Anti-oxidant supplements do not reduce your risk of developing cancer, according to a trial involving more than 7,500 women. The researchers gave vitamins C, E, beta-carotene or placebo pills to patients and followed their progress for an average of nearly 10 years. The results showed that the supplements, either on their own or in combination, did not protect the women against cancer.
Beloved of health food shops and alternative therapists, anti-oxidant pills have been marketed as preventive therapies to ward off everything from cancer to the signs of ageing. Until recently, the theory behind much of this seemed sound. Numerous studies have shown that people who eat a healthy balanced diet with plenty of fruit and vegetables are less likely to develop cancer and one benefit of these foods is thought to be the anti-oxidant chemicals they contain. Why not get that benefit directly in a pill?
Several large studies have now compared the benefits of supplement pills against placebos and have conclusively shown that the benefits of a healthy diet are not shared by vitamin pills — and in some cases they have been shown to be harmful.
In the new research, Dr Jennifer Lin and her colleagues at Brigham and Women's Hospital in Boston, Massachusetts, gave vitamins C, E, beta-carotene or placebos to 7,627 women who were at high risk of cardiovascular disease. After an average of 9.4 years' follow-up, 624 of the women had developed cancer, of which 176 died. But these cancer cases were distributed evenly between the different treatment groups, and there was no statistical difference between the number of deaths among people taking single anti-oxidants or combinations and the group taking the placebos.
"Supplementation with vitamin C, vitamin E, or beta-carotene offers no overall benefits in the primary prevention of total cancer incidence or cancer mortality," the authors wrote in the Journal of the National Cancer Institute. "In our trial, neither duration of treatment nor combination of the three antioxidant supplements had effects on overall fatal or nonfatal cancer events."
The results agree with those of a separate randomised controlled clinical trial of vitamin C and E supplements, published in November. That study, which involved nearly 15,000 men in the US, found no cancer prevention effect from taking the supplements.
The advice from Cancer Research UK is that supplements cannot take the place of eating a healthy diet. "The best way to get your full range of vitamins and minerals is to eat a healthy, balanced diet, with a variety of fruit and vegetables. Supplements do not substitute for a healthy diet, although some people may be advised to take them at certain times in their lives."
