A vitamin supplement, usually in pill or tablet form, is intended to complement a person’s diet and treat vitamin deficiencies. A vitamin is an organic compound that is required by an organism to function but cannot be produced in sufficient quantities by the organism themselves. For example, if a person gets enough exposure to ultraviolet light, they can produce vitamin D through their skin; a person not getting enough ultraviolet light exposure would benefit from taking vitamin D as a supplement. There is much ongoing research into the health benefits of various vitamin supplements, though they are not regulated by the FDA in the United States, and manufacturer health claims should always be met with caution.