Thursday, November 11, 2004

To E or Not To E

A study making headlines about the possible downside of taking vitamin E sounds inconclusive to me. I'm eager to have a look at their research methods.

Here's what I hear from the news:
Elderly people who took at least 200 IUs of vitamin E a day died earlier than those taking less.

Here's what people may take away from this:
Taking vitamin E will make me die earlier.

Here's why I caution drawing this conclusion:
1. People who take supplements are a unique group and do not represent a cross section of the population. One reason people take supplements is as therapy for a preexisting ailment, or as insurance against a chronically poor diet. People who take vitamin E are also apt to be taking other supplements. Did the researchers account for these confounding factors?

2. One cannot draw a risk statement (or a statement of cause and effect) from this type of study. That is, you cannot say that vitamin E caused people to die early, you can only say that people who died early also happened to be taking vitamin E. In fact, the lead author of the study admits he does not know the reason for the association he reported.

3. Was the supplement intake primarily self-reported? Self-reporting of intake is fraught with errors ... desire to please the questioner, memory lapses, lack of knowledge about quality, quantity, and frequency of intake. And self-reporting is especially problematic in an elderly population.

4. The study in question is a meta-analysis of 19 studies that were published between 1993 and 2004. The data for the 19 studies was collected in years prior to publication. And some data (we don't know unless we read each of the 19 studies) may be based on data even older than 1990. Why is this important? Because we now know that intake of vitamin E in only the alpha-tocopherol form has been implicated in heart disease. (Possibly because it blocks absorption of the other vitamin E compounds.) Most vitamin E on the market prior to 2000 contained only alpha-tocopherol. Synthetic vitamin E (labeled, sometimes incorrectly, as all-rac alpha-tocopherol, all-rac alpha tocopheryl acetate, or dl-alpha-tocopherol), another popular form of vitamin E in supplements in past years is known to lack the benefits of natural vitamin E and may also be problematic.

I think I will continue to take vitamin E, at least until a mechanism can be explained for possible risk.

Note: Vitamin E is actually a complex, much like Vitamin B Complex. We know of 8 compounds, 4 tocopherols and 4 tocotrienols (described by alpha-, beta-, gamma, and delta- for each class), that comprise it. Of the 8, alpha-tocopherol is the most abundant in our bodies, but studies have revealed unique and important activities for the lesser compounds.

It's best to take a vitamin E supplement that consists of mixed tocopherols and tocotrienols. The DRI for vitamin E (based only on alpha-tocopherol) is about 15 mg/day. Antioxidant effect was seen at intakes of around 80 mg. The upper limit is 1000 mg (1500 IU).

1 mg. alpha-tocopherol = 1.49 IU alpha-tocopherol, e.g. 268 mg. = 400 IU.

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