Lactose intolerance is the inability to digest lactose, the sugar found in milk and dairy products, due to lactase enzyme deficiency in the small intestine. This leads to gastrointestinal symptoms after consuming lactose-containing foods.
🧬 Pathophysiology
- Lactase breaks down lactose into glucose and galactose for absorption.
- In lactase deficiency, lactose remains undigested → fermented by colonic bacteria → producing gas and short-chain fatty acids.
- Causes bloating, diarrhea, and abdominal pain.
⚠️ Types of Lactose Intolerance
| Type | Description |
|---|---|
| Primary (adult-type) | Most common; lactase production decreases after infancy (genetic predisposition) |
| Secondary | Due to intestinal injury/disease (e.g., celiac disease, gastroenteritis, Crohn’s) |
| Congenital | Rare; genetic mutation causing complete absence of lactase from birth |
😖 Symptoms
- Abdominal bloating and cramps
- Diarrhea (watery, sometimes explosive)
- Flatulence
- Nausea (occasionally)
- Symptoms usually begin 30 minutes to 2 hours after lactose ingestion
🧪 Diagnosis
1. Hydrogen Breath Test (Gold Standard)
- Measures hydrogen produced by bacterial fermentation of undigested lactose.
- Positive if hydrogen rises significantly after lactose ingestion.
2. Lactose Tolerance Test
- Measures blood glucose after lactose intake.
- Blunted glucose rise indicates malabsorption.
3. Empiric Lactose-Free Diet Trial
- Symptom improvement after removing lactose.
💊 Management
Dietary
- Limit or avoid lactose-containing foods (milk, soft cheeses, ice cream)
- Use lactose-free dairy products or plant-based alternatives (almond, soy, oat milk)
- Hard cheeses and yogurt often better tolerated due to lower lactose content or presence of lactase-producing bacteria
Enzyme Replacement
- Over-the-counter lactase enzyme supplements can be taken before lactose ingestion
Nutritional Considerations
- Ensure adequate calcium and vitamin D intake from other sources or supplements
📉 Complications
- Usually no serious complications, but long-term dairy avoidance may cause calcium deficiency if not managed.