Lactose intolerance
Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management
Definition
Lactose intolerance in children refers to the inability to digest lactose due to insufficient lactase enzyme activity, leading to gastrointestinal symptoms after lactose ingestion.
Aetiology
- Primary lactose intolerance: genetically programmed decline in lactase activity, more common in older children and certain ethnic groups.
- Secondary lactose intolerance: occurs due to mucosal damage from infections (e.g., viral gastroenteritis), coeliac disease, or inflammatory bowel disease.
- Congenital lactase deficiency: rare autosomal recessive disorder where lactase is absent from birth.
- Developmental lactose intolerance: seen in preterm infants due to immature digestive systems.
Pathophysiology
- Lactose is normally hydrolysed into glucose and galactose by lactase in the small intestine.
- In lactase deficiency, undigested lactose reaches the colon, where bacterial fermentation produces gas (hydrogen, methane) and short-chain fatty acids.
- This leads to osmotic diarrhoea, bloating, and abdominal discomfort.
Risk Factors
- Family history of lactose intolerance.
- Ethnic background (higher prevalence in African, Asian, and Hispanic populations).
- Gastrointestinal infections (e.g., rotavirus, norovirus).
- Coeliac disease or inflammatory bowel disease.
- Prematurity (immature lactase production).
Signs and Symptoms
Symptoms typically occur 30 minutes to 2 hours after consuming lactose-containing foods:
- Gastrointestinal symptoms:
- Abdominal bloating and cramping.
- Flatulence (excess gas production).
- Diarrhoea (osmotic, watery stools).
- Nausea and occasional vomiting.
- Systemic symptoms (less common): fatigue, headaches.
Investigations
- Dietary elimination test: symptom resolution with lactose avoidance suggests diagnosis.
- Hydrogen breath test: measures hydrogen production after lactose ingestion (gold standard).
- Stool acidity test (in infants): detects lactic acid from undigested lactose.
- Small bowel biopsy: rarely required, only if underlying conditions like coeliac disease are suspected.
Management
1. Dietary Modifications:
- Avoidance of lactose-containing foods: milk, soft cheeses, cream, butter.
- Lactose-free alternatives: lactose-free milk, plant-based alternatives (soya, almond, oat).
- Fermented dairy: some yoghurts and hard cheeses contain lower lactose levels and may be better tolerated.
2. Enzyme Replacement Therapy:
- Lactase enzyme supplements: taken before consuming lactose-containing foods to aid digestion.
3. Nutritional Considerations:
- Calcium and vitamin D intake: ensure adequate intake from alternative sources (e.g., green leafy vegetables, fortified foods, supplements if required).
4. Managing Secondary Lactose Intolerance:
- Treat underlying condition: management of coeliac disease, IBD, or gut infections may improve lactose tolerance.
- Lactose intolerance may resolve once intestinal health improves.
5. Referral:
- Paediatrics: referral if symptoms persist despite dietary changes or if an underlying gastrointestinal disorder is suspected.
- Dietitian: for advice on maintaining adequate nutrition while avoiding lactose.