Evaluation of in vitro fermentation characteristics and tolerance of lactose-free milk powder for lactose intolerant subjects

Abstract

The global prevalence of lactose malabsorption (LM) ranges from 65% to 70%, even reaching 100% in some Asian regions, while that of lactose intolerance (LI) remains unclear due to diagnostic complexity. Caused by reduced lactase activity, LI arises from colonic lactose fermentation and subsequent gastrointestinal discomfort. This study evaluated lactose-free milk powder (LFMP) via two approaches: in vitro fermentation using fecal microbiota from LI adults, and a randomized self-controlled clinical trial involving 41 LI subjects (trial 1: 14-day intervention + 14-day washout period (A), n=22; trial 2: 28-day intervention, n=19 (B)), with outcomes assessed by the Gastrointestinal Symptom Rating Scale (GSRS) and Short Form 36 Health Survey (SF-36). Compared with regular milk powder (RMP), LFMP showed higher fermentation pH, lower gas production (24–48 h, p < 0.05), enriched beneficial bacteria (Bacteroides, Blautia, Lactococcus) and reduced harmful bacteria (Shigella) at 24 h. LFMP also altered short-chain fatty acid profiles, increasing valerate and decreasing butyrate (p < 0.05). All subjects tolerated LFMP well, with only one case of transient mild discomfort. Conclusion: LFMP does not induce intestinal discomfort, confirming its safety for LI populations.