Dietary flavanols preserve upper- and lower-limb endothelial function during sitting in high- and low-fit young healthy males.

Sedentary behaviour is very prevalent in modern societies, with young adults spending approximately 6 h/day sitting. Sitting induces declines in endothelial function, increasing the risk of cardiovascular diseases. Nutrition during sitting may be used as a strategy to minimise such effects. This acute randomised, counterbalanced, double-blinded, cross-over, placebo-controlled human study investigated whether intake of dietary flavanols prior to a 2 h sitting bout could preserve upper- and lower-limb endothelial function in high- and low-fit individuals. Forty young healthy males (20 high fit; 20 low-fit) completed a 2 h sitting trial after consuming either a high-flavanol (150 mg (-)-epicatechin) or low-flavanol (<6 mg (-)-epicatechin) cocoa intervention. The primary outcome, superficial femoral artery flow-mediated dilatation (SFA FMD) and secondary outcomes, brachial artery (BA) FMD, resting shear rate, blood flow and blood pressure (BP) were assessed before and after sitting. Medial gastrocnemius microvasculature haemodynamics were assessed before, during and after sitting. Sitting significantly reduced FMD in the SFA and BA and increased diastolic BP in both fitness groups. The high-flavanol intervention prevented FMD declines in both arteries, with no effects on BP. Sitting significantly decreased shear rate and blood flow in both arteries in both fitness groups, with no effects of the flavanol intervention. Sitting further resulted in declines in tissue oxygenation (TOI), detectable within 10 min, and impaired TOI desaturation and speed of reperfusion during hyperaemia 2 h post-sitting, with no effects of flavanols. Flavanol-rich foods may be efficacious at counteracting sitting-induced endothelial dysfunction during prolonged sitting in both high- and low-fit individuals. KEY POINTS: Prolonged sitting temporarily impairs vascular function and blood pressure. Dietary strategies during sitting may ameliorate or aggravate the effects of sitting on vascular health. In this study, dietary cocoa flavanols consumed just before 2 h of uninterrupted sitting were effective at preventing sitting-induced reductions in vascular function in both the brachial and femoral arteries (as measured by flow-mediated dilatation) in young healthy men, with no effects on microvascular function or blood pressure. Flavanols were equally effective at preserving vascular function in individuals with high and low cardiorespiratory fitness during sitting. Individuals' high cardiorespiratory fitness did not protect against declines in vascular function and blood pressure during sitting. Consuming high-flavanol foods during sedentary periods may be used alone or in combination with other strategies (e.g. breaking up sitting) to reduce the impact of inactivity on the vascular system.