The Impact of Cocoa Flavanols in Modulating Resting Cerebral Blood Flow During Prolonged Sitting in Healthy Young and Older Adults

Background: Sitting is highly prevalent among young and older adults and can transiently reduce cerebral blood flow. Dietary flavanols confer benefits to the peripheral vasculature and may be effective at counteracting the impact of sitting in the cerebrovasculature. The aim of this study was to investigate whether the acute ingestion of flavanols prior to sitting improves common carotid artery (CCA) blood flow/shear rate (BF/SR) in young and older individuals. Methods: Two acute randomized, double-blinded, cross-over, placebo-controlled studies were conducted in 40 healthy young males (high-fit: 22.2 ± 2.9 yr., low-fit: 23.2 ± 4.1 yr., N = 20 per group) and 20 healthy older adults (72.4 ± 5.0 yr.). Participants consumed either a high- (695 mg) or low-flavanol (5.6 mg) cocoa beverage just before a 2 h sitting bout. Resting CCA retrograde/anterograde BF and SR, as well as arterial diameter, were assessed before and after the intervention. Results: Sitting reduced anterograde BF and/or SR in young and older individuals (p < 0.001) but only resulted in increases in retrograde BF (p = 0.021) and SR (p = 0.022) in the older group. Flavanols did not affect anterograde BF/SR in either group (p > 0.05) but mitigated (non-significant interaction: p = 0.053) sitting-induced increases in retrograde BF/SR in older individuals, with retrograde BF (p = 0.028) and SR (p = 0.033) increasing significantly only after intake of the low-flavanol beverage. No changes in arterial diameter were detected. Conclusions: This suggests that flavanols may have the potential to attenuate the detrimental sitting-induced increases in retrograde BF and SR in older adults, although larger well-powered studies are required to confirm this.