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Megavitamin therapy


Also listed as: Orthomolecular programming, Megadose vitamin therapy
Related terms
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Related Terms
  • Herbs, megadose therapy, megaminerals, minerals, orthomolecular medicine, orthomolecular programming, orthomolecular psychiatry, orthomolecular therapy, supplements, vitamins.
  • Note: Please see the Natural Standard Foods, Herbs & Supplements database for more information about individual vitamins.

  • Megavitamin therapy, also known as megadose vitamin therapy or orthomolecular therapy, involves taking vitamins in doses that exceed the recommended dietary allowance (RDA) in an effort to cure or prevent physical or mental disorders. The RDA refers to the recommended nutritional intake levels that have been established by the Food and Nutrition Board. Megavitamin therapy involves taking doses of vitamins that are up to 10 times greater than the RDA or up to five times greater with vitamin D. (Vitamin D is especially likely to have toxic effects when taken in high doses.)
  • Megavitamin therapy dates back to the early 1930s when psychiatrists began prescribing excessive doses of supplemental nutrients to treat severe mental problems. Vitamin B3 was the original substance used to treat conditions such as schizophrenia. Years later other vitamins, minerals, and hormones were added to treatments. In the 1950s, Biochemist Linus Pauling coined the term, "orthomolecular," which he defined as: "the preservation of good health and the treatment of disease by varying the concentration in the human body of substances that are normally present in the body."
  • Vitamins are nutrients that the body needs in order to grow, develop, and function normally. There are 13 essential vitamins that the body needs: vitamins A, C, D, E, K, and the B vitamins (thiamine, riboflavin, niacin, pantothenic acid, biotin, vitamin B-6, vitamin B-12, and folate). Each vitamin plays a different role in the body. For instance, vitamin C is necessary for the body to form collagen in bones, cartilage, muscle, and blood vessels. Because vitamins are found in food, a well-balanced diet typically provides all of the nutrients that the body needs.
  • Doctors often recommended multivitamins to individuals who eat poor diets or have difficulty absorbing nutrients. For example, multivitamins are usually recommended for people older than 60 years of age because as the body ages, it becomes more difficult to absorb certain vitamins. However, experts disagree whether multivitamins are necessary if a person eats a healthy and well-balanced diet.
  • Not everyone requires the same amount of each vitamin. The recommended daily dose varies depending on a person's age, gender, overall health and eating habits. For instance, when a woman becomes pregnant, her body requires 50% more iron to support the growing fetus.
  • There are two main types of vitamins: fat-soluble and water-soluble. Unlike water-soluble vitamins that need to be replaced regularly in the body, fat-soluble vitamins are stored in the liver and fatty tissues. Then, when these vitamins are needed, the body takes them out of storage to be used. Therefore, fat-soluble vitamins are generally eliminated much more slowly that water-soluble vitamins. Eating fats or oils that are not easily digested may cause deficiencies of fat-soluble vitamins. In general, the higher the percentage of saturated fatty acids in a fat, the more difficult the fat is to digest. Beef fat is one of the most difficult fats to digest. However, deficiencies of fat-soluble vitamins are uncommon in the United States.
  • Water-soluble vitamins are easily absorbed by the body. Unlike fat-soluble vitamins, bile acids are not needed to absorb them. The body does not store large amounts of water-soluble vitamins. Instead, the water-soluble vitamins that are not needed are removed by the kidneys and excreted in the urine. Therefore, these vitamins need to be consumed regularly. Water-soluble vitamins are less likely to cause toxicity than fat-soluble vitamins.
  • Because vitamins are vital to a person's health, vitamin deficiencies may cause serious health problems. For example, if a person does not consume enough iron in the diet, he/she may develop iron deficiency anemia (low levels of iron in the blood). Individuals who do not consume enough vitamin D may develop a condition called osteomalacia. This condition causes the bones to become soft. Vitamin K is another important vitamin. If a person does not consume enough vitamin K, he/she may have an increased risk of bleeding.
  • When vitamins are consumed in excess of the body's physiological needs, they may have drug-like effects and may also compromise the effectiveness of standard medical treatments. For instance, vitamin K may interfere with blood-thinning drugs (e.g. warfarin) and increase the risk of clotting. Therefore, megavitamin therapy should be use cautiously under the strict supervision of a healthcare professional.

Theory / Evidence
  • Megavitamin therapy has been used to treat cancer, heart disease, schizophrenia, attention deficit hyperactivity disorder (ADHD), and the common cold. Research suggests that increased amounts of certain vitamins and minerals, including vitamins A, C, E, B6 (pyridoxine), and folic acid, may help prevent or delay the onset of some diseases. However, some megavitamin therapies, especially ones that involve vitamins A, D, E, K, and B6 (pyridoxine) may cause potentially serious adverse effects and are unsafe. Some vitamins or minerals, such as niacin, are beneficial at low levels, but toxic at high levels. Megavitamin therapy with other types of vitamins are not supported by conclusive scientific evidence.


Author information
  • This information has been edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (

  1. BC Cancer Agency. Vitamin Therapy, Megadose/Orthomolecular Therapy. .
  2. Haslam RH. Is there a role for megavitamin therapy in the treatment of attention deficit hyperactivity disorder? Adv Neurol. 1992;58:303-10.
  3. Hathcock J N. Vitamins and minerals: efficacy and safety. Am J Clinical Nutrition. 1997;66:427-437.
  4. National Institutes of Health (NIH).
  5. Natural Standard: The Authority on Integrative Medicine.
  6. Vaughan K, McConaghy N. Megavitamin and dietary treatment in schizophrenia: a randomised, controlled trial. Aust N Z J Psychiatry. 1999 Feb;33(1):84-8.

Copyright © 2011 Natural Standard (

The information in this monograph is intended for informational purposes only, and is meant to help users better understand health concerns. Information is based on review of scientific research data, historical practice patterns, and clinical experience. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions.

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