Potential causes for cancer are numerous. Infections. Radon gas. Cigarette smoking. Sun exposure. Obesity. With over 200 types of cancer, each with a different pathophysiology, there may be an equal (and probably greater) number of causes. Although many causes can be easily eliminated, such as stopping smoking, testing your house for radon, getting an HPV vaccine to prevent human papillomavirus infections, and wearing sunblock to reduce the risk of melanomas, the sheer complexity and number of types of cancer means that there is probably not going to be any simple panacea to preventing (or even curing) cancer. In fact, some hereditary cancers, such as those individuals who carry genes that are implicated in breast and ovarian cancers, may not be preventable at all.
Other than eliminating direct risks, are there things that can be done to actually prevent “cancer”? Once again, with over 200 types of cancer, this may be an impossibility, but the two most popular cancer prevention ideas are supplements and nutrition. Vitamins and other supplements are a $61 billion industry in the US. They generate these sales with minimal regulation, minimal quality control over the quality and dosage, and no requirement to actually provide evidence that the supplements do what is claimed by the supplement industry, aka Big Herbal. The FDA only gets involved with the industry if there’s some dangerous side effect, or when the claims of the industry are so outrageous that the FDA has no choice but to get involved.
The number of supplements that have failed, in clinical trials or epidemiological studies, to show any evidence of efficacy in preventing cancer. Vitamin D. Vitamin E and selenium. Beta-carotene, alpha-tocopherol or retinol actually increase lung cancer, squamous cell skin cancer, non-melanoma skin cancers, and prostate cancer risks by significant levels.
A 2012 study examined what effect folic acid supplements may have on cancers. Supplementation with folate to decrease the risk of certain types of birth defects, especially neural tube defects, is supported by the strongest possible evidence. But other than that one critical use (which should never be stopped, unless some other evidence appears), what can folic acid do? There are frequent claims by Big Herbal that folate prevents cancer, but the best research disputes such claims. The authors first state that the evidence that folate can prevent cancer just isn’t there. In fact, there is actually some evidence that excess folate can contribute to some cancers; for example, there is evidence that long-term folic acid supplementation increases the risk of advanced colorectal adenomas, prostate cancer, and breast cancer. Because the US and other countries have mandated folate fortification of foods, which has the very narrow benefit of preventing birth defects. Once the mother has delivered the baby, the need for folic acid drops off to the amounts normally obtained in a balanced diet.
A recently published study examined the effect of folic acid on various cancers, and also found that it had no effect. After looking at studies involving nearly 50,000 people, researchers said folic acid did not make a difference when it came to cancers of the large intestine, prostate, lung, breast or any other specific site. In other words, they found nothing. Their conclusion is “folic acid supplementation does not substantially increase or decrease incidence of site-specific cancer during the first 5 years of treatment. Fortification of flour and other cereal products involves doses of folic acid that are, on average, an order of magnitude smaller than the doses used in these trials.” In this study, they show no risk of additional cancers, which may mean that current level of supplementation in our food sources is safe.
Martinez et al. conclude that:
Nutritional supplementation is now a multibillion-dollar industry, and about half of all US adults take supplements. Supplement use is fueled in part by the belief that nutritional supplements can ward off chronic disease, including cancer, although several expert committees and organizations have concluded that there is little to no scientific evidence that supplements reduce cancer risk. To the contrary, there is now evidence that high doses of some supplements increase cancer risk. Despite this evidence, marketing claims by the supplement industry continue to imply anticancer benefits. Insufficient government regulation of the marketing of dietary supplement products may continue to result in unsound advice to consumers. Both the scientific community and government regulators need to provide clear guidance to the public about the use of dietary supplements to lower cancer risk.
There is an old joke that people who take lots of supplements have the most expensive urine in the world, since much of the excess supplements are just filtered out by the kidneys. There is just so little evidence that supplements prevent (let alone cure) cancers. But there is growing evidence that many of these supplements could increase your risk of cancer, there is no reason to waste so much money on useless and potentially dangerous supplements. Of course, most individuals will just ignore this because their “belief” matters more than “evidence.” Evidence, especially that from careful, well-designed research always trumps anecdote and belief.
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- Martínez ME, Jacobs ET, Baron JA, Marshall JR, Byers T. Dietary supplements and cancer prevention: balancing potential benefits against proven harms. J Natl Cancer Inst. 2012 May 16;104(10):732-9. doi: 10.1093/jnci/djs195. Epub 2012 Apr 25. PubMed PMID: 22534785; PubMed Central PMCID: PMC3352833.
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