Effects of inorganic nitrate and beetroot supplementation on endothelial function: a systematic review and meta-analysis

• Published in: European journal of nutrition Vol. 55; no. 2; pp. 451 - 459
• Main Authors: Lara, Jose, Ashor, Ammar W, Oggioni, C, Ahluwalia, A, Mathers, John C, Siervo, Mario
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.03.2016; Springer Nature B.V
• Subjects: beets; Beta vulgaris - chemistry; blood pressure; Blood Pressure - drug effects; Body Mass Index; Cardiovascular Diseases - prevention & control; Chemistry; Chemistry and Materials Science; cross-over studies; diet; Dietary Supplements; Endothelium - drug effects; Endothelium - metabolism; Humans; meta-analysis; Metabolic Syndrome - prevention & control; nitrates; Nitrates - administration & dosage; Nutrition; Original Contribution; placebos; Plant Roots - chemistry; randomized clinical trials; Randomized Controlled Trials as Topic; risk; Risk Factors; systematic review; Treatment Outcome; Beetroot; Inorganic nitrate; Flow-mediated dilation; Endothelial function; Cardiovascular risk; Meta-analysis
• ISSN: 1436-6207; 1436-6215; 1436-6215
• DOI: 10.1007/s00394-015-0872-7

BACKGROUND: Diets rich in inorganic nitrate are associated with lower blood pressure, an effect that may be mediated by an improvement of endothelial function (EF). Therefore, a systematic review and meta-analysis of randomised controlled trials (RCTs) were conducted to examine the effects of inorganic nitrate and beetroot supplementation on measures of EF. METHODS: MEDLINE, EMBASE and Scopus databases were searched from inception until November 2014. Specific inclusion criteria were as follows: (1) RCTs; (2) trials comparing inorganic nitrate or beetroot supplementation with placebo control groups; and (3) trials reporting effects of these interventions on outcomes of vascular function. Random-effect models were used to assess the pooled effect sizes showed as standardised mean differences (SMD). RESULTS: Nine crossover trials and three parallel trials met our inclusion criteria. The trials were conducted between 2008 and 2014 and included a total of 246 participants with 10–64 participants per study. The duration of each intervention ranged from 1.5 h to 28 days. Inorganic nitrate and beetroot consumption was associated with an improvement in vascular function (SMD 0.36; 95 % CI 0.16, 0.56; P < 0.001). The effect on EF was significantly associated with the dose of inorganic nitrate (β = 0.04, SE = 0.01, P < 0.001), age (β = −0.01, SE = 0.004, P = 0.02), baseline BMI (β = −0.04, SE = 0.02, P = 0.05) and systolic BP (β = −0.01, SE = 0.005, P = 0.02). CONCLUSIONS: Inorganic nitrate and beetroot supplementation was associated with beneficial effects on EF. These effects appear to be reduced in older subjects and in subjects with greater cardiometabolic risk.