Zinc. Necessary for normal immune system function, cell division, contributes to normal skin structure, acid-base metabolism, carbohydrate metabolism, cognitive function, DNA synthesis, fertility and reproduction, micronutrient metabolism, fatty acid metabolism, metabolism of Vit A, protein synthesis, normal taste & smell,  maintenance of normal bones, hair & skin, testosterone levels in blood, normal vision, protection cells from oxidative stress, cell division, constituent of insulin & many vital enzymes, to maintain normal Vit E levels in blood and increase the absorption of Vitamin A.