Evidence check: FUT2 in the context of gut health

FUT2 (fucosyltransferase 2) determines secretor status. Individuals with an inactive variant (non-secretors) lack fucosylated glycans on mucosal surfaces, which alters gut microbiome composition—particularly reducing Bifidobacterium-supporting oligosaccharides. Non-secretors often have lower Bifidobacterium abundance and a higher risk of vitamin B12 deficiency due to impaired intrinsic factor-mediated absorption. They are also more susceptible to certain infections (e.g., norovirus). Evidence comes from human observational studies and GWAS, but effects are modifiable: diet (prebiotics, B12-rich foods) and lifestyle play a major role. A DNA test provides insight, not a diagnosis. If B12 deficiency is suspected, confirm with blood work. Evidence: human-moderate.