On the mechanism by which dietary nitrate improves human skeletal muscle function.

Published onlineReviewThis is the final version of the article. It first appeared from Frontiers Media via http://dx.doi.org/10.3389/fphys.2015.00211Inorganic 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.Research in the authors’ laboratories is currently supported by the Medical Research Council (New Investigator Research Grant G1100165/1 to CA), Gatorade Sports Science Institute (Grants PEP-1330 and PEP-1420 to AJ), the Exeter Leukaemia Fund (Grant ST-06354 to AJ), the Dunhill Medical Trust (Grant R269/1112 to AJ) and the NIHR Exeter Clinical Research Facility (PW and MS). The views and opinions shown within this paper are those of the authors and do not necessarily represent those of the NIHR, NHS or the Department of Health