The Inside Study: Oligosaccharides Versus Placebo in Functional Constipation

In order to be eligible to participate in this study, a subject must meet all of the following criteria, as considered by a medical doctor: * Written informed consent * Aged 1-3 years * Children that meet the Rome IV criteria for functional constipation Exclusion Criteria: A potential subject who meets any of the following criteria will be excluded from participation in this study: * Children who suffer from any other GI complaints than functional constipation, known structural GI abnormalities, or previous GI surgery * Any condition that would make it unsafe for the child to participate. * Children with clinically significant cardiac, vascular, liver, pulmonary, psychiatric disorders, severe renal insufficiency, human immunodeficiency virus, acquired immunodeficiency syndrome, hepatitis B or C or known abnormalities of haematology, urinalysis, or blood biochemistry * Children who are allergic to cow's milk or fish * Use of antibiotics or other medicines or food supplements, and breast milk-feeding, 4 weeks prior to the study, except for the allowed escape medication * Children that participate in another clinical trial