A milk protein hydrolysate, for use in the prevention and/or treatment of diarrhoea, wherein the protein hydrolysate is capable of inhibiting neprilysin enzyme with an IC50 from 0.005 to 0.600 mg/ml, and it is obtainable by a method comprising the steps of: (a) adding to a composition comprising milk protein that comprises milk casein selected from the group consisting of beta-casein, alpha-casein, and mixtures thereof, in a total milk protein concentration from 3 % to 20 % weight/volume (w/v), at least a protease system that is active at an optimal pH from 5.5 to 8.5, said protease system comprising a protease selected from the group consisting of thermolysin, or a mixture of neutral protease and alkaline protease; and (b) incubating at a constant pH from 6 to 8 and to a temperature from 45 ° C to 55 °C the mixture of (a) to hydrolysate the milk protein until a degree of hydrolysis of the composition is from 1.0 to 40.0 %; wherein DH is calculated by means of the following formula: DH = B × Nb × 1 / a × 1 / MP × 1 / Htot × 100; wherein B is the volume in millilitres (ml) of consumed base used for titrating released amino groups during hydrolysis of the composition comprising milk protein, Nb is the normality of the base used for titrating, 1/a is the average degree of dissociation of the amino groups related with the pK of said amino groups at a particular pH and temperature, MP is the amount in grams of the composition comprising milk protein to be incubated with the protease system, and Htot in milliequivalents per g (meq/g) is the sum of the millimoles of individual amino acids per gram of protein associated with the composition comprising milk protein; and wherein the IC50 is the concentration of the hydrolysate that inhibits 50 % of the neprilysin enzyme activity, said IC50 determined by a fluorogenic enzymatic assay with a fluorescence excitation wavelength of 320 nm and with a fluorescence emission wavelength of 405 nm, the assay performed at 37 °C with dilutions of hydrolysate samples from no dilution to a dilution of at least 1/100 in water, in order to obtain a curve of percentage of inhibition of the enzyme per assayed hydrolysate dilution. (a) adding to a composition comprising milk protein that comprises milk casein selected from the group consisting of beta-casein, alpha-casein, and mixtures thereof, in a total milk protein concentration from 3 % to 20 % weight/volume (w/v), at least a protease system that is active at an optimal pH from 5.5 to 8.5, said protease system comprising a protease selected from the group consisting of thermolysin, or a mixture of neutral protease and alkaline protease; and (b) incubating at a constant pH from 6 to 8 and to a temperature from 45 ° C to 55 °C the mixture of (a) to hydrolysate the milk protein until a degree of hydrolysis of the composition is from 1.0 to 40.0 %; B is the volume in millilitres (ml) of consumed base used for titrating released amino groups during hydrolysis of the composition comprising milk protein, Nb is the normality of the base used for titrating, 1/a is the average degree of dissociation of the amino groups related with the pK of said amino groups at a particular pH and temperature, MP is the amount in grams of the composition comprising milk protein to be incubated with the protease system, and Htot in milliequivalents per g (meq/g) is the sum of the millimoles of individual amino acids per gram of protein associated with the composition comprising milk protein; and