Effect of Low-Lactose Processed Milk on Clinical Symptoms and Gut Microbiome Modulation in Lactose-Intolerant Adults

This study aimed to evaluate the effects of low-lactose processed milk consumption on body composition, clinical indicators, hydrogen breath levels, and gut microbiome changes in Korean adults with lactose intolerance. A total of 32 participants diagnosed with lactose intolerance, as determined by a hydrogen breath test, were enrolled in the study. During the 30-day intervention period, participants consumed one serving per day of banana-flavored milk containing 10.2 g of lactose. Stool and breath samples were collected before and after the intervention to assess changes in gut microbiota composition and lactose malabsorption. Following the intervention, significant improvements were observed in body composition, including reductions in body fat percentage ( P < .001) and increases in fat-free mass ( P < .001), skeletal muscle mass ( P < .001), and soft-tissue lean mass ( P < .001). Blood pressure also decreased; however, no significant changes were observed in hematological markers. Hydrogen breath test results demonstrated a significant reduction in hydrogen breath levels, and 40.6% of participants were reclassified as negative for lactose intolerance post-intervention. While no significant changes were observed in alpha diversity or overall microbial composition across all participants, a significant increase in the relative abundance of the Weissella confusa group ( P = .007) was detected in individuals who tested negative for lactose intolerance after consuming the intervention food. These findings suggest that consuming low-lactose processed milk improves lactose intolerance, body composition, and gut microbiota composition, providing a feasible dietary strategy for managing lactose intolerance in adults.