Vitamins, unlike macronutrients, do not serve structural functions, nor does their catabolism provide significant energy, but they can still be considered crucial for essential metabolic functions. In fact, the common forms of most vitamins require some metabolic activation to their functional bioactivity. Although the vitamins share these general characteristics, they display chemical and functional similarities. Briefly, vitamins are emphatically grouped into fat-soluble vitamins (A, D, E, and K) and water-soluble vitamins (B-complex and C) based on their absorption potential in either fat or water, in addition to the region of their physiological activity. For instance, several vitamins act as enzymatic cofactors (vitamins A, K, and C; thiamin; niacin; riboflavin; vitamin B6; biotin; pantothenic acid; folate; and vitamin B12). Others are natural antioxidants (vitamins E and C) or can act as cofactors in metabolic oxidation-reduction reactions (vitamins E, K, and C, niacin, riboflavin, and pantothenic acid). Vitamins A and D have been reported to exhibit properties of skin hormones, such as organized metabolism, activation, inactivation, and elimination in specialized cells of the tissue, exertion of biological activity, and release in the circulation. Also, vitamin A serves as a photoreceptive cofactor in vision. On the other hand, water-soluble vitamins movement freely through the body, and excessive amounts usually are excreted by the kidneys through urine. Human body requires water-soluble vitamins in recurrent small doses. These vitamins are not as likely as fat-soluble vitamins to reach toxic levels. However, niacin, vitamin B6, folate, choline, and vitamin C have higher consumption limits. Fat-soluble vitamins are stored in the body's fat cells and are not excreted as easily as water-soluble vitamins. Taking into consideration,understanding the significance as well as the magnitude of the severity of this micronutrient’s malnutrition, and providing adequate control and preventive measures is very crucial for human health promotion.