Is Lactose Tolerance Genetic and What the Research Tells Us

Table of Contents

Lactose Intolerance

Date of Content: August 30, 2023
Written by: Jessica Gayo
Reviewed by: Maarit Tiirikainen, PhD

How many people do you know can’t drink milk or consume anything with dairy because it “doesn’t agree with them”? While the effects of lactose may vary from person to person, they can all agree that lactose intolerance can be uncomfortable, if not downright painful. Nowadays, nutritional genetic testing lets you know if your DNA is more likely to make you lactose intolerant.

What Is Lactose Tolerance?

Lactose intolerance is a condition in which the body cannot fully digest lactose, a sugar found in milk and milk byproducts. This is due to the lack of an enzyme called lactase in the small intestine. As a result of this malabsorption, consuming dairy may cause bloating, gassiness, and diarrhea.

Some people who are lactose intolerant can still consume dairy products in small amounts, while others need to eliminate lactose from their diet completely. It all depends on how badly the symptoms manifest for an individual and what their healthcare provider recommends

Some tests can be done to determine if you are lactose intolerant. The hydrogen breath test and the lactose intolerance test are two of the most common methods healthcare professionals use to determine if an individual has this condition. 

The hydrogen breath test is done by making an individual drink a liquid with plenty of lactose and then measuring the hydrogen levels in their breath afterward. Too much hydrogen means you are lactose intolerant. 

The lactose intolerance test makes you drink a liquid with high levels of lactose, and then your blood will be drawn two hours later to see if glucose levels rose. If glucose remains the same, your body is not digesting lactose, and you are intolerant.

Note that lactose intolerance is not the same as milk allergy. A dairy allergy, or milk allergy, occurs when the immune system overreacts to the presence of proteins in milk. Symptoms may include swelling, breathing problems, and anaphylaxis. Lactose intolerance, on the other hand, is not an allergy because it does not involve the immune system but instead the body’s lack of ability to digest dairy properly.


Top 7 FAQs About Lactose Intolerance

Today, we’re answering your most frequently asked questions about lactose intolerance

lactose Tolerance

Who Is Most Likely To Have Lactose Intolerance?

While children and younger adults are less likely to be lactose intolerant, they can still develop the condition at a later age. Some health experts even view lactose intolerance as a natural condition of the human body that is related to aging, rather than being a serious condition that needs to be treated. Apart from age, ethnic background may also be a factor for individuals with lactose intolerance.

How Long Do Symptoms of Lactose Intolerance Last?

Symptoms of lactose intolerance usually manifest anytime between 30 minutes to 2 hours after an individual has consumed dairy. They can last for up to 48 hours, depending on how much dairy is consumed.

Does Lactose Intolerance Cause Constipation?

Apart from the typical symptoms of bloating, flatulence, diarrhea, and abdominal pain, a good number of cases of lactose intolerance also have constipation as a symptom. This particular symptom can also be as uncomfortable and painful as diarrhea.

What Happens If You Ignore Lactose Intolerance?

Lactose intolerance is usually harmless if the symptoms are only mild to moderate. Some people have symptoms that are mild enough to be ignored. Thus, they continue to consume dairy in moderate amounts. Lactose intolerance symptoms can vary in severity, but if you suspect you have severe digestive problems, contact your primary care physician immediately.

Can You Reverse Lactose Intolerance?

If lactose intolerance is caused by an underlying condition, getting treatment for the pre-existing disease might help alleviate the symptoms of lactose intolerance, if not completely restore the body’s ability to digest the lactose. However, if lack of lactase causes the symptoms, there is not much an individual can do except manage their symptoms and avoid dairy.

Can Stress Cause Lactose Intolerance?

Researchers have long seen a link between gastric and digestive problems and mental and psychological issues. According to these experts, stomach problems may have little to do with what an individual has consumed and more to do with anxiety, stress, depression, and other psychological conditions. 

What Is The Genetic Basis of Lactose Intolerance In Humans?

Does Genetics Affect Lactose Intolerance?

Yes, lactose intolerance can be influenced by your DNA. For people who consume dairy with genetic lactose sensitivity, there may be excess gas, pain, and other digestive problems. One of the genes we analyze for your lactose tolerance is your MCM6 gene. Discover your genetic likelihood of lactose intolerance today based on DNA with our LifeDNA Nutrition Report.

LCT Gene

Variations affecting the LCT gene, which encodes the lactase enzyme, are the main contributors to lactose intolerance. The enzyme lactase converts lactose, a sugar present in milk and dairy products, into glucose and galactose, two sugars that can be absorbed by the body.

MCM6 Gene

One of the main genetic polymorphisms linked to lactase persistence, or the capacity to digest lactose into adulthood, is the MCM6 gene (SNP rs4988235). On chromosome 2, the MCM6 gene is next to the LCT (Lactase) gene and has regulatory components that affect how the LCT gene is expressed. The rs4988235 SNP, which is specifically positioned in an enhancer region of the MCM6 gene, affects the expression of the nearby LCT gene, which in turn affects lactase synthesis.


The “T” allele of rs4988235 is linked to lactase persistence, which means that people who possess this allele are more likely to produce lactase enzyme throughout adulthood and have the capacity to digest lactose without feeling too uncomfortable. Particularly in areas where dairy products have been a dietary mainstay for decades, this allele is frequently discovered in cultures with a history of dairy production and consumption.


The “C” allele of rs4988235, on the other hand, is linked to lactase non-persistence, which indicates that people who have this allele experience a decline in lactase synthesis during childhood, resulting in lower lactose digestion and a higher chance of experiencing the symptoms of lactose intolerance.


The SNP rs4988235 in MCM6 gene region is the most extensively researched and well-known variation (also known as the LCT T-13910C polymorphism) that impacts lactase expression. It is the main variant that has been thoroughly studied and connected to lactase persistence, while other genetic variations for example  in the MCM6 or LCT genes that affect this feature may exist. Genetic differences connected to lactase persistence may vary throughout groups, and the interaction between these variations can lead to varied levels of lactase activity and lactose tolerance. 


An individual’s genotype at the rs4988235 locus can be determined by genetic testing, and this information can reveal whether they are likely to be lactase persistent (and lactose tolerant) or not. However, as heredity only accounts for a small portion of lactose intolerance, environmental variables and cultural customs can significantly affect a person’s actual tolerance to lactose-containing foods.


To avoid uncomfortable symptoms, people with the lactase non-persistence SNP may need to limit their dairy intake. Consuming lactose-free dairy products, taking lactase enzyme supplements prior to consuming dairy, or selecting dairy substitutes are all ways to manage lactose sensitivity.

LifeDNA’s Genetic Testing For Food Intolerances

LifeDNA offers a non-invasive test for food tolerance testing. This genetic testing is done via a saliva sample and analyzed by the best scientific labs. 

We also offer a DNA upload option to make it easier for people who have already taken a test to optimize their wellness with LifeDNA. 

Using the latest research for the most accurate results, LifeDNA’s  Nutrition Report will tell you about your body’s response to certain foods based on DNA. This includes your potential food sensitivities, allergies, and intolerances.

How To Manage Lactose Intolerance

A lactose-free diet is more relaxed than it sounds. Fruits, vegetables, meat, poultry, seafood, soy products, whole grains, nuts, and healthy fats can still be fully enjoyed by lactose-intolerant individuals. As a precaution, consult with your doctor before making any major changes in your diet.

Additionally, be extra careful when consuming dairy and dairy-based products. Try the elimination diet and slowly reintroduce dairy products in small amounts into your diet and see how much is too much and what moderate means. You can also find dairy alternatives such as plant-based products and byproducts but make sure you are still getting your daily recommended dose of calcium.

Making dietary and lifestyle decisions that reduce the discomfort and symptoms brought on by consuming lactose-containing foods is essential to managing lactose intolerance. Here are some recommendations for managing lactose intolerance:

  1. Pick out the trigger foods. Keep a list of the foods and drinks that make you feel unwell. While some persons with lactose intolerance are able to handle modest doses of lactose, others must completely avoid it. To find out how much dairy you can tolerate, try out various dairy products.
  2. Select lactose-free dairy products. Lactose-free versions of dairy goods like milk, cheese, yogurt, and ice cream are widely available in grocery shops. These goods have had the lactose removed or broken down, which makes them simpler to digest.
  3. Try dairy substitutes. Investigate non-dairy substitutes such as oat or rice-based lactose-free products, soy milk, coconut milk, and almond milk. To assist satisfy your nutritional needs, make sure to choose alternatives that are fortified with calcium and vitamin D.
  4. Step by step raise intake. Over time, some people who are lactose intolerant can tolerate modest doses of lactose. Incorporate dairy products into your diet gradually to see how your body reacts to them.
  5. Take supplements with the lactase enzyme. You can buy supplements containing the lactase enzyme over-the-counter to aid in the digestion of lactose. Take these before consuming foods or beverages that contain lactose.
  6. Recognize hidden lactose. Unexpected sources of lactose include processed foods, baked products, salad dressings, and some medicines. Keep an eye out for hidden sources of lactose by reading labels carefully.
  7. Speak with your primary care physician or a registered dietitian. Consider speaking with a certified dietitian if you’re unsure how to manage your lactose intolerance or are worried about receiving enough nutrition. They can assist you in developing a healthy, lactose-free diet plan.

Keep in mind that everyone has a different level of tolerance, so what works for one person might not work for another. Finding a strategy that works for your body and lifestyle while yet meeting your nutritional needs is crucial.

Are you thinking about doing genetic analysis to discover what foods work best for you and your unique body? Try LifeDNA today.


  • Lactose intolerance is a condition in which the body cannot fully digest lactose, a sugar found in milk and milk byproducts. 
  • The lack of an enzyme called lactase in the small intestine causes the malabsorption of dairy, and consuming it may cause bloating, gassiness, and diarrhea.
  • Some tests can be done to determine if you are lactose intolerant. The hydrogen breath test and the lactose intolerance test are two of the most common methods.
  • Lactose intolerance can be influenced by genetics. One of the main genes analyzed for lactose tolerance is the MCM6 gene.
  • Consuming lactose-free dairy products, taking lactase enzyme supplements prior to consuming dairy, or selecting dairy substitutes are all ways to manage lactose sensitivity.

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*Understanding your genetics can offer valuable insights into your well-being, but it is not deterministic. Your traits can be influenced by the complex interplay involving nature, lifestyle, family history, and others.

Our reports and suggestions do not diagnose or treat any health conditions or provide any medical advice. Consult with a healthcare professional before making any major lifestyle changes or if you have any other concerns about your results.