Following an application from Cross Vetpharm Group UK Ltd, submitted for authorisation of a health claim pursuant to Article 14 of Regulation (EC) No 1924/2006 via the Competent Authority of the United Kingdom, the EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA) was asked to deliver an opinion on the scientific substantiation of a health claim related to β-galactosidase from Kluyveromyces lactis in Colief® and a reduction of gastrointestinal discomfort. The Panel considers that the food is sufficiently characterised in relation to the claimed effect. A reduction of gastrointestinal discomfort is a beneficial physiological effect for infants and young children. The applicant provided two human intervention studies for the substantiation of the health claim. No conclusions could be drawn from one of the two studies for the scientific substantiation of the claim, as the information provided in the publication and that supplied later by the applicant was inadequate to allow a scientific evaluation. The second study with methodological limitations showed an effect of the food on crying time in infants fed exclusively with milk. This study also provided some evidence for the proposed mechanism by which β-galactosidase could exert the claimed effect. In weighing the evidence, the Panel took into account that one study with methodological limitations showed an effect of β-galactosidase from Kluyveromyces lactis in Colief® on infant crying time, that no other human studies in which these results have been replicated were provided, and that there was some evidence for a mechanism by which the food could exert the claimed effect. The Panel concludes that the evidence provided is insufficient to establish a cause and effect relationship between the consumption of β-galactosidase from Kluyveromyces lactis in Colief® and a reduction of gastrointestinal discomfort.