Dietary nitrate supplementation attenuates the reduction in exercise tolerance following blood donation

We tested the hypothesis that dietary nitrate (NO3-)-rich beetroot juice (BR) supplementation could partially offset deteriorations in O-2 transport and utilization and exercise tolerance after blood donation. Twenty-two healthy volunteers performed moderate-intensity and ramp incremental cycle exercise tests prior to and following withdrawal of similar to 450 ml of whole blood. Before donation, all subjects consumed seven 70-ml shots of NO3--depleted BR [placebo (PL)] in the 48 h preceding the exercise tests. During the 48 h after blood donation, subjects consumed seven shots of BR (each containing 6.2 mmol of NO3-, n = 11) or PL (n = 11) before repeating the exercise tests. Hemoglobin concentration and hematocrit were reduced by similar to 8-9% following blood donation (P < 0.05), with no difference between the BR and PL groups. Steady-state O-2 uptake during moderate-intensity exercise was similar to 4% lower after than before donation in the BR group (P < 0.05) but was unchanged in the PL group. The ramp test peak power decreased from predonation (341 +/- 70 and 331 +/- 68 W in PL and BR, respectively) to postdonation (324 +/- 69 and 322 +/- 66 W in PL and BR, respectively) in both groups (P < 0.05). However, the decrement in performance was significantly less in the BR than PL group (2.7% vs. 5.0%, P < 0.05). NO3- supplementation reduced the O-2 cost of moderate-intensity exercise and attenuated the decline in ramp incremental exercise performance following blood donation. These results have implications for improving functional capacity following blood loss.