LCT: are you lactose intolerant as an adult?
Almost every mammal stops digesting milk after weaning. Whether you're an exception comes down mostly to one variant.
Lactase is the enzyme that digests lactose, the sugar in milk. Most adults worldwide stop making much of it once they're past childhood. That's called lactase non-persistence, and it's the human default. One regulatory variant near the LCT gene, rs4988235, mostly decides whether you're the exception who keeps making lactase for life.
What LCT does
When you can't digest lactose, it sits in your gut and ferments. That's the bloating, the gas, the cramps an hour or two after dairy. The fix is easy. Take a lactase enzyme with the meal, or buy lactose-free milk and cheese.
This is about as clean as gene-trait links get. The variant predicts who tolerates dairy and who doesn't, and it holds up 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. |
We show genotypes on the forward strand and ignore letter order. Your own export may print the complementary letters. Same result either way.
What the research suggests
The rs4988235 non-persistence genotype means you make little lactase as an adult, so lactose passes undigested and ferments in the gut. A lactase enzyme taken with dairy, or simply choosing lactose-free products, handles most of the discomfort. This is about comfort, not a supplement your genes 'need'.
PubMed 11788828 · Enattah et al., Nat Genet 2002. Identified the regulatory variant (rs4988235, the -13910 C/T upstream of LCT) associated with adult-type hypolactasia: the persistence allele keeps lactase expression switched on past weaning, the other does not.
Educational only, not medical advice. “General evidence” means the finding is real, but the benefit isn’t specific to your genotype.
See this matched to your own DNA, free.
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Questions
Does rs4988235 mean I'm lactose intolerant?
The non-persistence genotype (GG/CC) means you make little lactase as an adult, so dairy is more likely to bother you. But it's a tendency, not a verdict. How much you can handle also depends on the amount you eat and how used to it your gut is.