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

Abstract

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 () can decline during Ramadan in parallel with reduced physical activity. We investigated whether dietary nitrate supplementation could attenuate the decrease in 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 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 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 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.