Vitamin E is a fat-soluble vitamin with several forms, but alpha-tocopherol is the only one used by the human body. Its main role is to act as an antioxidant, scavenging loose electrons—so-called “free radicals”—that can damage cells.  It also enhances immune function and prevents clots from forming in heart arteries. Antioxidant vitamins, including vitamin E, came to public attention in the 1980s when scientists began to understand that free radical damage was involved in the early stages of artery-clogging atherosclerosis, and might also contribute to cancer, vision loss, and a host of other chronic conditions. Vitamin E has the ability to protect cells from free radical damage as well as reduce the production of free radicals in certain situations. However, conflicting study results have dimmed some of the promise of using high dose vitamin E to prevent chronic diseases.
The Recommended Dietary Allowance (RDA) for vitamin E for males and females ages 14 years and older is 15 mg daily (or 22 international units, IU), including women who are pregnant. Lactating women need slightly more at 19 mg (28 IU) daily.
Vitamin E and Health
For a time, vitamin E supplements looked like an easy way to prevent cardiovascular disease. Large observational studies have shown a benefit from vitamin E supplements, whereas controlled clinical trials have produced mixed results.
- Observational studies: The Nurses’ Health Study  and Health Professionals Follow-Up Study  suggested 20-40% reductions in heart disease risk among individuals who took vitamin E supplements (usually containing 400 IU or more) for at least two years. 
- Randomized controlled trials: In the Women’s Health Study, which followed almost 40,000 healthy women for 10 years, vitamin E supplements of 600 IU taken every other day did not significantly reduce the risk of so-called “major cardiac events” (heart attack, stroke, or cardiovascular death). But there was some encouraging news in the findings: When these major cardiac events were analyzed separately, vitamin E supplementation was linked to a 24% lower risk of cardiovascular death.  And among women ages 65 and older, vitamin E supplementation reduced the risk of major cardiac events by 26%. A later analysis found that women who took the vitamin E supplements also had a lower risk of developing serious blood clots in the legs and lungs, with women at the highest risk of such blood clots receiving the greatest benefit. 
No Benefit Found
Based on such studies, the American Heart Association concluded that “the scientific data do not justify the use of antioxidant vitamin supplements (such as vitamin E) for CVD risk reduction.”  It is possible that in people who already have heart disease or are at high risk of heart disease, the use of drugs such as aspirin, beta blockers, and ACE inhibitors mask a modest effect of vitamin E, and that vitamin E may have benefits among healthier people.
More recent evidence introduces a theory that vitamin E supplements may have potential benefits only in certain subgroups of the general population. A trial of high-dose vitamin E in Israel, for example, showed a marked reduction in heart disease among people with type 2 diabetes who had a common genetic predisposition for greater oxidative stress. 
The story on vitamin E and cancer prevention has been a bit less encouraging than the story on vitamin E and heart disease. Taken as a whole, observational studies have not found that vitamin E in food or supplements offers much protection against cancer in general, or against specific cancers. [14–23] Some observational studies and clinical trials, however, suggested that vitamin E supplements might lower the risk of advanced prostate cancer in smokers. [16,24– 26]
Investigators had hoped that the Selenium and Vitamin E Cancer Prevention Trial (SELECT) would give more definitive answers on vitamin E and prostate cancer. SELECT’s 18,000 men were assigned to follow one of four pill regimens —vitamin E plus selenium, vitamin E plus a selenium placebo, selenium plus a vitamin E placebo, or a double placebo—and to be tracked for 7 to 12 years. But investigators halted the study halfway through in 2008 when early analyses showed that vitamin E offered no cancer or prostate cancer prevention benefit.  Though the trial ended, researchers continued to follow the men who had participated. In 2011, they reported a 17% higher risk of prostate cancer among men assigned to take vitamin E; there was no significant increased risk of prostate cancer among men who took vitamin E and selenium. 
Though these results may sound worrisome, two other major trials of vitamin E and prostate cancer had quite different results: The Alpha-Tocopherol Beta Carotene randomized trial, for example, followed nearly 30,000 Finnish male smokers for an average of six years.  It found that men assigned to take daily vitamin E supplements had a 32% lower risk of developing prostate cancer —and a 41% lower risk of dying from prostate cancer—than men given a placebo. Vitamin E’s protective effect was strongest for men whose cancers were far enough along that they could be detected by a clinical exam. The large and long-term Physicians’ Health Study II trial, meanwhile, found that vitamin E supplements did not increase or decrease the risk of prostate cancer or any other cancer. 
Why were the SELECT findings on vitamin E and prostate cancer so different from those of earlier studies? Previous studies of vitamin E supplements and prostate cancer found the greatest benefit in men who were smokers and who had more advanced cancers. [16,24–26] In the SELECT trial, however, fewer than 10% of the men were smokers and most had early-stage cancer detected through prostate specific antigen (PSA) blood tests. [27,28] Many early-stage, low-grade prostate cancers identified by PSA test would not become advanced cancers. There is also evidence that different processes may be at work in early versus late- stage prostate cancers. A large trial of a drug to prevent prostate cancer found opposite effects when used in early versus advanced prostate cancers. 
Bear in mind that most prostate cancer develops slowly, and any study looking at prostate cancer prevention needs to track men for a long time. By stopping the SELECT trial early, there is no way to tell if vitamin E could have helped protect against prostate cancer in some men if they had continued the trial over a longer period of time. Very few cases in the SELECT trial were of advanced prostate cancer, further limiting the interpretation of the findings.
A six-year trial found that vitamin E, in combination with vitamin C, beta carotene, and zinc, offered some protection against the development of advanced age-related macular degeneration (AMD), but not cataracts, in people who were at high risk of the disease. [31,32] On its own, however, vitamin E does not seem to offer much benefit against either AMD or cataracts. [33,34]
Scientists seeking to untangle the causes of Alzheimer’s, Parkinson’s, and other diseases of the brain and nervous system have focused on the role that free radical damage plays in these diseases’ development.  But to date, there is little evidence as to whether vitamin E can help protect against these diseases or that it offers any benefit to people who already have these diseases.
- Dementia: Some prospective studies suggest that vitamin E supplements, particularly in combination with vitamin C, may be associated with small improvements in cognitive function or lowered risk of Alzheimer’s disease and other forms of dementia, while other studies have failed to find any such benefit. [36–39] A three-year randomized controlled trial in people with mild cognitive impairment—often a precursor to Alzheimer’s disease—found that taking 2,000 IU of vitamin E daily failed to slow the progression to Alzheimer’s disease.  Keep in mind, however, that the progression from mild cognitive impairment to Alzheimer’s disease can take many years, and this study was fairly short, so it is probably not the last word on vitamin E and dementia.
- Parkinson’s Disease: Some, but not all, prospective studies suggest that getting higher intakes of vitamin E from diet—not from high-dose supplements —is associated with a reduced risk of Parkinson’s disease. [41–43] In people who already have Parkinson’s, high-dose vitamin E supplements do not slow the disease’s progression.  Why the difference between vitamin E from foods versus that from supplements? It is possible that foods rich in vitamin E, such as nuts or legumes, contain other nutrients that protect against Parkinson’s disease. More research is needed.
- Amyotrophic Lateral Sclerosis (ALS): One large prospective study that followed nearly 1 million people for up to 16 years found that people who regularly took vitamin E supplements had a lower risk of dying from ALS than people who never took vitamin E supplements.  More recently, a combined analysis of multiple studies with more than 1 million participants found that the longer people used vitamin E supplements, the lower their risk of ALS.  Clinical trials of vitamin E supplements in people who already have ALS have generally failed to show any benefit, however.  This may be a situation where vitamin E is beneficial for prevention, rather than treatment, but more research is needed.
- Wheat germ oil
- Sunflower, safflower, and soybean oil
- Sunflower seeds
- Peanuts, peanut butter
- Beet greens, collard greens, spinach
- Red bell pepper
Signs of Deficiency
Because vitamin E is found in a variety of foods and supplements, a deficiency in the U.S. is rare. People who have digestive disorders or do not absorb fat properly (e.g., pancreatitis, cystic fibrosis, celiac disease) can develop a vitamin E deficiency. The following are common signs of a deficiency:
- Retinopathy (damage to the retina of the eyes that can impair vision)
- Peripheral neuropathy (damage to the peripheral nerves, usually in the hands or feet, causing weakness or pain)
- Ataxia (loss of control of body movements)
- Decreased immune function
There is no evidence of toxic effects from vitamin E found naturally in foods. Most adults who obtain more than the RDA of 22 IU daily are using multivitamins or separate vitamin E supplements that contain anywhere from 400-1000 IU daily. There have not been reports of harmful side effects of supplement use in healthy people. However, there is a risk of excess bleeding, particularly with doses greater than 1000 mg daily or if an individual is also using a blood thinning medication such as warfarin. For this reason, an upper limit for vitamin E has been set for adults 19 years and older of 1000 mg daily (1465 IU) of any form of tocopherol supplement. 
Did You Know?
Due to occasional reports of negative health effects of vitamin E supplements, scientists have debated whether these supplements could be harmful and even increase the risk of death.
Read more on: vitamin e