Thursday, December 19, 2013

Thoughts On Multivitamins

The Annals of Internal Medicine, a well-respected medical journal, recently published an editorial titled "Enough Is Enough: Stop Wasting Money on Vitamin and Mineral Supplements." The piece was then widely disseminated to the news media both home and abroad. The editorial claims that the research indicating the uselessness of multivitamins is now so overwhelming as to condemn their use on a vast scale.

It is with sadness that I have to critique this piece. Naturopathic physicians such as myself, both individually and as a profession, have long strived to further research into nutritional approaches to disease and complementary therapies, not to mention furthering the cause of research generally. It is rare that I have to describe an article as unconstructive, but this editorial is such a piece. As I'll argue, this editorial is poorly conceived, poorly intended, and does not engender constructive scientific dialogue.

But before I go further into discussing the particulars, I'd like to discuss a point of irony. The point of irony is that I am not a big advocate for the use of multivitamins. In working with patients, I am far more interested in fostering good eating habits than recommending a multivitamin to "cover the bases." It is perhaps ironic therefore that I might criticize a piece whose point I do agree with. So given that, why argue with it?

Well, there are two big reasons I'm forced to differ with this editorial. The first is that despite claims of overwhelming evidence, the editorial is based on imperfect evidence. It took into account only about 32 studies, some of which are older (a colleague of mine called them "academic leftovers"). While that's no small number, compare it to the article I discussed last week, which examined nearly 300 studies in an effort to understand the role of vitamin D supplementation in disease.

The editorial was written in specific response to two studies published in the Annals of Internal Medicine this month, which bear attention.

The first article found that multivitamins did not appear to provide protection against cognitive decline. This piece suffered from significant limitations, including the fact that it was performed on physicians, who in general eat above average diets and may not need additional nutritional supplementation. Additionally, the use of a multivitamin to prevent cognitive decline is unorthodox, even in complementary medicine, and slowing of cognitive decline is not an outcome that could be reasonably expected from the use of a multivitamin. The most authoritative reference I know of, Nutritional Medicine by Dr. Alan Gaby, includes no references to the use of multivitamins in cognitive decline; this is an exhaustive reference book that draws on published medical literature as far back as the 1940s. This study then, is a prospective study examining a completely novel use for multivitamins, but has been misrepresented as a refutation of the use of multivitamins for a given condition.

The second article discusses the use of multivitamins in prevention of cardiovascular events (such as heart attack, stroke, chest pain, or death) in patients who had previously had a heart attack. Patients who were taking part in the study were also undergoing conventional medical therapy. Here also, the use of a multivitamin in preventing a second cardiovascular event is not common practice. This study is not a refutation of an accepted practice, as it is presented in the editorial, but a prospective study that failed to find a positive effect. Though individual nutrients have been studied in regards to various cardiovascular risk factors, including some with positive results, it would not have been reasonable to anticipate that a multivitamin would have the effect of preventing a second event. Additionally, this particular study was confounded by low levels of compliance with treatment, and the study authors themselves admitted that firm conclusions could not be drawn.

A weak rationale for the editorial is one reason that I have to object to the argument.

The second reason I have to object is that the tone of the editorial, especially when taken in light of the evidential basis, leads me to strongly suspect that the authors were writing with substantial bias against the use of nutritional supplements. While attitudes are changing to an extent within the medical profession, there nonetheless remains a strong undercurrent of bias against nutritional medicine and other complementary therapies. As a provider committed to integrative medicine, which incorporates the use of conventional and complementary therapies, recommended on an individual basis, I find it disappointing that the authors did not check their biases at the door. Scientific method has been developed to decrease the influence of bias in research, and it does no good to bring bias back into the equation when interpreting results.

Of course, the editorial itself is not the entire problem. Of greater frustration is the fact that this editorial was then widely disseminated via the news media, during which it received an additional level of distortion. Given that the articles that incited this process found that multivitamins did not engender an additional benefit on top of a balanced diet or conventional treatment, and for conditions that would not be expected to benefit from use of a multivitamin, it is incomprehensible that the subsequent news articles bore titles such as "Should We Toss Our Vitamin Pills?" and "Vitamin supplements are a waste of money, say scientists." It is difficult to know whether the blame lies at the feet of the journalists or the publicists, but it is clear that limited evidence was spun dramatically out of proportion as this made its way from the lab to the public. While the information gained in the clinical trials is valid and deserves to be incorporated into clinical practice, it does not warrant a massive news campaign intended to convince the public to stop taking vitamins.

Finally, experience and an understanding of scientific progress has taught me that it never pays to close doors, as these authors are suggesting. Statements of absolute certainty rarely hold up under scientific scrutiny, and the broader-reaching they are, the faster they tend to succumb to criticism and new evidence. In the final analysis, this editorial was unconstructive for this reason. It offered little new knowledge, and proposed a radical departure from well-established norms. Had the editorial been limited and stuck to concrete information, I would probably have been chiming in my agreement, because after all, we've learned that multivitamins are unlikely to prevent cognitive decline, though they may have other benefits, and that they are also not a helpful addition to conventional medical therapy immediately after a heart attack. But to take that evidence and then goad the news media into publishing articles that deride vitamins as useless is not helpful, not constructive, and frankly, bad science.