Effects of L-citrulline supplementation on blood pressure: A systematic review and meta-analysis

We aimed to conduct a systematic review and meta-analysis of clinical trials that examined the effects of L-citrulline supplementation on blood pressure (BP). We searched MEDLINE, SCOPUS, PUBMED and Google scholar databases from inception to November 16, 2017 and 811 papers were identified, of which 8 trials with 10 data sets met the inclusion criteria. Inclusion criteria were: (1) application of randomized clinical trial with either crossover or parallel designs; (2) studies conducted in adults (≥18 y); (3) oral supplementation with L-citrulline compared to control group; (4) expression of sufficient data about systolic and diastolic BP at baseline and at the end of the study in each group. BP effects were pooled by random-effects models, with trials weighted by inverse variance. The included studies’ sample size ranged between 12 and 34 subjects. The mean age of the participants in these trials ranged between 22 and 71 years. Dosage of L-citrulline supplementation varied from 3 to 9 g/day. Duration of the intervention ranged between 1 and 17 weeks. The pooled changes in systolic and diastolic BP were (MD, −4.10 mm Hg; 95% CI [−7.94, -0.26]; p=0.037) and (MD −2.08 mm Hg; 95% CI [−4.32, 0.16]; P=0.069), respectively. The subgroup analysis showed a significant diastolic BP reduction in studies that used doses of ≥6 g/day (MD −2.75 mm Hg; 95% CI [−5.37, -0.12]; p=0.04). Our results suggest that L-citrulline supplementation may reduce systolic BP. A significant reduction in diastolic BP was observed only in the studies that used doses ≥ 6 g/day.