Zinc, selenium snd skin helath: overview of their biochemical and physiological functions

This chapter provides an overview of the biochemical and physiological functions of zinc. Zinc is an essential element in human and animal nutrition with different and important roles. Zinc plays catalytic, structural, or regulatory functions in the more than 300 metalloenzymes that have been identified in biological systems involved in nucleic acid and protein metabolism and the production of energy. Physiologically, zinc is vital for growth and development, sexual maturation and reproduction, dark vision adaptation, olfactory and gustatory activity, insulin storage and release, and a variety of host immune defenses. Selenium, although toxic in large doses, is an essential micronutrient for animals. It is a component of the unusual amino acids selenocysteine and selenomethionine. In humans, selenium is a trace element nutrient that functions as a cofactor for reduction of antioxidant enzymes such as glutathione peroxidases and certain forms of thioredoxin reductase found in animals and some plants. Selenium deficiency results also in atrophy degeneration and necrosis of cartilage tissue. The selenoproteins that result from expression of these genes are responsible for the biochemical functions of selenium. The possible functional use of Se in cosmetics is linked to its role in preventing oxidative stress due to free radical molecules.