Cocoa compounds may support blood vessel function and heart health

Research on cocoa suggests that its compounds may help blood vessels work better and may slightly reduce blood pressure, according to small clinical studies. But these short-term results should not be mistaken for evidence that chocolate or cocoa supplements can prevent heart attacks or strokes.

The difference is important because attractive food claims often spread faster than the data supporting them. Scientists are focusing on cocoa flavanols, a class of naturally occurring plant compounds, rather than assuming all chocolate products contain the same substances or produce the same effects.

There is a clear biological hint: some cocoa preparations appear to help blood vessels respond more efficiently. What remains unclear is how much of that benefit, if any, carries over into long-term protection against disease beyond the changes seen in short studies.

One 2015 trial published in Age included 42 healthy men from younger and older age groups. They drank either a flavanol-rich beverage or a matched comparison drink twice a day for two weeks, and the researchers measured several circulation markers.

In both age groups, blood vessel function improved, including the ability to widen in response to increased blood flow. Some measures tied to vessel stiffness and blood pressure also improved, pointing to effects on circulation rather than showing that the heart itself had become stronger.

A second 2015 study, published in the British Journal of Nutrition, involved 100 healthy adults aged 35 to 60. After one month, the flavanol drink improved vessel function and lowered blood pressure compared with the control drink.

Changes in blood pressure, however, need to be interpreted carefully because the way readings are taken can affect the results.

Systolic pressure, the top number, dropped by about 4.4 millimeters of mercury, while diastolic pressure fell by about 3.9. The researchers also noted cholesterol changes and used a formula to estimate participants’ future cardiovascular risk.

That estimate suggested a lower predicted risk, but it did not show fewer actual heart attacks. A one-month shift in a risk score cannot reveal what will happen over the next decade, especially in a relatively small study.

A much larger later trial adds important context. COSMOS, reported in 2022 in The American Journal of Clinical Nutrition, followed 21,442 older adults and found no statistically significant reduction in its main combined cardiovascular outcome with cocoa extract over about 3.6 years.

COSMOS did report fewer cardiovascular deaths, a secondary finding that deserves more study. Overall, the evidence still leaves open the possibility of benefit, but it does not prove that routine cocoa supplementation prevents cardiovascular disease.

Ordinary chocolate is also not the same as the standardized products used in research, and processing can change flavanol levels. Cocoa-containing foods can fit into a healthy overall diet, but these findings do not make chocolate a treatment or a substitute for proven blood pressure and cholesterol care.

If you are interested in this topic, please read articles about How dark chocolate helps lower blood pressure, and Flavonoid-rich foods could help reduce death risk in heart disease.

For more information, please see articles about The DASH diet is a simple way to lower high blood pressure, and Salt and heart health: does less really mean more?.

Source: University Hospital Düsseldorf; FLAVIOLA Consortium; Brigham and Women’s Hospital.