The Multivitamin Maelstrom

November 7th, 2011

By Cathie Dunal, MD, MPH: The media’s most recent — and unsubstantiated — medical claim comes from the Iowa Health Study in an article in the Annals of Internal Medicine: researchers state that mortality rates increase in older women who take daily multivitamin and mineral supplements. This claim has circled throughout the major media carriers, even landing in the Chicago Tribune, “…older women who took a daily vitamin supplement — even just a multivitamin — had an increased risk of dying of cardiovascular disease and cancer.” Look thoroughly at the research before you throw away your vitamins!

A closer look shows that the Iowa Health Study article is not the rigorous, randomized study that is the gold standard in medical research; instead, it is simply observational. Women (average age: 61.6) self-reported their health status in 1986, 1997 and 2004. Finally, in 2008, after twenty-two years and only three checks, researchers tallied the number of women who had passed away due to cardiovascular disease, cancer or “other causes”.

Clearly the structure of the study wasn’t optimal, and furthermore, the study simply ignored the baseline health levels of the respondents. (Were they all basically healthy? Did any of the respondents have high blood pressure? How high? A family history of heart disease? Were they big fast food eaters?) We can’t accurately determine the respondents’ baseline health levels — and that, in a nutshell, is one of the major reasons the study is flawed.

As well, we have to address the supplements themselves: Were they of a high quality? Were the women taking supplements to cure an existing complaint, or taking them preventively to maintain optimal health levels? The study found that participants who took iron had the greatest mortality rate — and this finding, I argue, raises just these questions.

If we momentarily backtrack to the Seventies — remembering that the average age of the participants was over sixty at the beginning of the study — we’ll remember that media outlets had been saturated with Geritol® commercials promising to fix “iron-poor blood” or “tired blood”. Iron was marketed as a cure for tiredness, and Geritol® was the largest selling iron and B vitamin supplement in the US until 1979. I suspect that a significant number of the respondents who took iron were self-medicating tiredness — or other symptoms that could very well have been caused by underlying medical conditions. As the study fails to provide contextual information regarding the rationale behind supplement-taking, it becomes almost impossible to accurately analyze the study’s claims.

And finally, the findings in the Iowa Health Study are contradicted by a wealth of other research.  Literally the next day after the Iowa Health Study was published, a summary article appeared in the Harvard Health Newsletter reporting better health with folic acid supplements and Vitamins B6 and B12. Quite contradictory.

The bottom line: this is a flawed study that has been overblown by the media.  It will be interesting to see more research on the topic, as it is clearly a hot-button issue in the medical community.  Meanwhile, I’m still taking my vitamins!

Comments are closed.