In vitro assessment of the effect of lactose‐free milk on colon microbiota of lactose‐intolerant adults

Summary Milk is an essential food, but a large part of adult's population is uncapable to digest lactose. Lactose intolerance can seriously affect the intestinal ecology and compromise the host's well‐being. In this scenario, the role of human gut microbiota is crucial, but little is known about that because few research studies were conducted, via either clinical trials or in vitro models. Also, due to the call to reduce animal testing in science, an in vitro model with the gut microbiota of lactose‐intolerant adults is necessary. This paper proposes an in vitro model coupling oro‐gastro‐duodenal digestion to colonic fermentation to evaluate lactose impact on colon microbiota of lactose‐intolerant adults. Microbiomics and metabolomics with respect to a baseline of fermentation were compared. Generally, when the insult was given, taxa specialised for dairy sugars were unaffected, but Bacteroidaceae and Lachnospiraceae were underrepresented. Lactose triggered raise of opportunistic Proteobacteria dominated by harmful Klebsiella. In addition, an important reduction of essential short‐chain fatty acids was observed, and in particular, that of butyrate. Although more observations need to be conducted, as well as a comparison with the healthy condition, the present work gives results for pre‐clinical application in the sight to reduce animal testing. Lactose free milk and milk with lacotse were compared to test some actions on gut microbiota of lactose intolerant adults in an in vitro model. In vitro oral‐gastro‐duodenal digestion was followed by in vitro human colon microbiota of lactose‐intolerant adults. Microbial colon metabolism and microbial colon populations were assesd by 'omics. The lactose insult generates 2.2. times more abundance of Klebsiella, 6.7 times less abundant Faecalibacterium prausnitzii, 5.2 times more Roseburia, 2.2 times more acetate and 1.5 times more p‐cresol.