Myths vs facts: FUT2 and fatigue

Claims that the FUT2 gene directly causes fatigue are not supported by strong evidence. FUT2 (fucosyltransferase 2) determines secretor status and influences gut microbiome composition and susceptibility to certain infections (e.g., norovirus). Some studies suggest links between gut microbiota and fatigue, but the evidence for a direct causal pathway from FUT2 variants to fatigue is weak and mostly mechanistic. Most commercial DNA tests overstate the clinical relevance of such markers. Factors like sleep quality, stress, diet, and exercise have a far greater impact on energy levels. Therefore, a FUT2 test cannot reliably predict or explain fatigue. Evidence: mechanistic, no controlled trials. Beware of exaggerated marketing claims.