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 non-linear (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.

Incremental Doses of Nitrate-Rich Beetroot Juice Do Not Modify Cognitive Function and Cerebral Blood Flow in Overweight and Obese Older Adults: A 13-Week Pilot Randomised Clinical Trial

“…Other results have been reported elsewhere [ 33 ]. Briefly, a one-way ANOVA revealed that there was a statistically significant increase in the change from baseline in plasma NO 3 − concentration at 13 weeks ( p < 0.001) with increasing beetroot juice consumption.…”

“…Our participants were asked to maintain their habitual dietary habits, physical activity, and medication throughout the study. Finally, the increase in concentrations of NO 3 − and NO 2 − biomarkers with increasing beetroot juice dose (as reported elsewhere [ 33 ]) provide assurance that the participants were compliant in consuming the beetroot juice supplements.…”

“…Body composition, waist circumference, and biological samples, including blood, saliva, and urine samples, as well as salivary strips, were collected. Biological sample collection procedures and related results have been reported elsewhere [ 32 , 33 ]. Self-reported physical activity was assessed using the short version of the international physical activity questionnaire (IPAQ).…”

“…Participants were also instructed to maintain their habitual dietary habits and physical activity and to avoid using mouthwash during the study [ 34 ]. Self-reported dietary NO 3 − intake for the participants (excluding the intervention supplement) during the study was also assessed via an online validated platform (Intake 24) [ 33 ].…”

“…Compliance with the intervention was assessed subjectively by completing a daily compliance log, which was used to record the time when participants consumed the beetroot juice. Compliance was also assessed objectively by measuring NO 3 − and nitrite (NO 2 − ) concentrations in plasma, saliva, and urine samples [ 33 ].…”