What is the potential importance of taking beta-carotene?
Beta-carotene is a precursor to vitamin A, but may have a separate role in human health. Controlled research has shown that beta-carotene supplements can increase the numbers of some white blood cells and enhance cancer-fighting immune functions in healthy people who take 25,000 to 100,000 IU per day.11 12 However, some studies of smokers have reported that supplements of synthetic beta-carotene increased the risk of both heart disease13 14 and lung cancer.15 16 Other trials found no positive or negative effect of synthetic beta-carotene on the risk of many other diseases, including several types of cancer,17 18 19 20 21 22 23 24 angina pectoris,25 diabetes,26 age-related eye disease,27 28 or intermittent claudication.29 Natural beta-carotene, though similar to synthetic, was found in one preliminary study to reverse pre-cancerous changes, while synthetic beta-carotene did not.30 No other studies have investigated whether natural beta-carotene could be more effective than synthetic in
