Antioxidants

Chapter summary

• Consumers do not realise megavitamins may raise cancer and heart disease risk and shorten life.
• Do not take vitamins to get “antioxidants”. Avoid sugar and cheap, simple carbohydrates instead.
• Save the money and eat extra green vegetables.
• Antioxidants are not necessarily vitamins, though some vitamins are antioxidants.

The theory

• Cells in mitochondria turn food into energy using oxygen (oxidation). One result is free radicals, which can damage DNA, cell membranes and artery linings, and are linked to ageing, cancer and heart disease.
• The body makes antioxidants to neutralise them. Fruit and vegetables supply selenium, beta-carotene and vitamins A, C and E.
• People who eat more fruit and vegetables have less cancer and heart disease and live longer. The logic follows that antioxidant pills should help too.

What happened in trials

• 1994 Finnish ATBC trial: Vitamin E and beta-carotene did not reduce lung cancer in male smokers. Beta-carotene was linked to more lung cancer.
• 1996: 18,000 people at risk of lung cancer (asbestos or smoking) took vitamin A plus beta-carotene or placebo. The study was stopped because lung cancer deaths were 46% higher in the vitamin group.
• 2004 Cochrane review: 14 randomised trials found vitamins A, C, E, beta-carotene and selenium taken to prevent intestinal cancers increased mortality.
• US National Cancer Institute: Nine trials of antioxidant supplements gave no evidence of benefit in primary cancer prevention.

Where views differ

• Supplement makers: Antioxidants are healthy and megavitamins are safe. In 1972 the FDA tried to regulate doses over 150% of the recommended allowance, and the industry fought it.
• Researchers: The NCI says antioxidants from whole foods act differently from purified pills, which contain single chemicals instead of complex mixtures.
• The author: The fruit and vegetable benefit may come from eating less sugar and simple carbohydrate, plus other behaviours.

The antioxidant paradox

• Free radicals are needed to kill bacteria and eliminate new cancer cells.
• High doses of antioxidants can tip the balance too far and weaken the immune system.
• Respected health organisations do not recommend them for healthy people.

Take-away points

• If you want a higher cancer risk, take antioxidant pills.
• Eat fruit and vegetables. Fruit juice is not fruit.
• Spend the money on something useful.

References

• The Alpha-Tocopherol, Beta Carotene Cancer Prevention Study Group (1994) The effect of vitamin E and beta carotene on the incidence of lung cancer and other cancers in male smokers. N Engl J Med 330:1029-1035.
• Omenn, G. et al. (1996) Effects of a combination of beta carotene and vitamin A on lung cancer and cardiovascular disease. N Engl J Med 334:1150-1155.
• Bjelakovic, G. et al. (2004) Antioxidant supplements for prevention of gastrointestinal cancers. Lancet 364:1219-28.
• Offit, P. (2013) Don’t take your vitamins. New York Times.
• National Cancer Institute (2013) Antioxidants and cancer prevention: fact sheet.