How to make sense of conflicting health studies

Science often seems to change its mind: what was good for you yesterday now threatens your life.


Photo: Andrew B. Myers

Studies about the dire effects of supplements dominated headlines recently, sending some Canadians running to their medicine cabinets to clear the shelves. Considering that more than 70% of us use a natural health product every day, and that an even greater percentage don’t read beyond the headlines, it’s easy to imagine fears of a looming health disaster. Relax. Under those headlines often lie more balanced stories. Even then, you need to view them with a critical eye.

The problem with a title like “Study links vitamins to higher death rates in women,” which ran on CTV’s news website, is that the study’s authors did not reach that conclusion; the headline writer did. The study’s findings, originally published in the Archives of Internal Medicine, were much more nuanced: “In older women, several commonly used dietary vitamin and mineral supplements may be associated with increased total mortality risk; this association is strongest with supplemental iron,” the authors write. “In contrast to the findings of many studies, calcium is associated with decreased risk.” The subjects were women between the ages of 55 and 69. A more accurate headline would have been, “Not all supplements are a fountain of youth.”

Such leaps to sensational oversimplification are partly why it seems that medical research keeps changing its mind. One day, a food or an activity is touted for doing wonders for your health; the next, some study identifies it as a silent killer. The actual research is rarely so black and white.

Take the recently published results of a clinical trial that found participants who took vitamin E, believed to be neutral or beneficial in fighting cancer, had a 17% higher risk of prostate cancer. An alarming finding, but critics have suggested the results were skewed by the researchers’ use of a synthetic vitamin E, which lacks the powerful antioxidants found in the natural kind. That info likely wouldn’t appear in the headline.

So how do you know what to believe and when to change your diet or lifestyle? First, you need to get media savvy. Imagine if you saw the headline “Blue chip equities linked to losing portfolios.” Would you dump all your stock without reading further or calling your investment adviser? We need to apply equal research discipline to managing our health as we do to managing our money. And to do that, we need to know how to interpret medical stories. Some tips:

Don’t rely on the article or TV report. If it’s about a health issue relevant to you, find the abstract of the actual study which provides the scientists’ conclusions.

Identify who funded the study. American studies funded by the National Institute of Health and Canadian ones backed by the National Research Council of Canada are generally non-biased. But studies funded by less scientifically rigorous biotech companies may be designed to have a preferred outcome.

Do background checks on the authors. In most medical journals, physicians must declare any conflict of interest alongside their expertise and university affiliation. Those on the payroll of a drug company as clinical advisers may be seen as conflicted, especially (but not only) if that company is funding the study.

Assess the methodology. Did the study run long enough? Research projects that are too short may not see changes that occur later, while in overly long trials other variables, such as lifestyle change or new health conditions, may affect the results. What variables were included or excluded, and should they have been? For example, in diabetic studies diet and activity levels should be accounted for as they affect sugar levels. Finally, was the study’s sample size large enough to have statistical significance?

Listen to your gut. If it’s telling you this can’t be so simple, it probably isn’t. Dig deeper. Watch how experts weigh the findings by searching out peer reactions online. And if the research is particularly important to your health, seek out a specialist and review the study with them.

New research appears daily that may alter our assumptions about how we have been doing things or what we should do tomorrow. As knowledge evolves, “my doctor knows best” may not hold. In health care, as in personal finance, the “buyer beware” rule should apply when reading about the latest breakthroughs or scares.