Changes in gut microbiota and lactose intolerance symptoms before and after daily lactose supplementation in individuals with the lactase non-persistent genotype

About 70∼100% of the Asian adult population is lactase non-persistent (LNP). The literature shows that many individuals with the LNP-genotype can consume ≤12g of lactose without experiencing gastrointestinal discomfort. Repetitive consumption of lactose may reduce intolerance symptoms via adaptation of the gut microbiota. This study aimed to assess the effects of daily consumption of incremental lactose doses on microbiota composition and function, and intolerance symptoms. Twenty-five healthy adults of Asian origin, carrying the LNP-genotype were included in this 12-week before-and-after intervention trial. Participants consumed gradually increasing lactose doses from 3 to 6g to 12g twice daily, each daily dose of 6, 12, or 24g being provided for 4 consecutive weeks. Participants handed in repeated stool samples and underwent a 25g lactose challenge hydrogen breath test (HBT) before and after the 12-week intervention. Daily gastrointestinal symptoms and total symptom scores (TSS) during the lactose challenge were recorded. A significant increase from 5.5±7.6% to 10.4±9.6% was observed in Bifidobacterium relative abundance after the intervention (p=0.009), accompanied by a two-fold increase (570±269U/g; p