[Lactose Malabsorption and Intolerance].

Lactose malabsorption and lactose intolerance are common yet clinically distinct conditions. Lactose malabsorption refers to the passage of undigested lactose into the colon due to lactase deficiency, whereas lactose intolerance involves the onset of gastrointestinal symptoms following lactose ingestion in the presence of malabsorption. Alactasia is a rare congenital disorder characterized by complete absence of lactase activity. Primary hypolactasia is a physiological and genetically determined decline in lactase activity occurring in adulthood. Globally, the prevalence of lactose malabsorption affects up to two-thirds of the population, with particularly high rates in Latin America and Mexico. Diagnosis can be established through non-invasive methods such as the hydrogen breath test, genetic testing, the gaxilose test, and lactose tolerance testing, or through invasive procedures like enzymatic activity measurement in duodenal biopsies. Management should aim to control symptoms without compromising nutritional status and may include low-lactose diets, oral lactase enzyme supplementation, and the use of probiotics or prebiotics. Avoiding unnecessary dietary restrictions is essential to prevent nutritional deficiencies or the development of avoidant/restrictive food intake disorder. An individualized diagnostic and therapeutic approach improves both clinical outcomes and quality of life in affected patients.