Are the compounds found in dark chocolate really good for your health? (Credit: George Rudy/Shutterstock)
In A Nutshell
- Healthy plant compounds called flavanols are naturally present in cocoa, though processing strips out much of it before chocolate reaches store shelves.
- The largest trial ever run on cocoa flavanols tested a concentrated supplement, not chocolate bars.
- The trial’s main result was a near-miss, but a secondary finding held up. Total cardiovascular events dropped 10%, which wasn’t statistically significant, while cardiovascular deaths specifically fell a significant 27%.
- A separate review found cocoa flavanols significantly lower blood pressure, though industry-funded studies reported somewhat larger effects than independent ones.
A square of dark chocolate has long been sold as one of life’s rare guilty pleasures that might actually be good for you. But as scientists take a closer look at cocoa’s powerful plant compounds called flavonols, the real story is proving more complicated.
What Are Cocoa Flavonols, And Why Do Researchers Keep Testing It?
Flavanols are a class of plant compounds found in cocoa, tea, grapes, and berries, and cocoa’s most-studied version is called epicatechin. Lab and clinical research has linked flavanols to increased nitric oxide production in blood vessels, which relaxes and widens them, a plausible mechanism for effects on blood pressure and circulation.
The definitive test came from COSMOS, the Cocoa Supplement and Multivitamin Outcomes Study. It’s a randomized, placebo-controlled trial led by researchers at Brigham and Women’s Hospital and published in the American Journal of Clinical Nutrition in 2022. More than 21,000 U.S. adults, women 65 and older and men 60 and older, took a daily capsule with 500 mg of cocoa flavanols, including 80 mg of epicatechin, or a placebo, for an average of 3.6 years.
The results were mixed in a specific, instructive way. The trial’s primary outcome, a composite of total cardiovascular events, dropped by 10% in the flavanol group. But that difference wasn’t statistically significant. A pre-specified secondary endpoint told a more encouraging story: cardiovascular death fell by a significant 27%.
When researchers limited the analysis to participants who reliably took their pills, the effect strengthened further, to a 15% reduction in total cardiovascular events and a 39% reduction in cardiovascular death.
Cocoa flavanols had no significant effect on cancer risk, the trial’s other major outcome. Study leader JoAnn Manson was careful to frame the results as promising but preliminary, saying any real health benefit would need confirming in a future trial before it could be recommended.
Does Eating Dark Chocolate Give You The Same Effect?
Not reliably, and the trial’s own authors said so directly. “COSMOS was not a chocolate trial,” Manson explained, noting the supplement contained far more flavanols than anyone could realistically eat in chocolate without excess calories, fat, and sugar.
Chocolate manufacturing routinely strips out much of the flavanol content cocoa beans start with, and levels vary enormously by brand. An FDA review of one high-flavanol dark chocolate product found around 230 mg of total flavanols in a 46-gram serving, while more typical bars deliver far less.
A separate line of evidence backs this up at a smaller scale. A Cochrane systematic review pooling 35 randomized trials found cocoa products produced a small but statistically significant reduction in blood pressure. However, the reviewers flagged that industry-funded studies reported somewhat larger effects than independently funded ones, a common source of bias worth naming.
A 2022 meta-analysis in the journal Foods similarly found real blood pressure benefits from cocoa and dark chocolate, but only once daily flavanol intake reached roughly 900 mg or epicatechin reached 100 mg, thresholds well above what an average chocolate bar provides.
What Does The Evidence Actually Support?
Taken together, the research points to flavanols themselves, not chocolate as a food, as the biologically active ingredient worth continued study. Even there the evidence is a signal rather than a settled conclusion: one large trial missed its main endpoint but hit a meaningful secondary one, and blood pressure benefits from food sources depend heavily on dose and processing.
Eating dark chocolate in moderation isn’t harmful and may deliver some flavanols, but it isn’t a validated substitute for the doses tested in COSMOS, and no researcher involved in that work recommends it as one.
