Preventive Medicine Column
Dr. David L. Katz
A recent issue of the Annals of Internal Medicine featured three studies about multivitamin/mineral supplements. An accompanying editorial was entitled “Enough Is Enough: Stop Wasting Money on Vitamin and Mineral Supplements”- which would seem to indicate the flagrantly negative findings of the studies. The New York Times recently ran an opinion piece entitled “Skip the Supplements.” So clearly we must have decisive indications that nutrient supplementation is useless, right?
Wrong. The publications that spawned the recent round of unfounded pontification represented three studies. One examined the role of multis in preserving cognitive function among male physicians and found no clear benefit over placebo. Just under 6,000 participants were followed for roughly 12 years. Taking a multinutrient supplement did not, all other things being equal, make male physicians smarter- or keep them smarter longer. Even as this study continues to propagate the jump to conclusions about the uselessness of nutrient supplements, another study came out just this week in JAMA showing that high dose vitamin E did, in fact, preserve functional ability in Alzheimer’s patients (whereas the drug, memantine, did not).
The second study in the Annals examined the effect of multis on recurrent heart disease over an average span of four and a half years in slightly fewer than 2000 adults who had already had one heart attack. The rate of such events was, in fact, lower in the group assigned to multis, but not significantly lower than in the placebo group. There was no evidence of any harmful effects of the multis.
And, finally, study three, a systematic review that aggregated prior research, concluded that we lack clear evidence that multis can prevent heart disease or cancer. The actual conclusion was that “Limited evidence supports any benefit from vitamin and mineral supplementation for the prevention of cancer or CVD.” There was no sweeping rhetoric about uselessness, proof of ineffectiveness, or net harm.
Leaving aside valid concerns about the doses and quality of supplements in these trials, let’s just imagine that multis actually do work- both to prevent cancer, and heart attacks. Realistically, any such effect would be modest compared to that of lifestyle, or medication use. Let’s imagine the effect in question translates to one less heart attack and one less cancer per 100,000 people taking a multi for two years. If a randomized trial assigned 100,000 people to multis, and a corresponding 100,000 to placebo, and followed these 200,000 people for a full decade, there would be 5 fewer heart attacks and 5 fewer cancers in the multi group.
Such a small difference in so large a population would almost certainly fail to meet the standards of statistical significance, and the conclusion would be reached that multis don’t work. Yet, for every million people taking them for a decade, there would be 50 fewer heart attacks and 50 fewer cancers. If 100 million of us took them for that long, multis would have prevented 5,000 heart attacks and 5,000 cancers. Try telling those 10,000 families that such an effect is “trivial.”
I am not saying multis exert such an effect; I very much doubt it. But I am saying they COULD exert just such an effect, and all of the research done to date, collated together, would be insufficient to show it. That is the important difference between absence of evidence, and the evidence of absence some seem inclined to pretend we have.
There is another important consideration. Most people don’t bank on a multivitamin to prevent heart attacks and cancer. In my experience, people take supplements to feel and function a bit better every day. Maybe they exert this effect; maybe they don’t. The recent studies did not examine this. The notion that supplements are a useless waste of money because they don’t exert an effect most people weren’t expecting of them in the first place is not the most compelling example of logic I’ve seen.
Supplements are, at best, supplements to, not substitutes for, the power of lifestyle as medicine. If we are genuinely interested in the prevention of heart disease and cancer, we are all invited to invoke the consistent and robust evidence indicating that eating well, being active, avoiding tobacco, controlling our weight, sleeping enough and managing stress can do just that at least 80% of the time. No supplement, and no drug, can compare.
But supplements can confer potential benefits. They are no panacea, and of course, can do harm. But recent headlines seem to reflect preconceived notions rather than science considered carefully and dispassionately, resulting predictably in a badly muddled message.
Dr. David L. Katz