This is the author’s version of a work that was accepted for publication in Free Radical Biology and Medicine. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published at doi:10.1016/j.freeradbiomed.2015.05.014. ; BACKGROUND: Dietary nitrate supplementation has been shown to reduce the oxygen (O2) cost of exercise and enhance exercise tolerance in healthy individuals. This study assessed whether similar effects could be observed in individuals with type 2 diabetes (T2DM). METHODS: In a randomised, double blind, placebo-controlled cross-over study, 48 participants with T2DM supplemented their diet for four days with either nitrate rich beetroot juice (70ml/day, 6.43mmol nitrate/day) or nitrate depleted beetroot juice as placebo (70ml/day, 0.07mmol nitrate/day). After each intervention period, resting plasma nitrate and nitrite concentrations were measured subsequent to participants completing moderate-paced walking. Pulmonary gas exchange was measured to assess the O2 cost of walking. Following a rest period, participants performed the six-minute walk test (6MWT). RESULTS: Relative to placebo, beetroot juice resulted in a significant increase in plasma nitrate (placebo: 57±66 vs. beetroot: 319±110µM; P