Caution:Synthetic beta-carotene has been linked to increased risk of lung cancer in smokers. Until more is known, smokers should avoid all beta-carotene supplements.

Beta-carotene supplementation, even in very large amounts, is not known to cause any serious side effects,^{16, 17} however, excessive intake (more than 100,000 IU, or 60 mg per day) sometimes gives the skin a yellow-orange hue. People taking beta-carotene for long periods of time should also supplement with vitamin E, as beta-carotene may reduce vitamin E levels.¹⁸ Beta carotene supplementation may also decrease blood levels of lutein, another carotenoid.¹⁹

Preliminary studies in animals indicate that beta-carotene supplementation, when combined with heavy alcohol consumption, may enhance liver toxicity.²⁰ Until more is known, alcoholics and persons who consume alcohol on a daily basis should avoid supplementing with beta-carotene.

One study showed a slightly increased risk of vascular surgery among people with intermittent claudication who took beta-carotene supplements.²¹ Until more is known, persons wishing to use beta-carotene supplements should first consult with their doctor.