Despite numerous studies that have found that antioxidants are vital for good long-term health, the Harvard research team concludes that antioxidant supplements not only don't protect against heart disease or cancer, they also "in some cases may actually do more harm than good."
Turning to the B vitamins - B6, B12 and folic acid - the researchers say the B vitamins don't prevent heart disease and, worse, folic acid may cause cancer. They point to a study of men who were taking 1000 mcg of folic acid - more than twice the recommended daily amount - and they developed more colorectal adenoma and prostate cancers than those taking a placebo. However, every participant was already at high risk of developing colorectal cancer before the trial began.
(Source: Harvard Men's Health Watch, March 2008).