LCT
Lactase (phlorizin hydrolase)
Gene Number: 3938
Location: 2q21.3
Key Functions: Lactose digestion, breakdown of milk sugar, intestinal carbohydrate absorption
LCT produces lactase, the enzyme that breaks down lactose—the main sugar in milk—into glucose and galactose for absorption in the small intestine. Lactase production usually decreases after childhood, but some genetic variants help maintain it into adulthood. This is called lactase persistence [R].
This report examines rs4988235, a common variant involved in adult lactose digestion. It sits in a regulatory region within the neighboring MCM6 gene, where it helps control LCT activity.
Explore your genotype below, or visit PPARG and insulin sensitivity and ADIPOQ and metabolic health to explore other genetic influences on how your body processes nutrients.
SNP ID | Your Genotype | Alt Allele | Interpretation |
|---|---|---|---|
rs4988235 | Analyze your DNA to see your genotype | A | Analyze your DNA to see a personalized result. |
rs4988235 — Lactase Persistence and Lactose Digestion
AA – Lactase persistence; can digest milk as an adult (R).
AG – Mostly lactase persistent; ~80% can digest milk as adults (R).
GG – Lactase non-persistence; likely lactose intolerance in adulthood (R).
Functional effect: rs4988235 lies in an enhancer within MCM6 that regulates the nearby LCT gene. The A allele, called −13910*T in research, increases enhancer activity and helps maintain lactase production after childhood. It changes gene regulation rather than the lactase protein itself (R).
Does GG Mean You Cannot Have Dairy?
Reduced lactose digestion does not always cause symptoms, and lactose intolerance is different from a milk allergy [R].
Many people with lactose intolerance can tolerate approximately 12 grams of lactose—about one cup of milk—with no symptoms or only mild symptoms. Individual tolerance varies, and yogurt, hard cheeses and lactose-free milk may be easier to tolerate [R].
Why Ancestry Matters
This marker is particularly informative in people of European ancestry. Other lactase-persistence variants occur in African and Middle Eastern populations, so GG does not rule out continued lactase production across all ancestries [R].
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