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Beta carotene is the most well-known of the hundreds of carotenoid pigments that have been identified in plants. Carotenoids give cantaloupes, carrots, sweet potatoes, and other fruits and vegetables their yellow/orange color. Various carotenoids in addition to beta carotene also occur naturally in dark leafy green vegetables and other foods rich in chlorophyll. Beta carotene is the carotenoid found in the highest amounts in the foods we eat. Recent studies have found, however, that other carotenoids may have beneficial health effects that rival beta carotene’s.

There is evidence indicating that taking beta carotene regularly by itself may increase the risk of cancer in smokers. Experts caution that it may be safer to take beta carotene in conjunction with other carotenoids and non-carotenoid antioxidants, or seek to obtain as much as possible from food sources, which are not associated with any cancer risk.

Why is it essential? Beta carotene is a precursor of vitamin A, a fat-soluble micronutrient essential for healthy vision, cell reproduction, immune function, wound healing, and other crucial bodily functions. In its preformed state vitamin A is derived only from animal sources. The body is able to convert, however, plant- derived beta carotene to vitamin A. Beta carotene is apparently the most bioavailable of the sixty or so carotenoids that act as precursors to vitamin A. In addition to its role as a vitamin A precursor, beta carotene and other related carotenoids are increasingly being recognized as having further important health- related roles in the body.

Benefits and uses: Vitamin A helps cells reproduce normally—a process called differentiation. Cells that have not properly differentiated are more likely to undergo precancerous changes. Vitamin A, by maintaining healthy cell membranes, helps prevent invasion by disease-causing microorganisms. Vitamin A stimulates immunity and is needed for formation of bone, protein, and growth hormone. Beta carotene also acts as an antioxidant and immune system booster. Vitamin A or beta carotene may help treat or prevent eye- and vision-related conditions such as acne, cataracts, conjunctivitis and blepharitis, and macular degeneration. Beta carotene may also benefit those who suffer from minor injuries, premenstrual syndrome, and vaginitis.

Deficiency risk factors: Among the signs of a vitamin A deficiency are poor night vision, dry skin, increased infections, fatigue, and loss of appetite. Alcoholics and the elderly often suffer from vitamin A deficiencies.

Optimal intake: An optimal daily dose for an average adult is 5,000 to 10,000 IU of preformed vitamin A plus 25,000 to 50,000 IU (15 to 30 mg) of beta carotene or, preferably, beta carotene plus mixed carotenoids.

Food sources: Dark green and orange-yellow vegetables are good sources of beta carotene. Concentrated green foods, such as spirulina and blue-green algae, and the dried juice of young shoots of cereal plants such as barley and wheat grass, are rich in beta carotene as well as other carotenoids. Eating a diverse, carotenoid-rich diet supplies an estimated 5 to 10 mg of beta carotene daily; average adult consumption of beta carotene on the standard American diet is much lower at 1 to 2 mg daily.

Safety: Beta carotene is much less toxic than preformed, meat- based vitamin A. Taking high doses of preformed A can allow it to accumulate in the body and cause potentially serious adverse health effects. The body converts to vitamin A only as much beta carotene as it needs. Extra beta carotene is stored, but the only apparent adverse effect of such storage is a slight orange tinge to the skin, which may occur from taking more than 100,000 IU, or 60 mg per day.

However, there is evidence from a large study of lifelong male smokers (Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study) that taking 20 mg of beta-carotene daily may moderately increase the risk of lung cancer. And evidence from a rodent study also indicate some increased cancer risk from taking beta-carotene alone. Many nutrition researchers believe it may be safer to balance the action of beta carotene by taking supplemental beta carotene as part of an antioxidant formula containing a range of carotenoids (lycopene, alpha-carotene, lutein, xanthophyll, etc.) and the antioxidant vtamins E and C.

What types of beta carotene products are available? Beta carotene comes in capsules, tablets, softgels, and powders. Potency typically ranges from 10,000 to 50,000 IU, with the most popular potency probably being 25,000 IU. A few products provide as much as 83,000 IU per capsule. Many supplements contain only beta carotene (derived either synthetically or from carrots or algae), though others have added preformed vitamin A (usually derived from cold-water fish liver oil), alpha and gamma carotene, and such carotenoids as lycopene, lutein, and cryptoxanthin.

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• Albanes D, et al. Alpha-Tocopherol and beta-carotene supplements and lung cancer incidence in the alpha-tocopherol, beta-carotene cancer prevention study: effects of base-line characteristics and study compliance. J Natl Cancer Inst. (1996 Nov 6), 88(21):1560-70.

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