What causes vitamin E toxicity?

Updated: Dec 26, 2017
  • Author: Mark Rosenbloom, MD, MBA; Chief Editor: Michael A Miller, MD  more...
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Answer

Vitamin E is any of a group of at least 8 related fat-soluble compounds with similar biological antioxidant activity, particularly alpha-tocopherol but also including other isomers of tocopherol and the related compound tocotrienol. Vitamin E is found in vegetable oil, nuts, sunflower, wheat, green leafy vegetables, and fish. It is a fat-soluble vitamin that acts as an antioxidant and free-radical scavenger in lipophilic environments. Bile is required for absorption; 25% of vitamin E is absorbed orally. Storage of the vitamin occurs in adipose tissue, the liver, and muscle.

Vitamin E may block absorption of vitamins A and K. In addition, it decreases low-density lipoprotein (LDL) cholesterol level at doses more than 400 IU/day.

One milligram of synthetic vitamin E (all-rac-alpha-tocopherol acetate) is equivalent to 1 IU of vitamin E. One milligram of natural vitamin E (RRR–alpha tocopherol) is equivalent to 0.45 IU of vitamin E.

In a 2000 report, the Food and Nutrition Board of the National Academy of Sciences specified the RDA of vitamin E as 15 mg/day and listed the tolerable upper intake level (UL) of any alpha-tocopherol form as 1000 mg/day (1500 IU/day). The UL is the upper level that is likely to pose no risk of adverse health effects to almost all people in the general population.

While in most healthy adults, short-term supplementation with up to 1600 IU of vitamin E appears to be well tolerated and have minimal side effects, the long-term safety is questionable. [11, 12] Data suggest a possible increase in mortality and in the incidence of heart failure with long-term use of vitamin E (400 IU or more), especially in patients with chronic diseases. [11] Therefore, a UL of 1000 mg/day may be too high, especially if only the alpha-tocopherol form of vitamin E is used (vitamin E consists of 8 compounds and supplementing only one form can be detrimental). Supplements usually are 100-1000 IU per capsule.


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