What multivitamins don’t do

Multivitamins won’t help you … fly. Or cliff dive. They won’t help you leap tall buildings in a single bound. They won’t help you teleport, read minds or shoot laser beams from your eyeballs. Oh, and they won’t help you measureably reduce your risk of dying from a heart attack, either. Surprise!

The big medical news of this past week was yet another metaanalysis showing that multivitamins don’t do what nobody I know thought they did in the first place: reduce the risk of heart attack, stroke or cardiovascular death.

No, a multivitamin is not likely to reduce measureably your risk of cardiovascular death. Not this time, not last time — and, spoiler alert — not next time either. Get excited about the next batch of indistinguishable headlines as the spirit moves you.

Consider what it would take to show that multivitamins do, in fact, reduce the risk of, say, cardiovascular mortality. One option would be to study perfectly healthy people and compare those who do and don’t take multis. Another would be to compare people with established cardiovascular disease, or at least significant risk factors, and do the same. Either way, for the information to be useful, the comparisons need to be between groups alike in all other relevant ways, but differing with regard to MVM use.

In a group of very healthy people who do, or don’t take multis — but who eat well, don’t smoke, exercise routinely, sleep enough, aren’t stressed out, don’t drink excessively and have no overt cardiac risk factors — very, very few people are going to die of a heart attack. It simply doesn’t matter in this group if multis are “good” for the heart, because you can’t fix what isn’t broken.

Then, there is the other end of the spectrum. People with significant risk factors for heart disease, or with established coronary disease already, are going to have heart attacks, and die from heart disease, at a much higher rate. But, of course, people known to have coronary disease participating in clinical trials are all receiving state-of-the-art treatment; any alternative would be unethical.

So, in this group, multivitamins again cannot possibly fix what isn’t broken. The study question in this case is not if multis reduce the risk of heart disease or death; rather, it is — do multis measureably reduce those risks beyond what the best drugs and procedures can do?

Showing risk reduction is nearly impossible when risk is very low to begin with, because tiny or rare effects take massive sample size and duration to detect. Showing risk reduction when risk is high all around and being managed in all the ways we know how is also nearly impossible, because the effect is consigned to the realm of “residual benefit,” which is inevitably apt to be fairly small.

Despite all of these hurdles, the new paper in Circulation, a systematic review and meta-analysis of prior studies (both randomized and observational trials) — was, like its predecessors on this topic, actually rather far from entirely negative. In the author’s own words, “…MVM supplement use was inversely related to the incidence of CHD when all studies were considered.” This finding simply didn’t hold up when analyzed further, or when limited to randomized trials only.

The team also found, apparently to their surprise, that there was a net benefit of MVM use in studies conducted outside the

U.S. Perhaps some of the populations outside the U.S. are more subject to nutrient deficiencies, and MVMs fixed those. If so, then this study actually suggests that MVM use to redress deficiencies may, indeed, reduce heart disease risk. As for the U.S., the findings leave room for benefit, and suggest that at worst — MVMs do not harm the heart.

If you want to reduce your risk of cardiovascular disease, eat well, be active, avoid toxins, and…so on. Use lifestyle as medicine, in other words. Don’t rely on a MVM for this purpose, obviously. But if you have other reasons for taking a multivitain, this study, like all before it, leave room for potential benefit, while pretty reliably ruling out any meaningful harm. So, supplement as the spirit moves you — but don’t bank on it to improve your cliff diving. And let’s all recall that no matter how effusive the media coverage, research rarely produces answers any better than the questions.