Vitamin E Supplementation: Should You or Shouldn't You?

Joel Mason, M.D.

Recently, there has been considerable media attention as to whether or not vitamin E supplementation is safe or helpful. The attention has been largely driven by publication of two papers in medical science journals over the past year which reported potential adverse health effects of vitamin E supplementation10,11. As a result, physicians and other health professionals have been deluged with questions from their patients about vitamin E and sales of vitamin E supplements have plummeted.

What is the scientific basis of the claims of benefits and harms conveyed by vitamin E supplements?

Why Vitamin E Supplements are Popular

Over the past two decades, some scientists have proposed a so-called 'oxidant theory of disease.(12) This hypothesis contends that oxidative metabolism, and the free radicals that arise from it, is the core pathophysiologic mechanism underlying a number of chronic degenerative diseases including cancer and cardiovascular disease (CVD). This theory, furthermore, postulates that adequate, or even large doses of anti-oxidant nutrients such as vitamins C, E, the carotenoids and selenium can protect against such damage. Amongst all of these possible benefits, the potential protective effects against CVD and cancer have been the two most extensively submitted to the test of randomized clinical trials.

How Widespread is the Use of Vitamin E Supplements?

The daily use of dietary supplements, and in particular vitamin E, has grown to be a widespread habit. Most surveys performed in the past five years have observed regular intake (more than 5 times/week) among 25-50% of the adult population and, in almost all cases, the prevalence incrementally increases by age and with the presence of chronic degenerative diseases.(1) Commonly, these adults take daily doses of 400 mg or more. Even among doctors, vitamin E supplementation for their personal consumption is a growing practice.(2)(3)

A Perspective on the Doses Contained in Vitamin E Supplements

The growing acceptance of vitamin E as a useful nutritional supplement has been greatly enhanced by the apparent safety of the vitamin, with upper limits of safe intake set by the National Academy of Sciences at 1000 mg/day, or approximately seventy times the recommended daily allowance (RDA) for the vitamin. So, although the most commonly used dosage for single-nutrient vitamin E supplements is 400 mg or roughly 30-fold greater than the RDA, that level of supplementation is still less than half the purported upper limit of safe intake.

With such a wide array of benefits and with an apparent solid margin of safety, it is not surprising that large segments of the public, as well as health professionals, have adopted the same philosophy uttered recently by a prominent heart researcher, who said about high dose vitamin E: 'It can't hurt and might help, so why not take it?'(4)

So, just what do the studies with respect to presumed risk benefit for coronary heart disease and cancer show? And do they confirm the perspective expressed by this researcher?

Vitamin E Supplements and Cardiovascular Disease

Large, observational studies published in the latter part of the 1980s and early 1990s consistently observed a strong association between habitual vitamin E consumption and the risk of coronary heart disease, with risk reductions of 30-60%. These studies demonstrated a remarkably strong decrease in risk associated primarily with the use of high doses of vitamin E but considerably weak effects of low doses of the vitamin.(5)(6)

However, when scientists tried to duplicate these findings in controlled studies of volunteers divided into two groups — one given vitamin E, one given a placebo — where the individuals were followed going forward in time, the results were considerably different. Three large trials observed a neutral effect of vitamin E: neither benefits nor harm were seen. In addition, two other studies — named HATS and HOPE-TOO — also provided no compelling evidence for a consistent benefit of vitamin E in the secondary prevention of cardiovascular disease but nevertheless raised concerns about potential negative side effects. In the HATS trial, the use of vitamin E supplements diminished the angiographic benefits obtained from the use of niacin and a cholesterol-lowering statin drug. In the HOPE-TOO trial, the use of vitamin E supplements slightly, but significantly, increased the risk of congestive heart failure.

However, because one large study, the CHAOS trial, did demonstrate substantial and significant benefits, the case for or against vitamin E is still confused. To resolve this uncertainty, medical statisticians tried to solve the dilemma with a technique called meta-analysis, which we shall come to shortly.

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