In the media and in medical journals, it has become something of a national pastime to attack the science on dietary supplements. While there are too many instances to list here, in the past few years there has been more than one article questioning the health benefits of fish oil, an editorial in the Annals of Internal Medicine (Annals) claiming that vitamin and mineral supplements are a waste of money, and an entire book based partly on the suggestion that supplements are unnecessary for the majority of people eating a healthy diet. Yet, an article published in September of last year on the popular blog, FiveThirtyEight, entitled “Don’t Take Your Vitamins,” may be the most illustrative case of how the arguments against supplements are deeply flawed, yet present enough truth to mask their flaws from casual readers.
The FiveThirtyEight article begins by supposedly deconstructing the science around vitamin D and vitamin E. Of course, there is nothing wrong with a thorough review of the scientific literature regarding a particular supplement ingredient—medicine, both conventional and alternative, should always be based on an assessment of the evidence for and against a particular treatment. The problem is that it is nearly impossible to make blanket statements about all or most supplement ingredients based on a handful of examples, which is exactly what the article does. There are hundreds of supplement ingredients (if not thousands), each with their own body of evidence; and there are thousands of relevant studies on supplement ingredients in total. There is no reason to suppose that the evidence relating to vitamins D and E is somehow representative of this large and varied collection of scientific research. In fact, it is not at all difficult to find randomized, controlled trials in PubMed (a scientific database that is part of the US National Library of Medicine) showing positive results from the administration of supplement ingredients—although, the FiveThirtyEight article makes this seem like a rare discovery. While it would be too cumbersome to list all of those trials here, clinical research has shown, for example, that multivitamin-mineral preparations have a wide range of benefits, including increasing energy and stress tolerance, improving pregnancy outcomes, decreasing infection rates, slowing bone loss, and improving cognitive function in schoolchildren. As for vitamin D, there may not be any substantial benefits from supplementation when it comes to reducing one’s risk of diabetes, weight loss, and cancer, as the article points out. Not every supplement works for every condition. But, also somewhat selectively, the article mostly ignores the established body of randomized, controlled trials showing that vitamin D supplementation may be helpful for preventing osteoporosis and fractures. The article only mentions in passing that the best-case scenario is that vitamin D “might help a little” if you are an elderly woman who is vitamin D-deficient. The article does not say what vitamin D might help with, or explain why it helps only “a little.” Similarly, for vitamin E supplementation, although the evidence is conflicting, there have been randomized trials showing a benefit for a handful of conditions, such as intermittent claudication (pain in the legs during walking, due to arterial obstruction). Yet, these trials do not get any mention in the article.
The bottom line is that it is very easy to construct a case against supplements by selectively looking at only some of the research, not fully explaining the research, making unqualified statements relating to the research, and then presenting this research as being representative of supplement science as a whole. What is harder, and arguably more forthright and scientific, is to take a nuanced view of all the data for a particular supplement ingredient, and present the benefits and lack of benefits in a comprehensive and unbiased fashion. Since the knowledge gained from clinical trials on supplements can only advance the practice of medicine and public health, it would be unfortunate if it were disregarded or misconstrued based on incomplete facts and flimsy reasoning.