The Effects of Soy Protein-Rich Meals on Muscle Health of Older Adults Are Linked to Gut Microbiome Modifications.

Soy protein intervention preserved calf circumference in older adults while the control group experienced a decrease over 12 weeks.

• 12-week randomized controlled trial with 84 older adults from a long-term care facility
• Intervention group consumed three daily meals containing 10 g of soy protein (totalling 30 g/day); control group maintained usual diets
• W12-W0 change: Intervention group 0.56 ± 0.22 cm; Control group -0.91 ± 0.26 cm
• p(interaction) < 0.001

The soy protein intervention increased the abundance of SCFA-producing bacteria, specifically Roseburia faecis and Agathobaculum butyriciproducens.

• Roseburia faecis change: Intervention 0.42 ± 0.21%, Control -0.06 ± 0.16%, p(interaction) < 0.05
• Agathobaculum butyriciproducens change: Intervention 0.02 ± 0.007%, Control -0.04 ± 0.01%, p(time) < 0.01
• Faecal samples from 53 participants were collected at Weeks 0, 6, and 12 for metagenomic analysis

The soy protein intervention decreased the abundance of bacterial species associated with poorer muscle outcomes, including Alistipes putredinis and Eubacterium_sp_CAG_38.

• Alistipes putredinis change: Intervention -0.88 ± 0.40%, Control 0.62 ± 0.63%, p(interaction) < 0.05
• Eubacterium_sp_CAG_38 change: Intervention -0.64 ± 0.28%, Control 0.10 ± 0.22%, p(interaction) < 0.05
• These species were identified as associated with poorer muscle outcomes

The soy protein intervention enriched anaerobic amino acid degradation pathways and vitamin biosynthesis while depleting inflammatory pathways, particularly lipopolysaccharide biosynthesis.

• Functional pathway analysis was conducted via metagenomic analysis
• Enrichment of anaerobic amino acid degradation pathways and vitamin biosynthesis was observed in the intervention group
• Depletion of inflammatory pathways, particularly lipopolysaccharide biosynthesis, was observed in the intervention group

The soy protein intervention decreased aerobic bacteria abundance compared to the control group.

• Microbiome phenotype prediction was used to assess aerobic bacteria abundance
• W12-W0 change: Intervention -0.004 ± 0.002, Control 0.001 ± 0.001
• p(interaction) < 0.05

Within-group increases in short-chain fatty acids (butyric acid, isobutyric acid, and isovaleric acid) were observed at Week 6 in the intervention group only, with partial reversal by Week 12.

• Butyric acid at Week 6: Intervention 0.74 ± 0.34 mg/g, p(time) < 0.05; Control 0.12 ± 0.43 mg/g
• Isobutyric acid at Week 6: Intervention 0.14 ± 0.08 mg/g, p(time) < 0.05; Control 0.08 ± 0.10 mg/g
• Isovaleric acid at Week 6: Intervention 0.27 ± 0.14 mg/g, p(time) < 0.05; Control 0.16 ± 0.20 mg/g
• The interaction (group × time) for SCFA was not statistically significant
• SCFA increases were positively correlated with improved muscle function parameters