Beta-carotene is a safe precursor of vitamin A. Human intestinal enzymes convert dietary betacaroteneinto active vitamin A. The extent of this conversion appears to be based on the need forvitamin A since even very large amounts of betacarotene do not increase plasma or liver vitamin Alevels above normal. One milligram of beta-carotene provides 1,667 I.U. of vitamin A activity. Betacarotenenot converted to vitamin A is absorbed intact and has other functions in the body.
Beta-carotene is an important antioxidant nutrientthat protects healthy cells from oxidative and free radical damage. Free radicals are unstable chemicalsformed in the body during metabolism and from exposure to environmental sources such as pollutionand cigarette smoke. Free radicals are necessary for energy metabolism and immune function, but whenan excessive number of free radicals are formed, they can attack healthy cells, especially their membranelipids and proteins. This, in turn, is thought to contribute to a number of degenerative diseases.
Beta-carotene efficiently quenches a chemicallyreactive species of oxygen called singlet oxygen. Singlet oxygen participates in oxidative reactionswhich can impair or destroy important cellular components, such as membranes, nucleic acids(DNA), and enzymes. In addition, singlet oxygen reactions can generate free radicals which lead tofurther damage. Beta-carotene's long, conjugated molecule can absorb the energy of singlet oxygen andrelease it safely as heat. In the process, singlet oxygen is converted to less dangerous, regularoxygen. One molecule of beta-carotene can quench about a thousand molecules of singlet oxygen.
Numerous studies have demonstrated the importance of beta-carotene for normal immune function. The immune benefits of beta-carotene are due to itsvitamin A precursor role and its antioxidant functions.
Beta-carotene is present in selected fruits andvegetables such as carrots, sweet potatoes, and green leafy vegetables. The U.S. Department ofAgriculture and the National Cancer Institute recommend an intake of 5 mg (8,335 I.U.) or more ofbeta-carotene. Unfortunately, most diets provide only 1-2 mg (1,667 - 3,334 I.U.) per day.
Adults take 1 capsule daily or as directed byphysician.