A vitamin is an organic compound, essential in very small amounts for supporting normal physiological function. Vitamins occur naturally in all living things, plants and animals alike. They regulate a variety of bodily functions, are essential for building bodily tissues such as bones, blood, glands, nerves and skin, and assist in metabolising (digesting) proteins, carbohydrates and fats to produce energy. As vitamins cannot generally be biosynthesised quickly enough to meet the needs of the body, most need to be ingested through the food we eat.