Flavanols in cocoa can protect blood vessel function following uninterrupted sitting - study

New research from the University of Birmingham shows that eating flavanol-rich foods—like tea, berries, apples, and cocoa—can protect vascular health in men from the harmful effects of prolonged sitting.

Sedentary behaviour is prevalent in modern societies; it is estimated that young adults sit for approximately six hours a day, but sitting for long periods induces declines in vascular function.

Previous studies have shown that a 1% reduction in vascular function, as measured by brachial Flow-mediated dilatation (FMD), which measures the elasticity of the arteries, leads to a 13% increased risk of cardiovascular disease, such as heart disease, strokes, and heart attacks.

The researchers wanted to explore if there was a way that diet, particularly foods that are high in flavanols, could help protect against the risk to our vascular system associated with periods of uninterrupted sitting.

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.

Flavanols are a type of polyphenol compound that occur naturally in some fruits, tea, and nuts, and cocoa beans. They have been shown to have cardiovascular health benefits, such as protecting the vascular system during periods of mental stress.

The research has been published today (29 Oct) in the Journal of Physiology.

Dr Catarina Rendeiro, Assistant Professor in Nutritional Sciences at the University of Birmingham, and leading author, said: “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.”

Deaths of cardiovascular disease are on the rise; the British Heart Foundation reports that deaths of working-aged adults in the UK increased by 18% to 21,975 in 2023, compared to 2019. In addition, recent studies have found that cardiovascular diseases cost the UK an estimated £29 billion.

The researchers tested whether consuming flavanols just before two hours of sitting could preserve blood vessel function in the arms and legs. Forty young healthy men, 20 who had higher levels of fitness and 20 who had a lower level of fitness, consumed either a high-flavanol (695 mg of total flavanols per beverage) or low-flavanol cocoa drink (5.6 mg of total flavanols per beverage), before completing a two-hour sitting trial.

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.

The study was not carried out with women, as changes in oestrogen levels during the menstrual cycle are suspected to affect the impact of flavanols on vascular health during sitting. This should be the focus of another future trial.

The team took a range of vascular measures before and after sitting, 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

Both the lower and higher fitness groups who had the low-flavanol cocoa before sitting, experienced FMD declines in the arteries in their arms and legs. This suggests that higher levels of fitness do not provide protection from sitting. It also significantly increased diastolic blood pressure, decreased shear rate and blood flow in both arteries, and resulted in declines in muscle oxygenation in both fitness groups.

However, the research found that those groups who consumed the high-flavanol cocoa drink, again in both fitness groups, did not experience FMD declines in either of the arteries in their arms or legs. This is the first time flavanols have been shown to be effective at preventing sitting-induced vascular dysfunction, in young healthy men.

Dr Sam Lucas, Professor of Cerebrovascular, Exercise & Environmental Physiology at the University of Birmingham and co-author of the study, 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 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 flavanol intake regardless of their levels of physical fitness.

It is actually quite easy to add high flavanol foods to your diet (...) 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.

Alessio Daniele, PhD student from the University of Birmingham, added: “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 concluded: “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.”

Featured staff