Lactose intolerance (LI) (due to lactase deficiency, down-regulation of lactase activity, lactose malabsorption causing abdominal symptoms upon lactose-containing products) [5,6,7] and fructose intolerance (due to fructose malabsorption with symptoms upon ingestion of fructose-containing foods) in adults [8] can easily mimic several FGIDs. This evidence concerns the gene LCT and lactose intolerance.