Vitamin E is the generic term used to refer to a group of eight fat-soluble molecules, including four tocopherols and four tocotrienols.^[9][10][11] These molecules function primarily as antioxidants, protecting cell membranes from oxidative damage caused by free radicals,^[12] which are unstable molecules that can damage cells and contribute to aging and disease.^[9][10][11] Vitamin E is classified as an “essential” nutrient because it cannot be synthesized in the body. Consequently, humans must obtain vitamin E in their diet.

Vitamin E is sold as a dietary supplement typically containing alpha-tocopherol; however, vitamin E is easy to obtain in the diet, and high amounts per serving are found in several foods, including nuts (e.g., almonds, peanuts), seeds (e.g., sunflower seeds), vegetable oils (e.g., sunflower, safflower, and soybean oils), leafy greens (e.g., spinach, collard greens, broccoli, kale), and fortified cereals.^[8][13][1] Consult the FoodData Central database to check the amounts of vitamin E in the foods you eat. The recommended dietary allowance (RDA) for vitamin E in adults is 15 milligrams per day.^[8]

Because vitamin E is an antioxidant that protects cells from oxidative damage,^[12] supplementation is claimed to have several benefits, including lowered cancer risk, enhanced exercise recovery, and improved brain health, liver health, eye health, skin health, and immune health. These claims probably arise from epidemiological evidence, because observational studies have shown that a higher level of dietary vitamin E intake is associated with a reduced risk of several conditions,^[14] including gastrointestinal diseases (e.g., nonalcoholic fatty liver disease or NAFLD),^[15] dementia,^[16] Alzheimer’s disease,^[16] metabolic syndrome,^[17] and coronary artery disease.^[18][19] However, associations from observational studies do not prove cause and effect, and, therefore, the findings do not suggest that supplementation with vitamin E prevents or treats these diseases.

Although supplementation with vitamin E may lower some circulating markers of inflammation (TNF-alpha and CRP)^[2] and liver enzymes (particularly in people with NAFLD),^[3][4] it is currently uncertain whether these effects lead to improved health outcomes.^[4][2] Furthermore, the claimed benefits of vitamin E on disease risk and improved health described above are not supported by the evidence from meta-analyses, which have found that supplementation with vitamin E does not improve exercise recovery^{[20][21][22][23][24][25]} or reduce the risk of stroke,^[26][27][28] cancer,^[29] or dementia (including Alzheimer’s disease).^[30][31] Additionally, a large randomized controlled trial in people at high risk for heart disease or cancer found that long-term supplementation with vitamin E did not lower the incidence of heart attacks, stroke, or cancer,^[32] and supplementation with vitamin E has not been found to improve all-cause mortality.^{[33][34][35][36]}

Overall, for the average person, there is little evidence that supplementing with vitamin E will improve health, prevent diseases, or extend lifespan beyond ensuring a person consumes the recommended dietary allowance (RDA) from a balanced diet. Benefits might be more likely in people with vitamin E deficiency. However, vitamin E deficiency is uncommon because vitamin E is present in high amounts in several common foods. Therefore, diets containing a range of foods with high vitamin E levels will maintain adequate vitamin E levels in the body.

A main drawback of vitamin E is the general lack of benefit of supplementation on health outcomes (except in people with vitamin E deficiency). Another main drawback is that high-dose vitamin E can have adverse effects — while the normal dietary intake of vitamin E is safe and necessary, “more is not always better”.^{[37][6][38][8]}

For example, meta-analyses indicate that the long-term intake of high levels of vitamin E — greater than 300–400 IU/day or 135–180 mg/day — might slightly increase all-cause mortality^{[39][40][33][34][35]} and the risk of certain cancers, like prostate cancer and bladder cancer.^[41][42][43] In patients with heart disease or type 2 diabetes, long-term high-dose vitamin E supplementation has also been linked to a small increase in heart failure risk.^[32] Furthermore, in some studies, participants who took very high doses have reported nausea, diarrhea, fatigue, or blurred vision.

High levels of vitamin E intake can worsen the impairment in blood clotting found in people with vitamin K deficiency,^[6] leading to a higher tendency of bleeding.^[44] For example, one meta-analysis found that supplementation with vitamin E was associated with a 22% higher risk of hemorrhagic stroke (a severe form of stroke associated with bleeding in the brain).^[26]

The recommended dietary allowance (RDA) for vitamin E in adults is 15 milligrams per day, and the tolerable upper intake level (UL) for vitamin E in adults is 1,000 milligrams per day.^[8] The adverse effects described above are typically associated with long-term daily intakes greater than the RDA. Given the risks, the lack of benefits, and the ease with which vitamin E can be obtained in the diet, supplementation with vitamin E is rarely necessary. Seek advice from your doctor if you are unsure.

Evidence from in vitro experiments shows that vitamin E’s antioxidant properties help protect cells from damage caused by free radicals (unstable molecules).^[9][10][11] In vitro experiments have also found that vitamin E can modulate the release of inflammatory cytokines.^[45] These mechanisms explain how the normal dietary intake of vitamin E supports immune function and protects the body against cellular damage and inflammation.^[9][10][11]