Gastroenterology
Lactose Intolerance
유당불내증
Lactose malabsorption from small bowel lactase deficiency
- How common
- East Asian 90%+
- Typical age
- Adult onset
What is it?
Lactase deficiency at small bowel villi prevents lactose hydrolysis; lactose is fermented in colon causing gas and osmotic diarrhea.
Commonly affected: Small bowel (absorption), colon (fermentation)
How it develops
- Lactase non-persistenceLCT gene activity declines after weaning
- Lactose malabsorptionLactose not hydrolyzed in small bowel
- Colonic fermentationBacteria ferment lactose → H2, CH4, SCFAs
- Osmotic diarrhea/gasUnabsorbed sugar draws water into lumen
Symptoms
- Bloating/flatulence30-120 min after dairy
- Abdominal crampingLower abdominal pain
- DiarrheaOsmotic, frothy
- Nausea/belchingIndigestion
How it is examined
- Elimination/rechallengeEliminate dairy → symptoms return on rechallenge
- Hydrogen breath testLactose load → H2 rise ≥20 ppm = positive
- Lactose tolerance testGlucose rise <20 mg/dL = positive
Imaging
Imaging not needed.
- Clinical
Workup for IBS, celiac, SIBO if needed.
- Differential workup
Non-surgical care
- Lactose restrictionLimit milk, condensed milk, ice cream
- Lactase supplementsTake before meals (Lactaid)
- Fermented dairyYogurt and aged cheese have less lactose
- Calcium/vit D supplementPrevent deficiency from dairy avoidance
Conservative options are generally tried first. Medications listed here can have side effects — discuss them with your prescriber.
When surgery is considered
None
Outlook
Excellent with dietary control; some tolerate small amounts.