SPENDING long hours sitting has become a defining feature of modern life, particularly for young adults who may spend around 6 hours a day seated at work, studying, or using digital devices. While this sedentary behaviour may feel harmless, growing evidence shows that prolonged sitting can temporarily impair blood vessel function, increasing long-term risks to heart and vascular health. Now, a new study suggests that what people consume before sitting down for long periods could help counteract some of these harmful effects.
How Sedentary Behaviour Affects Blood Vessels
Researchers found that 2 hours of uninterrupted sitting led to measurable declines in endothelial function, the ability of blood vessels to widen and allow healthy blood flow. This impairment was seen in both the legs and arms and occurred in young, otherwise healthy men. The study also observed a rise in diastolic blood pressure during sitting, highlighting how quickly sedentary behaviour can affect the cardiovascular system.
Importantly, high levels of physical fitness did not protect participants from these short-term declines, suggesting that even active individuals may be vulnerable to the vascular effects of prolonged sitting.
Cocoa Flavanols and Sedentary Behaviour
The study explored whether dietary flavanols, naturally occurring compounds found in foods such as cocoa, tea, and berries, could help protect blood vessels during sedentary behaviour. Participants consumed either a high-flavanol cocoa drink or a low-flavanol control before completing the 2-hour sitting period.
Those who consumed the flavanol-rich drink showed no decline in blood vessel function after sitting. In contrast, participants given the low-flavanol drink experienced the expected reductions in vascular function. These protective effects were observed in both the upper and lower limbs and were consistent regardless of participants’ fitness levels.
However, flavanols did not prevent all sitting-related changes. Measures of microvascular blood flow and tissue oxygenation still declined during sitting, and blood pressure was unaffected by the dietary intervention.
What This Means for Everyday Sedentary Behaviour
The findings suggest that flavanol-rich foods may offer a simple, practical strategy to help reduce the vascular impact of prolonged sitting. While they are not a replacement for movement, such foods could complement other approaches, such as taking regular breaks from sitting or incorporating light physical activity into the day.
Experts caution that sedentary behaviour remains a major public health concern, and dietary strategies should be viewed as part of a broader lifestyle approach. Nonetheless, the study adds to growing evidence that nutrition can play a role in protecting heart health, even during periods of unavoidable inactivity.
Reference
Daniele A et al. Dietary flavanols preserve upper- and lower-limb endothelial function during sitting in high- and low-fit young healthy males. J Physiol. 2025; DOI:10.1113/JP289038.
