Effects of dietary nitrate supplementation on the oxygen cost of exercise and walking performance in individuals with type 2 diabetes: a randomized, double-blind, placebo-controlled crossover trial

Dietary nitrate supplementation has been shown to reduce the oxygen (O-2) 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). In a randomized, double-blind, placebo-controlled crossover study, 48 participants with T2DM supplemented their diet for 4 days with either nitrate-rich beetroot juice (70 ml/day, 6.43 mmol nitrate/clay) or nitrate-depleted beetroot juice as placebo (70 ml/day, 0.07 mmol 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 O-2 cost of walking. After a rest period, participants performed the 6-min walk Lest (6MWT). Relative to placebo, beetroot juice resulted in a significant increase in plasma nitrate (placebo, 57 +/- 66 vs beetroot, 319 +/- 110 mu M; P < 0.001) and plasma nitrite concentration (placebo, 680 +/- 256 vs beetroot, 1065 +/- 607 nM; P < 0.001). There were no differences between placebo juice and beetroot juice for the O-2 cost of walking (946 +/- 221 vs 939 +/- 223 ml/min, respectively; P = 0.59) and distance covered in the 6MWT (550 +/- 83 vs 554 +/- 90 m, respectively; P = 0.17). Nitrate supplementation did not affect the O-2 cost of moderate-paced walking or improve performance in the GMWT. These findings indicate that dietary nitrate supplementation does not modulate the response to exercise in individuals with T2DM. (C) 2015 Elsevier Inc. All rights reserved.