Vitamin A - Vitamin A is the collective name for a group of fat-soluble vitamins. The most useable form of the vitamin is retinol. Vitamin A palmitate (retinyl palmitate) and vitamin A acetate (retinyl acetate) are the principal forms used as nutritional supplements. The precursors of vitamin A (retinol) are the carotenoids (most commonly beta-carotene). Vitamin A is one of the most versatile vitamins, with roles in such diverse functions as vision, immune defenses, maintenance of body linings and skin, bone and body growth, normal cell development, and reproduction.
Vitamin D - Vitamin D actually refers to a group of steroid molecules. Vitamin D is called the sunlight vitamin because the body produces it when the sun's ultraviolet B (UVB) rays strike the skin. Vitamin D is important for the proper absorption of calcium from food. It is vital for the control of the levels of calcium in the blood and also controls the rate at which the body excretes calcium in the urine. Low levels of vitamin D and insufficient sunlight exposure are associated with osteoporosis. Maintaining sufficient vitamin D levels may help decrease the risk of several autoimmune diseases.
Vitamin E - Vitamin E is actually an umbrella term for a group of compounds called tocopherols and tocotrienols. Alpha-tocopherol is the name of the most active form of vitamin E in humans. Vitamin E is one of the many nutrients that have protective properties. The main function of vitamin E is to maintain the integrity of the body's intracellular membrane by protecting its physical stability and providing a defense line against tissue damage caused by oxidation. Vitamin E is an antioxidant that prevents free radical damage in biological membranes.
Vitamin K - Vitamin K is a group of 2-methilo-naphthoquinone derivatives. Vitamin K is involved in the carboxylation of certain glutamate residues in proteins to form gamma-carboxyglutamate residues. Vitamin K plays an important role in blood clotting and bone metabolism (carboxylation of osteocalcin). Vitamin K supplements may improve bone mass in postmenopausal women. itamin K is used to reduce risk of bleeding in liver disease, jaundice, malabsorption, or in association with long-term use of aspirin or antibiotics.