LCT rs4988235: Lactose Intolerance and Dairy Digestion

LCT rs4988235 is one of the best-known genetic markers linked to lactose digestion. If milk, ice cream, or other dairy products cause bloating, gas, diarrhea, nausea, or stomach discomfort, this variant may help explain part of why [R]. The key idea is simple: lactose is the natural sugar found in milk and many dairy foods. To digest lactose, your small intestine needs enough lactase, the enzyme produced from the LCT gene [R]. Many people naturally produce less lactase after childhood. Others continue producing enough lactase into adulthood, a trait called lactase persistence.

The rs4988235 variant helps explain that difference, especially in people with European ancestry. It does not diagnose lactose intolerance by itself, but it can add useful genetic context. You can analyze how your LCT rs4988235 at GenesUnveiled for free.

How LCT rs4988235 affects lactose digestion

The LCT gene provides instructions for making lactase. Lactase breaks down lactose so it can be absorbed properly. When lactase activity is low, lactose may remain undigested and move into the colon, where it can contribute to gas, bloating, diarrhea, and other digestive symptoms [R, R].

The rs4988235 variant is located in a regulatory region near the LCT gene. It is often described as C/T(-13910) because of its position relative to LCT. Although the variant sits in the nearby MCM6 region, it affects whether LCT activity tends to remain higher into adulthood [R].

For this SNP, the A allele is generally associated with lactase persistence, while GG is most often associated with lactase nonpersistence in European populations [R].

What GG, GA, and AA may mean

For most readers, the genotype interpretation is the most useful part:

• GG: more likely to have lactase nonpersistence and reduced lactose digestion in adulthood

• GA: more likely to retain some adult lactase activity

• AA: more likely to have lactase persistence and stronger lactose digestion in adulthood

This does not mean the result is perfectly binary. Some research suggests lactase activity may exist on a spectrum, with GG generally lowest, GA intermediate, and AA highest [R].

That matters because people with the same genotype may not react exactly the same way to dairy. Dose, age, gut health, food form, and overall diet can all affect symptoms. Some people with lower lactase activity can still tolerate small amounts of lactose, especially in fermented dairy products such as yogurt or certain cheeses.

LCT rs4988235 and lactose intolerance

Lactose intolerance happens when lactose malabsorption leads to symptoms after consuming lactose-containing foods or drinks.

Common symptoms include [R]:

• bloating

• gas

• diarrhea

• abdominal pain

• nausea

But lactose malabsorption and lactose intolerance are not identical. Some people digest lactose poorly but have few symptoms. Others may have symptoms from other digestive issues that look similar to lactose intolerance.

That is why LCT rs4988235 is best understood as a genetic clue, not a diagnosis. It can help explain whether your body is genetically more likely to keep producing lactase into adulthood, but it cannot prove exactly how you will feel after eating dairy.

Why ancestry matters for this SNP

The rs4988235 variant is especially useful for predicting lactase persistence in many European populations. However, lactase persistence evolved more than once in human history, and different populations can have different lactase-persistence variants.

That means rs4988235 is not equally informative for everyone. In some non-European populations, other variants may be more relevant. A person can also have digestive symptoms for reasons unrelated to this SNP, including irritable bowel syndrome, celiac disease, inflammatory bowel disease, small intestinal bacterial overgrowth, or other gut conditions [R].

This is one reason raw DNA results should be interpreted carefully. A single SNP can be useful, but it rarely tells the whole story.

What raw DNA can and cannot tell you

A raw DNA file can show whether you have the GG, GA, or AA genotype for rs4988235 if that marker is included in your file. That can help explain inherited lactase persistence or nonpersistence [R].

But raw DNA analysis cannot directly measure:

• your current lactase enzyme level

• how much lactose you personally tolerate

• whether dairy is causing your symptoms

• whether you have a milk allergy

• whether another digestive condition is involved

What this means in practice

If your result is GG, you may be more likely to have reduced lactose digestion in adulthood. That does not mean you must avoid all dairy forever, but it may help explain symptoms after higher-lactose foods such as milk or ice cream.

If your result is GA or AG, you may be more likely to retain some lactase activity, although tolerance can still vary by amount and food type.

If your result is AA, you are more likely to have lactase persistence, meaning your genetics are more favorable for digesting lactose into adulthood. Still, digestive symptoms can come from many causes, so a AA result does not guarantee that dairy will always feel good.

How GenesUnveiled can help you understand LCT rs4988235

At GenesUnveiled, you can analyze your DNA and explore research-based interpretations of variants like LCT rs4988235. GenesUnveiled is designed to help turn a raw DNA file into clearer reports across traits, nutrition and metabolism, health-related markers, gene activity, pharmacogenetics, and more.