The vitamin E study

I just got around to looking at the vitamin E study that was publicized at the AHA meetings two weeks ago and published online at the Annals website (to be published in print in January).

It is a meta-analysis of randomized trials of vitamin E, that looks at overall mortality. Trials were analyzed by vitamin E dosage. There were 8 low-dose trials where the vitamin E dose was less than 400 IU daily, with a total of 95,000 subjects; there was no effect on mortality. Pooling the results of the 11 trials (about 41,000 subjects) where the dose was 400 IU or greater, there was an increase in mortality in the vitamin E group. The actual calculated number was 63 deaths per 10,000 persons.

My take on this:

The actual derived number is not meaningful, since results are pooled across a heterogeneous group of subjects, methods and doses. The number 63 per 10,000 should not be taken as is, especially since the confidence interval is 6-119!

On the other hand, the graphic representation of the 19 trials is highly instructive (a picture really is worth a lot of words). Even if one doesn’t place any stock in the pooling of results, just looking at the graphic summary of the trials is very convincing. I believe this is the biggest value of metanalyses: providing a graphic summary of multiple studies.

Since the inflection point for increased risk seems to be around 400 IU daily, and since that is a rather common vitamin E dose, it’s not clear exactly what to think about that dose. But I do feel fairly comfortable telling people who ask about 400 IU of vitamin E or more that I wouldn’t recommend it for prevention and would consider stopping it if they are taking this dose.

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