“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,” they wrote in Frontiers in Nutrition, noting that larger trials are needed to confirm the findings and clarify mechanisms.
Building on previous research on the metabolic benefits of fermented milk products, the researchers chose to evaluate protein sources in a study population during a phase of rapid growth and development, when sufficient amino acids are required to support sports activities.
“The fermented milk protein beverage used in this study is a postbiotic, containing 2.6 × 1011 CFU of inanimate lactic acid bacteria,” they noted. “It has been suggested that the mechanism of action for the health benefits conferred by postbiotics may be similar to that of probiotics”.
Differences in milk proteins
Milk proteins contain branched-chain amino acids (BCAAs), which can help to build muscle. The main proteins in milk are whey and casein, and while both have nutritional value, whey protein is more readily absorbed and digested.
Casein aggregates in the stomach’s acidic conditions, causing it to coagulate and digest more slowly. Therefore, most people choose whey protein to elevate blood amino acid concentrations and boost muscle synthesis.
Fermented milk, produced by fermenting milk with lactic acid bacteria, is commonly consumed in products such as yogurt and cheese. Some of the proteins in fermented milk are partially hydrolyzed during fermentation, aiding absorption and digestion, and the casein doesn’t coagulate in the stomach as much as regular milk.
Animal studies suggest that fermented milk may increase amino acid concentrations, enhancing muscle protein synthesis more effectively than non-fermented milk. However, human studies are limited, and more research is required.
Additionally, some research suggests that fermented milk products may be more beneficial for modulating energy balance, obesity, and skeletal muscle function, working via the gut-muscle axis.
Study details
The researchers randomly assigned 44 healthy boys aged 10 to 12 who regularly played soccer to consume either a daily fermented milk protein drink, a milk protein drink, or a placebo for eight weeks.
Both milk drinks contained 12g of protein per 200ml. The researchers conducted pre- and post-intervention measurements, including height, sitting height, and body composition, took a brief dietary history, and evaluated the gut microbiota.
Following the measurements, the participants completed a warm-up, then a 20-m sprint, a countermovement jump, a standing long jump, and a Yo-Yo test.
The findings showed “significant improvements in 10-m sprint time based on pre- to post-intervention changes” in both milk drinks compared to placebo, and a greater increase in total body mass in the fermented milk group. There were no significant differences between groups for lean body mass.
The fermented drink group showed an increase of Bacteroides massiliensis, “and a correlation was observed between its relative abundance and changes in both exercise performance and body weight,” the researchers wrote.
They acknowledged the study’s limitations, including a small sample size and the assessment methodology, and called for future research to address them.
Source: Front. Nutr., https://doi.org/10.3389/fnut.2026.1755943, “Fermented milk protein consumption improves exercise performance and total body mass in prepubertal children: a randomized double-blind, placebo-controlled pilot trial”, Authors: A. Kanda et al.
