We report that the FADS Indel, a functional 22 bp insertion-deletion polymorphism in FADS2 (rs66698963), which is known to direct FADS1-dependent synthesis and availability of the n–6 HUFA AA, stratifies participants in the seAFOod trial that display colorectal polyp prevention by the n–3 HUFA EPA. Here, FADS2 is linked to polyp of large intestine.