GLOSSARY

Lactose intolerance is the occurrence of gastrointestinal symptoms (such as bloating, gas, abdominal pain, and diarrhoea) after consuming lactose in people with lactase deficiency; undigested lactose reaches the colon, draws in water by an osmotic effect, and is fermented by bacteria.

Types

• Primary (lactase non-persistence): the most common; a genetic, gradual decline in lactase after childhood.
• Secondary: damage to the intestinal mucosa (such as from gastroenteritis, coeliac disease, and Crohn’s disease); often temporary.
• Congenital: very rare; absence of lactase from birth.
• Developmental: in premature infants.

Diagnosis

• Hydrogen breath test: a rise in H₂ of more than 20 ppm after a lactose load.
• Genetic testing (the LCT-13910 polymorphism).
• Elimination and challenge test: removing dairy for 2 weeks, then reintroducing it.

Difference from Milk Allergy

Milk protein allergy (to casein or whey) is an immune reaction that may be dangerous (hives, swelling, and anaphylaxis), whereas lactose intolerance is a