Protocol and recruitment results from a 13-week randomized controlled trial comparing the effects of different doses of nitrate-rich beetroot juice on cognition, cerebral blood flow and peripheral vascular function in overweight and obese older people

摘要

BackgroundNitrate-rich food can increase NO production and may induce positive effects on brain function. This study examined the feasibility of a randomized clinical trial (RCT) testing the effects of prolonged consumption of incremental doses of dietary nitrate (NO3?) in overweight and obese older participants. Secondary aims tested dose-dependent changes in cognitive, vascular and pulmonary functions and cerebral blood flow (CBF).MethodsThis was a single blind, four-arm parallel RCT conducted in 60 overweight and obese older participants. Eligible participants were randomized to:1) high NO3? (140?ml of beetroot juice (BJ) per day, ~800?mg of NO3?/day), 2) moderate NO3? (70?ml of BJ per day, ~400?mg of NO3?/day), 3) low NO3? (70?ml on alternate days, ~400?mg of NO3?) or 4) NO3? depleted (70?ml on alternate days, ~0.001?mg of NO3). Measurements of cognitive, vascular and pulmonary functions and CBF were conducted at baseline and 13-weeks NO3? intake was assessed by six 24-h recalls, and by measuring NO3? intake biomarkers. Feasibility was assessed by obtaining qualitative feedback and evaluating trial recruitment, retention, compliance with study visits and measurement protocols.ResultsParticipant recruitment started in July 2018 and ended in April 2019. Of all the recruitment strategies that were used, advertisement of the study via Facebook generated the highest response rate. Sixty-two participants consented and were enrolled. Overall, characteristics of included participants matched our recruitment criteria.ConclusionThe findings from this study provide evidence of the acceptability and feasibility of an intervention investigating the effects of incremental doses of high-nitrate BJ over a prolonged period.Trial registrationThe intervention study was registered with clinical trial ISRCTN registry (ISRCTN14746723) on 27 December 2018.