Sedentary lifestyles are extremely common, with young adults spending six hours a day on average seated; extended sitting is known to reduce how well blood vessels function. Even a 1% drop in how well blood vessels function, measured through flow-mediated dilation (FMD), corresponds to a 13% rise in heart disease, stroke, and heart attacks.

Researchers in the present study, published in the Journal of Physiology, sought to determine if dietary flavanols could help to improve vascular health in people who sit for prolonged periods of time. Flavanols are naturally occurring polyphenols found in cocoa, tea, fruits, and nuts.

“Whether we are sitting at desks, behind the wheel of a car, on a train, or on the sofa reading a book or watching TV, we all spend a lot of time seated,” said Catarina Rendeiro, PhD, assistant professor in nutritional sciences at the University of Birmingham and lead author of the study. “Even though we are not moving our bodies, we are still putting them under stress. Finding ways to mitigate the impact that sitting for uninterrupted periods has on our vascular system could help us cut the risk of developing cardiovascular diseases.”

The researchers examined the effects of either a high-flavanol cocoa drink or a low-flavanol cocoa drink as a control during a two-hour sitting session, divided among 40 healthy young men; 20 men had higher fitness levels, and 20 men had lower fitness levels, divided evenly among treatment and control groups. According to the researchers, women weren’t included in this study due to how fluctuations in estrogen during the menstrual cycle may influence how flavanols affect vascular function.

Before and after the sitting period, the team measured several indicators of vascular health, including:

• Flow-mediated dilation (FMD) in the superficial femoral artery and the brachial artery
• Arterial resting shear rate and blood flow
• Systolic and diastolic blood pressure
• Leg muscle oxygenation

Regardless of fitness level, those who consumed the low-flavanol drink showed declines in FMD measures, increased diastolic blood pressure, reduced shear rate and blood flow, and lower leg muscle oxygenation. Therefore, simply being physically fit didn’t appear to prevent sitting-induced vascular dysfunction in young men.

In contrast, those who consumed the high-flavanol beverage, regardless of fitness level, didn’t show declines in FMD in either the arm or leg arteries. These findings are the first of their kind, the authors noted.

“Our experiment indicates that higher fitness levels do not prevent the temporary impairment of vascular function induced by sitting when only drinking low-flavanol cocoa. Importantly, after the high-flavanol drink, both fitter and less-fit participants kept their FMD the same as it was before sitting for two hours,” said Sam Lucas, PhD, professor of cerebrovascular, exercise, and environmental physiology at the University of Birmingham and co-author.

“It is actually quite easy to add high flavanol foods to your diet,” said Alessio Daniele, PhD student at the University of Birmingham. “There are cocoa products available in supermarkets and health stores which are processed through methods that preserve flavanol levels.”

“Given how common sedentary lifestyles have become, and the increased risk this can have to vascular health, using flavanol-rich food and drink, especially in combination with breaking up periods of inactivity by going for a short walk or standing up, could be a good way to enhance long-term health, no matter the individual’s fitness level,” Renderio added.