Other common name(s): none
Scientific/medical name(s): alpha-tocopherol, tocopherols, tocotrienols
Vitamin E is an essential fat-soluble nutrient that serves as an antioxidant and is also used in cell signaling, regulating gene expression and immune function. (Antioxidants block the action of free radicals, which are activated molecules that can damage cells.) There are 8 natural forms of vitamin E. The most important one to the human body is alpha-tocopherol.
The main sources of vitamin E in the diet are vegetable oils (especially safflower oil, sunflower oil, and cottonseed oil), green leafy vegetables, nuts, cereals, meats, egg yolks, wheat germ, and whole-wheat products.
Vitamin E deficiency is extremely rare. It happens almost exclusively in people with an inherited or acquired condition that impairs their ability to absorb this vitamin, such as cystic fibrosis, short-bowel syndrome, or blocked bile flow. Deficiency can also happen with severe protein-calorie malnutrition (starvation). Symptoms of vitamin E deficiency include muscle weakness, vision problems, immune system changes, numbness, trouble walking, tremor, and a poor sense of balance. Over a long time, vitamin E deficiency may progress to blindness, heart disease, permanent nerve damage, and impaired thinking. Supplements are usually only necessary for people with vitamin E deficiency or a condition that puts them at risk for this deficiency.
Early observational studies suggested a protective effect of vitamin E against prostate, bladder, and colorectal cancer. Most carefully controlled clinical studies show that vitamin E supplements do not have any overall health benefit or any reduced risk of heart disease or cancer, and may even lead to increased risk of heart failure. One such study has actually shown an increase in prostate cancer in men who took Vitamin E supplements. Available scientific evidence does not support claims that vitamin E significantly affects the growth of cancers that have already formed.
How is it promoted for use?
Some proponents claim vitamin E plays a role in protecting the body against cancer by bolstering the immune system. It’s also an antioxidant, which helps prevent damage to DNA and other important parts of cells. Some also believe the vitamin can help some chemotherapy drugs work better and may reduce some side effects of chemotherapy and radiation therapy. But others believe high doses of vitamin E during treatment might interfere with the effectiveness of radiation therapy and chemotherapy by preventing cancer cells from being destroyed.
Proponents also claim that vitamin E supplements protect against heart attacks by preventing a build-up of harmful cholesterol and blood clots in the blood. There are also claims that vitamin E eases the inflammation associated with arthritis, speeds wound healing in people who have suffered burns or have had surgery, and slows the progress of Parkinson’s disease and Alzheimer’s disease. Some say that it may help prevent or treat eye problems like cataracts and age-related macular degeneration. Vitamin E is also promoted to protect against the effects of pollution and overexposure to the sun.
What does it involve?
A balanced diet normally gives the body the amount vitamin E it needs, especially a diet high in green leafy vegetables and fiber from grains and cereals. The recommended daily allowance (RDA) of vitamin E for adults is 15 milligrams per day from food, with 19 milligrams per day recommended for women who are breast-feeding. (Vitamin E is often measured as IU (International Units); one milligram equals 1.5 IU.) This recommendation was revised by the National Academy of Science (NAS) in April 2000. It also set the upper limit of intake from supplements at 1,000 milligrams (1 gram or 1,500 IU) per day.
In general, US residents get more than enough vitamin E from foods, although those who choose a low-fat diet may get somewhat less than the RDA.
Vitamin E supplements are often taken as capsules, with a typical dose being 400 IU per day.
What is the history behind it?
Since the 1940s, researchers and others have thought that vitamin E might prevent heart disease. Researchers have observed that people who have cancer often also have low levels of vitamin E in their blood. More recently, several clinical trials have been completed (and others are still in progress) comparing the risk of cancer among volunteers randomly assigned to get either vitamin E supplements or a placebo (look alike sham pills).
What is the evidence?
The early evidence for the preventive effects of antioxidants like vitamin E came from animal studies and from observational epidemiologic studies that use surveys to estimate how much vitamin E a person gets from food and supplements. The most reliable studies on this issue are controlled clinical trials, such as a large 1994 study of antioxidant vitamins and cancer conducted by the National Cancer Institute (NCI) and the National Public Health Institute of Finland. The study was designed to find out whether antioxidant vitamins in high doses (50 milligrams daily) could reduce the incidence of lung cancer, other types of cancer, and other illnesses among 29,000 male smokers. The study found vitamin E supplements did not reduce lung cancer risk. It found lower rates of prostate and colorectal cancer, but higher rates of bladder, stomach, and other types of cancer in those who got high doses of vitamin E.
Individual clinical trials can sometimes provide misleading results because of variation in research methods or random statistical variation. Because of this, researchers often analyze the combined data from many studies. This is called meta-analysis. A meta-analysis published in 2005 combined data from 19 clinical trials that looked at vitamin E supplements. The results showed that vitamin E supplements, overall, do not lower the risk of heart disease or cancer, and that people who got the placebo actually lived slightly longer than those getting the supplements.
Another large clinical trial published in 2005 also found no risk reduction for heart disease or cancer overall. It even suggested that heart failure was slightly more common in people taking vitamin E. And a 2007 review of 68 studies of antioxidant vitamin supplements found that people taking vitamin E supplements had a shorter life expectancy than those who did not take these supplements.
The Women’s Health Study began in 1991. This clinical trial looked at whether vitamin E could protect women from heart attack, stroke, or cancer. Results published in 2005 showed that vitamin E had no effect on cardiovascular disease or on the most common cancers in women: lung, breast, and colorectal cancers.
The SELECT (Selenium and Vitamin E Cancer Prevention Trial) looked at the effect of vitamin E alone or in combination with selenium (an antioxidant mineral) on prostate cancer risk. (See our document Selenium for more information.) The SELECT enrolled more than 35,000 men, and was expected to end in 2013. But a preliminary analysis in 2008 showed no difference in prostate cancer risk between the groups taking the vitamin E supplement and the placebo, and the results suggested that vitamin E might even have slightly increased the risk of developing prostate cancer. The increase was not statistically significant at the time, meaning it could have been due to chance. The selenium supplement did not appear to be helpful, either, and early results suggested that it might slightly increase the risk of developing diabetes. (Again, the increase was not statistically significant.) Because of these possible risks, the researchers advised participants to stop taking the supplements, but they continued to observe the men. The risk of prostate cancer kept rising, and by 2011 had climbed high enough to be considered a significant increase in prostate cancer among the men who took the vitamin E supplements. This means that these findings are not likely to be due to chance.
Vitamin E has also been studied in clinical trials of people who have had one cancer in order to see if it could keep the cancer from coming back (cancer recurrence) or prevent a second, new cancer. Clinical trials of people with head and neck cancer found it did not reduce the risk of recurrence or the risk of a second cancer.
The American Cancer Society recommends that adults should eat at least 2½ cups of fruits and vegetables every day to get their required nutrients. Choose whole grains over refined grains and sugars, and limit red meats and processed meats. If you drink alcohol, limit your intake – no more than 1 drink per day for women and 2 drinks per day for men. Select foods that help you get to and maintain a healthy weight. Get at least 150 minutes of moderate intensity or 75 minutes of vigorous intensity physical activity each week (or a combination of these), preferably spread throughout the week. For most people, this will help keep weight under control, reduce risk of some cancers, and reap many other health benefits. If a supplement is taken, the best choice for most people is a balanced multivitamin/mineral supplement that contains no more than 100% of the “Daily Value” of most nutrients.
Should you take vitamin or mineral supplements during cancer treatment?
Many researchers and clinicians believe that taking high doses of antioxidant vitamins may change how well radiation therapy and some chemotherapy drugs work, but they often disagree as to whether the changes are helpful or harmful. Some researchers and doctors think antioxidants like vitamin E might reduce side effects or even improve effectiveness of radiation or chemotherapy. Others are concerned that antioxidants will reduce effectiveness of these treatments. Very few studies have yet been done in humans to test these theories, and there is no clear consensus yet. Most oncologists advise their patients to avoid antioxidant vitamin and mineral supplements during treatment, but some surveys suggest this advice is often ignored by patients. Further studies are needed to resolve this important question.
Are there any possible problems or complications?
Vitamin E supplements found in foods and in multivitamins are generally considered safe. Large doses of vitamin E (more than 533 milligrams or 800 IU) taken over a long time can cause nausea, vomiting, stomach pain, and diarrhea. It may also cause heart problems and change the blood’s ability to form clots, which might cause bleeding or even stroke in a few people. Megadoses of vitamin E supplements are not advised for people who are taking blood-thinning medicines, like warfarin (Coumadin®), because the supplements might increase the effects of the drugs. More research is needed on the effects of large doses of vitamin E.
People with cancer should talk to their doctors before taking vitamin E or any other vitamin supplements, especially while they are getting chemotherapy or radiation therapy. Relying on this type of treatment alone and avoiding or delaying conventional medical care for cancer may have serious health consequences.
To learn more
More information from your American Cancer Society
The following information on complementary and alternative therapies may also be helpful to you. These materials may be found on our Web site (www.cancer.org) or ordered from our toll-free number (1-800-ACS-2345).
The ACS Operational Statement on Complementary and Alternative Methods of Cancer Management
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Note: This information may not cover all possible claims, uses, actions, precautions, side effects or interactions. It is not intended as medical advice, and should not be relied upon as a substitute for consultation with your doctor, who is familiar with your medical situation.
Last Revised: 01/16/2013