A new study from the University of Birmingham, published in The Journal of Physiology, reports that consuming flavanol-rich cocoa before a long period of uninterrupted sitting helped preserve blood vessel function in healthy young men. Participants who drank a high-flavanol cocoa beverage maintained artery function over a two-hour sitting period, while those given a low-flavanol drink experienced declines.
Researchers at the University of Birmingham have reported that flavanols — a class of polyphenols found in foods such as tea, berries, apples, nuts and cocoa — can help protect blood vessel function during prolonged sitting in healthy young men.
The findings, published on October 29, 2025 in The Journal of Physiology, are described in a University of Birmingham news release and related coverage on ScienceDaily. The study examined whether consuming a flavanol-rich cocoa drink before a period of uninterrupted sitting could prevent temporary impairments in vascular function.
According to the University of Birmingham, sedentary behaviour is highly prevalent, with many adults spending large portions of the day seated. Previous research has shown that extended sitting can acutely reduce blood vessel function, although the Birmingham release and ScienceDaily summary do not specify the “six hours seated daily” figure or quantify population averages.
The researchers conducted a double-blind trial in 40 young, healthy men, who were divided into higher- and lower-fitness groups based on cardiorespiratory fitness measures. Participants consumed either a high-flavanol cocoa beverage or a low-flavanol control drink before sitting without interruption for two hours. University and HealthDay/Drugs.com summaries report that the trial included 20 high-fit and 20 low-fit participants.
Several outlets, including Drugs.com (via HealthDay) and Natural Health Research Institute, report that the high-flavanol drink provided about 695 mg of total flavanols (around 150 mg epicatechin), while the low-flavanol drink contained less than 6 mg epicatechin. These dosing details are based on secondary reporting of the Journal of Physiology paper rather than the University news release itself.
Women were not included in this experiment. The Birmingham and ScienceDaily summaries state that the study was conducted in healthy young men; they do not give a specific rationale for excluding women, such as oestrogen-related influences, although such hormonal factors are often cited generally in vascular research. Any plans for future research in women are mentioned only in general terms in some media coverage and are not detailed in the institutional release.
Measurements taken before and after the sitting period included flow-mediated dilatation (FMD) in the brachial and superficial femoral arteries, along with blood pressure and blood flow-related variables. Reports from HealthDay/Drugs.com indicate that sitting significantly reduced FMD in both the superficial femoral and brachial arteries when participants consumed the low-flavanol cocoa. In contrast, those who drank the high-flavanol cocoa maintained their pre-sitting FMD levels in both arteries, regardless of their fitness level.
The Drugs.com summary and other secondary reports also note changes in diastolic blood pressure and arterial blood flow with low-flavanol intake, but the University of Birmingham news release and ScienceDaily article do not provide full numerical details for blood pressure, shear rate, blood flow or leg muscle oxygenation. As a result, broad statements about reduced shear rate, reduced blood flow and lower leg oxygenation across all low-flavanol participants cannot be fully verified from the institutional summary alone, though they are consistent with the general pattern of impaired vascular function described.
In the University of Birmingham release, Dr Catarina Rendeiro, Assistant Professor in Nutritional Sciences and lead author, is quoted as saying: “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.” She also notes 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” and suggests combining flavanol-rich foods with short walks or standing breaks to enhance long-term health.
Co-author Dr Sam Lucas, Professor of Cerebrovascular, Exercise & Environmental Physiology, is quoted in the ScienceDaily summary as saying that higher fitness levels alone did not prevent the temporary impairment of vascular function when participants consumed low-flavanol cocoa. He adds that after the high-flavanol drink, both fitter and less-fit participants kept their FMD at the same level as before sitting for two hours.
PhD student Alessio Daniele, the study’s lead researcher, is quoted in the Birmingham and ScienceDaily materials explaining that it is straightforward to incorporate high-flavanol foods into everyday diets. He notes that some cocoa products are processed to preserve flavanol levels and points to common foods such as apples, plums, berries, nuts, and black and green tea as readily available sources of flavanols.
The authors and the University emphasise that the study shows two main points: that prolonged sitting can temporarily impair blood vessel function in healthy young men, and that this effect is not offset by higher baseline fitness when a low-flavanol drink is consumed. At the same time, intake of a flavanol-rich cocoa beverage appeared to preserve endothelial function during a two-hour sitting bout in both high- and low-fitness participants.
The researchers and institutional statements stress that these findings apply to acute, short-term changes in vascular function and that further work is needed to determine the long-term health implications, to explore effects in women and in older or clinical populations, and to clarify how practical dietary doses of flavanols might be used alongside regular movement breaks.
Some of the original article’s broader claims — including a specific statistic linking a 1% drop in FMD to a 13% increased risk of cardiovascular events, daily average sitting times in young adults, and current UK cardiovascular death numbers and economic costs — are not reported in the University of Birmingham or ScienceDaily summaries of this study and could not be independently confirmed from those documents. They have therefore been omitted from this version to keep the focus on findings directly supported by the available sources.
Overall, the study adds to a growing body of evidence suggesting that flavanol-rich foods and drinks may offer a simple dietary strategy to help counter some of the immediate vascular effects of prolonged sitting, particularly when combined with regular breaks in sedentary time.
