Vitamin E supplementation and cardiovascular events in high risk patients
This randomized trial of 400 IU of vitamin E vs. placebo failed to show any decrease in cardiovascular events after 4.5 years of follow-up. This, despite the fact that multiple observational trials had suggested a beneficial effect. One of the areas where observational trials are most likely to be influenced by bias is when analyzing data that reflect "healthy" behaviors. Since healthy diets and vitamin supplementation are strongly associated with other beneficial lifestyle aspects, it is extremely difficult to avoid the intruduction of bias.
The trial was halted early because of a significant benefit in the ACE inhibitor portion of the study. This could have led to an inadequate length of follow-up to detect a beneficial effect of vitamin E. But, as the authors point out, a beneficial effect of vitamin E would have been expected before the 4.5 years of follow-up that were available here, so the early termination is unlikely to have played a major role in the negative result.
This study does not disprove the role of vitamin E in cancer prevention (still being followed in some of the patients enrolled in this trial), does not necessarily disprove a potential role when combined with other antioxidants, and certainly doesn't negate the potential beneficial role of a diet that is naturally high in vitamin E. It does, however, call into question the role of vitamin E supplements alone for the prevention of cardiovascular events.
July 4, 2000
ReferencesReferences related to this article from the NLM's PubMed database.
July 5, 2000
Dear Dr Jacobson,
Thank you for always interesting cases. It is important to stress that a single cause for vascular disease and events does not apply or else it would have been sorted out earlier.
First, we need to look at the stress factor involved in these patients and this might be difficult.
Second, we need to know in younger generations that are at high risk whether vit e is preventive before disease starts, like 20 - 30 years of age, as probably prevention is much more effective than treatment in those patients.
Third, we hope that genetics will give us insight on who wil benefit and who willl not.
thank you, samim
July 5, 2000
This study deals entirely with "secondary prevention" of CV events in a fairly sick population. I would be interested to know same outcomes for a "primary prevention" point of view. Example: patients without CV proven disease but with hyperlipidemia, HTN, Diabetes, etc.
Enrique S. CorvalŠn, MD, ABFP, FAAFP
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