Study finds cocoa flavanols help protect blood vessel function during prolonged sitting

New research indicates that consuming flavanol-rich foods, including cocoa and berries, helps protect men’s vascular health from the negative effects of extended sitting.

New research from the University of Birmingham indicates that routinely consuming flavanol-rich foods - such as tea, berries, apples, and cocoa—may help safeguard men’s blood vessels from the harmful effects that develop during extended periods of sitting.

Sedentary behaviour is widespread in modern society. Young adults spend an average of six hours a day seated, and long, uninterrupted sitting is known to impair normal blood vessel function.

Past studies have demonstrated that even a modest 1% decrease in vascular function, measured using brachial Flow-mediated Dilatation (FMD), is associated with a 13% increase in the risk of cardiovascular problems, including heart disease, stroke, and heart attack.

The authors of this new study aimed to determine whether certain dietary habits—specifically the consumption of foods high in flavanols—could help counteract the vascular decline that occurs when people remain seated without moving.

Flavanols are naturally occurring polyphenols found in a variety of fruits, teas, nuts, and cocoa beans. Previous evidence has linked them to cardiovascular benefits, including improved vascular responses during psychological stress.

This study, published in the Journal of Physiology, expands on that earlier work.

Dr. Catarina Rendeiro, Assistant Professor of Nutritional Sciences at the University of Birmingham and lead author, explained: “Whether we’re sitting at a desk, driving, commuting, or relaxing on the sofa with a book or the TV on, we spend a great deal of time seated. Even without physical movement, we still place stress on our bodies. Identifying strategies to reduce the impact that sustained sitting has on the vascular system could help lower the risk of developing cardiovascular disease.”

Rates of cardiovascular disease continue to increase. The British Heart Foundation reports that deaths among working-age adults in the UK rose by 18% - reaching 21,975 in 2023 - compared with 2019. Recent estimates also suggest cardiovascular disease costs the UK around £29 billion annually.

To investigate whether flavanols help maintain vascular function, the research team analysed physiological responses during a two-hour sitting session. Forty healthy young men participated—20 with higher fitness levels and 20 with lower fitness levels. Before sitting, each individual consumed either a high-flavanol cocoa drink (695 mg total flavanols) or a low-flavanol cocoa drink (5.6 mg total flavanols).

Women were excluded from the trial because hormonal fluctuations across the menstrual cycle may alter vascular responses to flavanols; the authors note that this should be examined in future studies.

Before and after the sitting period, the researchers assessed multiple markers of vascular health, including:

• FMD in the superficial femoral and brachial arteries

• resting arterial shear rate and blood flow

• systolic and diastolic blood pressure

• leg muscle oxygenation

Participants in both fitness groups who consumed the low-flavanol drink experienced reductions in FMD in both arm and leg arteries. They also showed increases in diastolic blood pressure, decreases in shear rate and blood flow, and reductions in muscle oxygenation in the legs. These findings show that higher physical fitness alone does not prevent the vascular dysfunction caused by prolonged sitting.

By contrast, men in both fitness categories who drank the high-flavanol cocoa did not display declines in FMD in either artery. This is the first study to demonstrate that flavanols can prevent sitting-related vascular dysfunction in healthy young men.

Dr. Sam Lucas, Professor of Cerebrovascular, Exercise & Environmental Physiology at the University of Birmingham and co-author, noted: “Our experiment shows that higher fitness levels do not stop the temporary impairment of vascular function caused by sitting when participants consume only the low-flavanol drink. Crucially, after the high-flavanol drink, both fitter and less-fit individuals maintained their pre-sitting FMD values.”

The study also shows for the first time that baseline cardiorespiratory fitness does not alter the body’s response to flavanol intake, suggesting flavanols may support vascular health regardless of a person’s fitness status.

Alessio Daniele, PhD student at the University of Birmingham, added: “It’s actually quite simple to include high-flavanol foods in your diet. Some cocoa products sold in supermarkets and health shops are processed in ways that preserve flavanol content. And if cocoa isn’t preferred, fruits like apples, plums, and berries, as well as nuts and both black and green tea, are common household items.”

Dr. Catarina Rendeiro concluded: “Our findings show that consuming high-flavanol foods and drinks during periods of sitting is an effective way to reduce some of the physiological strain that inactivity places on the vascular system.

“Given how common sedentary lifestyles have become and the risks they pose to vascular health, using flavanol-rich foods and beverages—particularly alongside simple breaks in sitting, such as standing or taking short walks - may help improve long-term health, no matter someone’s fitness level.”

Source: University of Birmingham
ImageCredits: Freepik