Myths vs facts: FUT2 and Darmgesundheit

The FUT2 gene encodes fucosyltransferase 2, which determines whether a person is a 'secretor' (about 80% of Europeans) or a 'non-secretor'. Secretors produce fucosylated H-antigens in body fluids and on the gut mucosa, which serve as food for certain bacteria. Studies show that non-secretors have an altered gut microbiota – fewer Bifidobacteria, more potentially pathogenic microbes – and an increased risk for Crohn's disease and norovirus infections. However, many direct-to-consumer claims are exaggerated: a FUT2 test alone does not predict a definite gut disorder, and evidence for specific dietary recommendations (e.g., certain prebiotics) is still weak. The associations come from GWAS and cohort studies, but effect sizes are small, and clinical relevance for individuals remains unclear. Knowing your FUT2 status should be considered one factor among many – not a sole basis for drastic dietary changes. A sound approach is to support the microbiota with a high-fiber, diverse diet regardless of genotype.