Sedentary behaviour is increasingly common, with young adults estimated to spend around six hours a day seated.

Extended sitting is known to reduce vascular function, measured through brachial Flow-Mediated Dilatation (FMD).

Earlier research shows that even a 1% drop in FMD is associated with a 13% increase in the risk of cardiovascular conditions, including heart disease and stroke.

In the study, published in the Journal of Physiology, researchers examined whether flavanols could mitigate sitting-related declines in vascular health. Forty healthy young men—half with higher fitness levels and half with lower—consumed either a high-flavanol cocoa drink (695 mg total flavanols) or a low-flavanol cocoa drink (5.6 mg). Women were not included due to variations in estrogen levels that may influence vascular responses, reported Science Daily website.

Participants then sat for two hours while researchers measured vascular markers including FMD in the arm and leg arteries, blood pressure, blood flow, shear rate, and leg muscle oxygenation.

Men who consumed the low-flavanol drink showed reduced FMD, increased diastolic blood pressure, reduced shear rate, and lower muscle oxygenation. Fitness level did not protect against these declines.

In contrast, participants who consumed the high-flavanol cocoa did not show declines in FMD, regardless of fitness level—marking the first evidence that flavanols can prevent sitting-induced vascular dysfunction in healthy young men.

Researchers said the findings suggest flavanol-rich foods may support vascular health, particularly in sedentary environments. They noted that high-flavanol cocoa products, berries, apples, plums, nuts, and black or green tea are widely accessible dietary sources.

The team added that combining flavanol intake with short activity breaks—such as brief walks or standing—may help counter long periods of inactivity.