Abstract
BACKGROUND: Few studies evaluated the effect of different proportions of dietary plant- and animal-based protein on metabolic syndrome (MetS) and its related biomarkers. OBJECTIVE: Considering the effect of various types of dietary sources of protein on metabolic health and inconsistent results, this study sought to examine the impact of partially substituting animal protein with plant protein in the diet on the components of MetS, atherogenic index of plasma, and serum adropin values. METHODS: In this parallel, randomized clinical trial with two arms, 73 participants with MetS were randomly allocated to one of two slightly calorie-restricted intervention diets with different proportions of protein sources, including a plant-based protein diet (70% plant-based protein and 30% animal-based protein) and an animal-based protein diet (30% plant-based protein and 70% animal-based protein) for 10 weeks. All analyses were performed based on both intention-to-treat and per-protocol principles. RESULTS: Mean age in the plant and animal-based protein groups was 44.0 ± 9.8 and 43.9 ± 9.8 years, respectively. Within each group, weight, body mass index, systolic and diastolic blood pressure, and atherogenic index of plasma significantly decreased, and adropin levels significantly increased after the intervention (P < 0.05). However, waist circumference (WC) and triglyceride (TG) levels showed a significant decrease only in the plant protein group, and high-density lipoprotein cholesterol (HDL-c) levels illustrated a significant increase only in the animal protein group (P < 0.05). Between-group differences in both crude and adjusted models did not show any significant changes between the two intervention arms (P > 0.05). However, findings of per-protocol analyses illustrated a significant difference only in mean adropin values in two study arms. CONCLUSION: Our findings revealed that both diets based on plant and animal protein were associated with improved in anthropometric indices, MetS components, atherogenic index of plasma, and elevated serum adropin levels. Nevertheless, no statistically significant difference was identified between the two groups.