Q: I heard that taking vitamin E supplements might be dangerous.
Should I stop taking them?
Q: I heard that taking vitamin E supplements might be dangerous. Should I stop taking them?
A: You’re probably referring to a study that received recent attention in the news.
The report pooled findings from 19 different studies involving a total of more than 136,000 people who took vitamin E for one reason or another. Researchers found that the overall risk of dying was greater for people who took 400 international units (IU) of vitamin E (the amount found in a typical capsule) or more daily, compared to those who took lower doses. And the risk of dying rose with increasing doses above 150 IU per day.
But the study has some drawbacks. For one thing, the people using doses of 400 IU or more were largely older adults with chronic diseases. So the findings don’t necessarily apply to younger, healthy adults.
Also, in 10 of the 19 trials, people took other nutritional supplements as well, making it hard to single out vitamin E as the sole culprit. Finally, the amount of increased risk was very small. And in those taking doses of 150 IU per day or less, the risk of death from all causes was actually lower. So some experts aren’t convinced there’s any increased risk.
Vitamin E’s popularity stemmed from a number of earlier studies that hinted that the vitamin could stave off common health problems such as heart disease, cancer and cataracts. Many health-care professionals recommended the vitamin and took it themselves. But in recent years, this once-lauded vitamin started losing its luster. What happened?
n Heart disease: Two large studies from Harvard Medical School found that people who took at least 100 IU of vitamin E per day had a lower risk of heart disease.
But these were observational studies, meaning they relied largely on the participants’ own reports of their past dietary habits and supplement use.
When people were split at random into groups and assigned to take vitamin E or a placebo, these findings were not confirmed. In nearly all of these types of studies, known as randomized controlled trials, vitamin E pills did not protect against heart disease. Nor did they prevent further worsening in people who already had heart disease.
n Cancer: The evidence on cancer has followed a similar pattern. Some observational studies found that people who consumed more vitamin E were less likely to develop breast, colon or prostate cancer. But controlled trials found no such advantage.
For example, in one study, people taking vitamin E to help prevent colon cancer were just as likely to develop colon polyps, which sometimes lead to colon cancer, as those who didn’t take the vitamin.
n Dementia and Alzheimer’s disease: The findings on dementia are somewhat conflicting. Once again, observational studies suggested that taking vitamin E might protect against Alzheimer’s disease and other forms of dementia.
One randomized trial also found that vitamin E might delay the progression of Alzheimer’s. But some researchers pointed to flaws in the study’s design, and the dose used was 2,000 IU per day – well above the current safe upper limit for the vitamin.
n Cataracts: Controlled trials of vitamin E supplements have not upheld observational findings of a lower rate of cataracts in regular vitamin E users.
The U.S. Preventive Services Task Force, an independent panel that issues health advisories, recommends neither for nor against vitamin E supplements for preventing heart disease or cancer.
The American Heart Association goes further. Its guidelines on preventing heart disease and stroke in women specifically advise against using supplements such as vitamin E.
And the Alzheimer’s Association recommends that patients take vitamin E only under the care of a physician. One reason for their concern is that high-dose vitamin E can interfere with the blood’s clotting ability, raising the risk of hemorrhagic (bleeding) strokes. People who take blood-thinning medications such as warfarin (Coumadin) should be especially cautious.
The recommended dietary intake of vitamin E is 15 milligrams (mg) per day. That’s the equivalent of 22.5 international units (IU), the amount found in most multivitamins.
Taking a daily supplement containing 150 to 200 IU is unlikely to be harmful. Determining whether it is helpful depends on the results of ongoing trials.
In the meantime, try to get most of your vitamin E from food (see chart). There’s strong evidence that diets containing large amounts of vitamin E-rich foods are good for your health.
Submit questions to the Harvard Medical School Adviser at www.health.harvard.edu/adviser. Unfortunately, personal responses are not possible.