What to watch with FUT2 and Sport?

The FUT2 variant determines whether you secrete blood group antigens into body fluids (secretor status). This influences gut microbiota composition and vitamin B12 absorption. In a sports context, non-secretor status (e.g., rs601338 A allele) may be linked to higher risk of B12 deficiency and altered immune response to respiratory infections – both potentially relevant for performance. However, these insights come mainly from population genetic and mechanistic studies; direct athletic performance data are lacking. Moreover, the effect of a single SNP is small. A FUT2 test alone does not warrant drastic training or diet changes. If you have deficiency symptoms or frequent infections, it is reasonable to check B12 levels clinically and focus on a balanced, microbiota-supporting diet. The evidence is currently rated as 'mechanistic'.