Antioxidant supplements often used by health food shops 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 did not protect the women against cancer.
Antioxidant pills have been marketed as preventive therapies to ward off everything from cancer to the signs of ageing.
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.
Supplement pills and placebos have been repeatedly compared and have shown 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 antioxidants or combinations and the group taking the placebos.
The research, published in the Journal of the National Centre Institute, said: "Supplementation with vitamin C, vitamin E, or beta-carotene offers no overall benefits in the primary prevention of total cancer incidence or cancer mortality. 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.
