Vitamin A has roles in normal reproduction, the visual cycle, glycoprotein synthesis, mitochondrial membrane function, and as an antioxidant. Vitamin D promotes calcium and phosphate absorption and regulates calcium levels. It also promotes bone mineralization, growth, and dental health. Vitamin E is a potent antioxidant that protects cell membranes and is involved in reproduction, muscle integrity, and heme synthesis. Vitamin K is needed for blood clotting factor synthesis and carboxylation. Vitamin C acts as a reducing agent and cofactor for hydroxylases involved in collagen synthesis, carnitine formation, and adrenal function. It also aids iron absorption and tetrahydrofolate formation.