Effects of dietary nitrate supplementation on peak oxygen uptake following 10 days of Ramadan fasting in healthy adults.

Ramadan is a sacred religious practice observed by Muslims that involves abstaining from food and water from sunrise to sunset for 1 month. Prior work has reported that peak oxygen uptake ( V ̇ O 2 peak ) can decline during Ramadan in parallel with reduced physical activity. We investigated whether dietary nitrate supplementation could attenuate the decrease in V ̇ O 2 peak during 10 days of Ramadan fasting. In a randomized design, 21 healthy participants (13 females) were assigned to ingest 70 mL of beetroot juice (∼6.45 mmol nitrate; n = 10), twice a day for 10 days consecutively, or a non-supplement control (n = 11). The V ̇ O 2 peak was assessed by indirect calorimetry during a maximal cycle ergometer ramp test. After 10 days of Ramadan fasting, the change in body mass was not different between groups [change (∆), -0.91 ± 1.3 vs. -0.27 ± 1.2 kg (control vs. nitrate), P = 0.25], nor were the changes in resting systolic (P = 0.21) or diastolic (P = 0.53) blood pressure or urine specific gravity (P = 0.17). Subjective sleep quality declined over time in both groups (P < 0.01). Participants self-reported a decline (n = 17) or no change (n = 4) in regular physical activity, and the number of exercise bouts during the 10 days of Ramadan did not differ between groups (2.5 ± 2.0 vs. 3.3 ± 2.4, P = 0.44). Absolute V ̇ O 2 peak decreased in the control group compared with the dietary nitrate supplementation group (∆, -155 ± 168 vs. +67 ± 162 mL min-1, P < 0.01), as did V ̇ O 2 peak relative to body mass (∆, -2.4 ± 2.5 vs. +0.3 ± 1.9 mL kg-1 min-1, P = 0.02) and peak power output (∆, -12 ± 16 vs. ∆+2 ± 10 W, P = 0.04). Dietary nitrate supplementation might represent a practical nutritional strategy to preserve aerobic capacity during Ramadan fasting.