Vitamin E is an antioxidant that fights damaging natural substances known as free radicals. It works in lipids (fats and oils), which makes it complementary to vitamin C, which fights free radicals dissolved in water. As an antioxidant, vitamin E has been widely advocated for preventing heart disease and cancer. However, the results of large, well-designed trials have generally not been encouraging. Many other proposed benefits of vitamin E have also failed to stand up in studies. There are no medicinal uses for vitamin E with solid scientific support.

Requirements/Sources

Vitamin E dosage recommendations are a bit complex because the vitamin exists in many forms.

New vitamin E recommendations are in milligrams of alpha-tocopherol. Alpha-tocopherol can come from either natural vitamin E (called, somewhat incorrectly, d-alpha-tocopherol) or synthetic vitamin E (called, also somewhat incorrectly, dl-alpha-tocopherol). However, much of the alpha-tocopherol in synthetic vitamin E is inactive. For this reason, you have to take about twice as much of it to get the same effect. 1-3

There are other forms of vitamin E as well, such as beta-, delta-, and gamma-tocopherols, all of which occur in food. These other forms may be important; for example, preliminary evidence hints that gamma-tocopherol may be the most important (or, perhaps, the only) form of vitamin E for preventing prostate cancer. 4,211 On this basis, it has been suggested that the best vitamin E supplement would be a mixture of all these. 5-7

To make matters even more confusing, vitamin E dosages are commonly listed on labels as international units (IU). Here's how you make the conversion. One IU natural vitamin E equals 0.67 mg alpha-tocopherol; one IU synthetic vitamin E equals 0.45 mg alpha-tocopherol. Therefore, to meet the new dietary recommendations for vitamin E (15 mg per day), you need to get either 22 IU natural vitamin E (22 IU x 0.67 = 15 mg) or 33 IU synthetic vitamin E (33 IU x 0.45 = 15 mg). The official US and Canadian recommendations for daily intake of vitamin E are as follows:

  • Infants
    • 0-6 months: 4 mg
    • 7-12 months: 5 mg
  • Children
    • 1-3 years: 6 mg
    • 4-8 years: 7 mg
    • 9-13 years: 11 mg
  • Males and Females
    • 14 years and older: 15 mg
  • Pregnant Women : 15 mg
  • Nursing Women : 19 mg

In developed countries, mild dietary deficiency of vitamin E is relatively common. 8-10

The best food sources of vitamin E are polyunsaturated vegetable oils, seeds, nuts, and whole grains. To get a therapeutic dosage, though, you need to take a supplement.

Therapeutic Dosages

The optimal therapeutic dosage of vitamin E has not been established. Most studies have used between 50 IU and 800 IU daily, and some have used even higher doses. This would correspond to about 50 mg to 800 mg of synthetic vitamin E (dl-alpha-tocopherol), or 25 mg to 400 mg of natural vitamin E (d-alpha- or mixed tocopherols).

If you wish to purchase natural vitamin E, look for a label that says "mixed tocopherols." However, some manufacturers use this term to mean the synthetic dl-alpha-tocopherol, so you need to read the contents closely. Natural tocopherols come as d-alpha-, d-gamma-, d-delta-, and d-beta-tocopherol.

Therapeutic Uses

Observational studies raised hopes that vitamin E supplements could help prevent various forms of cancer as well as heart disease . 82-84,86,104-107,144,145 However, observational studies are notoriously unreliable for determining the effectiveness of treatments. Only double-blind trials can do that (for information why, see Why Does This Database Rely on Double-blind Studies? ), and such studies have, on balance, found vitamin E ineffective for preventing heart disease or any common form of cancer other than, possibly, prostate cancer. 75-78,81,96-102,146,155,157-159,180-182,201 . In fact, use of high-dose vitamin E for a long period might slightly increase death rate. 177,210

Other potential uses of vitamin E have limited supporting evidence.

Intriguing but far from definitive studies suggest that vitamin E might improve immune response to vaccinations, 42 decrease symptoms of menstrual pain , 139,183 reduce symptoms of premenstrual syndrome (PMS) , 61,62 control symptoms of restless legs syndrome , 59 and help prevent deep venous thrombosis (DVTs) . 213

While there is weak evidence that vitamin E supplements can reduce discomfort in rheumatoid arthritis, 44,45,147-149 there is strong evidence that it does not prevent it. 219

Although preliminary studies hinted that use of vitamin E might prevent or slow the progression of cataracts , 51-54 in a 10-year study of almost 40,000 female healthcare professionals, use of natural vitamin E at a dose of 600 mg every other day failed to have any effect on cataract development. 216

Evidence regarding whether vitamin E can slow the progression of Alzheimer's disease is inconsistent. 43,184 A very large study failed to find vitamin E helpful for preventing mental decline (resulting from any cause) in women over 65. 209

Studies of vitamin E in combination with vitamin C for prevention of preeclampsia have yielded inconsistent results. 41,185-186

Vitamin E has also shown equivocal promise in diabetes. One double-blind trial found benefits for cardiac autonomic neuropathy , 40 a complication of diabetes. Weaker evidence hints at possible benefits for diabetic peripheral neuropathy . 46,47 However, the best-designed study of all, a long-term trial involving 3,654 people with diabetes, found that use of vitamin E did not protect against diabetes-induced kidney or heart damage. 157 Similarly, while a few studies performed by one research group suggested that vitamin E might be helpful for improving glucose control in people with diabetes, 55-57 subsequent evidence found that the benefits, if they exist at all, are limited to the short-term. 169,187 In addition, in an extremely large double-blind study, use of vitamin E at a dose of 600 IU every other day failed to reduce risk of participants developing type 2 diabetes. 202 Finally, a study unexpectedly found that when people with diabetes took 500 mg of vitamin E daily (either as natural alpha tocopherol or a mixture of alpha and gamma tocopherol), their blood pressure increased . 208

Similarly, studies on whether vitamin E is helpful for allergic rhinitis (hay fever) have produced conflicting results. 168,193

A small double-blind study conducted in Iran reported that vitamin E (400 IU daily) was more effective than placebo for treating menopausal hot flashes . 212 However, a larger US study failed to find vitamin E significantly helpful for hot flashes associated with breast cancer treatment. 74

Vitamin E might help reduce the lung-related side effects caused by the drug amiodarone (used to prevent abnormal heart rhythms). 66

Studies have yielded mixed results on whether vitamin E is helpful for controlling seizures in people with epilepsy , 160-163 reducing symptoms of tardive dyskinesia , 29-33 aiding recovery during heavy exercise , 63,64,65,170 and treating male infertility . 49,50

When combined with vitamin C , vitamin E may protect against sunburn to a small extent. 34-38 The same combination has also shown promise for acute anterior uveitis . 39 A separate study failed to find vitamin E alone (at the high dose of 1,600 mg daily) helpful for macular edema (swelling of the center of the retina) associated with uveitis. 188

Vitamin E has been tried for amyotrophic lateral sclerosis (Lou Gehrig's disease), but the results in the first reported double-blind study showed questionable benefits if any. 137 Some vitamin E proponents felt that the dose of vitamin E used in this study might have been too low. Accordingly, they conducted another study using 10 times the dose, this one lasting 18 months and enrolling 160 people. 171 Once again, vitamin E failed to prove significantly more effective than placebo.

In one observational study, high intake of vitamin E was linked to decreased risk of progression to AIDS in people with HIV infection. 67 However, a double-blind study of 49 people with HIV who took combined vitamins C and E or placebo for 3 months did not show any significant effects on the amount of HIV virus detected or the number of opportunistic infections. 68 It has been suggested that vitamin E may enhance the antiviral effects of AZT, but evidence for this is minimal. 69

Vitamin E has been suggested for preventing the cardiac toxicity caused by the drug doxorubicin . However, while it has shown promise in animal studies, when studied in people vitamin E has persistently failed to prove effective for this purpose. 204-207

Vitamin E is sometimes recommended for osteoarthritis . However, a 2-year, double-blind, placebo-controlled study of 136 people with osteoarthritis of the knee failed to find any benefit in terms of symptom control or slowing disease progression. 164 A previous 6-month, double-blind, placebo-controlled trial of 77 individuals with osteoarthritis also failed to find benefit. 138

A 4-year, double-blind, placebo-controlled trial of 1,193 people with macular degeneration failed to find vitamin E alone helpful for preventing or treating macular degeneration. 165 Vitamin E has also so far failed to prove helpful for preventing or treating alcoholic hepatitis , 173asthma , 172congestive heart failure , 80fibrocystic breast disease , 70 or Parkinson's disease . 71-73

In a very large study involving over 29,000 male smokers, researchers failed to find benefit of alpha-tocopherol (50 IU/day), beta-carotene (20 mg/day), or the two taken together for the prevention of type 2 diabetes over 5-8 year period. 214

What Is the Scientific Evidence for Vitamin E?

Cancer Prevention

The results of observational trials have been mixed, but on balance, they suggest that high intake of vitamin E and other antioxidants is associated with reduced risk of lung cancer and many other forms of cancer, including bladder, stomach, mouth, throat, laryngeal, liver, and prostate. 83-95,144,145,166,218 Based on these and other results, researchers developed the hypothesis that antioxidants can help prevent cancer and set in motion very large, long-term, double-blind, placebo-controlled studies to verify it. Unfortunately, these studies generally failed to find vitamin E helpful for the prevention of cancer in people at high risk for it. 14,146,158,159,189-190

The one positive note came in a double-blind trial of 29,133 smokers. 25 In this study, 50 mg of synthetic vitamin E (dl-alpha-tocopherol) daily for 5 to 8 years caused a 32% reduction in the incidence of prostate cancer and a 41% drop in prostate cancer deaths. 81

Surprisingly, results were seen soon after the beginning of supplementation. This was unexpected because prostate cancer grows very slowly. A cancer that shows up today actually started to develop many years ago. The fact that vitamin E almost immediately lowered the incidence of prostate cancer suggests that it somehow blocks the step at which a hidden prostate cancer makes the leap to being detectable.

Nonetheless, the negative results regarding most other types of cancer have made scientists hesitant to place too much hope in these findings. It has been suggested that alpha-tocopherol alone is less effective than the multiple forms of tocopherol that occur in nature; in particular, it has been suggested that gamma-tocopherol rather than alpha-tocopherol might be the most relevant form of vitamin E for cancer prevention. 211 Interestingly, use of alpha-tocopherol supplements may deplete both gamma- and delta-tocopherol levels, potentially producing a negative effect. 174 However, gamma-tocopherol has not yet been tested in meaningful controlled trials, and it is quite possible that were one to be performed, the results would prove as disappointing as those for other forms of vitamin E.

In addition, under certain circumstances, vitamin E may have a pro-oxidant effect—the reverse of what is desired. 203

Cardiovascular Disease

Most but not all observational studies have found associations between high intake of vitamin E and reduced risk of cardiovascular disease ( heart disease and strokes ). 104-107,150,151 However, as we’ve explained, observational studies by themselves cannot be relied upon to identify useful treatments. Double-blind studies, which provide much more convincing evidence of effectiveness, have generally failed to find vitamin E supplements effective.

The Heart Outcomes Prevention Evaluation (HOPE) trial found that natural vitamin E (d-alpha-tocopherol) at a dose of 400 IU daily did not reduce the number of heart attacks, strokes, or deaths from heart disease any more than placebo. 96 The trial followed more than 9,000 men and women who had existing heart disease or were at high risk for it.

Negative results were seen in numerous other large trials, as well. 99-102,129,152,153,157,175,194-195

When the results of these studies began to come in, some antioxidant proponents suggested that the people enrolled in these trials already had disease too advanced for vitamin E to help. However, a subsequent large trial found vitamin E ineffective for slowing the progression of heart disease in healthy people as well. 155 Moreover, in an extremely large placebo-controlled trial involving over 14,000 US male physicians at low risk for heart disease, 400 IU of vitamin E every other day failed to lower the risk of major cardiovascular events or mortality over a period of 8 years. 220 On the contrary, vitamin E was associated with a slightly increased risk of stroke.

As with preventing cancer, critics have suggested that the form of vitamin E used in these studies (alpha-tocopherol) was not the best choice, and that gamma-tocopherol might be more helpful. 140-142,154 Gamma-tocopherol is present in the diet much more abundantly than alpha-tocopherol, and it could be that the studies showing benefits with dietary vitamin E actually tracked the influence of gamma-tocopherol. However, an observational study specifically looking to see if gamma-tocopherol levels were associated with risk of heart attack found no relationship between the two. 143 Nonetheless, intervention trials of gamma-tocopherol are currently underway.

In addition, as noted above, under certain circumstances, vitamin E may have a pro-oxidant effect, and this could explain the negative outcomes. 203

Interestingly, one study found that vitamin E might help prevent serious cardiovascular events in patients with diabetes who also have a particular genetic marker known as “Hp 2.” 215 It has been hypothesized that people with the Hp 2 gene have an inadequate endogenous (“built-in”) antioxidant defense system, and for this reason, they might be particularly benefited by taking antioxidant supplements such as vitamin E. However, this concept still remains highly preliminary.

Preeclampsia Prevention

Preeclampsia is a dangerous complication of pregnancy that involves high blood pressure, swelling of the whole body, and improper kidney function. A double-blind, placebo-controlled study of 283 women at increased risk for preeclampsia found that supplementation with vitamin E (400 IU daily of natural vitamin E) and vitamin C (1,000 mg daily) significantly reduced the chances of developing this disease. 112

While this research is promising, larger studies are necessary to confirm whether vitamins E and C will actually work. The authors of this study point out that studies of similar size found benefits with other treatments, such as aspirin, that later proved to be ineffective when large-scale studies were performed. Furthermore, keep in mind that we don't know whether such high dosages of these vitamins are absolutely safe for pregnant women.

Tardive Dyskinesia

Between 1987 and 1998, at least five double-blind studies were published that indicated vitamin E was beneficial in treating tardive dyskinesia (TD). 113,114 Although most of these studies were small and lasted only 4 to 12 weeks, one 36-week study enrolled 40 individuals. 115 Three small double-blind studies reported that vitamin E was not helpful. 116,117 Nonetheless, a statistical analysis of the double-blind studies done before 1999 found good evidence that vitamin E was more effective than placebo. 118 Most studies found that vitamin E worked best for TD of more recent onset. 119

However, in 1999, the picture on vitamin E changed with the publication of one more study—the largest and longest to date. 120 This double-blind study included 107 participants from nine different research sites who took 1,600 IU of vitamin E or placebo daily for at least 1 year. In contrast to most of the previous studies, this trial did not find vitamin E effective in decreasing TD symptoms.

Why the discrepancy between this study and the earlier ones? The researchers, some of whom had worked on the earlier, positive studies of vitamin E, were at pains to develop an answer. 121,122 They proposed a number of possible explanations. One was that the earlier studies were too small or too short to be accurate, and that vitamin E really didn't help at all. Another was the most complicated: that vitamin E might help only a subgroup of people who have TD—those with milder TD symptoms of more recent onset—and that fewer of these people had participated in the latest study. They also pointed to changes in schizophrenia treatment since the last study was done, including the growing use of antipsychotic medications that do not cause TD.

The bottom line: The effectiveness of vitamin E for a given individual is simply not known. Given the lack of other good treatments for TD and the general safety of the vitamin, it may be worth discussing with your physician.

Immune Support

Seniors often do not respond adequately to vaccinations. One double-blind study suggests that vitamin E may be able to strengthen the immune response to vaccines. In this trial, 88 people over the age of 65 were given either placebo or vitamin E at 60 IU, 200 IU, or 800 IU dl-alpha-tocopherol daily. 123 The researchers then gave all participants immunizations against hepatitis B, tetanus, diphtheria, and pneumonia, and looked at subjects' immune response to these vaccinations. The researchers also used a skin test that evaluates the overall strength of the immune response.

The results were promising. Vitamin E at 200 mg per day and, to a lesser extent, at 800 mg per day significantly increased the strength of the immune response.

However, it is not clear whether vitamin E has a general “immune support” effect. One study in seniors found that use of vitamin E did not help prevent colds and other respiratory infections, and, in fact, seemed to slightly increase the severity of infections that did occur. 156 In a similar-sized double-blind study of long-term care residents, use of vitamin E at 200 IU daily failed to reduce incidence or number of days of respiratory infection or antibiotic use. 176 The researchers managed to find some evidence of benefit by breaking down the respiratory infections by type, but such after-the-fact analysis is questionable from a statistical perspective. Subsequently, the same researchers repeated the study with a larger group and did find a reduction in frequency of colds. 191 Another researcher found evidence that vitamin E can have either a harmful or a helpful effect depending on who takes it (the exact differences being as yet undefined). 200

Alzheimer's Disease

Evidence is conflicting regarding whether high-dose vitamin E can slow the progression of Alzheimer's disease . 124

In a double-blind, placebo-controlled study, 341 people with Alzheimer's disease received either 2,000 IU daily of vitamin E (dl-alpha-tocopherol), the antioxidant drug selegiline, or placebo. Those given vitamin E took nearly 200 days longer to reach a severe state of the disease than the placebo group. (Selegiline was even more effective.)

However, negative results were seen in a study of 769 people at high risk of developing Alzheimer's disease based on early symptoms. 192 Participants were given either 2,000 IU of vitamin E, the drug donepezil, or placebo for 3 years. Neither treatment reduced the percentage of people who went on to develop Alzheimer's disease.

Warning: Such high dosages of vitamin E should not be taken except under a doctor's supervision. (See Safety Issues .)

Dysmenorrhea (Menstrual Pain)

In a double-blind, placebo-controlled trial, 100 young women complaining of significant menstrual pain were given either 500 IU of vitamin E or placebo for 5 days. 139 Treatment began 2 days before and continued for 3 days after the expected onset of menstruation. While both groups showed significant improvement in pain over the 2 months of the study (presumably due to the power of placebo), pain reduction was greater in the treatment group as compared to the placebo group.

Benefits were also seen in an Iranian, 4-month, double-blind, placebo-controlled study of 278 adolescent girls. 196 The dose used in this study was 200 IU twice daily.

Low Sperm Count/Infertility

In a double-blind, placebo-controlled study of 110 men whose sperm showed subnormal activity, treatment with 100 IU of vitamin E daily resulted in improved sperm activity and higher actual fertility (measured in pregnancies). 125 However, a smaller double-blind trial found no benefit. 126 

Cardiac Autonomic Neuropathy

People with diabetes sometimes develop irregularities of their heart-beat called cardiac autonomic neuropathy . A 4-month, double-blind, placebo-controlled trial found that vitamin E at a dose of 600 mg daily might improve these symptoms. 127

Safety Issues

The adult safe upper intake level (UL) for vitamin E is set at 1,000 mg daily. 128 The equivalent amounts are 1,500 IU of natural vitamin E and 1,100 IU of synthetic vitamin E. (For technical reasons, the conversion factor is a bit different than in the daily intake recommendations above.) For pregnant women under 19 years of age, the upper limit is 800 mg.

Vitamin E has a blood-thinning effect that could lead to problems in certain situations. In one study of 28,519 men, vitamin E supplementation at the low dose of about 50 IU synthetic vitamin E per day caused an increase in fatal hemorrhagic strokes, the kind of stroke caused by bleeding. 129 (However, it reduced the risk of a more common type of stroke, 130 and the two effects essentially canceled out.) Based on its blood-thinning effects, there are concerns that vitamin E could cause problems if it is combined with medications that also thin the blood, such as warfarin (Coumadin), heparin, clopidogrel (Plavix), ticlopidine (Ticlid), pentoxifylline (Trental), and aspirin. Theoretically, the net result could be to thin the blood too much, causing bleeding problems. A study that evaluated vitamin E plus aspirin did in fact find an additive effect. 131 In contrast, the results of a study on vitamin E and Coumadin found no evidence of interaction, but it would still not be advisable to combine these treatments except under a physician's supervision. 132

There is also at least a remote possibility that vitamin E could also interact with supplements that possess a mild blood-thinning effect, such as garlic , policosanol , and ginkgo . Individuals with bleeding disorders, such as hemophilia, and those about to undergo surgery or labor and delivery should also approach vitamin E with caution.

In addition, vitamin E might at least temporarily enhance the body's sensitivity to its own insulin in individuals with adult-onset diabetes. 133,134 This could lead to a risk of blood sugar levels falling too low. In addition, one study found that use of vitamin E can raise blood pressure in people with diabetes. 197

The bottom Line: If you have diabetes, do not take high-dose vitamin E without first consulting your physician.

When all major vitamin E studies are statistically combined through a process called “meta-analysis,” some evidence appears suggesting that long-term usage of vitamin E at high doses might increase overall death rate, for reasons that are unclear. 177,210

The results of one large study involving 29,000 males indicate that vitamin E supplementation may increase risk of tuberculosis in heavy smokers. Curiously, however, this was only true in those participants who also consumed high levels of vitamin C (at least 90 mg/d) in their diet. Consuming high levels of vitamin C without supplemental vitamin E actually led to a reduction in tuberculosis risk. 217

Finally, considerable controversy exists regarding whether it is safe or appropriate to combine vitamin E with standard chemotherapy drugs. 135,178 The reasoning behind this concern is that some chemotherapy drugs may work in part by creating free radicals that destroy cancer cells. Antioxidants like vitamin E might interfere with this beneficial effect. However, there is no good evidence that antioxidants actually interfere with chemotherapy drugs, growing evidence that they do not, and some evidence of potential benefit under certain circumstances. 136,167,179,198 Nonetheless, in view of the high stakes involved, we strongly recommend that you do not take any supplements while undergoing cancer chemotherapy, except on the advice of a physician.

One study appeared to find evidence that use of vitamin E plus beta-carotene may impair the effectiveness of radiation therapy for head and neck cancers. 199

Interactions You Should Know About

  • Seek medical advice before taking vitamin E if you are taking blood thinning drugs, such as:
  • Vitamin E may help protect you from lung-related side effects if you are taking amiodarone .
  • Vitamin E may help reduce side effects if you are taking phenothiazine drugs .
  • Seek medical advice before taking vitamin E if you are taking chemotherapy drugs.
  • High-dose vitamin E might cause your blood sugar levels to fall too low, requiring an adjustment in medication dosage, if you are taking oral hypoglycemic medications .