Lactose Tolerance

Your result, the DNA positions behind it, and what the research says.

10/10 confidence.

About Lactose Tolerance

This trait reads a control region of the MCM6 gene that switches the neighboring lactase gene (LCT) on or off as you grow up. A persistence version keeps lactase switched on into adulthood, so you can digest the lactose in milk; without one, it fades after early childhood. Dairy farming arose in several places independently and each region evolved its own separate persistence variant, so a single position cannot answer this for everyone. This card reads three of them: the European variant and the Middle Eastern and African ones.

Good to know: A single persistence copy is usually enough to handle dairy comfortably. Lactase can fade gradually with age, so let your own comfort be the guide. Persistence evolved separately in Europe, the Middle East and Africa, which is why more than one position has to be read.

Fun fact: Drinking milk as an adult is the exception, not the rule - most humans worldwide stop making lactase after childhood.

Discovery: The European lactase-persistence variant was identified in 2002.

The Variants

The 3 positions this trait reads

Gene: MCM6

rs4988235 European persistence variant (-13910C>T)

rs41380347 Middle Eastern persistence variant (-13915T>G)

rs41525747 African persistence variant (-13907C>G)

Location: Chr 2:135,851,076

dbSNP rs4988235

The studies

World-wide distributions of lactase persistence alleles and the complex effects of recombination and selection (Liebert A et al., Human genetics, 2017)

Tracing the Distribution of European Lactase Persistence Genotypes Along the Americas (Guimarães Alves AC et al., Frontiers in genetics, 2021)

The molecular basis of lactase persistence: Linking genetics and epigenetics (Cohen CE et al., Annals of human genetics, 2025)

Association of lactose intake and lactase persistence genotype with microbial taxa and function in healthy multi-ethnic U.S. adults (Tang Y et al., Food & function, 2025)

Ileal Lactase Expression Associates with Lactase Persistence Genotypes (Nowak JK et al., Nutrients, 2021)

Other lifestyle traits

Galactose Handling: A common change in GALT, the enzyme that processes galactose, half the sugar in milk. It marks a lower-activity version without settling whether you carry it.

Histamine Clearance: A change in diamine oxidase, the gut enzyme that breaks down histamine arriving in food, affecting how quickly you clear it.

Secretor Status: A change that decides whether you secrete your blood group antigens into saliva, tears and gut fluid, which shapes the bacteria your gut hosts.

Back to All Traits

Content updated September 2026.

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