On the mechanism by which dietary nitrate improves human skeletal muscle function.
Inorganic nitrate is present at high levels in beetroot and celery, and in green leafy vegetables such as spinach and lettuce. Though long believed inert, nitrate can be reduced to nitrite in the human mouth and, further, under hypoxia and/or low pH, to nitric oxide. Dietary nitrate has thus been associated favorably with nitric-oxide-regulated processes including blood flow and energy metabolism. Indeed, the therapeutic potential of dietary nitrate in cardiovascular disease and metabolic syndrome-both aging-related medical disorders-has attracted considerable recent research interest. We and others have shown that dietary nitrate supplementation lowers the oxygen cost of human exercise, as less respiratory activity appears to be required for a set rate of skeletal muscle work. This striking observation predicts that nitrate benefits the energy metabolism of human muscle, increasing the efficiency of either mitochondrial ATP synthesis and/or of cellular ATP-consuming processes. In this mini-review, we evaluate experimental support for the dietary nitrate effects on muscle bioenergetics and we critically discuss the likelihood of nitric oxide as the molecular mediator of such effects.
School of Biomedical and Healthcare Sciences, Plymouth University Peninsula Schools of Medicine and Dentistry, Plymouth University Plymouth, UK.
Charles
C
Affourtit
Department of Sport and Health Sciences, College of Life and Environmental Sciences, University of Exeter Exeter, UK.
Stephen J
SJ
Bailey
Department of Sport and Health Sciences, College of Life and Environmental Sciences, University of Exeter Exeter, UK.
Andrew M
AM
Jones
Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, University of Exeter Exeter, UK.
Miranda J
MJ
Smallwood
Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, University of Exeter Exeter, UK.
Paul G
PG
Winyard
ATP turnover; cellular bioenergetics; coupling efficiency of oxidative phosphorylation; dietary nitrate; nitric oxide; nitrite; oxygen cost of human exercise; skeletal muscle mitochondria