What it does in the body
- Primary energy source for infant mammals
- Galactose source for brain glycolipid synthesis
- Prebiotic effect (promotes beneficial gut bacteria when partially malabsorbed)
- Enhances calcium and magnesium absorption
- Provides sustained energy release (lower GI than glucose or sucrose)
How much you need (Daily Value)
| Group | Recommended | Source |
|---|---|---|
| Adult male | No RDA; not essential. Typical intake 10-30g/day in dairy-consuming populations | N/A |
| Adult female | No RDA; same as male | N/A |
| Pregnancy | Dairy recommended for calcium; lactose-free options for intolerant women | WHO |
| Children | Breast milk provides ~7g lactose per 100mL; essential in infancy | WHO/AAP |
| Older adults | Lactose tolerance often decreases with age; fermented dairy preferred | EFSA |
Richest food sources
| Food | Amount | Where |
|---|---|---|
| Human breast milk | 7g per 100mL | global |
| Cow's whole milk | 5g per 100mL | global |
| Ice cream | 4g per 100g | global |
| Yogurt (plain) | 3.5g per 100g | global |
| Cottage cheese | 3g per 100g | europe |
| Goat milk | 4.5g per 100mL | middle-east |
| Buffalo milk (dahi) | 5g per 100mL | south-asia |
| Cheddar cheese (aged) | 0.1g per 100g (minimal) | europe |
If you don't get enough
Mild: Not essential for adults; reduced dairy intake may limit calcium and vitamin D intake
Moderate: Not applicable — lactose itself is not required
Severe: Not applicable for lactose per se; but calcium/vitamin D deficiency from dairy avoidance is a clinical concern
Time to onset: Not applicable for lactose deficiency
Too much
Upper limit: No UL for lactose-tolerant individuals. Most lactose malabsorbers tolerate 12-15g per sitting. Over-consumption in intolerant individuals causes symptoms but no long-term harm
In intolerant individuals: bloating, flatulence, abdominal cramps, osmotic diarrhea within 30 minutes to 2 hours of consumption
How well you absorb it
Requires lactase for hydrolysis to glucose + galactose; absorption near 100% in lactase-persistent individuals
Helped by: Lactase enzyme supplement, Fermentation (yogurt, kefir reduce lactose content), Slow consumption and small portions
Hindered by: Lactase non-persistence (genetic), Brush border damage (celiac, Crohn's, rotavirus), Rapid gastric emptying
Cooking & storage
Heating milk above 100°C does not significantly break down lactose. Fermentation is the most effective way to reduce lactose content. Aged cheese-making removes nearly all lactose through whey drainage and bacterial fermentation.
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