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

• Published in: American journal of physiology. Heart and circulatory physiology Vol. 311; no. 6; pp. H1520 - H1529
• Main Authors: McDonagh, Sinead T. J., Vanhatalo, Anni, Fulford, Jonathan, Wylie, Lee J., Bailey, Stephen J., Jones, Andrew M.
• Format: Journal Article
• Language: English
• Published: United States American Physiological Society 01.12.2016
• Subjects: Adult; Beta vulgaris; Blood & organ donations; Blood Donors; Dietary Supplements; Double-Blind Method; Exercise; Exercise Test; Exercise Tolerance - drug effects; Female; Fruit and Vegetable Juices; Healthy Volunteers; Hematocrit; Hemoglobins - metabolism; Humans; Male; Nitrates; Nitrates - pharmacology; Oxygen; Oxygen Consumption - drug effects; Young Adult; blood withdrawal; O2 uptake; beetroot juice; O2 transport; nitric oxide; exercise performance
• ISSN: 0363-6135; 1522-1539
• DOI: 10.1152/ajpheart.00451.2016

We tested the hypothesis that dietary nitrate (NO 3 − )-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 ∼450 ml of whole blood. Before donation, all subjects consumed seven 70-ml shots of NO 3 − -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 NO 3 − , n = 11) or PL ( n = 11) before repeating the exercise tests. Hemoglobin concentration and hematocrit were reduced by ∼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 ∼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). NO 3 − 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.