Consumption of different soymilk formulations differentially affects the gut microbiomes of overweight and obese men

The effects of consuming foods on the intestinal microbiome of obese individuals remain unclear. The objective of this study was to compare the effects of consuming low glycinin soymilk (LGS, 49.5% β-conglycinin/6% glycinin), conventional soymilk (S, 26.5% β-conglycinin/38.7% glycinin) or bovine milk (M, 0% β-conglycinin/0% glycinin) on the intestinal microbiome in overweight and obese men. In a randomized double-blind study, participants (64 men, BMI > 25, 20-45 y old), organized in three groups, consumed 500 mL of LGS, S or M daily for 3 mo. Three fecal samples were collected before (baseline) and after 3 mo of consumption. Dietary energy and macronutrient intake were monitored monthly and remained constant throughout the study (p > 0.05). Microbial composition was analyzed with qPCR and bTEFAP. Within groups, qPCR analysis showed that the total bacteria increased in all treatments over time (p < 0.001). Bacteroides-Prevotella (p = 0.001) and Lactobacillus (p < 0.001) increased in LGS and M, respectively. Bifidobacterium was significantly reduced in LGS (p = 0.003) and S (p < 0.001). Bacterial diversity decreased for LGS, S and M (p = 0.004, 0.005, 0.001; respectively). Unweighted UniFrac analysis revealed that the microbial communities were more similar within than between individuals. The Firmicutes to Bacteroidetes ratio decreased in both LGS and S groups and remained relatively unchanged in the M group (Time p = 0.012; Interaction p = 0.059). Indicator analysis revealed several genera that were indicative of each treatment including Lactobacillus and Prevotella. Consumption of the three beverages differentially altered the microbiota in overweight and obese men including a potentially beneficial alteration of the Firmicutes to Bacteroidetes ratio in both soymilk groups.