A widely recognized dietary trigger for gastrointestinal upset is lactose in those with lactase deficiency, where the osmotic effect of poorly absorbed lactose and its sub- sequent rapid fermentation can lead to bloating and diar- rhea. Because of this knowledge, all enteral formulae are free of lactose. However, there are other poorly absorbed and rapidly fermentable short-chain carbohydrates, col- lectively termed FODMAPs (Fermentable, Oligo-, Di-, Mono-saccharides And Polyols), that act similarly to undi- gested lactose. These include FOS, galacto-oligosaccha- rides (GOS), and fructose (in patients with fructose malabsorption). FODMAPs significantly increase output from the small bowel due to osmotic effects and present rapidly fermentable substrates to colonic bacteria with subsequent excessive and ongoing gas production in the intestines.