Effect of nitrate supplementation on hepatic blood flow and glucose homeostasis: a double-blind, placebo-controlled, randomized control trial.
What this study found
Nitrate-rich beetroot juice increased plasma nitrate and nitrite versus placebo, with older adults showing faster nitrite rise; increases persisted for 3 hours. Hepatic diffusion (ADC) and portal vein flux did not change with nitrate. Portal vein velocity decreased after nitrate in young adults but not in older adults. Plasma glucose, active/total GLP-1, and C-peptide were not reduced by nitrate; blood pressure did not differ. Authors conclude that acute dietary nitrate elevates circulating nitrite but does not modulate hepatic blood flow or glucose homeostasis in healthy young and older…
- Study & population
- Double-blind, placebo-controlled, crossover randomized trial; 37 participants enrolled (17 healthy young adults and 20 healthy older adults); 31 completed (16 young, 15 older); hepatic diffusion (ADC), portal vein flux and velocity measured by MRI; blood measures included plasma nitrate, nitrite, glucose, GLP-1 (total and active), and C-peptide at baseline…
- Intervention
- Beetroot juice beverage (140 mL) containing 11.91 mmol nitrate (nitrate-rich) or nitrate-depleted beetroot juice containing 0.01 mmol nitrate (placebo); consumed with a standardized breakfast; single acute dose per testing session; hourly MRI scans for 3 hours post-ingestion; 7-day washout between sessions.
- Key limitation
- Small sample size with limited power to detect small or age-specific effects; baseline differences in older adults for portal vein flux; short 3-hour observation window; MRI-based measures of hepatic diffusion/portal hemodynamics have variability; cross-over design potential carryover; findings in healthy individuals…
View source
Open PDFOriginal abstract
Nitric oxide alters gastric blood flow, improves vascular function, and mediates glucose uptake within the intestines and skeletal muscle. Dietary nitrate, acting as a source of nitric oxide, appears to be a potential low-cost therapy that may help maintain glucose homeostasis. In a randomized, double-blind, placebo-controlled crossover study, 31 young and older adult participants had a standardized breakfast, supplemented with either nitrate-rich beetroot juice (11.91 mmol nitrate) or nitrate-depleted beetroot juice as placebo (0.01 mmol nitrate). MRI was used to assess apparent diffusion coefficient (ADC), portal vein flux, and velocity. Plasma glucose, incretin, and C-peptide concentrations and blood pressure were assessed. Outcome variables were measured at baseline and hourly for 3 h. Compared with a placebo, beetroot juice resulted in a significant elevation in plasma nitrate and plasma nitrite concentration. No differences were seen for the young or older adult cohorts between placebo and beetroot juice for ADC, or portal vein flux. There was an interaction effect in the young adults between visits for portal vein velocity. Nitrate supplementation did not reduce plasma glucose, active GLP-1, total GLP-1, or plasma C-peptide concentrations for the young or older adult cohorts. Despite a significant elevation in plasma nitrite concentration following an acute dose of (11.91 mmol) nitrate, there was no effect on hepatic blood flow, plasma glucose, C-peptide, or incretin concentration in healthy adults.