Effects of short-term dietary nitrate supplementation on blood pressure, O-2 uptake kinetics, and muscle and cognitive function in older adults

Kelly J, Fulford J, Vanhatalo A, Blackwell JR, French O, Bailey SJ, Gilchrist M, Winyard PG, Jones AM. Effects of shortterm dietary nitrate supplementation on blood pressure, O-2 uptake kinetics, and muscle and cognitive function in older adults. Am J Physiol Regul Integr Comp Physiol 304: R73-R83, 2013. First published November 21, 2012; doi:10.1152/ajpregu.00406.2012.-Dietary nitrate (NO3-) supplementation has been shown to reduce resting blood pressure and alter the physiological response to exercise in young adults. We investigated whether these effects might also be evident in older adults. In a double-blind, randomized, crossover study, 12 healthy, older (60-70 yr) adults supplemented their diet for 3 days with either nitrate-rich concentrated beetroot juice (BR; 2 x 70 ml/day, similar to 9.6 mmol/day NO3-) or a nitrate-depleted beetroot juice placebo (PL; 2 x 70 ml/day, 0.01 mmol/day NO3-). Before and after the intervention periods, resting blood pressure and plasma [nitrite] were measured, and subjects completed a battery of physiological and cognitive tests. Nitrate supplementation significantly increased plasma [nitrite] and reduced resting systolic (BR: 115 +/- 9 vs. PL: 120 +/- 6 mmHg; P < 0.05) and diastolic (BR: 70 +/- 5 vs. PL: 73 +/- 5 mmHg; P < 0.05) blood pressure. Nitrate supplementation resulted in a speeding of the Vo(2) mean response time (BR: 25 +/- 7 vs. PL: 28 +/- 7 s; P < 0.05) in the transition from standing rest to treadmill walking, although in contrast to our hypothesis, the O-2 cost of exercise remained unchanged. Functional capacity (6-min walk test), the muscle metabolic response to low-intensity exercise, brain metabolite concentrations, and cognitive function were also not altered. Dietary nitrate supplementation reduced resting blood pressure and improved V. O-2 kinetics during treadmill walking in healthy older adults but did not improve walking or cognitive performance. These results may have implications for the enhancement of cardiovascular health in older age.