Background: Lactose intolerance is a common gastrointestinal condition resulting from insufficient intestinal lactase activity and the subsequent fermentation of undigested lactose. Fermented beverages have attracted increasing attention as potentially better-tolerated dietary options. However, their clinical effects vary according to microbial composition, fermentation substrate, residual lactose content, and the availability of microbial β-galactosidase.
Objective: To critically examine clinical and mechanistic evidence regarding dairy and non-dairy fermented beverages in individuals with lactose maldigestion or intolerance, emphasizing milk kefir, water kefir, kombucha, and yogurt.
Methods: A focused literature review was conducted using accessible biomedical literature and reference tracking. Human intervention studies, systematic reviews, mechanistic investigations, and microbiological studies were considered. Evidence was categorized according to direct clinical relevance, indirect gastrointestinal outcomes, and compositional or mechanistic plausibility. Because a fully reproducible, independently screened database search was not completed, the review is presented as a critical scoping-style synthesis rather than a completed PRISMA-ScR systematic scoping review.
Results: Live-culture yogurt has the most consistent evidence for improving lactose digestion, supported by clinical studies and systematic reviews. A small randomized study involving 15 adults demonstrated that milk kefir reduced breath hydrogen production and flatulence compared with milk. Water kefir and kombucha are traditionally lactose-free, but clinical evidence demonstrating improvement in lactose-specific symptoms is lacking. Recent kombucha trials suggest heterogeneous effects on gastrointestinal symptoms and microbiota without establishing therapeutic efficacy for lactose intolerance.
Conclusions: Fermented beverages should not be considered clinically interchangeable. Yogurt and milk kefir may facilitate digestion of residual lactose, whereas water kefir and kombucha primarily offer non-dairy alternatives. Standardized clinical trials are needed to establish whether non-dairy fermented beverages provide benefits beyond lactose avoidance.