UPDATE ON THE BIOLOGICAL CHARACTERISTICS OF THE ANTIOXIDANT MICRONUTRIENTS - VITAMIN-C, VITAMIN-E, AND THE CAROTENOIDS

Under normal circumstances, free radicals that are produced through bi ological processes and in response to exogenous stimuli are controlled by various enzymes and antioxidants in the body. Laboratory evidence suggests that oxidative stress, which occurs when free radical formati on exceeds the ability to protect against them, may form the biologica l basis of several acute medical problems, such as tissue injury after trauma, and chronic conditions, such as atherosclerosis and cancer. A potential role for the antioxidant micronutrients (vitamin C, vitamin E, and the carotenoids) in modifying the risk for conditions that may result from oxidative stress has stimulated intense research efforts, increased interest in micronutrient supplements, and heightened consu mer interest in these compounds. Much remains to be learned, however, about the bioavailability, tissue uptake, metabolism, and biological a ctivities of these micronutrients. These biological characteristics wi ll ultimately determine their clinical usefulness in modulating oxidat ive stress. Also, whether the antioxidant mechanism explains their rel ationship with risk for acute and chronic disease in epidemiologic stu dies remains to be determined. Increased knowledge in this area of nut rition science will have an impact on both clinical dietetics practice and public health nutrition guidelines.