Acute dietary nitrate supplementation attenuates caffeine-induced increase in arterial stiffness in healthy adults: a randomized controlled trial

Purpose: Inorganic nitrate (NO3 -) supplementation and caffeine have been shown to have conflicting effects on various aspects of cardiovascular function. This study evaluated whether NO3 -supplementation would attenuate caffeine-induced cardiovascular strain. Methods: Twenty-four (17 males; age: 24 ± 3 yrs) healthy participants completed four trials in a randomized, double-blind, placebo-controlled crossover design. The trials were nitrate (NO3 -)-rich (400 mg NO3 -) and NO3 -depleted (92 mg NO3 -) beetroot powder consumed, with (BR-CAF and CAF) and without (BR and PL) 6 mg/kg caffeine. Brachial and central blood pressure (BP) and arterial stiffness variables were measured pre-and post-supplementation (2.5 h). Macrovascular endothelial function was assessed post-supplementation using flow mediated dilation (FMD). Results: Arterial stiffness measures of augmentation pressure and index were higher following CAF (+3 ± 2 mmHg and 10 ± 9%) than PL (+1 ± 3 mmHg and +4 ± 11%) and BR (+0 ± 3 mmHg and +1 ± 11%; P<0.001-0.007), with no difference between BR-CAF (+1 ± 3 mmHg and +3 ± 10%) and PL or BR (P=0.505-0.689). Brachial BP, central BP and macrovascular endothelial function were not altered with BR or CAF compared to PL (P=0.067-0.359). Plasma [nitrite] was higher in BR and BR-CAF than PL and CAF (P<0.001). There were no between-group differences in plasma [cyclic guanosine monophosphate] (P=0.370).Conclusion: Acute NO3 -supplementation offset caffeine-induced increases in arterial stiffness variables. These findings improve our understanding of the cardiovascular health benefits afforded by acute NO3 -consumption under cardiovascular strain.