Vitamin E Flunks More Tests
It's become a frustratingly familiar tale: A vitamin or mineral is hailed for its power to ward off disease. Sales of the supplement soar. But then studies suggest that the claims may have been overblown. Eventually, more definitive research--in the form of large, randomized trials--confirms that the supplement is ineffective and possibly even harmful.
Such is the disappointing story of vitamin E, an antioxidant that previous research has suggested may help ward off cancer and heart disease. But several recent studies have cast doubt on the idea. And now two large trials are putting some final nails in the coffin.
One is a massive study, funded by the National Cancer Institute, that involves 35,000 men age 50 and older. Known as SELECT, it was designed to determine whether vitamin E and the mineral selenium, taken either alone or together, prevent prostate cancer. The answer is no, according to an initial review of the data. What's more, those who took vitamin E had a slightly higher risk of prostate cancer, though it's possible the finding was due to chance. As a precaution, researchers recently decided to halt the trial early and advised participants to stop taking their supplements.
Another large randomized trial, involving more than 14,000 male physicians age 50 and older, recently found that subjects who took vitamin E supplements had no fewer heart attacks, strokes, or cardiovascular-related deaths than those who got a placebo.
When vitamin E fails tests such as these, proponents are sometimes quick to blame the research. One common complaint is that studies used synthetic vitamin E rather than the "natural" form. (You can tell which is which by looking at the label; dl-alpha-tocopherol means it's synthetic, while a "d" instead of "dl" indicates it's natural.) Though some vitamin users and sellers believe that natural vitamin E is more effective, there's no compelling evidence to support such assertions.
Other possible explanations are that the dose (400 IUs daily in both studies) wasn't optimal or that the follow-up periods (an average of five years in SELECT and eight in the heart disease trial) were too short.
Perhaps. But the information yielded by health studies is rarely perfect. We have to make decisions based on what's known--not what we hope is true. And multiple studies--involving different doses and different populations, using different forms of vitamin E--have now shown that it does not live up to its earlier billing.
The take-home message is that we need to be careful not to swallow supplement claims prematurely. First, do some homework. Databases provided by the Mayo Clinic and Consumer Reports, which objectively review the scientific evidence for a host of dietary supplements, are two good places to start.