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Tuesday, March 11, 2008

Cancer Myths Debunked: Antioxidant Supplements Protect You From Cancer

Ask 10 random women on the street today if antioxidants like vitamin E and vitamin C help protect them against cancer and 9.5 of them will answer: Yes.

It’s not their fault; it has been drilled into them by countless magazines, product ads, and television commercials. Vitamin C, pomegranate, resveratrol, coffeeberry: Eat them! Apply them to your face! Add them to your cereal! Surely soaking up bad free radicals must protect you against cancer, no?

Well, if you are standing right now, then I suggest you sit. I have bad news. There is little if any good data to show that taking antioxidant supplements protect you against against cancer. In fact, the best data seems to suggest just the opposite — it increases your risk for cancer. Are you sitting now?

A study last year published in the Journal of Nutrition found that women who took a vitamin C, vitamin E, beta-carotene, selenium, and zinc supplement (thats one mega antioxidant pill) developed skin cancer at a rate of 1.3%.

In contrast, the women who were not taking the supplement developed skin cancer at a rate of only 0.7%; this was significantly less.

In particular, the study found that the rate of melanoma was 0.3% in women on the antioxidant pills and 0.08% in women not taking the pills. Again, significantly higher in the women taking antioxidants.

This is not the first study to show an increased risk of cancer in patients taking antioxidant supplements. A large trial of smokers several years ago showed that those taking high does of vitamin A actually had increased risk of lung cancer compared to those not taking vitamin A. A different study showed that patients taking vitamin E had increased mortality as compared to those not taking vitamin E. Another study has shown that taking dietary supplements of antioxidants leads to increased risk of colon cancer. Several aggregated analyses (studies that look at all published studies together) have concluded that beta-carotene, vitamin A, and vitamin E all increase the risk of death, while vitamin C seems to have no effect either way.

How can this possibly be?

It is plausible that cancer cells are at increased risk of damage from oxidative stress compared to your normal, healthy cells. In other words, taking antioxidants might ironically be protecting your cancer cells, allowing them to survive more than anything else.

It is likely that because cancer develops from long term damage to your cells, as in the case of skin and lung cancer, that trying to limit damage for a relatively short period of time by taking antioxidants like vitamin E or vitamin A probably has little or no effect. It is analogous to a car that is already rusted when you apply a protective sealant to it. The damage has already been done. Just as the sealant is protecting the already rusted car, the antioxidant is protecting the already cancerous cells.

Here are some recommendations that have stood the test of time and clinical study in preventing cancer:

  • Eat a diet high in fruits and vegetables every day (in contrast to supplements).
  • Limit your intake of simple sugary carbohydrates such as white bread, chips, etc.
  • Exercise every day and keep your weight down.
  • Protect yourself from the sun with broad spectrum sunscreens and protective clothing.
  • If you decide to take a daily supplement, the only vitamin that I recommend taking everyday is vitamin D. There is good evidence that vitamin D supplements can be protective against certain cancers. Taking 1,000 mg of vitamin D3 a day is the best way (much better than sun exposure) for elevating your vitamin D levels. More on this in a later post.
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