Clinical Fact Sheet-Beta-Carotene (pro-vitamin A)
January 2001; Volume 4; S2
Beta-carotene belongs to a carotenoid family of plant compounds, which provide the yellow, orange, and red pigmentation in fruits and vegetables. Beta-carotene is made up of two vitamin A molecules linked head-to-head, which are separated and made bioavailable by enzymes found in the lining of the intestinal tract.
Dietary Reference Intakes (DRI)
No DRIs have been established for beta-carotene. The National Academy Press recommends 3-6 mg/d from five or more servings of fruits and vegetables to maintain plasma concentrations within the range associated with reduced risk of various chronic diseases.
Active Constituents
Beta-carotene consists of a number of isomers. Few data exist on the pharmacology of beta-carotene and the differences that may exist among the various isomers.
Food Sources
Beta-carotene occurs exclusively in plant foods, including green leafy vegetables, carrots, sweet potatoes, squash, spinach, apricots, peaches, cantaloupe, and green, yellow, and red peppers.
Mechanism of Action
• Beta-carotene functions as a chain-breaking antioxidant, stopping the chain reaction of lipid peroxidation by trapping free radicals.
• There is some evidence that beta-carotene retinoid metabolites with pharmacological activity can accumulate and have carcinogenic effects.
Clinical Uses
• To reduce the risk of breast cancer in premenopausal women with a family history of the disease.
• To reduce the risk of prostate carcinoma in men with low plasma beta-carotene concentrations.
• To induce remission in patients with oral leukoplakia.
• To reduce the risk of macular degeneration, cataracts, cardiovascular disease, and stroke in male smokers.
• To decrease exercise-induced asthma.
• Among malnourished women, to reduce pregnancy-related maternal, fetal, and early infant mortality, and the occurrence of night blindness.
• As a source of vitamin A, beta-carotene is used to treat vitiligo and to reduce photosensitivities.
Adverse Effects/Toxicity
• Chronic, large doses of beta-carotene can result in carotenosis, a harmless orange coloring of the skin that disappears with discontinuation of beta-carotene.
• Supplemental beta-carotene in doses greater than 20 mg/d is associated with a significantly higher risk of lung and prostate cancer in smokers. Smokers should not be given beta-carotene alone as an antioxidant.
Interactions/Nutrient Depletion
• Beta-carotene levels can be reduced by cholestyramine resin, cholchicine, probenecid, colestipol, mineral oil, neomycin, orlistat, and proton pump inhibitors.
• Concomitant use of orlistat can reduce the absorption of some fat-soluble vitamins.
• Beta-carotene deficiencies are associated with the symptoms of vitamin A deficiency, and include dry, scaly, and rough skin, caused by obstruction of hair follicles.
• The primary cause of beta-carotene deficiency is inadequate intake of colorful fruits and vegetables.
Resources
Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids. Washington, DC: National Academy Press; 2000. Available at http://books.nap.edu/books/0309069351/html/95.html. Accessed November 15, 2000.
Pelton R, et al. Drug-Induced Nutrient Depletion Handbook. Hudson, OH: Lexi-Comp; 1999.
Natural Medicines Comprehensive Database [database online]. Stockton, CA: Therapeutic Research Center, Inc., 2000.
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