&hearts A vitamin is an organic substance that is needed in small quantities to maintain normal health. They are mostly obtained through diet, however some are produced in the body. Vitamins are important for many bodily functions such as maintaining a healthy immune system, regulating metabolism, converting fat and carbohydrates into energy and assisting in forming bone and tissue. They also help form blood cells, hormones and genetic material. Vitamins are found in meat and dairy products, vegetables, fruits, cereals and grains. They cannot be assimilated without ingesting food.