Lactose digestion needs a specialized enzyme, commonly called lactase. Lactase is a β-galactosidase that can be found on the upper surface of enterocytes on the microvilli of the small intestine, and it is maximally expressed in the medium jejunum (where the bacterial concentration is low and, therefore, little fermentation.
After ingestion, lactose passes into the small intestine where it comes into contact with lactase at the intestinal brush border where it is hydrolyzed into the monosaccharides glucose and galactose, which can be readily absorbed.
Lactose malabsorption (LM) refers to any cause of failure to digest and/or absorb lactose in the small intestine. This includes primary genetic and also secondary LD (lactase deficiency) due to infection or other conditions that affect the mucosal integrity of the small bowel.
The most frequent cause of lactose malabsorption is lactase non-persistence, a common condition in which lactase expression decreases during infancy. Lactase deficiency (LD) is the failure to express the enzyme that hydrolyses lactose into galactose and glucose in the small intestine.
Lactose malabsorption
