Associations of high protein supplements with gut microbiota and skeletal muscle mass in hospitalized older people.

High-protein supplementation significantly increased skeletal muscle mass index in male participants during the intervention phase.

• Skeletal muscle mass index (SMI) increased from 6.0 to 6.3 kg/m² at 3 months in the male group (P < 0.05)
• SMI declined back to 6.1 kg/m² at 6 months (after the control phase without protein supplementation) (P < 0.05)
• No significant changes in SMI were observed in female participants (P > 0.05)
• The study enrolled 43 older patients aged 60 to 90 years with low skeletal muscle mass

Gut microbiota diversity and microbial structure were affected by protein supplementation and differed by sex.

• Bacterial diversity and microbial structure were both influenced by high-protein supplementation
• Sex-based differences were observed in the gut microbiota response to protein supplementation
• Males exhibited a greater abundance of SMI- and SMM-associated beneficial bacteria following protein intake
• The intervention consisted of approximately 36 g of high-protein supplementation daily, comprising both casein and whey proteins over 3 months

Microbial metabolic pathways related to amino acid synthesis were positively correlated with SMI-linked bacterial species.

• Metabolic pathway analysis indicated that microbial functions related to amino acid synthesis were positively correlated with SMI-linked species
• Specific species positively correlated with SMI included Blautia wexlerae and Corynebacterium dentalis
• These findings suggest a functional link between gut microbial metabolism and skeletal muscle regulation

The study was designed as a self-controlled trial with sequential intervention and control phases in hospitalized older adults.

• A self-controlled study design was used with 43 older patients aged 60 to 90 years with low skeletal muscle mass
• During the 3-month intervention phase, participants received approximately 36 g of high-protein supplementation daily comprising casein and whey proteins
• This was followed by a 3-month control phase in which participants received standard nursing care without protein supplementation
• The trial was registered at Chinese Clinical Trial Registry with identifier ChiCTR2400085432 on 07/06/2024

The findings suggest the existence of a gut-muscle axis that may mediate the effects of protein supplementation on muscle mass in older hospitalized patients.

• The authors highlight 'the presence of a gut-muscle axis' based on the associations between gut microbiota changes and skeletal muscle mass outcomes
• Gut microbial composition was proposed to mediate muscle regulation in hospitalized older people
• The results highlight 'the potential of targeted protein interventions to counteract inactivity-related muscle loss in older patients'
• Prolonged bed rest was identified as highly prevalent among hospitalized older adults and as markedly accelerating loss of muscle mass and physical function