The effects of beetroot and nitrate supplementation on body composition: A GRADE-assessed systematic review and meta-analysis.

This systematic review and meta-analysis aimed to investigate the effects of beetroot (BR) or nitrate supplements on body composition indices. A systematic search was conducted for randomized controlled trials (RCTs) published up to August 2022 among online databases including Scopus, PubMed/Medline, Web of Science, and Embase. Meta-analyses were carried out using a random-effects model. The I 2 index was used to assess the heterogeneity of RCTs. A total of 12 RCTs met the inclusion criteria for this meta-analysis. The pooled effect size of included studies indicated that BR or nitrate supplementation did not change body weight (WMD: -0.14 kg, 95% CI: -1.22, 1.51; P=0.836; I 2 = 0%), body mass index (BMI) (WMD: -0.07 kg/m 2 , 95% CI: -0.19,0.03; P= 0.174, I 2 = 0%), fat mass (FM) (WMD: -0.26 kg, 95% CI: -1.51, 0.98; P= 0.677, I 2 = 0%), waist circumference (WC) (WMD: -0.28 cm, 95% CI: -2.30, 1.74; P= 0.786, I 2 = 0%), body fat percentage (BFP) (WMD: 0.18%, 95% CI: -0.62, 0.99; P= 0.651, I 2 = 0%), fat-free mass (FFM) (WMD: 0.31 kg, 95% CI: -0.31, 1.94; P= 0.703, I 2 = 0%), and WHR (WMD: 0, 95% CI: -0.01, 0.02; P= 0.676, I2 = 0%). Subgroup analyses based on trial duration, BR or nitrate dose, study design, baseline BMI, and athletic status (athlete versus nonathlete) demonstrated similar results. Certainty of evidence across outcomes ranged from low to moderate. This meta-analysis study suggests that BR or nitrate supplements cannot efficiently ameliorate body composition indices regardless of supplement dosage, trial duration, and athletic status.