But a new study, published July 2019 in the journal Annals of Internal Medicine, indicated that few nutritional supplements — or even dietary interventions — offer any protection against heart disease. In fact, some may actually do more harm than good. Drawing from 277 trials representing about one million people, investigators analyzed data for 16 nutritional supplements and eight dietary approaches. They found that most vitamins, minerals, supplements, and diets examined had no protective effects against cardiovascular health. The vitamins and supplements that appear to have little effect on cardiovascular health and longevity according to the research include:

MultivitaminsSeleniumVitamin AVitamin B6Vitamin CVitamin EVitamin DCalciumFolic acidIronFish oil

“Only folic acid for stroke, omega-3 fatty acid for heart attack, and a low-salt diet for total or cardiovascular mortality had proven benefits,” says Safi Khan, MD, lead author and an internal medicine specialist at West Virginia University in Morgantown. Dr. Khan added that there were a few caveats to these beneficial supplements: The benefit of folate supplements was largely derived from an analysis of a Chinese population, a group that in general does not consume a folate-rich diet. And supplementation with omega-3 fatty acids was only beneficial at very large doses in high-risk patients. On the negative side, Khan and his colleagues note that their research found that calcium together with vitamin D might raise the risk for stroke. “Calcium plus vitamin D can increase calcium content in the blood and increase calcium deposition in blood vessels,” says Khan. “This initiates atherosclerosis and blood clot formation and consequently causes stroke.” RELATED: 10 High-Sodium Foods to Avoid

Study authors were especially surprised by data showing no heart health benefits from dietary interventions such as the Mediterranean diet, reduced saturated fat intake, modified fat intake, and reduced dietary fat intake. Many health experts, including the American Heart Association, have recommended such eating plans to help prevent heart disease. Khan says that these findings contradict the PREDIMED trial published in The New England Journal of Medicine, which found that the incidence of cardiovascular disease in the Mediterranean diet groups was lowered by approximately 30 percent when compared with the control diet. “In this umbrella review, we included six trials of Mediterranean diet,” he says. “Pooling results from all the trials did not support cardiovascular risk. So the totality of evidence is still inconclusive about benefits of this particular eating style. Similarly, the totality of evidence is not consistent for the efficacy of reduced saturated fats.” Satjit Bhusri, MD, a cardiologist with Lenox Hill Hospital in New York City, argues that “more powerful, diet specific trials” have demonstrated heart-protective gains from the Mediterranean diet.

Study Limitations May Dilute Results

“When one looks under the hood of this meta-analysis, its effective power and utility in real practice are lowered by the studies and patient populations used,” says Dr. Bhusri. The research authors and an accompanying editorial published in Annals of Internal Medicine from Scripps Research Translational Institute admit that the findings are limited by the quality of the evidence. Scientists took most of their information from studies that relied on food diaries. Because these records depend on patient memories and estimates, they can often be inaccurate. Khan advocates for future quality randomized, controlled trials targeting well-defined populations to acquire better answers. “Unfortunately, the current study leaves us with the same foggy conditions that we started with,” wrote Amitabh Pandey, MD, and Eric Topol, MD, in an editorial response. “Until these conditions clear, it would be reasonable to hold off on any supplement or diet modification in all guidelines and recommendations.” For now, Khan suggests that sticking to a wholesome meal plan may be the best course of action. “People should focus on healthy diet from nutritional food sources — not vitamins or supplements — in combination with a healthy lifestyle that includes regular physical activity and not smoking,” he says.