Vitamins and Minerals

Micronutrients—vitamins and minerals—are required by the body in far smaller amounts than macronutrients, typically milligrams or micrograms per day, yet they are indispensable for growth, immune function, and nearly every metabolic reaction that sustains life. Vitamins are organic compounds, meaning they contain carbon, that the body generally cannot synthesize in sufficient quantities and must therefore obtain from food or, in a few cases such as vitamin D and vitamin K, partly from sunlight exposure or synthesis by gut bacteria. Thirteen vitamins are recognized as essential to human nutrition, and they are classified into two broad categories based on their solubility: the fat-soluble vitamins A, D, E, and K, and the water-soluble vitamins, comprising the eight B-complex vitamins and vitamin C. This solubility distinction has significant practical consequences, since it governs how each vitamin is absorbed, transported, stored in the body, and excreted, and therefore how readily deficiency or toxicity can develop.