Reducing meat and/or dairy consumption in adults: a systematic review and meta-analysis of effects on protein intake, anthropometric values, and body composition

Abstract

Context: Consumers are increasingly encouraged to reduce meat and dairy consumption. However, few meta-analyses of randomized controlled trials (RCTs) on the effect of reducing meat and/or dairy on (absolute) protein intake, anthropometric values, and body composition are available.

Objective: The aim of this systematic review and meta-analysis was to evaluate the effect of reducing meat and/or dairy consumption on (absolute) protein intake, anthropometric values, and body composition in adults aged ≥ 45 years.

Data Sources: The MEDLINE, Cochrane CENTRAL, Embase, ClinicalTrials.gov, and International Clinical Trials Registry Platform databases were searched up to November 24, 2021.

Data Extraction: Randomized controlled trials reporting protein intake, anthropometric values, and body composition were included.

Data Analysis: Data were pooled using random-effects models and expressed as the mean difference (MD) with 95%CI. Heterogeneity was assessed and quantified using Cochran’s Q and I2 statistics. In total, 19 RCTs with a median duration of 12 weeks (range, 4–24 weeks) and a total enrollment of 1475 participants were included. Participants who consumed meat- and/or dairy-reduced diets had a significantly lower protein intake than those who consumed control diets (9 RCTs; MD, −14 g/d; 95%CI, −20 to −8; I2 = 81%). Reducing meat and/or dairy consumption had no significant effect on body weight (14 RCTs; MD, −1.2 kg; 95%CI, −3 to 0.7; I2 = 12%), body mass index (13 RCTs; MD, −0.3 kg/m2; 95%CI, −1 to 0.4; I2 = 34%), waist circumference (9 RCTs; MD, −0.5 cm; 95%CI, −2.1 to 1.1; I2 = 26%), amount of body fat (8 RCTs; MD, −1.0 kg; 95%CI, −3.0 to 1.0; I2 = 48%), or lean body mass (9 RCTs; MD, −0.4 kg; 95%CI, −1.5 to 0.7; I2 = 0%).

Conclusion: Reduction of meat and/or dairy appears to reduce protein intake. There is no evidence of a significant impact on anthropometric values or body composition. More long-term intervention studies with defined amounts of meat and dairy are needed to investigate the long-term effects on nutrient intakes and health outcomes.