The results from a long-running clinical trial that sought to compare the benefits of taking a cocoa flavanol supplement or a multivitamin over multiple years ended up being quite compelling. Researchers found that consuming cocoa flavanols lowered the risk of cardiovascular death by 27 percent.

The COcoa Supplement and Multivitamin Outcomes Study, or COSMOS, is believed to be the largest study focused on a single bioactive ingredient. Initiated and led by Brigham and Women’s Hospital, an affiliate of Harvard Medical School, the randomized, doubled-blind, placebo-controlled study involved more than 21,000 participants over the age of 60 who consumed either a 500 mg capsule of cocoa flavanols, a multivitamin tablet, both, or nothing at all. Participants were initially free from cardiovascular disease and recently diagnosed cancers, and the study’s intervention phase was from June 2015 through December 2020.

Researchers found three statistically significant areas of impact related to heart health.

While cocoa flavanol supplements only lowered the risk of experiencing cardiovascular events by 10%, there was a 27% reduction in cardiovascular death and greater cardiovascular benefits among those taking the study pills regularly.

Overall heart disease risk also dropped by 15% among study participants and they were 39% less likely to die from cardiovascular disease.

Third, measurable events related to heart attacks, strokes. and cardiovascular deaths dropped significantly in severity among participants taking cocoa flavanols.

Notably, the study—published in the American Journal of Clinical Nutrition—found .taking a daily multivitamin did not have a significant impact on cardiovascular disease or cancer outcomes.

While the study was partially funded by a division of candy giant Mars—Mars Edge, established to support human health through nutrition—it would be very difficult to consume the amount of cocoa flavanols studied in COSMOS from chocolate products without adding a large amount of fat, sugar and calories to a person’s diet.

Aside from cocoa, flavanol-rich foods include apples, berries and drinks like red wine and tea. Flavanols have been linked to lower blood pressure, improving brain health. and stimulating brain-blood oxygenation levels.

“When we look at the totality of evidence for both the primary and secondary cardiovascular endpoints in COSMOS, we see promising signals that a cocoa flavanol supplement may reduce important cardiovascular events, including death from cardiovascular disease,” study co-leader Howard Sesso said in a press release. “These findings merit further investigation to better understand the effects of cocoa flavanols on cardiovascular health.”

Study authors do temper expectations in their paper, calling for “cautious interpretation” of the results. But. the researchers say they will continue to follow COSMOS participants in an effort to help clarify any longer-term effects on cancer and death, and investigators and collaborators “are also leveraging COSMOS to study cognitive decline, falls, eye disease. and other aging-related outcomes that may be influenced by the supplements.”