vitamin e

Vitamin E is a fat-soluble nutrient and antioxidant that occurs naturally in foods; the form the body preferentially uses is alpha-tocopherol. According to the NIH Office of Dietary Supplements, the richest dietary sources are vegetable oils (such as wheat germ, sunflower, and safflower oils), nuts, seeds, and green leafy vegetables, with smaller amounts in fortified foods. The body needs it for immune function and to help protect cells from oxidative damage; frank deficiency is rare in otherwise healthy people.

For the conditions people most often hope it helps, the evidence is largely negative or weak. The NCCIH reports that pooled analyses of large trials showed no benefit of vitamin E supplements for preventing cancer or cardiovascular disease, and the NIH ODS states that vitamin E supplements do not seem to prevent heart disease, that research indicates it does not help prevent cancer and may be harmful in some cases, and that there is little evidence it helps healthy people maintain brain health or prevents Alzheimer's. The one qualified exception is eye disease: in the AREDS trials, a multi-nutrient formula that included vitamin E (combined with vitamin C, zinc, copper, and beta-carotene or, in later formulations, lutein/zeaxanthin) reduced the risk of progression from intermediate to advanced age-related macular degeneration by about 25 percent. However, NCCIH cautions that vitamin E on its own may have little or no effect on AMD progression, with evidence of low certainty. Any apparent benefit reflects these specific combination formulas, not vitamin E by itself.

The NIH ODS recommended dietary allowance (RDA) is 15 mg per day for adults (slightly higher, about 19 mg, while breastfeeding), an amount most people can get from a balanced diet. Many single-ingredient supplements provide far more — often 100 IU (about 67 mg) or more — well above the RDA. The tolerable upper intake level for adults is 1,000 mg per day of supplemental vitamin E (equivalent to about 1,500 IU of the natural form or 1,100 IU of the synthetic form). Because high-dose vitamin E may carry risks and can interact with medicines, talk to a doctor or pharmacist before taking supplements, especially at doses above the RDA.

Getting vitamin E from food is considered safe. In supplement form, the NIH ODS warns that high doses might increase the risk of bleeding and of serious bleeding in the brain (hemorrhagic stroke). The NIH ODS also notes that men who took 400 IU (180 mg) of synthetic vitamin E per day for several years had an increased risk of prostate cancer (a finding from the SELECT trial). Stay at or below the 1,000 mg/day upper limit, and avoid high-dose supplements without medical advice, particularly if you are at higher risk of bleeding.

At normal dietary amounts, vitamin E rarely causes problems. According to the NIH ODS, high-dose supplements might reduce the blood's ability to clot, which could increase the risk of bleeding, including the more serious risk of bleeding in the brain (hemorrhagic stroke). Other adverse effects are uncommon below the upper limit, but the potential bleeding risk tends to rise as the dose increases.

Vitamin E supplements can interact with several medicines, per the NIH ODS. They may add to the bleeding risk of anticoagulant and antiplatelet drugs such as warfarin (Coumadin). When combined with other antioxidants, vitamin E reduced the heart-protective effects of a statin-plus-niacin regimen in one study. The NIH ODS also notes that antioxidant supplements taken during chemotherapy or radiation therapy could alter the effectiveness of those cancer treatments. Tell your healthcare provider about any vitamin E supplements you take.