Vitamin E Toxicity

Relatively large amounts of vitamin E usually cause no harm, but occasionally muscle weakness, fatigue, nausea, and diarrhea occur. The most significant risk is bleeding, mainly with doses > 1000 mg a day.

Vitamin E is a group of compounds (including tocopherols and tocotrienols) that have similar biologic activities. The most biologically active is alpha-tocopherol, but beta-, gamma-, and delta-tocopherols, 4 tocotrienols, and several stereoisomers may also have important biologic activity. These compounds act as antioxidants, which prevent lipid peroxidation of polyunsaturated fatty acids in cellular membranes (see table Sources, Functions, and Effects of Vitamins). Dietary sources of vitamin E include vegetable oils and nuts.

Plasma tocopherol levels vary with total plasma lipid levels. Normally, the plasma alpha-tocopherol level is 5 to 20 mcg/mL (11.6 to 46.4 mcmol/L).

vitamin E for such reasons (1); whether supplements can protect against tardive dyskinesiaAlzheimer disease or decrease the risk of cancer; one study suggested an increased risk of prostate cancer with vitamin E supplementation (2). It is uncertain whether vitamin E supplementation affects stroke risk (3).

Although the amount of vitamin E in many fortified foods and supplements is given in units, current recommendations are to use milligrams alpha-tocopherol.

> 1000 mg/day or the patient takes oral coumarin or warfarin. Thus, the upper limit for adults aged ≥ 19 years is 1000 mg for any form of tocopherol.

Vitamin E toxicity is treated by stopping the vitamin or reducing intake to less than the upper limit of 1000 mg per day.

(See also Overview of Vitamins.)