Cocoa and Tea May Protect Your Heart From the Hidden Damage of Sitting

Eating foods rich in flavanols – such as tea, berries, apples and cocoa – could help to protect male vascular health from the harmful effects of prolonged sitting.

This finding comes from new research published in the Journal of Physiology, led by Dr. Catarina Rendeiro, an assistant professor in nutritional sciences at the University of Birmingham.

“Our work suggests that drinking or eating a food high in flavanols can be used as a strategy to mitigate some of the negative impact of sitting on the body’s arteries. This can help us make more informed decisions about what we eat and drink during periods in which we have to sit down uninterrupted for a period (for work, etc.),” Rendeiro told Technology Networks.

“If possible, breaking up sitting with standing or short walks should be the main strategy used. However, in situations in which that is not possible, using healthy dietary strategies (rich in flavanols) may help mitigate some of the negative effects of sitting on vascular function.”

The harms of prolonged sitting

According to figures from the World Health Organization, approximately one-third of adults worldwide do not meet the recommended levels of physical activity per week. Additional studies estimate that the average American adult is sedentary for nearly eight hours per day.

Sedentary lifestyles have been linked to an increase in all-cause mortality as well as numerous adverse health effects, including increased risks for obesity, chronic respiratory diseases, type 2 diabetes, cardiovascular diseases and some cancers.

One aspect of a sedentary lifestyle that researchers are particularly interested in is the effects of prolonged sitting on the body. Many office workers may sit uninterrupted for hours at a time; studies have shown that sitting for almost all of the workday without frequent breaks is associated with an increased risk of self-reported poor general health and back/neck pain. Prolonged sitting has also been shown to negatively impact several markers of peripheral vascular health, particularly the vasodilation of leg arteries.

“There are likely many mechanisms by which sitting impacts vascular health, but one of them is by inducing impairments in the ability of the arteries to dilate in response to blood [flow] changes, which will result in increases in blood pressure, leading to hypertension, for example,” Rendeiro explained.

Flow-mediated dilation (FMD) is a non-invasive test that measures the ability of arteries to dilate in response to changes in blood flow and blood pressure. Previous studies have shown that a 1% reduction in vascular function, as measured by FMD, is associated with a 13% increased risk of cardiovascular disease.

Berries and tea could protect the vascular system

Flavanols are a type of polyphenol compound that occurs naturally in some fruits, teas, nuts and cocoa beans. Natural flavanols are known to function as antioxidants, with some dietary flavanols having been linked to protective effects against diabetes, cancer and cardiovascular disease.

In this latest study, researchers set out to explore whether dietary flavanols’ beneficial effects on cardiovascular health might extend to protection from the harms of sitting.

The study took 40 young and healthy men – 20 of whom reported high levels of cardiovascular fitness and 20 with lower fitness levels – and asked them to consume one of two cocoa drinks before sitting for two hours. One drink contained a high amount of flavanols (695 mg total flavanols per beverage) and the other a significantly lower dose (5.6 mg per beverage).

Before and after the sitting period, the researchers took a range of measures of vascular health, including:

• FMD in the femoral and brachial arteries
• Arterial resting shear rate and blood flow
• Systolic and diastolic blood pressure
• Leg muscle oxygenation

They found that, in both fitness groups, those who had drunk the low-flavanol beverage experienced FMD declines in the arteries in their arms and legs. In contrast, those who drank the high-flavanol beverage did not experience these FMD declines.

This finding – that consuming foods high in flavanols can prevent sitting-induced vascular dysfunction – demonstrates the potential benefits of flavanols for those who sit for long periods. This study is also the first to show that baseline levels of cardiorespiratory fitness do not alter the effects of flavanol intake on FMD – meaning that an individual's physical fitness would not lessen the benefit.

However, both the high- and low-flavanol groups showed increased diastolic blood pressure, as well as decreased shear rate, blood flow and leg muscle oxygenation after sitting, implying that flavanol intervention does not have any significant effects on these measures of cardiovascular health.

What does this mean for your health?

High-flavanol foods can be incorporated into a person’s diet rather easily. When asked whether the amounts of flavanols consumed in this study would also be achievable through eating natural whole foods, Rendeiro responded: “Yes, [though eating] a combination of green tea/black tea, fruits such as berries, apples and plums and high-flavanol natural cocoa powders (processed through methods that preserve flavanols).”

Rendeiro was equally upfront in recognizing the limitations of this research. For example, the study sample only included men, as changes in estrogen levels during the menstrual cycle are thought to potentially affect the impact of flavanols on vascular health.

“One of the main limitations of the study was the fact that we did not include women, which means that we cannot say whether these benefits are also present in women,” Rendeiro said. “A future study focused on women needs to be pursued in the future to carefully capture how flavanol intake may benefit vascular function in women during sitting periods throughout the menstrual cycle, in pre-menopausal and post-menopausal women.”

Rendeiro also believes it would be beneficial to pursue additional studies that directly investigate whether the timing of consuming flavanols might be significant.

“It would be important to investigate whether consuming a high-flavanol diet habitually is protective against sitting,” she said. “This would mean that individuals would not need to necessarily eat these foods specifically to target these sedentary periods, but just eating flavanols habitually may also be effective.”

Dr. Ian Johnson, a nutrition researcher and Emeritus fellow at the Quadram Institute, who was not involved in the study, echoed the need for further research.

“For many people, prolonged sitting is unavoidable and therefore validated dietary strategies to mitigate some of the potentially adverse effects on vascular health would be welcome,” Johnson told the Science Media Centre.

“It should be borne in mind, however, that these results have been achieved using a relatively high dose of a well-defined cocoa extract, previously shown to have beneficial effects on endothelial function and blood pressure in humans. Achieving similar results using more conventional plant foods, such as berries and teas, may be more difficult due to their variable flavonoid content and bioavailability. As the authors themselves acknowledge, further research will be necessary to translate these encouraging results to everyday diets.”

For those who do spend long periods of time sitting at work or during leisure activities, Rendeiro offers the following advice: “The first advice I would give is to try and break up sitting with standing or short bursts of walking, or any type of movement, at least every 30 minutes. In situations in which individuals are not able to break up their sitting frequently, choosing to have flavanol-rich foods while sitting may help alleviate some of the impairments in vascular function that occur as a consequence of sitting.”

 

Alexander Beadle was speaking with Dr. Catarina Rendeiro, assistant professor in nutritional sciences at the University of Birmingham.

Reference: Daniele A, Lucas SJE, Rendeiro C. Dietary flavanols preserve upper‐ and lower‐limb endothelial function during sitting in high‐ and low‐fit young healthy males. J Physiol. 2025:JP289038. doi: 10.1113/JP289038