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Nitrate-rich food increases nitric oxide (NO) production and may have beneficial effects on vascular, metabolic, and brain function. This pilot study tested the effects of prolonged consumption of a range of doses of dietary nitrate (NO 3 - ), provided as beetroot juice, on cognitive function and cerebral blood flow (CBF) in overweight and obese older participants. The study had a 13-week single-blind, randomised, parallel design, and 62 overweight and obese older participants (aged 60 to 75 years) received the following interventions: (1) high NO 3 - (2 × 70 mL beetroot juice/day) (2) medium NO 3 - (70 mL beetroot juice/day), (3) low NO 3 - (70 mL beetroot juice on alternate days), or (4) placebo (70 mL of NO 3 - -depleted beetroot juice on alternate days). Cognitive functions were assessed using the Computerised Mental Performance Assessment System (COMPASS) assessment battery. CBF, monitored by concentration changes in oxygenated and deoxygenated haemoglobin, was assessed in the frontal cortex using near-infrared spectroscopy. The findings of this pilot study showed that cognitive function and CBF were not affected by supplementation with NO 3 - -rich beetroot juice for 13 weeks, irrespective of the NO 3 - dose administered. These findings require confirmation in larger studies using more sophisticated imaging methods (i.e., MRI) to determine whether prolonged dietary NO 3 - supplementation influences brain function in older overweight people.

Nitrate-rich food can increase nitric oxide production and improve vascular and brain functions. This study examines the feasibility of a randomised controlled trial (RCT) testing the effects of prolonged consumption of different doses of dietary nitrate (NO 3 - ) in the form of beetroot juice (BJ) in overweight and obese older participants. A single-blind, four-arm parallel pilot RCT was conducted in 62 overweight and obese (30.4 ± 4 kg/m 2 ) older participants (mean ± standard deviation (SD), 66 ± 4 years). Participants were randomized to: (1) high-NO 3 - (HN: 2 × 70 mL BJ/day) (2) medium-NO 3 - (MN: 70 mL BJ/day), (3) low-NO 3 - (LN: 70 mL BJ on alternate days) or (4) Placebo (PL: 70 mL of NO 3 - -depleted BJ on alternate days), for 13 weeks. Compliance was checked by a daily log of consumed BJ, NO 3 - intake, and by measuring NO 3 - and NO 2 - concentrations in plasma, saliva, and urine samples. Fifty participants completed the study. Self-reported compliance to the interventions was >90%. There were significant positive linear relationships between NO 3 - dose and the increase in plasma and urinary NO 3 - concentration (R 2 = 0.71, P < 0.001 and R 2 = 0.46 P < 0.001, respectively), but relationships between NO 3 - dose and changes in salivary NO 3 - and NO 2 - were non-linear (R 2 = 0.35, P = 0.002 and R 2 = 0.23, P = 0.007, respectively). The results confirm the feasibility of prolonged BJ supplementation in older overweight and obese adults., Competing Interests: The authors declare no conflict of interest.