Ageing modifies the effects of beetroot juice supplementation on 24-hour blood pressure variability: An individual participant meta-analysis.
OBJECTIVE
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.
Human Nutrition Research Centre, Institute of Cellular Medicine, Newcastle University, Campus for Ageing and Vitality, Newcastle upon Tyne NE4 5PL, UK. Electronic address: mario.siervo@ncl.ac.uk.
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Siervo
Human Nutrition Research Centre, Institute of Cellular Medicine, Newcastle University, Campus for Ageing and Vitality, Newcastle upon Tyne NE4 5PL, UK.
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Lara
Human Nutrition Research Centre, Institute of Cellular Medicine, Newcastle University, Campus for Ageing and Vitality, Newcastle upon Tyne NE4 5PL, UK.
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Jajja
Human Nutrition Research Centre, Institute of Cellular Medicine, Newcastle University, Campus for Ageing and Vitality, Newcastle upon Tyne NE4 5PL, UK.
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Sutyarjoko
Human Nutrition Research Centre, Institute of Cellular Medicine, Newcastle University, Campus for Ageing and Vitality, Newcastle upon Tyne NE4 5PL, UK.
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Ashor
Human Nutrition Research Centre, School of Agriculture, Food & Rural Development, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK.
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Brandt
Human Nutrition Research Centre, School of Agriculture, Food & Rural Development, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK; Food Science Department, Faculty of Agricultural Science, University of Sulaimani, Iraq-Kurdistan Region, Sulaimani, Iraq.
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Qadir
Human Nutrition Research Centre, Institute of Cellular Medicine, Newcastle University, Campus for Ageing and Vitality, Newcastle upon Tyne NE4 5PL, UK.
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Mathers
NIHR Exeter Clinical Research Facility and Institute of Biomedical and Clinical Science, University of Exeter Medical School (previously Peninsula College of Medicine and Dentistry), University of Exeter, Exeter EX2 5AX, UK.
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Benjamin
NIHR Exeter Clinical Research Facility and Institute of Biomedical and Clinical Science, University of Exeter Medical School (previously Peninsula College of Medicine and Dentistry), University of Exeter, Exeter EX2 5AX, UK.
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Winyard
NIHR Exeter Clinical Research Facility and Institute of Biomedical and Clinical Science, University of Exeter Medical School (previously Peninsula College of Medicine and Dentistry), University of Exeter, Exeter EX2 5AX, UK.
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Anning
NIHR Exeter Clinical Research Facility and Institute of Biomedical and Clinical Science, University of Exeter Medical School (previously Peninsula College of Medicine and Dentistry), University of Exeter, Exeter EX2 5AX, UK.
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Shore
NIHR Exeter Clinical Research Facility and Institute of Biomedical and Clinical Science, University of Exeter Medical School (previously Peninsula College of Medicine and Dentistry), University of Exeter, Exeter EX2 5AX, UK.
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Gilchrist
D000368:Aged; D000375:Aging; D027461:Beta vulgaris / Q000737:chemistry*; D001628:Beverages; D001794:Blood Pressure; D018660:Blood Pressure Monitoring, Ambulatory; D019587:Dietary Supplements; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009566:Nitrates / Q000737:chemistry / Q000378:metabolism; D009573:Nitrites / Q000737:chemistry / Q000378:metabolism; D013997:Time Factors
D009566:Nitrates; D009573:Nitrites
Ageing; Ambulatory blood pressure; Beetroot juice; Hypertension; Inorganic nitrate