Table 1.
Hypolactasia | Any deficiency of the lactase enzyme |
Lactase non-persistence | This is considered the “wild-type” condition, as most individuals have reduced lactase activity at the jejunal border after weaning. In a minority of humans, a high level of activity of the lactase enzyme is present through all adulthood (lactase persistence phenotype) |
Lactose maldigestion | Inefficient digestion of lactose, due to lactase deficiency (either lactase non-persistence or other intestinal conditions) |
Lactose malabsorption | Inefficient absorption of lactose, due to lactose maldigestion, as lactose cannot be absorbed in the undigested form |
Lactose intolerance | Gastrointestinal symptoms due to lactose malabsorption |