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Primary topic: lactose digestion genetics pathway

Lactose Digestion Pathway: Adult Lactase Persistence and Dairy Tolerance Context

This pathway focuses on adult lactase expression, the main genetic factor behind whether lactose digestion tends to persist after childhood.

What this pathway does

Lactase breaks lactose, the sugar in milk, into absorbable sugars. Regulatory variants near LCT can keep lactase expression active in adulthood.

Why it matters

It matters because lower lactase persistence can make milk dose, fermentation, and gut context more important for symptoms.

What creates pressure on this pathway

  • lower adult lactase persistence genotype at the main LCT/MCM6 enhancer marker
  • missing or ancestry-specific persistence markers that require cautious interpretation

Validation markers to consider

  • lactose symptom and dose diary
  • hydrogen breath test when confirmation is needed
  • difference between milk, yogurt, kefir, and hard cheese response

Genes and SNPs connected to this pathway

Lactose is the milk sugar in dairy. Adult digestion depends mainly on whether lactase enzyme expression stays active after childhood.

Study rows support the SNP/gene claim. The pathway connection comes from the curated gene-to-pathway map.

What may run higher

Your DNA may support continued adult lactase activity, so lactose is more likely to be tolerated from a genetics perspective.

What may work more slowly

Your DNA may point toward lower adult lactase activity. Dairy symptoms, dose, fermentation, and gut context decide whether this matters.

What to check next

Track symptoms after milk versus yogurt or hard cheese, review dairy dose, and consider lactose hydrogen breath testing if the result needs confirmation.

2mapped genes
3mapped SNPs
3SNP/gene claims
3report eligible
LCT2 SNPs - 2 claimsShow SNPsOpen gene page
rs37546891 claims - 2 study rows

expression - TT

Secondary ileal LCT expression context

Moderate

rs3754689 TT is associated with lower ileal LCT expression support relative to the reported higher-expression rs3754689 GG context.

rs3754689 TT is scored only as secondary LCT-expression context and must not override the primary LCT/MCM6 rs4988235 enhancer marker.

Likely effectLower gene expression signal
Signal sizeSmall signal
Evidence supportModerate support
Report useIncluded in pathway scoring
Show study evidence
dbSNP rs3754689identity only - unknowndbSNP confirms rs3754689 identity and genomic-forward alleles in the LCT locus.Ileal LCT expression by rs3754689 genotypefunctional assay - directThe human ileal mucosa expression study reported higher LCT expression for rs3754689 GG than AG or AA; the sample's genomic-forward TT is interpreted as the lower-expression homozygous context after LCT transcript-strand harmonization.
rs49882351 claims - 4 study rows

enzyme activity - GG

Adult lactase persistence capacity

Strong

rs4988235 GG, equivalent to the older -13910 C/C notation, is associated with lower adult lactase persistence capacity.

LCT/MCM6 rs4988235 GG is scored as lower adult lactase-persistence capacity, not as a diagnosis of lactose intolerance.

Likely effectLower enzyme activity signal
Signal sizeModerate signal
Evidence supportStrong support
Report useIncluded in pathway scoring
Show study evidence
dbSNP rs4988235identity only - unknowndbSNP confirms rs4988235 identity in the MCM6/LCT regulatory region; identity evidence does not assign effect direction.Enattah 2002 adult-type hypolactasia associationbiomarker association - directThe primary association study identified C/T-13910 upstream of LCT as tightly associated with biochemically verified lactase non-persistence; the current genomic-forward GG genotype corresponds to the non-persistence C/C context.Olds and Sibley 2003 LCT enhancer assayfunctional assay - directReporter assays showed the -13910 region acts as a cis element and that the persistence-associated T allele increased lactase promoter activity more than the C allele; the GG genotype is therefore scored as lower enhancer support.ClinVar lactase persistence association recordclinical curation - close proxyClinVar records rs4988235 as associated with lactase persistence and maps the GRCh38 genomic-forward A allele to the persistence-associated variant; the GG genotype lacks that persistence allele.
MCM61 SNPs - 1 claimsShow SNPsOpen gene page
rs8690519671 claims - 3 study rows

expression - C

African -14009*G lactase-persistence context

Strong

rs869051967 C, corresponding to the -14009*G enhancer allele, is associated with lactase-persistence enhancer support in specific African ancestry contexts.

rs869051967 C is tracked as population-specific lactase-persistence support, not as absence-based intolerance evidence.

Likely effectHigher gene expression signal
Signal sizeSmall signal
Evidence supportStrong support
Report useIncluded in pathway scoring
Show study evidence
dbSNP rs869051967identity only - unknowndbSNP confirms rs869051967 identity and genomic-forward A/C alleles in the MCM6/LCT enhancer region.Liebert 2016 infrequent LCT enhancer functional assayfunctional assay - directThe in vitro enhancer study reported that the -14009*G construct increased LCT promoter reporter activity in Caco-2 cells; genomic-forward rs869051967 C corresponds to the -14009*G allele.World-wide lactase-persistence allele distributionbiomarker association - close proxyThe world-wide LCT enhancer survey treats -14009*G as one of the established functional lactase-persistence alleles and maps its distribution/haplotype context across Old World populations.

Where DNA analysis helps

DNA helps separate likely lactase non-persistence from broader dairy intolerance, allergy, or gut irritation questions.

Example interpretation

A lower adult lactase-persistence signal means lactose dose may matter more, especially for milk, but symptoms and testing decide whether this is active.

Suggested validation: lactose dose diary or hydrogen breath test.

What to do next

  • compare symptoms after different dairy forms before eliminating all dairy
  • use a breath test if the result needs objective confirmation
  • avoid treating DNA as proof of current intolerance

Related pages

LCT

LCT gene lactose digestion

MCM6

MCM6 LCT enhancer lactase persistence

Histamine intolerance

histamine intolerance genetics

DAO activity

DAO activity and histamine clearance

How accurate are DNA metabolism reports?

how accurate are DNA metabolism reports

23andMe vs Metastate metabolism report

23andMe vs Metastate metabolism report

Get the full report

Use your DNA file to see which pathways may be worth validating first.