Sitting for long periods of time temporarily impairs blood vessel function and blood pressure. Sedentary diet strategies may improve or worsen the effects of sitting on vascular health. In a new study, dietary cocoa flavanols taken immediately before two hours of continuous sitting were effective in preventing sitting-induced decline in vascular function in healthy young men. Flavanols were equally effective in preserving vascular function in individuals with high and low cardiorespiratory fitness during sitting. An individual’s high cardiorespiratory fitness did not prevent declines in vascular function and blood pressure during sitting.
Consuming foods high in flavanols during a sedentary lifestyle, either alone or in combination with other strategies (e.g. breaking the sitting posture), can reduce the effects of inactivity on the vascular system. Image Credit: Daniel except., doi: 10.1113/JP289038.
Sedentary behavior is very prevalent in modern society.
Over the past 20 years, the frequency of sedentary behavior, particularly sitting time, is estimated to have increased among young adults in the United States from 5.5 to 6.5 hours per day (equivalent to 18.2%).
Sitting is a very common type of sedentary behavior, including leisure activities such as watching TV and playing video games, as well as occupational sitting and commuting.
Previous research has shown that a 1% decrease in vascular function, as measured by brachial flow-mediated dilatation (FMD), which measures the elasticity of arteries, is associated with a 13% increase in the risk of cardiovascular diseases such as heart disease, stroke, and heart attack.
University of Birmingham researcher Catarina Rendeiro and her colleagues wanted to explore whether there were ways in which diet, particularly foods high in flavanols, could help protect against vascular risks associated with prolonged sitting.
Flavanols are a type of polyphenol compound that occurs naturally in some fruits, tea, nuts, and cocoa beans.
It has been shown to have cardiovascular health benefits, including protecting the vascular system during times of mental stress.
“We all spend a lot of time sitting, whether we’re sitting at a desk, in the driver’s seat of a car, on a train, or on the couch reading a book or watching TV,” Dr. Rendeiro said.
“Even if we don’t move our bodies, we’re still stressed.”
“Finding ways to mitigate the effects of continued sitting on the vascular system may help reduce the risk of developing cardiovascular disease.”
Researchers tested whether consuming flavanols just before two hours of sitting could preserve vascular function in the arms and legs.
Forty young healthy men, 20 with high and 20 with low fitness levels, consumed either a high-flavanol (695 mg total flavanols per drink) or a low-flavanol cocoa drink (5.6 mg total flavanols per drink) before completing a 2-hour sitting test.
The study was not conducted in women because changes in estrogen levels during the menstrual cycle are suspected to influence the effects of flavanols on vascular health while sedentary. This should be the focus of another trial in the future.
The team performed a variety of vascular measurements before and after sitting, including (i) FMD of the superficial femoral and brachial arteries, (ii) arterial resting shear rate and blood flow, (iii) systolic and diastolic blood pressure, and (iv) leg muscle oxygenation.
Both the low- and high-fitness groups who consumed low-flavanol cocoa before sitting experienced decreased FMD in the arteries of their arms and legs.
This means that higher levels of fitness do not prevent sitting.
Additionally, diastolic blood pressure increased significantly, shear rate and blood flow decreased in both arteries, and muscle oxygenation decreased in both fitness groups.
However, the scientists found that in both fitness groups, those who consumed the high-flavanol cocoa beverage did not experience a decrease in FMD in either arm or leg arteries.
This is the first time that flavanols have been shown to be effective in preventing sitting-induced vascular dysfunction in young, healthy men.
Professor Sam Lucas, from the University of Birmingham, said: “Our experiments show that even high levels of fitness cannot prevent the temporary damage to vascular function caused by sitting when drinking only low-flavanol cocoa.”
“Importantly, after drinking the beverage high in flavanols, the FMD of both healthy and less healthy participants remained the same as before sitting for two hours.”
This study is also the first to demonstrate that baseline levels of cardiorespiratory fitness do not alter the vascular effects of flavanol intake.
This means that individuals can benefit from consuming flavanols regardless of their fitness level.
“It’s actually very easy to add foods high in flavanols to your diet,” said Alessio Daniele, a PhD student at the University of Birmingham.
“You can buy cocoa products from supermarkets or health food stores that have been processed in ways that preserve flavanol levels.”
“If you don’t like cocoa, fruits like apples, plums, strawberries, nuts, black tea, and green tea are all common kitchen staples and readily available.”
“Our research has shown that consuming foods and drinks high in flavanols during sedentary time is a good way to reduce the effects of inactivity on the vascular system,” said Dr. Rendeiro.
“Given how common a sedentary lifestyle has become and the increased risks this can pose to vascular health, using flavanol-rich foods and drinks can be a great way to improve long-term health, regardless of an individual’s fitness level, especially in conjunction with breaking up periods of inactivity by taking short walks or standing up.”
that study Published in October 2025. journal of physiology.
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Alessio Daniele except. Dietary flavanols preserve upper and lower extremity endothelial function during sitting in fit and healthy male bodies. journal of physiologyPublished online October 29, 2025; doi:10.1113/JP289038
