Un-absorbable, water-soluble solutes in the bowel that retain water through osmosis (movement of water from low to high concentrations of solute). Examples of these particles are lactose in lactose intolerant people and sugar substitutes (such as sorbitol, mannitol and high fructose syrups).
The presence of osmotic load in the intestine results in bloating since these particles attract water to the intestine giving a sensation of distension and discomfort. (1)