Researchers at University of Birmingham, UK conducted a randomized trial in 40 healthy young men, split into higher and lower fitness groups. They tested vascular function before and after 2 hours of uninterrupted sitting. Participants consumed either a high-flavanol cocoa drink or a low-flavanol version immediately before sitting.
Participants who consumed the low-flavanol drink experienced a marked decline in vascular function after two hours of uninterrupted sitting, reflected by reduced flow-mediated dilation in both the superficial femoral and brachial arteries, along with increased diastolic BP and decreased shear rate and blood flow. In contrast, those who consumed the high-flavanol cocoa beverage maintained their vascular function, with FMD values in both the arms and legs remaining similar to pre-sitting levels despite prolonged sitting.
Flavanol-rich foods are excellent sources of plant-based compounds known for their antioxidant, anti-inflammatory, and cardioprotective properties. Flavanols belong to the flavonoid family of phytonutrients, commonly found in cocoa, tea, fruits, and certain vegetables.
The beneficial effect of the flavanol-rich drink was consistent across participants regardless of cardiorespiratory fitness, indicating that both fitter and less-fit individuals derived comparable vascular protection. However, the study did not observe significant changes in microvascular parameters.
Flavanols may support vascular health by enhancing nitric oxide bioavailability, reducing oxidative stress, and improving vasodilation when sitting causes reduced blood flow and shear stress in the arteries.
Key Summary of the Study
The study was acute (only 2 hours of sitting, one intervention). We don’t know the effects of longer periods or repeated exposure.
Only healthy young men were studied. The findings may not apply to women or to older men, diseased, or high-risk populations.
- While FMD is a good surrogate marker of endothelial function, it is not a clinical endpoint (like reduced heart attack incidence) so we can’t directly say this intervention lowers actual cardiovascular event risk based on this study alone.
- Flavanols are not a substitute for movement. Sitting still remains detrimental, and breaking up sitting is still strongly recommended.
If you anticipate a long uninterrupted sitting period (for instance at a desk, in travel, or during meetings), including a high-flavanol cocoa drink (or other flavanol-rich food) might help buffer some of the acute vascular impairment. However do not rely on flavanols alone. Movement breaks (standing, walking, calf raises, etc) continue to be a primary strategy to maintain vascular health during sedentary periods.
