You want chocolate. You need flavanols.

Howard Sesso.

Veasey Conway/Harvard Staff Photographer

Health
You want chocolate. You need flavanols.

Research strengthens evidence for role of inflammation in disease – especially as we age

Alvin Powell

Harvard Staff Writer

September 30, 2025 4 min read

New findings from Harvard researchers pinpoint reduced inflammation as the key to cocoa’s effects against cardiovascular disease.

The work follows a large probe of the possible health benefits of cocoa that ran from 2014 to 2020. Called COSMOS, the study showed that cocoa supplements reduced cardiovascular disease mortality by 27 percent among 21,442 subjects 60 and older. What that study didn’t explain is how.

The new work, published in the journal Age and Ageing, analyzed COSMOS blood samples and shows that a widely accepted marker of inflammation called high sensitivity C-reactive protein fell 8.4 percent annually compared with placebo.

Howard Sesso, an associate professor of medicine at Harvard Medical School and associate director of the Division of Preventive Medicine at Brigham and Women’s Hospital, said that the findings provide more evidence of the impact of inflammation as we age, evidence that has become strong enough that specialists have coined the term “inflammaging.”

“The term ‘inflammaging’ recognizes the fact that inflammation on its own is an important risk factor not just for cardiovascular disease, but also for other conditions related to vascular health, such as cognition,” said Sesso, also an associate professor of epidemiology at the Harvard T.H. Chan School of Public Health. “The aging piece simply acknowledges that as we’re aging, a lot of these things we think about for cardiovascular disease prevention also extend to other aging-related outcomes.”

The study, supported by the National Institutes of Health, examined five age-related markers of inflammation among subjects receiving cocoa extract supplementation every day. The markers included high sensitivity C-reactive protein; an immune mediating protein called IFN-g, which increased modestly during the study; and a pro-inflammatory protein called IL-6, which fell slightly among women.

Those results, researchers said, provide an avenue for future studies. The other markers, a pro-inflammatory protein and an anti-inflammatory protein, showed no change.

The new work is part of a broader effort to mine the extensive data collected during COSMOS, which stands for the “COcoa Supplement and Multivitamin Outcomes Study.” The initiative’s size and multiyear follow-up give researchers the chance to subdivide results and peer deeper into what the data can tell us.

In fact, Sesso and colleagues did just that in another recent paper examining whether cocoa extract affects high blood pressure, which is also more common as we age. The work, published in the journal Hypertension, found that cocoa supplementation didn’t help older subjects who already had elevated blood pressure — those with systolic readings between 120 and 139 — but that it was protective against developing high blood pressure for those with favorable initial systolic readings below 120.

“Clearly, blood pressure and inflammaging are all somehow related in explaining how cocoa extract might be lowering cardiovascular disease risk,” Sesso said.

Sesso cautioned that COSMOS doesn’t make dietary recommendations. The work explores the reported health benefits of cocoa through supplements of cocoa extract, which is rich in bioactive molecules called flavanols, not of chocolate or other foods high in cocoa.

Flavanols are also found in blueberries, strawberries, tea, and grapes. Cocoa is problematic from a dietary standpoint, Sesso said, since many foods rich in cocoa are highly processed, contain added sugars and fats, and have unknown levels of flavanols. The extra calories one might consume through those products would likely cancel any health benefits.

Flavanols are also not listed on most nutrition labels, though Sesso said the COSMOS results raise the question of whether they should be, a step that would require additional research. Until then, he recommended that health-conscious consumers focus on controllable lifestyle factors, such as eating a healthy diet and exercising, before they visit the supplement aisle.

“COSMOS was not a trial to evaluate whether eating chocolate is good for you,” Sesso said. “It instead asks, ‘Is there something about the cocoa bean and the bioactive components in it that could be beneficial for health?’”