Vitamin E

How much you need

The official Recommended Dietary Allowance for adults, per day:

Amounts are mg of alpha-tocopherol, the only form of vitamin E the recommendations count. 1 mg is 1 mg of the natural form (RRR-alpha-tocopherol, labelled d-alpha-tocopherol) or 2 mg of the synthetic form (all rac-alpha-tocopherol, labelled dl-alpha-tocopherol), which is half as active. Older labels used International Units — 1 mg equals 1.49 IU of the natural form or 2.22 IU of the synthetic form.

People aged 18 fall in the official 14–18 group, which has the same values — 15 mg a day, and 19 mg when breastfeeding. Its upper limit for supplemental vitamin E is lower, at 800 mg. Pregnancy and breastfeeding change what you need — confirm yours with your midwife, obstetrician or doctor.

Upper limit

Below the limit is not safe for everyone. Large doses of vitamin E taken with warfarin or another blood thinner can increase the risk of bleeding, probably from above 400 IU a day, well under the upper limit. Talk to your doctor before taking vitamin E with a blood thinner.

This limit applies only to supplemental alpha-tocopherol, natural or synthetic — not to vitamin E found naturally in food.

The limit is the most supplemental vitamin E a day that is unlikely to cause harm, not a target; it was set because high doses can cause bleeding. 1,000 mg is 1,500 IU of the natural form or 1,100 IU of the synthetic form. Two meta-analyses have linked vitamin E supplements to slightly higher death rates at doses below the limit, although what that means is unclear — see Too much, below.

What it does

Vitamin E is the name for a group of fat-soluble compounds with antioxidant activity: four tocopherols and four tocotrienols ^[1]. Only alpha-tocopherol is recognised as meeting human requirements, because the liver releases it into the blood and breaks down the other forms ^[1]. As an antioxidant, it stops the production of reactive oxygen species that form when fat is oxidised ^[1]. It is also involved in immune function and, mainly in studies of cells, in cell signalling and the regulation of gene expression ^[1]. It helps the lining of blood vessels resist blood cells sticking to it, and helps dilate blood vessels and inhibit the clumping of platelets ^[1].

Forms

Natural vitamin E is RRR-alpha-tocopherol, usually labelled d-alpha-tocopherol; the synthetic form is all rac-alpha-tocopherol, labelled dl-alpha-tocopherol, and is only half as active by weight ^[1]. Most vitamin E in American diets is gamma-tocopherol from soybean, canola, corn and other vegetable oils, but the recommendations count only alpha-tocopherol ^[1]. Supplements usually provide only alpha-tocopherol, often as an ester (alpha-tocopheryl acetate or succinate), which the body absorbs as well as alpha-tocopherol itself ^[1]. Most vitamin E-only supplements provide 67 mg (100 IU of the natural form) or more — far above the recommended amount ^[1].

Where it comes from

1. Wheat germ oil1 tablespoon20.3 mg
2. Sunflower seeds, dry roasted1 ounce7.4 mg
3. Almonds, dry roasted1 ounce6.8 mg
4. Sunflower oil1 tablespoon5.6 mg
5. Safflower oil1 tablespoon4.6 mg

How these five were chosen: The five foods with the most vitamin E per serving in the NIH fact sheet's food table. Fortified foods are marked.

Getting the most from it

The digestive tract needs fat to absorb vitamin E, so people with fat-malabsorption disorders are more likely to become deficient ^[1]. People with Crohn's disease, cystic fibrosis or an inability to secrete bile sometimes need water-soluble forms of vitamin E ^[1].

In the United States

Three national surveys have found that most Americans' diets provide less than the recommended amount of vitamin E, but these estimates might be low, because the amounts and types of fat added in cooking are often unknown ^[1]. The Food and Nutrition Board suggests that average intakes among healthy adults are probably above the recommended amount, but cautions that low-fat diets might provide too little unless food is chosen carefully, for example by eating more nuts, seeds, fruits and vegetables ^[1]. In 1999–2000, 11.3% of adults took vitamin E supplements containing at least 400 IU ^[1].

Who is most likely to run low

• People with fat-malabsorption disorders, such as Crohn's disease or cystic fibrosis, or an inability to secrete bile — the gut needs fat to absorb vitamin E ^[1]
• People with the rare inherited disorders abetalipoproteinemia and ataxia with vitamin E deficiency (AVED) ^[1]

What deficiency looks like

Frank deficiency is rare, and overt symptoms have not been found in healthy people who get little vitamin E from their diets ^[1]. Deficiency is more likely in people with fat-malabsorption disorders, and its symptoms include peripheral neuropathy (nerve damage), ataxia (loss of control of movement), muscle weakness, damage to the retina and impaired immune response ^[1]. Two rare inherited disorders — abetalipoproteinemia, which impairs fat absorption, and ataxia with vitamin E deficiency (AVED), in which the liver's transfer protein is missing or defective — cause deficiency severe enough to damage nerves unless very large doses of vitamin E are taken ^[1].

What the evidence supports, and what it doesn't

Established. Vitamin E is an essential antioxidant, and deficiency damages nerves and muscles ^[1]. The recommended amounts rest on blood levels that protect red blood cells in a laboratory test, and the Food and Nutrition Board acknowledged great uncertainty in those data ^[1].

Not supported by trials. Heart disease: in HOPE, almost 10,000 patients at high risk of heart attack or stroke took 400 IU of natural vitamin E (268 mg) a day or a placebo for 4.5 years with no fewer cardiovascular events; in the HOPE-TOO extension, after 7 years, those on vitamin E were 13% more likely to develop heart failure ^[1]. In almost 15,000 male physicians aged 50 and older, 400 IU of synthetic vitamin E (180 mg) every other day for a mean of 8 years did not prevent major cardiovascular events and was linked to more hemorrhagic strokes ^[1]. Cancer: in SELECT, 35,533 healthy men aged 50 and older took 400 IU of synthetic vitamin E (180 mg) a day, with or without selenium; it did not prevent prostate cancer, and after further follow-up the men who had taken vitamin E alone had 17% more prostate cancer ^[1]. The fact sheet concludes that the evidence does not support taking vitamin E to prevent cancer ^[1]. Cognitive decline: most research does not support vitamin E supplements to maintain cognitive performance in healthy or mildly impaired people ^[1].

Mixed. In the Women's Health Study, almost 40,000 healthy women aged 45 and older took 600 IU of natural vitamin E (402 mg) every other day or a placebo for an average of 10 years: overall cardiovascular events did not differ, but cardiovascular deaths were 24% lower ^[1]. Age-related macular degeneration: in AREDS, people at high risk of advanced AMD who took a daily supplement containing vitamin E (180 mg), beta-carotene, vitamin C, zinc and copper for 5 years had a 25% lower risk of advanced AMD, but two other trials of vitamin E supplements found no protective effect, and AREDS found no effect on cataracts ^[1]. Alzheimer's disease: in 341 patients with moderately severe disease, 2,000 IU of synthetic vitamin E a day for 2 years delayed functional decline, but those taking it had more falls ^[1].

Too much

No adverse effects from vitamin E in food have been found ^[1]. High doses of supplemental alpha-tocopherol can cause bleeding and interfere with blood clotting: two trials found more hemorrhagic strokes — one in Finnish male smokers taking 50 mg a day for an average of 6 years, the other in U.S. male physicians taking 180 mg of synthetic vitamin E every other day for 8 years, most of whom were also taking aspirin ^[1]. Two meta-analyses of trials linked vitamin E supplements to small but significant increases in deaths from any cause, one starting at 150 IU a day; the fact sheet calls the implications unclear, because the participants were typically middle-aged or older with chronic disease, and a review of trials in healthy people found no convincing increase ^[1]. In SELECT, 400 IU (180 mg) of synthetic vitamin E a day increased the risk of prostate cancer ^[1].

Medicines that interact

Vitamin E can inhibit platelet clumping and work against vitamin K-dependent clotting factors, so large doses taken with anticoagulant or antiplatelet drugs such as warfarin (Coumadin) can increase the risk of bleeding, especially with low vitamin K intake; the amount needed is unknown but probably above 400 IU a day ^[1]. Antioxidant combinations including vitamin E blunted the rise in HDL cholesterol in people taking simvastatin (Zocor) with niacin ^[1]. Oncologists generally advise against antioxidant supplements during chemotherapy or radiotherapy, because they might make the treatment less effective ^[1]. If you take any of these regularly, talk to your doctor or pharmacist before taking a vitamin E supplement.