Medium-term effects of dietary nitrate supplementation on systolic and diastolic blood pressure in adults: a systematic review and meta-analysis.
Dietary nitrate supplementation has been shown to lower blood pressure (BP) particularly in short-term clinical trials. Whether these effects are sustained in the long-term remains to be established. The objective was to conduct a meta-analysis of randomized controlled trials that examined whether dietary nitrate supplementation for more than 1 week has beneficial effects on SBP and DBP.



Electronic databases were searched from inception until May 2016. Specific inclusion criteria were duration at least 1 week, report of effects on SBP or DBP or both and comparison of inorganic nitrate or beetroot juice supplementation with placebo control groups. Random-effects models were used to calculate the pooled BP effect sizes.



Thirteen trials met eligibility criteria. The trials included a total of 325 participants with seven to 65 participants per study. The duration of each intervention ranged from 1 to 6 weeks. Ten trials assessed BP in resting clinic conditions, whereas 24-h ambulatory and daily home monitorings were used in six and three trials, respectively. Overall, dietary nitrate was associated with a significant decline in SBP [-4.1 mmHg (95% confidence interval: -6.1, -2.2); P < 0.001] and DBP [-2.0 mmHg (95% confidence interval: -3.0, -0.9); P < 0.001]. However, the effect was only significant when measured in resting clinical settings as no significant changes in BP were observed using 24-h ambulatory and daily home BP monitorings.



Positive effects of medium-term dietary nitrate supplementation on BP were only observed in clinical settings, which were not corroborated by more accurate methods such as 24-h ambulatory and daily home monitorings.
aHuman Nutrition Research Centre, Institute of Cellular Medicine, Campus for Ageing and Vitality, Newcastle University bDepartment of Applied Sciences, Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, UK.
Ammar W
AW
Ashor
Jose
J
Lara
Mario
M
Siervo
D000328:Adult; D000959:Antihypertensive Agents / Q000008:administration & dosage* / Q000627:therapeutic use; D001794:Blood Pressure / Q000187:drug effects*; D018660:Blood Pressure Monitoring, Ambulatory; D019587:Dietary Supplements; D006801:Humans; D006973:Hypertension / Q000188:drug therapy*; D009566:Nitrates / Q000008:administration & dosage* / Q000627:therapeutic use
D000959:Antihypertensive Agents; D009566:Nitrates