Skeptical Raptor's Blog hunting pseudoscience in the internet jungle

Antioxidant supplements for cancer–myth vs. science


I’ve never been a fan of vitamin supplements. Aside from a very few supplements intended for a few specific clinical conditions, like vitamin C and scurvy, they have little use in preventing or treating diseases. In fact, because mammalian physiology has evolved a homeostasis for these chemicals, any excess amount that can’t be stored in the fat or other tissue is cleared by the kidneys and becomes part of your urine. I’m willing to venture that the urine of many Americans is quite expensive, with all of the cleared vitamins and other micronutrients. A balanced diet over several weeks is sufficient to provide the body with all of the nutrients and vitamins to be healthy and strong. You are not even required to have all vitamins and nutrients every day, as storage of a few nutrients will be released as necessary, and clinical manifestations of nutrient deficiency may take weeks or months.  

Myth

One of the more popular group of  supplements is the antioxidants such as vitamin E and beta-carotene.  Presumably, these vitamins are taken to bind with free radicals (from a chemistry sense of the word, not hippies who haven’t been arrested)–free radicals are blamed for everything from cancer to arteriosclerosis, all without a lot of evidence in support. Joe Mercola, one of the leading woo-pushers, advertises a whole host of antioxidants to prevent cancers. 

But lots of mainstream food producers push foods that are known to have high levels of antioxidants. Grapes, blueberries, and other fruits and vegetables are known to have antioxidants.

Nevertheless, what’s really going on with antioxidants, at least with cancer?

Science

Well, to answer the previous question, that would be nothing. The Cochrane Reviews, my favorite source of evidence based medicine articles, recently published a meta-review of randomized clinical trials of antioxidants and cancer. Let’s jump right to the conclusion:

We found no evidence to support antioxidant supplements for primary or secondary prevention. Beta-carotene and vitamin E seem to increase mortality, and so may higher doses of vitamin A. Antioxidant supplements need to be considered as medicinal products and should undergo sufficient evaluation before marketing.

Wait. Some actually increase mortality!

This is a critical conclusion that not only are these supplements of no use to you, they may actually be harmful to you. This isn’t just a conclusion from one study, but is, in fact, a meta-analysis of 56 trials with 296,707 participants. That’s to the point where the statistics are beyond criticism.

About the only supplement that may have a positive benefit to preventing some cancers is Vitamin D, and even in that case, the evidence is controversial and has been criticized by many researchers

I know that this is a hard pill to swallow, but there probably isn’t a pill that can be swallowed that’s going to keep you from getting cancer.

My personal opinion

Good nutrition is critical to good health.  But unless you’re on a diet of eating nothing but fried chicken, you’re probably going to have enough nutrients to maintain your health to a high level. Don’t wast your money on vitamins or other supplements (very few, if any, work), unless there is a specific clinical need.

There are ways to prevent cancer that are proven scientifically. Stop smoking. Lose weight. Exercise. Don’t drink in excess. Eat a balanced, moderate calorie diet. You know what’s difficult about that? It’s hard work. Everyone prefers a pill, because it’s seductively easy to imagine a simple antioxidant pill will help prevent cancer, instead of stopping smoking and losing weight. 

Sorry to bring you the bad news. Just know that if you waste your money on the junk supplements sold by the woo-pushers, you’re not going to prevent cancer and you’re wasting money.

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