An in-vitro analysis of how lactose modifies the gut microbiota structure and function of adults in a donor-independent manner

Authors: Firrman, Jenni; Liu, Linshu; Mahalak, Karley; HU, WEIMING - The Children'S Hospital Of Philadelphia; BITTINGER, KYLE - The Children'S Hospital Of Philadelphia; MOUSTAFA, AHMED - The Children'S Hospital Of Philadelphia; JONES, STEVEN - The Children'S Hospital Of Philadelphia; Narrowe, Adrienne; Tomasula, Peggy

Submitted to: Frontiers in Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/14/2022
Publication Date: 1/26/2023
Citation: Firrman, J., Liu, L.S., Mahalak, K.K., Hu, W., Bittinger, K., Moustafa, A., Jones, S.M., Narrowe, A.B., Tomasula, M.M. 2023. An in-vitro analysis of how lactose modifies the gut microbiota structure and function of adults in a donor-independent manner. Frontiers in Nutrition. https://doi.org/10.3389/fnut.2022.1040744.
DOI: https://doi.org/10.3389/fnut.2022.1040744

Interpretive Summary: Milk is a staple of the American diet, and its consumption is associated with a number of health benefits due to its protein, healthy fatty acids, and mineral contents. However, the health benefits of lactose, the natural carbohydrate sugar in milk that gives it a slightly sweet taste, are not as understood. For those who are lactose-tolerant, the lactose in milk is either digested in the small intestine as a source of nutrition, or if partially digested, continues on to the large intestine where it interacts with the gut microbiota, a community of microbes that have specialized functions that contribute to human health. In this study, we examined the ability of lactose to exert changes on the gut microbiota community. The results indicated that lactose increased the bacteria associated with health benefits, such as lactic acid bacteria, and increased the levels of the bacterial byproducts that can promote cellular health in the colon. In conclusion, lactose promotes a healthy gut microbiota by increasing the presence of beneficial bacteria and production of their healthy metabolites.

Technical Abstract: Following consumption of milk, lactose, a disaccharide of glucose and galactose, is hydrolyzed and absorbed in the upper gastrointestinal tract (GIT) for those who are lactose-tolerant. However, hydrolysis and absorption are not always absolute, and some lactose will enter the colon where the gut microbiota has the ability to hydrolyze lactose and produce metabolic byproducts. In this study, the impact of lactose on the gut microbiota of healthy adults was examined, using a short-term, in vitro culturing strategy where fecal samples harvested from eighteen donors were cultured anaerobically with and without lactose. The data was compiled to identify donor-independent responses to lactose treatment. Metagenomic sequencing found that the addition of lactose decreased richness and evenness, while enhancing prevalence of the beta-galactosidase gene. Taxonomically, lactose treatment decreased relative abundance of Bacteroidaceae and increased lactic acid bacteria, Lactobacillaceae, Enterococcaceae, and Streptococcaceae, and the probiotic Bifidobacterium. This corresponded with an increased abundance of the lactate utilizers, Veillonellaceae. These structural changes coincided with increased total short-chain fatty acids (SCFAs), specifically acetate, and lactate. These results demonstrated that lactose could mediate the gut microbiota of healthy adults in a donor-independent manner and provided insight into how dietary milk consumption may promote human health through modifications of the gut microbiome.