Mediterranean Diet Increases Endothelial Function in Adults: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.

BACKGROUND: The endothelium plays a key role in the maintenance of vascular health and represents a potential physiological target for dietary and other lifestyle interventions designed to reduce the risk of cardiovascular diseases (CVD) including stroke or coronary heart disease. OBJECTIVE: To conduct a systematic review and meta-analysis of randomized controlled trials (RCTs) investigating the effects of the Mediterranean dietary pattern (MedDiet) on endothelial function. METHODS: Medline, Embase, and Scopus databases were searched from inception until January 2019 for studies that met the following criteria: 1) RCTs including adult participants, 2) interventions promoting the MedDiet, 3) inclusion of a control group, and 4) measurements of endothelial function. A random-effects meta-analysis was conducted. Metaregression and subgroup analyses were performed to identify whether effects were modified by health status (i.e., healthy participants versus participants with existing comorbidities), type of intervention (i.e., MedDiet alone or with a cointervention), study duration, study design (i.e., parallel or crossover), BMI, and age of participants. RESULTS: Fourteen articles reporting data for 1930 participants were included in the meta-analysis. Study duration ranged from 4 wk to 2.3 y. We observed a beneficial effect of the MedDiet on endothelial function [standardized mean difference (SMD): 0.35; 95% CI: 0.17, 0.53; P <0.001; I2 = 73.68%]. MedDiet interventions improved flow-mediated dilation (FMD)-the reference method for noninvasive, clinical measurement of endothelial function-by 1.66% (absolute change; 95% CI: 1.15, 2.17; P <0.001; I2 = 0%). Effects of the MedDiet on endothelial function were not modified by health status, type of intervention, study duration, study design, BMI, or age of participants (P >0.05). CONCLUSIONS: MedDiet interventions improve endothelial function in adults, suggesting that the protective effects of the MedDiet are evident at early stages of the atherosclerotic process with important implications for the early prevention of CVD. This study has the PROSPERO registration number: CRD42018106188.

Nitrate-Rich Beetroot Juice Reduces Blood Pressure in Tanzanian Adults with Elevated Blood Pressure: A Double-Blind Randomized Controlled Feasibility Trial.

BACKGROUND: In Sub-Saharan Africa, current strategies are struggling to control the burgeoning hypertension epidemic. Dietary interventions such as inorganic nitrate or folic acid supplementation could represent promising strategies for reducing blood pressure (BP) in this setting. OBJECTIVES: This feasibility study explores the effects of dietary inorganic nitrate supplementation, alone or in combination with folic acid, on BP in Tanzanian adults with elevated BP in Tanzania. METHODS: A placebo-controlled, double-blind, randomized controlled feasibility trial was conducted. Forty-seven middle-aged and older participants (age: 50-70 y, BMI: 26.3-29.1 kg/m2) were randomly assigned to 3 conditions for a period of 60 d: 1) high-nitrate beetroot juice (∼400 mg nitrate) and folic acid (∼5 mg folic acid) (N + F), 2) high-nitrate beetroot juice and placebo (N + P), or 3) nitrate-depleted beetroot juice and placebo (P + P). Clinic and 24-h ambulatory BP and measurements of compliance in plasma (nitrate and folate concentrations) and saliva (nitrate and nitrite) were obtained at baseline, 30 d, and 60 d. RESULTS: Baseline resting systolic and diastolic BP (mean ± SD) was 151.0 ± 19.4 mm Hg and 91.8 ± 11.7 mm Hg, respectively. Compliance to the interventions was high (>90%) in all groups which was confirmed by the significant increase in nitrate and folic acid concentrations in plasma and saliva samples in the treatment arms. After 60 d, 24-h systolic BP dropped by -10.8 ± 9.8 mm Hg (P < 0.001), -6.1 ± 13.2 mm Hg (P = 0.03), and -0.3 ± 9.7 mm Hg (P = 0.83) in the N + P, N + F, and P + P groups, respectively. There was a significant decrease in 24-h diastolic BP in the N + P group (-5.4 ± 5.0 mm Hg, P = 0.004), whereas changes were not significant in the N + F (-1.8 ± 8.1 mm Hg, P = 0.32) and P + P (1.6 ± 8.3 mm Hg, P = 0.43) groups. CONCLUSIONS: Dietary inorganic nitrate represents a potential nutritional strategy to lessen the hypertension epidemic in Sub-Saharan Africa. These findings support the rationale for future long-term investigations exploring the efficacy of dietary nitrate for lowering BP and attenuating cardiovascular disease risk in this setting.This trial was registered at isrctn.com as ISRCTN67978523.