Through our systematic literature review, we identified eight case-control studies (18,268 participants and 4780 cancer cases) covering three continents (i.e., America, Asia, and Europe) and three cancer sites (i.e., colon/rectum, prostate, and breast) that examined the association between dietary factors and cancer risk among participants who differ in PPARG2 Pro12Ala polymorphism. The gene discussed is PPARG; the disease is cancer.