LCT: are you lactose intolerant as an adult?
Most mammals stop digesting milk after weaning. Whether you're an exception is largely one variant.
Lactase is the enzyme that digests lactose, the sugar in milk. Most of the world's adults stop making much of it — 'lactase non-persistence.' A single regulatory variant near the LCT gene, rs4988235, largely decides whether you keep producing lactase into adulthood.
What LCT does
If you're lactase non-persistent, undigested lactose is what causes the bloating and discomfort after dairy. The fix is simple: a lactase enzyme taken with dairy, or lactose-free products.
This is one of the cleanest gene-trait links in nutrition — the variant predicts the trait well across populations.
Your variants, decoded
The T (A) allele confers lactase persistence; it's dominant, so one copy is usually enough.
| AA / TT | Lactase persistent — usually tolerate dairy. |
| AG / CT | One persistence copy — usually still tolerate dairy. |
| GG / CC | Non-persistent — little adult lactase; dairy more likely to bother you. |
Genotypes are shown order-insensitively and on the forward strand; your own export may print the complementary letters — the meaning is the same.
What the research suggests
Your LCT genotype is lactase non-persistent — you make little lactase as an adult. A lactase enzyme taken with dairy helps you digest lactose.
Educational only — not medical advice. “General evidence” means the finding is real but the supplement’s benefit isn’t unique to your genotype.
See this matched to your own DNA — free.
Upload your 23andMe or AncestryDNA file and get your actual LCT result, plus every other actionable variant — each line cited, your file never stored.
Questions
Does rs4988235 mean I'm lactose intolerant?
The non-persistence genotype (GG/CC) means you make little adult lactase, so dairy is more likely to cause symptoms — though real-world tolerance also depends on amount and gut adaptation.