Some adults can digest lactose easily.
Others cannot.
That difference is partly genetic and partly historical.
Lactose is the sugar found in milk.
To digest lactose, the body uses an enzyme called lactase.
Most infants make lactase.
In much of the world, lactase production decreases after childhood.
This can lead to lactose intolerance in adulthood.
Lactase persistence means the body keeps producing lactase into adulthood.
This allows adults to digest fresh milk more easily.
This trait became more common in populations with long histories of dairying and pastoralism.
Examples include parts of:
MedlinePlus Genetics notes that lactase nonpersistence is common globally and that lactose digestion into adulthood depends on inherited regulatory variants near the lactase gene. Research on lactase persistence also shows that some pastoralist populations in Africa, the Arabian Peninsula, and Central Asia developed lactase persistence through variants different from those common in Europe.
Dairy advice should not be the same for everyone.
For some people, milk is a traditional food.
For others, fresh milk may be poorly tolerated.
Fermented dairy such as yogurt or cheese may be easier to digest because fermentation reduces lactose.
Lactose tolerance shows that human diets are regional.
A food that works well in one ancestral context may not work the same way in another.
That is why ancestry and geography matter when discussing nutrition.
Dairy is not universally good or bad.
It depends on biology, tolerance, culture, food quality, and the broader diet.
© 2026 Internets. All rights reserved.