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Abstract:
The lactase-persistence (LP) genotype allows digestion of the milk sugar lactose in adults and confers lactose tolerance. Genetically lactase non-persistent (LNP) individuals can also be lactose tolerant, but responsible microbiota remain elusive. Here, we assessed lactose tolerance as H2-production in breath after lactose dose, LP/LNP genotype, and gut microbiome metagenomic diversity in 480 adults from Gabon (100% LNP), Vietnam (99% LNP), and Germany (23% LNP). In all three populations, ~ 13% of LNP were lactose tolerant though microbiomes differed. In-vitro lactose addition to stool showed low H2 production stemmed either from minimal breakdown of lactose, or breakdown producing metabolites of the Bifid shunt pathway - lactate and acetate - and the growth of Bifidobacterium. Our results indicate that Bifidobacterium can confer lactose tolerance across populations, including where the LP genotype is rare, and may have facilitated functional take-over by the human genome when dairying first began 12,000 years ago.
