Lactose intolerance

Definition
Lactose intolerance is a digestive disorder caused by the inability to digest lactose, the main sugar in milk and dairy products, due to insufficient levels of the enzyme lactase in the small intestine. This results in gastrointestinal symptoms after consuming lactose-containing foods or drinks.

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Types of Lactose Intolerance

1. Primary Lactose Intolerance

   • Most common type.

   • Gradual decline in lactase production after childhood.

   • Common in adults from African, Asian, Hispanic, and Mediterranean backgrounds.

2. Secondary Lactose Intolerance

   • Caused by damage to the small intestine from illness, injury, or surgery.

   • Conditions include celiac disease, Crohn’s disease, gastroenteritis.

3. Congenital Lactase Deficiency (rare)

   • Present from birth due to a genetic defect.

   • Infants are unable to digest breast milk or standard formula.

4. Developmental Lactose Intolerance

   • Seen in premature infants due to immature lactase-producing cells.

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Causes and Pathophysiology

• Lactase enzyme deficiency prevents the hydrolysis of lactose into glucose and galactose.

• Undigested lactose passes into the colon where it is fermented by bacteria, producing hydrogen, methane, and short-chain fatty acids, leading to symptoms.

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Clinical Presentation

Symptoms typically develop within 30 minutes to 2 hours after lactose ingestion:

• Abdominal bloating

• Flatulence

• Abdominal cramps

• Diarrhea (osmotic in nature)

• Nausea (sometimes vomiting)

Severity depends on:

• Amount of lactose consumed

• Degree of lactase deficiency

• Individual gut microbiota adaptation

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Diagnosis

Clinical Approach

• Symptom resolution after avoiding lactose-containing foods.

Diagnostic Tests

• Hydrogen Breath Test: Measures hydrogen after lactose ingestion (positive if elevated).

• Lactose Tolerance Test: Measures blood glucose after lactose ingestion (failure to rise suggests malabsorption).

• Stool Acidity Test: Used mainly in infants; acidic stool indicates carbohydrate malabsorption.

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Management

Dietary Modification (First-Line)

• Reduce or avoid lactose-containing foods such as milk, cream, and certain cheeses.

• Yogurt and hard cheeses may be tolerated better due to lower lactose content.

• Lactose-free milk and dairy alternatives (soy, almond, oat milk).

• Gradual reintroduction to determine personal tolerance levels.

Enzyme Replacement Therapy

• Lactase enzyme supplements (e.g., lactase tablets or drops):

  • Dose: 3,000–9,000 units orally immediately before consuming lactose-containing food or drink.

  • Brands vary in strength; dose adjusted based on amount of lactose ingested and symptom control.

Treatment of Secondary Lactose Intolerance

• Address underlying cause (e.g., treat celiac disease or infection).

• Temporary lactose restriction until intestinal mucosa recovers.

Calcium and Vitamin D Supplementation

• Recommended for individuals with restricted dairy intake to prevent bone loss:

  • Calcium carbonate or citrate: 500–600 mg elemental calcium orally twice daily.

  • Vitamin D3 (cholecalciferol): 800–1,000 IU orally daily.

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Pharmacological Symptom Relief

• Simethicone: 40–125 mg orally after meals and at bedtime for bloating relief.

• Loperamide: 2–4 mg orally after loose stools for diarrhea (short-term use only).

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Special Considerations

• Infants with congenital lactase deficiency require lactose-free infant formulas.

• Premature infants may improve as the gut matures.

• Elderly patients are more prone due to natural enzyme decline.

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Prognosis

• Primary lactose intolerance is lifelong but manageable with dietary and enzyme replacement measures.

• Secondary forms may resolve if the underlying cause is treated.

• With proper management, patients can maintain good nutrition and quality of life