Prolonged sitting can lead to a temporary decline in blood vessel function and blood pressure. Implementing specific eating strategies while in a sitting position may either alleviate or exacerbate these effects on vascular health. Recent research indicates that dietary cocoa flavanols, consumed prior to two hours of uninterrupted sitting, effectively counteract the deterioration in vascular function seen in young, healthy men. The beneficial effects of flavanols were consistent across individuals with varying levels of cardiorespiratory fitness, suggesting that even those with high fitness do not escape the decline in vascular function or blood pressure associated with sitting.

Sedentary behavior has become exceedingly common in contemporary society.

Over the past two decades, it has been reported that the time spent sitting among young Americans has escalated from an average of 5.5 to 6.5 hours per day (an increase of 18.2%).

Sitting encompasses not only professional or commuting scenarios but also leisure activities like watching television or playing video games.

Previous studies indicate that a 1% decrease in vascular function (measured via brachial flow-mediated dilatation, which reflects arterial elasticity) correlates to a 13% rise in the risk for cardiovascular diseases such as heart disease, stroke, and heart attack.

Researchers, including Catarina Rendeiro and her team at the University of Birmingham, sought to determine if diet—as specifically influenced by flavanol-rich foods—could mitigate the vascular risks associated with extended sitting.

Flavanols are polyphenolic compounds naturally found in certain fruits, teas, nuts, and cocoa beans.

Research has shown they provide cardiovascular benefits, notably in protecting vascular health during mental stress.

“We spend significant amounts of time seated, whether at a desk, driving, traveling, or relaxing on the couch,” Dr. Rendeiro notes.

“Even while inactive, our bodies can experience stress.”

“Identifying methods to alleviate the impacts of prolonged sitting on vascular function might significantly lower cardiovascular disease risk.”

To investigate this, researchers assessed whether ingesting flavanols shortly before two hours of sitting could preserve blood vessel function in the arms and legs.

A total of forty healthy young men (20 with high fitness and 20 with low fitness) were given either a high-flavanol (695 mg total flavanols per beverage) or low-flavanol cocoa beverage (5.6 mg total flavanols per beverage) before undergoing a two-hour sitting test.

This study focused solely on men due to potential fluctuations of estrogen during women’s menstrual cycles, which might impact how flavanols affect vascular health while sitting. Future trials will address this aspect.

The research team conducted various vascular measurements pre- and post-sitting, including (i) superficial femoral and brachial artery FMD, (ii) arterial resting shear rate and blood flow, (iii) systolic and diastolic blood pressure, and (iv) leg muscle oxygenation.

For both groups that consumed low-flavanol cocoa before sitting, there was a decrease in FMD in arm and leg arteries.

This indicates that even high fitness levels do not shield individuals from the effects of seated inactivity.

Both groups also exhibited a significant rise in diastolic blood pressure, reduced shear rate and blood flow in both arteries, and lower muscle oxygenation.

However, participants who consumed the high-flavanol cocoa drink retained their FMD levels in both the arm and leg arteries, demonstrating the protective effects of flavanols across various fitness levels.

This is the first instance where flavanols have been recognized for their ability to prevent vascular dysfunction linked to prolonged sitting in healthy young men.

Professor Sam Lucas remarked: “Our findings reveal that even those with high fitness levels are not immune to the temporary vascular impairments caused by sitting and consuming only low-flavanol cocoa.”

“Remarkably, after consuming the high-flavanol beverage, both fit and unfit participants maintained their FMD levels, unaffected by two hours of sitting.”

This study also uniquely demonstrated that pre-existing cardiorespiratory fitness levels do not influence how flavanol intake affects vascular function.

This means everyone, irrespective of fitness levels, can reap the rewards of flavanol consumption.

“Integrating flavanol-rich foods into your diet is quite simple,” asserts Alessio Daniele, a PhD candidate at the University of Birmingham.

“Cacao products that retain flavanol levels are readily found in supermarkets and health stores.”

“If cocoa isn’t your preference, consider incorporating apples, plums, berries, nuts, or black and green teas, which are common in kitchens.”

“Our findings suggest that consuming flavanol-rich foods and beverages during sedentary periods is an effective strategy to mitigate the impacts of inactivity on vascular health,” Dr. Rendeiro indicates.

“Given the upward trend in sedentary lifestyles and the associated risks to vascular health, integrating flavanol-rich foods and beverages with short breaks for walking or standing can promote long-term well-being, regardless of physical fitness levels.”

The study was published in October 2025 in the Journal of Physiology.

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Alessio Daniele et al.. Dietary flavanols maintain endothelial function in the upper and lower extremities during sitting in healthy men with high or low physical fitness. Journal of Physiology published online October 29, 2025. doi: 10.1113/JP289038