Megavitamin therapy is the use of large doses of vitamins, often many times greater than the recommended dietary
allowance (RDA) in the attempt to prevent or treat diseases. It is typically used in complementary and alternative
medicine by practitioners who call their approach "orthomolecular medicine", but also used in mainstream medicine
for "exceedingly rare" genetic conditions that respond to megadoses of vitamins.
In 2002, a review of these conditions identified about 50 that respond to "high-dose vitamin therapy". Further understanding of these conditions is expected to play a part in the emerging field of nutrigenomics. Nutrients may be useful in preventing and treating some illnesses, but the conclusions of medical research are that the broad claims of disease treatment by advocates of megavitamin therapy are unsubstantiated by the available evidence.
Critics have described some aspects of orthomolecular medicine as food faddism or even quackery. Research on nutrient supplementation in general suggests that some nutritional supplements might be beneficial, and that others might be harmful; several specific nutritional therapies are associated with an increased likelihood of the condition they are meant to prevent.
Below mentioned as some of the vitamin therapies.
1. Vitamin D Therapy