healthy people. Studies demonstrating the possible antioxidant effects of carotenoids in humans are available, at least with regard to beta-carotene, as are a large number of observational studies associating carotenoid intake or carotenoid status with a variety of health effects. In addition, some experimental studies of beta-carotene in humans are also available. Thus, an examination of the scientific evidence regarding beta-carotene and other carotenoids is warranted. The panel will review the available scientific evidence and, if it is adequate, will recommend DRIs for beta-carotene and possibly other carotenoids.
Vitamin C is found in abundance in fruits and vegetables. It is a cofactor in the biosynthesis of a number of different compounds including collagen, carnitine, and neurotransmitters. In addition, because it can donate electrons, it effectively quenches a variety of ROS and RNS in aqueous body compartments, and it has been shown in some cases to prevent oxidative damage in vivo to lipids and DNA. Under certain circumstances, vitamin C can promote the formation of ROS or RNS in vitro. Vitamin C is found widely throughout the body and is concentrated in tissues susceptible to oxidative damage including leukocytes, the lung, eye, brain, and heart. It is readily regenerated in vitro, and because of its high reductive capacity, has the potential ability to regenerate other body antioxidants. Vitamin C's role in preventing scurvy is relatively well defined and is distinct from its role in oxidant defense. A great deal of observational and experimental evidence is available regarding vitamin C's health effects. Thus, the panel will review the available scientific data and, if it is adequate, will establish DRIs for vitamin C.
Vitamin E is composed of a group of fat-soluble molecules that occur naturally in eight different forms (four tocopherols and four tocotrienols) that have similar chromanol structures. It occurs widely in the diet from both plant and animal sources, and adequate food composition data are available. Vitamin E has been demonstrated to possess antioxidant activity in vivo and can protect unsaturated lipids throughout the body. Under certain circumstances, vitamin E can act as a prooxidant in vitro. In addition, there is epidemiological and experimental evidence regarding the health-promoting effects of vitamin E. Thus, the panel will review the available scientific data and, if it is adequate, will establish DRIs for vitamin E.