Fermented milk protein consumption improves exercise performance and total body mass in prepubertal children: a...

Milk proteins are highly digestible and contain essential amino acids. Fermentation by lactic acid bacteria can modify protein characteristics and may influence digestion and downstream responses. Direct human comparisons of fermented versus non-fermented milk protein in prepubertal children are lacking. In this pilot randomized, double-blind, placebo-controlled trial, we examined whether an 8-week fermented milk protein beverage affects exercise performance, body composition, and gut microbiota in prepubertal boys.

A randomized, double-blind, parallel-group controlled trial was conducted in 44 healthy boys aged 10-12 years who regularly played soccer. Participants were randomly assigned to one of three groups: fermented milk protein beverage (FM; 93 kcal, 12 g protein/200 mL), milk protein beverage (MP; 93 kcal, 12 g protein/200 mL), or placebo beverage (PL; 93 kcal, 0 g protein/200 mL) group. Each group was instructed to consume the assigned beverage daily for 8 weeks. The prespecified primary outcome was the change in 10-m sprint time; and secondary outcomes included 20-m sprint time, countermovement jump, standing long jump, Yo-Yo test, total body mass, lean body mass (LBM), and exploratory gut microbiota analyses.

Compared with the PL group, both the FM and MP groups showed significant improvements in 10-m sprint time based on pre- to post-intervention changes (0.015 ± 0.013, -0.024 ± 0.013, and -0.045 ± 0.015 s for PL, FM, and MP, respectively). The FM group also exhibited a significantly greater increase in total body mass than the PL group (0.85 ± 0.19 kg vs. 0.28 ± 0.19 kg, respectively). No significant between-group differences were observed for LBM or other performance outcomes. Exploratory microbiota analyses indicated a within-group increase in Bacteroides massiliensis in FM and associative (non-causal) correlations with phenotype changes.

In this pilot study, daily fermented milk protein intake was associated with modest improvements in short-distance sprint performance and increased total body mass vs. placebo, while superiority over non-fermented milk protein was not consistently demonstrated. Larger trials are needed to confirm these findings and clarify mechanisms.

https://rctportal.mhlw.go.jp/en/detail?trial_id=UMIN000055618, UMIN-CTR UMIN000055618.