The objective of this study is to assess to what extent goat's milk is better tolerated than cow's milk among individuals who report being intolerant to cow's milk, and, if so, to understand the underlying factors. To achieve this, digestive discomfort sensations and postprandial kinetics of nutrients after ingestion of cow's or goat's milk will be compared in two populations: individuals intolerant to cow's milk but not to goat's milk, and individuals who show no symptoms of intolerance to either cow's or goat's milk. For this purpose, approaches based on stable isotope labeling of milk will be employed.