Carotenoids are generally regarded as safe, based primarily on studies with beta-carotene. Increased consumption of carotenoids may cause to the skin to turn orange or yellow—a condition known as “carotenodermia.” This occurrence is completely benign and is unrelated to jaundice—the yellowing of the skin that can result from liver disease or other causes.

Until more is known, people especially smokers should not supplement with synthetic beta-carotene. Two double-blind studies have shown that supplementation with isolated synthetic beta-carotene may increase the risk of lung cancer in people who smoke.^{7, 8} Moreover, three of four studies have found small increases in the risk of heart disease in people assigned to take synthetic beta-carotene compared with those assigned to take placebo.^{9, 10, 11, 12}