Beta Carotene

Beta carotene is one of several carotenoids, natural plant pigments found in deeply colored fruits and vegetables. Others include alpha carotene, lutein, lycopene, and zeaxanthin. Beta carotene and some other carotenoids are "provitamin A carotenoids," meaning that the body can convert them into vitamin A. Beta carotene is also an antioxidant; thus it may help deactivate free radicals, unstable molecules that are by-products of cells "burning" oxygen for energy. Free radicals can damage the basic structure of cells and thus lead to chronic diseases (notably cancer and heart disease) and accelerate the aging process. There is no daily recommended intake, or safe upper level.

Claims, purported benefits: Prevents cancer and heart disease; boosts immunity, supports good vision.

Bottom line: Some good research—mostly involving beta carotene from the diet—suggests that beta carotene could lower the risk of cancer and possibly other diseases. Thus, some nutrition experts once recommended beta carotene pills. Then came two first-rate studies showing that beta carotene supplements could cause serious harm, at least in smokers. The CARET study (full name: Beta Carotene and Retinol Efficacy Trial) tested beta carotene and vitamin A supplements in people at high risk for lung cancer—smokers, former smokers, and asbestos-industry workers. The study was halted when it became clear that those taking beta carotene (not even a high dose—just 30 milligrams a day) actually had a higher rate of lung cancer and higher mortality rate than those taking a placebo.

Don't assume that beta carotene or other antioxidants in supplement form are beneficial, or even harmless. Don’t take beta carotene pills, particularly if you’ve ever been a smoker. Beta carotene is plentiful in vegetables and fruits, and is safe and beneficial when consumed from such foods.