More than half of all Americans take dietary supplements every day. Many follow well-known diets to protect themselves from cardiovascular disease and prevent premature death. However, dietary intervention measures can be tricky for healthcare professionals to address with their patients. When faced with questions about popular and easily-accessible vitamins, minerals, or diets, there’s a fine line between provider expertise and widespread belief. But a new study published in Annals of Internal Medicine might make your conversations about the use of supplements a little easier and more evidence-based.

What Did the Study Find?

Researchers led by Dr. Safi U. Khan at West Virginia University School of Medicine analyzed 277 randomized control trials of approximately one million people. They measured the efficacy of 16 popular supplements and eight widely recommended diets to prevent heart disease. According to Khan, the bottom line is that Supplement-users should take claims of cardiovascular benefits with a grain of salt. “This large study has a very simple message,” Khan said. “Do not waste money on these supplements because they do not act.”

Of the 16 supplements examined, omega-3 — the long-chain fatty acids found in fish oil — was the only one that showed some protective benefit against heart attack. Folic acid showed some protective benefit against stroke, though this evidence was driven mainly by the inclusion of a study from China, where a folate-rich diet is not routine. Most alarmingly, one supplement indicated an increased risk for stroke: Calcium combined with vitamin D.

Of the eight diets, reduced-salt regimens improved mortality among participants with normal blood pressure. However, the researchers reported that other common diets — The Mediterranean diet, reduced dietary fat, modified dietary fat, and reduced saturated fat intake — did not affect cardiovascular risk.  

The authors of the study reported the remaining surveyed supplements had no significant effect on mortality or cardiovascular outcomes. These included: multivitamins, selenium, vitamin A, vitamin B6, vitamin C, vitamin E, vitamin D alone, calcium alone, folic acid, and iron. “The omega-3 fatty acid might be helpful,” Khan said. “But we have far [better] cardiovascular medications, which can provide you a more robust benefit compared to this.”

What Does This Mean for Healthcare Providers?

With many Americans regularly using the supplements mentioned above, Khan’s findings are bound to elicit skepticism. The study results were influenced by geographic considerations and reliance on participant memory. Furthermore, conclusions centered around diet can be hard to interpret, considering the vastly different ways patients react to nutritional changes.

“These findings were limited by suboptimal quantities of evidence,” Khan said. “But that said, they may inform discussions regarding the use of these interventions in patients at risk of cardiovascular disease.”

The researchers say, for now, it’s best to hold off on using and recommending supplements or diet modification for cardiovascular disease prevention.