The invention pertains to the use of pectin and alginate in the manufacture of a liquid nutritional composition in the treatment or prevention of gastro-oesophageal reflux in a patient, said composition comprising pectin and alginate, said composition exhibiting a maximum gel strength at a pH in the range between 3.5 and 5, said gel strength expressed as storage modulus G between 200 and 10,000 Pascal. A combination of low methylated pectin and (sodium) alginate was found to have the strongest thickening effect directly after entry in the stomach, which initial increase in viscosity (at the beginning of the stomach)is decreased later when the pH becomes lower than 4 (i.e. the pH at the end of the stomach). This decrease in viscosity at the lower part (antrum and pylorus) of the stomach stimulates the gastric emptying time of the food consumed.