Lactose Tolerance2q21.3

rs4988235 - Lactase Persistence - Can You Digest Milk?

Gene: MCM6 (LCT regulation)

rs4988235 controls whether you continue producing the lactase enzyme into adulthood. The ancestral G allele leads to declining lactase production after weaning (lactose intolerance). The derived A allele maintains lactase expression throughout life.

Genotype Interpretations

AA~35% (European)

Lactose tolerant - you produce lactase throughout life. Dairy is fine

AG~43% (European)

Likely lactose tolerant - one copy is usually sufficient for full lactase expression

GG~22% (European), ~95% (East Asian)

Lactose intolerant - lactase production declines after childhood. Dairy may cause bloating, gas, and diarrhea

Population Context

Lactase persistence evolved independently in at least 5 populations with dairy herding traditions. The European variant (rs4988235-A) spread ~7,500 years ago with cattle domestication. Different variants cause lactase persistence in East African (rs145946881) and Middle Eastern populations.

Clinical Relevance

GG individuals should consider lactose-free dairy alternatives or lactase supplements. Calcium and vitamin D intake should be monitored if avoiding dairy.

Sources

  • [1] Enattah NS et al. (2002) Nat Genet 30:233-7
  • [2] Itan Y et al. (2009) PLoS Comput Biol 5:e1000491

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