In man, autosomal recessive loss-of-function mutations in the KHK gene resulting in ketohexokinase deficiency, manifest as a benign condition “essential fructosuria” in which fructose is excreted in the urine because of impaired hepatic clearance (81) and likewise in mice Khk deletion has negligible phenotype (82) and in conjunction with AldB deficiency is protective (83). This evidence concerns the gene KHK and essential fructosuria.