US adults and an updated meta-analysis. Am J Clin Nutr 2011; 94: 1088–1096.
 Feskens EJ, Sluik D, van Woudenbergh GJ. Meat consumption, diabetes, and its complications. Curr Diab Rep 2013; 13: 298–306.