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The Supplement Debunker


Portrait of Safi Khan against a gray backdrop.

Qs by Stacey Elza
Photographed by Brian Persinger

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Go to just about any pharmacy, and you’ll find a dizzying array of supplements that claim to “support a healthy heart” and promote “optimal vascular health.” But do they? In 2019, Safi Khan — assistant professor in the School of Medicine — and his colleagues analyzed 277 randomized controlled trials to find out how nutritional supplements and special diets influenced mortality rates and cardiovascular outcomes. According to their findings, which appeared in the Annals of Internal Medicine, you might want to leave some of those supplements on the shelf.

What made you want to study supplements and diets in the first place? 

The reason we conducted this study was that nearly 1 million people in the United States and across the world consume supplements, but there was no good-quality evidence to suggest that these have any effect on cardiovascular protection. So, we selected high-quality randomized controlled trials. We gathered the information for a maximum number of interventions — both supplement and dietary. The most important thing was whether these supplements had any effect on improving the survival and cardiovascular outcomes, such as myocardial infarction, stroke or heart disease.

Which supplements did you find to be beneficial?

Folic acid had some protective effects on risk of stroke, and omega-3 fatty acids had some beneficial effects on risk of myocardial infarction and coronary heart disease events. However, the certainty of evidence suggesting these findings was suboptimal. The randomized controlled trials we included lacked precision and had issues related to heterogeneity of the baseline population.

In the future, how could studies of omega-3 fatty acids be improved so that their findings are better quality?

In my opinion, a clinical trial should be focused on a higher dose of omega-3 fatty acids in patients with baseline cardiovascular risk. Then researchers can see whether that would prove to be beneficial or not. I might be wrong, but I’ve got a feeling that if we use that population and a high dose of omega-3 fatty acids, it might change the survival endpoints. This has been shown in a recently published trial, too.

Which supplements might actually be harmful?

A calcium–vitamin D combination was found to be associated with a higher risk of stroke.

Which of your findings surprised you the most? 

We were surprised by the lack of cardiovascular benefit shown by the Mediterranean diet.

Do you take any supplements yourself? 


What advice would you give a bewildered shopper who is considering the supplements that crowd the shelves at the pharmacy or grocery store?

Do not waste your money. Instead, attain a healthy lifestyle by smoking cessation, exercise and a healthy diet.