Does my 23andMe file show if I'm lactose intolerant?
Partly. One marker, rs4988235 near the lactase gene, predicts whether you keep making lactase as an adult in people of European ancestry, but it misses other persistence variants common in parts of Africa and the Middle East, and it cannot tell you how your gut actually feels after a glass of milk.
What to look for in your file
Search your raw data file for rs4988235 (chromosome 2). 23andMe and AncestryDNA report it as the letters A and G. Research papers call the same position C/T-13910, written on the other DNA strand: your file's A is the paper's T (lactase persistence) and your file's G is the paper's C (non-persistence).
| Your letters | Associated with |
|---|---|
| A A | Lactase persistence: you likely keep digesting lactose into adulthood. |
| A G | Lactase persistence. One A is enough — persistence is dominant. |
| G G | Likely lactase non-persistence: lactase activity falls after childhood. This is the most common adult state worldwide, not a disease. |
The variant was identified by Enattah and colleagues, who found that C/T-13910 (A/G in your file) completely associated with biochemically verified lactase non-persistence in Finnish families and in 236 people from four populations (PMID 11788828).
How common is each result?
| Population group | A (persistence) letter | G G (estimated) |
|---|---|---|
| African | 2.7% | 95% |
| Admixed American | 21.6% | 61% |
| East Asian | 0% | 100% |
| European | 50.8% | 24% |
| South Asian | 11.3% | 79% |
Allele frequencies: 1000 Genomes phase 3 via Ensembl, read 2026-10-23. G G shares are estimated from those frequencies (Hardy–Weinberg), not counted directly.
So G G is the majority result in four of the five groups. If that is your result, you are in the majority of the world's adults.
What this marker cannot tell you
- Other persistence variants are not on this marker. Several other lactase-persistence variants occur in East Africa and the Middle East. If your ancestry is from there, G G can understate your ability to digest lactose.
- Genotype is not symptoms. Many people with G G drink some milk comfortably; others with an A still get gut symptoms for unrelated reasons.
- Not a diagnosis. Ongoing digestive symptoms deserve a conversation with a clinician, who can test for lactose intolerance directly.
- 23andMe states that only a subset of raw-data markers is individually validated and that raw data is for informational use.
What to do with it, in food terms
- With G G, notice how you feel after larger servings of milk. Many people with this genotype do well with smaller portions, lactose-free milk, yogurt, kefir and hard aged cheeses.
- If you cut back on dairy, get calcium from other foods: calcium-fortified alternatives and leafy greens, for example. Avoiding dairy can lower calcium intake over time, so it is worth replacing (PMID 30925689).
- With an A, this marker gives no reason to change how you eat dairy.
References
- Enattah NS et al. Identification of a variant associated with adult-type hypolactasia. Nat Genet 2002;30:233–7. PMID 11788828
- Cited in the Genomeats knowledge base for dairy and calcium intake: PMID 30925689
- 1000 Genomes Project phase 3 allele frequencies for rs4988235, via Ensembl.
- 23andMe Customer Care, "Accessing Your Raw Genetic Data".
Genomeats reads this marker on your phone — nothing is uploaded. Full write-ups for this trait are free. Coming soon to the App Store.