Acceptability and feasibility of a 13‐week pilot randomised controlled trial testing the effects of incremental doses of beetroot juice in overweight and obese older adults

Abstract

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 (NO3‐) 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/m2) older participants (mean ± standard deviation (SD), 66 ± 4 years). Participants were randomized to: (1) high‐NO3‐ (HN: 2 × 70 mL BJ/day) (2) medium‐NO3‐ (MN: 70 mL BJ/day), (3) low‐NO3‐ (LN: 70 mL BJ on alternate days) or (4) Placebo (PL: 70 mL of NO3‐‐depleted BJ on alternate days), for 13 weeks. Compliance was checked by a daily log of consumed BJ, NO3‐ intake, and by measuring NO3‐ and NO2‐ 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 NO3‐ dose and the increase in plasma and urinary NO3‐ concentration (R2 = 0.71, P < 0.001 and R2 = 0.46 P < 0.001, respectively), but relationships between NO3‐ dose and changes in salivary NO3‐ and NO2‐ were nonlinear (R2 = 0.35, P = 0.002 and R2 = 0.23, P = 0.007, respectively). The results confirm the feasibility of prolonged BJ supplementation in older overweight and obese adults.