Role of the gut microbiome in mediating lactose intolerance symptoms.

Misselwitz et al recently reviewed the multifactorial aspects of lactose intolerance (LI).1 Their work highlights the known effects of genetic makeup and dietary patterns in the occurrence of gastrointestinal symptoms in LI individuals. The authors define LI as the occurrence of gastrointestinal complaints on lactose exposure and discuss the wide variety of symptoms among LI patients.1 Regarding lactose metabolism, Misselwitz et al mention the influence of the gut microbiome, in particular that Bifidobacterium or other lactose-fermenting bacteria are reported to affect the levels of lactose in the gut. However, the impact of the gut microbiome on the occurrence of gut-related LI symptoms remains unclear. We previously observed that the Bifidobacterium abundance in the adult human gut depends on the interaction between LI genetic variants and dairy intake.2 This observation complements other findings indicating a mutual relationship between the gut microbiome and host lactose metabolism.3–8 However, these earlier analyses did not consider the occurrence of gastrointestinal symptoms. This inspired us to investigate whether the interplay of dairy consumption and Bifidobacterium affects the occurrence of gastrointestinal complaints in LI individuals. We analysed data on gut complaints, genetics, gut microbiome and diet in 959 participants of the Lifelines-DEEP Dutch population cohort. We classified LI genetic status based on the presence of the functional variant rs4988235 …