Vitamins are a class of trace organic substances that humans and animals must obtain from food in order to maintain normal physiological functions and play an important role in human growth, metabolism and development. Vitamins are neither involved in the composition of human cells nor do they provide energy for the body. Vitamins are a class of organic compounds that are necessary for the maintenance of health. These substances are neither raw materials for body tissues nor sources of energy in the body, but a class of regulatory substances that play an important role in the metabolism of substances.