Ageing modifies acute resting blood pressure responses to incremental consumption of dietary nitrate: a randomised, cross-over clinical trial

Beetroot (BR) is a rich source of nitrate (NO3-) that has been shown to reduce blood pressure (BP). Yet, no studies have examined the vascular benefits of BR in whole-food form and whether the effects are modified by age. This study was a four-arm, randomised, open-label, cross-over design in twenty-four healthy adults (young n 12, age 27 +/- 4 years, old n 12, age 64 +/- 5 years). Participants consumed whole-cooked BR at portions of (NO3- content in brackets) 100 g (272 mg), 200 g (544 mg) and 300 g (816 mg) and a 200-ml solution containing 1000 mg of potassium nitrate (KNO3) on four separate occasions over a 4-week period (>= 7-d washout period). BP, plasma NO3- and nitrite (NO2-) concentrations, and post-occlusion reactive hyperaemia via laser Doppler, were measured pre- and up to 5-h post-intervention. Data were analysed by repeated-measures ANOVA. Plasma NO2- concentrations were higher in the young v. old at baseline and post-intervention (P < 0 center dot 05). All NO3- interventions decreased systolic and diastolic BP in young participants (P < 0 center dot 05), whereas only KNO3 (at 240-300 min post-intake) significantly decreased systolic (-4 center dot 8 mmHg, -3 center dot 5 %, P = 0 center dot 024) and diastolic (-5 center dot 4 mmHg, -6 center dot 5 %, P = 0 center dot 007) BP in older participants. In conclusion, incremental doses of dietary NO3- reduced systolic and diastolic BP in healthy young adults whereas in the older group a significant decrease was only observed with the highest dose. The lower plasma NO2- concentrations in older participants suggest that there may be mechanistic differences in the production of NO from dietary NO3- in young and older populations.