This story is a part of The Elemental Guide to Vitamins. Here are the vitamins and supplements that are covered: multivitamins, vitamin D, vitamin C, calcium, B vitamins, omega-3, vitamin E, fiber, protein, and probiotics.
A lot of people assume that vitamin supplements are all upside. Worst case scenario, you pee out what your body doesn’t need. But the tale of a National Cancer Institute trial called SELECT should obliterate those assumptions.
SELECT stands for the Selenium and Vitamin E Cancer Prevention Trial, which began in 2001. Back then, researchers had turned up “considerable” evidence that vitamin E and selenium, taken either alone or together, could prevent some forms of cancer. The trial’s goal was to nail down these benefits. Researchers recruited more than 35,000 men age 50 or older and split them into groups. Some took a daily 400 IU vitamin E supplement, either by itself or with selenium, while others took placebos. The hope was that the men on vitamin E would experience lower rates of prostate cancer.
The trial’s preliminary findings were so alarming that the researchers ended the experiment prematurely. Rather than preventing prostate cancer, the men taking vitamin E seemed to be developing cancer at higher rates. The study team eventually determined that taking vitamin E increased the men’s risk for prostate cancer by 17%, which translated to 11 more cases of prostate cancer per 1,000 men.
In the aftermath of the trial, the researchers who led it wrote that their findings “emphasize the importance of large-scale, population-based, randomized trials in accurately assessing the benefits and harms of micronutrients as dietary supplements.” They pointed to estimates that, at that time, more than half of U.S. adults aged 60 and older were taking a supplement containing at least 400 IU of vitamin E. They also underscored the fact that the bulk of the cancer risks their study revealed did not show up until seven years after the men started taking the supplements, meaning short-term supplement studies could miss these and other health risks.
Even now, experts still aren’t sure how vitamin E may contribute to the development of prostate cancer. There’s some evidence that the supplements interacted with gene variants that play a part in prostate cancer risk. But there are other theories.
The book on vitamin E isn’t all bad. For one thing, there are eight naturally occurring forms of vitamin E. The cancer-prevention trial had included dl-alpha tocopherol acetate, and so it’s possible that other types of vitamin E would not come with the same cancer risks. In fact, some have been linked with benefits.
“Vitamin E is like the Tale of Two Cities,” says Dr. Mark Moyad, the Jenkins/Pokempner director of preventive and alternative medicine at the University of Michigan. While taking some forms of vitamin E raises cancer risks, “it seems to help in large trials of people with Alzheimer’s disease,” he says.
The evidence on vitamin E for Alzheimer’s is somewhat mixed. But some studies on vitamin E have found that its antioxidant effects seem to slow the progression of Alzheimer’s and improve cognitive functioning in some patients. When combined with several other supplements, vitamin E has also been shown to reduce a person’s risk for developing macular degeneration, which is the most common cause of blindness in old age.
Along with its antioxidant effects, vitamin E also plays a role in immune functioning, cell signaling, gene expression, and metabolism. And so its potential benefits are wide-ranging. But the National Institutes of Health notes that the data on proper vitamin E intakes — either from food or from supplements — is filled with “great uncertainty.” Most foods containing vitamin E are healthy ones. These include nuts, seeds, vegetable oils, and leafy greens. Whole “sprouted” grains are a particularly good source of tocotrienols, a category of vitamin E that tends to be lacking in other foods and that research has tied to immune benefits.
The bottom line: The research on vitamin E is inconclusive. Doctors may recommend a vitamin E pill for people with specific medical conditions, but it’s not clear that taking a vitamin E supplement is worth the risks for the average person.
This story is a part of The Elemental Guide to Vitamins.