Hypervitaminosis

Hypervitaminosis is a condition of abnormally high storage levels of vitamins, which can lead to various symptoms—whether physiological, such as pain, nausea, and tachycardia, or psychological, such as confusion, hyperactivity, and irritability—and even to toxicity. Specific medical names of the different conditions are derived from the given vitamin involved: an excess of vitamin A, for example, is called hypervitaminosis A. Hypervitaminoses are primarily caused by fat-soluble vitamins (especially D and A), as these are stored by the body for longer than the water-soluble vitamins. Generally, toxic levels of vitamins stem from high supplement intake. Toxicities of fat-soluble vitamins can also be caused by a large intake of highly fortified foods, but natural foods in modest levels seldom deliver extreme or dangerous levels of these vitamins. The Dietary Reference Intake recommendations issued by the United States Department of Agriculture define a "tolerable upper intake level" for most vitamins. Those who are entirely healthy and do not experience long periods of avitaminosis can avert vitamin overdose by not taking more than the normal or recommended amount listed on the container of any multi-vitamin supplement and not concurrently ingesting multiple vitamin-containing supplements containing the same vitamins.