< Durk Pearson and Sandy Shaw: Smart Basics Newsletter - Vitamin E

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"Do we need to wait for the results of Double Blind Placebo Controlled Trials of Vitamin E for the prevention of cardiovascular disease before making public recommendations on Vitamin E supplements?"

By Sandy Shaw & Durk Pearson

Two large epidemiological studies (where vitamin E consumption was compared to cardiovascular disease incidence) were just published in the May 20, 1993 New England Journal of Medicine. Epidemiological studies of men (39,910 U.S. male health professional subjects) and women (87,245 female nurses) found about a 35% reduced risk of cardiovascular disease for subjects taking supplements of at least 100 International Units (iu's) a day of vitamin E for two years or more, compared to those not taking vitamin E supplements.

However, the authors of both studies stated that public policy recommendations concerning vitamin E should await the results of ongoing and additional double blind placebo controlled trials with vitamin E. We disagree. There are no reputable scientists who doubt that smoking causes lung cancer. Yet, there has never been a double blind placebo controlled human trial to test this proposition and provide "unequivocal" proof. The current scientific conclusions concerning smoking and lung can cer are based upon three lines of evidence:

  1. Human epidemiological evidence, where lung cancer incidence in people who smoke is much higher than in people who do not smoke. Epidemiological studies, however, show correlations but do not prove cause and effect.
  2. Animal studies. For example, animals treated with tobacco tars develop various cancers on the site treated.
  3. Mechanisms. Knowledge of the chemical effects of tobacco smoke constituents (for example, metabolites of polynuclear aromatic hydrocarbons cause DNA damage) is another line of evidence of the carcinogenic effects of tobacco smoke.
These three kinds of evidence are the basis for widely disseminated public policy recommendations that people should stop smoking. This kind of evidence, not double blind placebo controlled trials, is also the basis of public recommendations to reduce dietary fat and cholesterol intake to lower the risk of cardiovascular disease. There has never been a double blind placebo controlled trial where people have been fed different amounts of fat and cholesterol over a period of years to examine the resulting i ncidence of cardiovascular disease. Yet, there is little scientific disagreement with these public recommendations which are based upon studies of human epidemiology, animal models, and knowledge of chemical mechanisms.

Enstrom, Kanim, and Klein were authors of "Vitamin C Intake and Mortality among a Sample of the U.S. Population Epidemiology 1992;3:194-202), an epidemiological study of 11,348 U.S. adults over a 10 year period comparing mortality versus vitamin C intake, which reported dramatic reductions of cardiovascular disease incidence in men taking about 800 mg. of vitamin C a day, mostly from supplements, compared to men getting average amounts of vitamin C.

These authors stated in their paper's discussion that ".. .the inverse relation of total mortality to vitamin C intake is stronger and more consistent in this population than the relation of total mortality to serum cholesterol and dietary fat intake, two variables on which strong public health guidelines have been issued over the years."

The kinds of evidence that support vitamin E's ability to reduce the risk of cardiovascular disease are of exactly the same sort as those supporting other major public policy recommendations, including stopping smoking, reducing dietary fat and cholesterol, and increasing exercise. The accumulating evidence that antioxidants can reduce the risk of cardiovascular disease (and also cancer) is so strong that nutritional researchers themselves frequently admit to taking antioxidant supplements. Nearly everybody we have talked to at scientific meetings on aging research is taking antioxidant supplements (although that wasn't true when we began attending these meetings over 20 years ago).

In the article on the new vitamin E studies (discussed above) in the May 31, 1993 Time, Dr. Eric Rimm, the scientist who headed the men's study, was quoted as saying that he himself is taking 200 units of vitamin E a day, as well as eating carefully and exercising. Well known scientist Dr. Bruce Ames, director of the National Institute of Environmental Health Sciences at the University of California at Berkeley was quoted in an article in the December 1992 Men's Health as saying "Every person I know in the nutritional research field is taking supplements."

We do not think it is ethical, because of the strong evidence that antioxidant vitamins can reduce the risk of cardiovascular disease, to put those in a clinical trial on a placebo that subjects them to a greater risk of developing cardiovascular disease. However, if double blind placebo controlled studies are done and are to have any meaning, subjects should have their serum levels of antioxidants measured to prevent the confounding effects of "cheating."

The May 31,1993 Newsweek article on the two vitamin E studies concluded that "...vitamin supplements cannot substitute for good health habits. Unfortunately for a quick-fix society, getting plenty of exercise, cutting down on dietary fat and quitting smoking remains far better prescriptions for preventing heart disease than anything one can obtain from a vitamin bottle."

There is simply no scientific justification for this conclusion. Taking antioxidant supplements is not a substitute for exercise or reducing dietary fat or quitting smoking, but neither are exercise, quitting smoking, or reducing the fat in one's diet a substitute for taking antioxidant supplements.

The unscientific conclusion that antioxidants are far less effective preventatives of cardiovascular disease is a bias that appears to us to reflect a puritanical attitude that an action that is relatively easy for people to take is morally inferior (and therefore not as "good") compared to an action that may require considerable effort or self-denial.

Furthermore, evidence indicates that those who take vitamins are somewhat more likely, rather than less so, to eat carefully and have other good health habits. This potentially confounding effect has been considered in the epidemiological studies mentioned above.

We do think that large studies ought to be done on different levels of antioxidant supplements, such as a study comparing the cardiovascular incidence in subjects taking, say, 200 units of vitamin E to others taking, say, 400 units of vitamin E a day. Information on the optimal levels of supplementation of antioxidants is greatly needed in order to make more appropriate public policy recommendations.

Although double blind placebo controlled clinical trials are of great importance in the study of new, potentially useful therapies, we have to recognize the limitations of such trials. They include an ethical problem with using people to demonstrate a scientific point when available evidence strongly indicates that many unnecessary deaths or disabilities would occur among those on placebo.

A further limitation is cost. Even if we wished to do double blind placebo controlled trials on all possible combinations of antioxidants and all possible doses to obtain "unequivocal" proof of the efficacy of mixtures of various antioxidants at various doses, we could not afford to do so. Many widely accepted and important public policy recommendations are being made on the basis of strong scientific evidence that does not come from double blind placebo controlled trials, but which includes evidence from animal studies, human epidemiological studies, and knowledge of chemical mechanisms. \

There is plenty of such evidence now to recommend the use of antioxidant supplements. Most Americans are not eating the recommended amounts of fruits and vegetables, the major dietary sources for vitamin C, vitamin E and carotenoids. Furthermore, mounting evidence indicates that higher than RDA levels of vitamins E and C-levels which may be difficult or even impossible to get in even a very good diet-provide substantial protection against cancer and cardiovascular disease.

It is hard to understand the motivations of those in positions of public authority and trust who, in the name of public health, exhort Americans not to take supplements of vitamins E and C and of beta carotene.

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