Lactose Intolerance: Complete Guide to Symptoms, Testing & Treatment

Lactose intolerance affects ~68% of the world's population (primary hypolactasia).

Symptoms

• GI: Bloating, gas, diarrhea, cramps, nausea.
• Onset: 30 min–2 hr after lactose ingestion.
• Threshold: Most tolerate 12–15 g (1 cup milk) if spread out.

Diagnostic Tests

Test	Principle	Positive Result
H₂ Breath	Colonic fermentation → H₂ absorption → exhaled	Rise >20 ppm at 60–120 min
Lactose Tolerance	Blood glucose after 50g lactose load	Δ <20 mg/dL
Genetic (C/T-13910)	LCT promoter variant	CC = non-persistent
Stool Acidity	Lactic acid from fermentation	pH <5.5, reducing substances +

Management Pyramid

1. Lactose-free dairy (identical nutrition).
2. Lactase enzyme (pills/drops) with dairy.
3. Fermented dairy (yogurt, kefir, aged cheese).
4. Plant-based fortified alternatives.
5. Calcium/Vit D supplementation if intake low.

Secondary LI: Treat cause (celiac, SIBO) → lactase may recover.