Ageing modifies the effects of beetroot juice supplementation on 24-hour blood pressure variability: An individual participant meta-analysis.

OBJECTIVES: Abnormal circadian oscillations of blood pressure (BP) and nocturnal-diurnal BP differences (i.e., dipping) increase cardiovascular risk. Whether inorganic nitrate supplementation influences 24-hr BP variability is currently unknown. We studied the effects of high-nitrate beetroot juice supplementation on BP variability measured by 24-hr ambulatory BP monitoring (24-hr ABPM) in older subjects. METHODS: Data from four independent randomised clinical trials were collated. Eighty-five older participants (age range: 55-76 years) were included in the final database. Two trials had an open-label, parallel design and two trials had a cross-over, double-blind design. Participants were randomised to either beetroot juice or placebo. Changes in 24-hr ABPM (daily, diurnal, nocturnal), variability (weighted-SDs), night-dipping, morning surge for systolic and diastolic BP were measured. Meta-analysis was conducted to obtain pooled estimates of the effect size for each BP outcome. Sub-group analyses were conducted to evaluate the influence of age, BMI, gender, BP status and changes in nitrite concentrations on the effect size. RESULTS: The pooled effect of beetroot juice on all BP outcomes was not significant. Beetroot juice ingestion determined a significant decrease in nocturnal systolic BP variability in subjects aged less than 65 y (2.8 mmHg, -4.5 -1.0, p = 0.002) compared to the older group (≥ 65 y; 1.0 mmHg, -2.2 4.2, p = 0.54). A greater change in NO2(-) concentrations after beetroot supplementation was associated with significant differences for nocturnal mean (-3.4 mmHg, -0.6 -2.4, p = 0.02) and variability (-0.8 mmHg, -1.5 -0.06, p = 0.03) of systolic BP. CONCLUSIONS: The vascular responsiveness to inorganic nitrate may be modified by mechanisms of vascular ageing influencing the reducing capacity to convert inorganic nitrate into nitrite and tissue-specific responses to dietary nitrate supplementation.

Beetroot supplementation lowers daily systolic blood pressure in older, overweight subjects.

Although inorganic nitrate and beetroot juice supplementation are associated with decreased systolic blood pressure (BP), these results have primarily been obtained from short-term trials that focused on healthy young adults. Therefore, we hypothesized that oral supplementation of beetroot juice concentrate would decrease systolic BP in overweight older participants but that the decline in BP would not be sustained after a 1-week interruption of the beetroot juice supplementation. For 3 weeks, 24 participants were randomized to either the beetroot juice concentrate or blackcurrant juice group, with a 1-week postsupplementation phase (week 4). Changes in systolic and diastolic BP were assessed during the supplementation and postsupplementation phases. Blood pressure was measured using 3 different methods: (1) resting clinic BP, (2) 24-hour ambulatory BP monitoring, and (3) home monitoring of daily resting BP. The first 2 methods were applied at baseline and after weeks 3 and 4. Daily measurements were conducted throughout the study, with 21 subjects completing the study (beetroot/blackcurrant = 10/11; male/female = 12/9; age = 62.0 ± 1.4 years; body mass index = 30.1 ± 1.2 kg/m(2)). After 3 weeks, beetroot juice supplementation was not associated with significant changes in resting clinic BP or 24-hour ABPM. Conversely, beetroot juice concentrate reduced daily systolic BP after 3 weeks (-7.3 ± 5.9 mm Hg, P = .02); however, the effect was not maintained after the interruption of the supplementation (week 4, 2.8 ± 6.1 mm Hg, P = .09). In overweight older subjects, beetroot juice concentrate supplementation was associated with beneficial effects on daily systolic BP, although the effects were not significant when measured by 24-hour ABPM or resting clinic BP.