Cocoa and tea may protect your heart from the hidden damage of sitting

Sedentary habits are widespread in modern life. Young adults spend an estimated six hours a day seated, and extended sitting is known to reduce how well blood vessels function.

Earlier research has shown that even a small 1% drop in vascular function, measured through brachial Flow-mediated dilatation (FMD), corresponds to a 13% rise in the risk of cardiovascular conditions such as heart disease, strokes, and heart attacks.

Researchers in the new study set out to determine whether specific dietary choices, particularly foods high in flavanols, could help offset the decline in vascular health that occurs during uninterrupted sitting.

What Flavanols Are and Why They Matter

Flavanols are naturally occurring polyphenols found in various fruits, tea, nuts, and cocoa beans. They have previously been linked to cardiovascular benefits, including support for the vascular system during psychological stress.

The study, which has been published in the Journal of Physiology, builds on this earlier evidence.

Dr. Catarina Rendeiro, Assistant Professor in Nutritional Sciences at the University of Birmingham and lead author, explained: "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. 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."

Cardiovascular disease continues to rise. According to the British Heart Foundation, deaths among working-aged adults in the UK increased by 18% to 21,975 in 2023 compared to 2019. Recent analyses also estimate that cardiovascular diseases cost the UK approximately £29 billion.

Testing Whether Flavanols Protect the Body During Sitting

To explore whether flavanols could help preserve vascular function, the researchers examined the effects of these compounds during a two-hour sitting period. Forty healthy young men took part. Twenty had higher fitness levels and twenty had lower fitness levels. Each participant consumed either a high-flavanol cocoa drink (695 mg of total flavanols per beverage) or a low-flavanol cocoa drink (5.6 mg of total flavanols per beverage) before beginning the sitting session.

Women were not included in the study because fluctuations in estrogen during the menstrual cycle may influence how flavanols affect vascular function. The researchers note that this should be explored in future trials.

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

• 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

High-Flavanol Cocoa Prevents Declines in Blood Vessel Function

Both the higher and lower fitness groups who consumed the low-flavanol drink showed declines in FMD in the arteries of their arms and legs. These participants also experienced increases in diastolic blood pressure, reductions in shear rate and blood flow, and lower leg muscle oxygenation. The results indicate that simply being more physically fit does not protect against the vascular effects of prolonged sitting.

In contrast, participants in both fitness groups who consumed the high-flavanol cocoa did not show declines in FMD in either the arm or leg arteries. This is the first study to demonstrate that flavanols can prevent sitting-induced vascular dysfunction in healthy young men.

Dr. Sam Lucas, Professor of Cerebrovascular, Exercise & Environmental Physiology at the University of Birmingham and co-author, said: "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."

The results also show for the first time that baseline cardiorespiratory fitness does not change how the body responds to flavanol intake. This suggests that flavanols may help support vascular health regardless of someone's fitness level.

Adding Flavanol-Rich Foods to Daily Routines

Alessio Daniele, PhD student at the University of Birmingham, noted: "It is actually quite easy to add high flavanol foods to your diet. There are cocoa products available in supermarkets and health stores which are processed through methods that preserve flavanol levels. If cocoa isn't your thing, fruits like apples, plums and berries, nuts, and black and green tea are all common kitchen staples and are readily available."

Dr. Catarina Rendeiro added: "Our research shows that consuming high-flavanol foods and drinks during periods spent sitting down is a good way to reduce some of the impact of inactivity on the vascular system.

"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."