Lactose Intolerance Genetic Testing | Dynamic DNA Labs
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Lactose Intolerance Genetic Testing

Lactose intolerance is the body’s inability to break down a naturally occurring sugar called lactose. You will commonly find lactose in dairy products, including cheese, milk, and yogurt.

The small intestine normally creates enzymes that make it possible to break down and digest lactose. However, with a lactose-intolerant individual, the small intestine is no longer making this enzyme, so undigested lactose finds its way into the large intestine.

There are bacteria that naturally live in your large intestine. When these interact with lactose, they create symptoms like gas, bloating, and diarrhea. These symptoms typically present themselves within 30 minutes to two hours of ingesting products that contain lactose.

Three Types of Lactose Intolerance

Lactose intolerance can be broken into three primary categories. They are primary lactose intolerance, secondary lactose intolerance, and congenital lactose intolerance.

1. Primary Lactose Intolerance

This is lactose intolerance that is part of the normal aging process. Most people with lactose intolerance have this type.

Humans are born with lactase. This is the enzyme that helps digest lactose. Babies need this in order to digest their mother’s milk.

As people age, lactase production may decrease. With age comes the ability to eat a more diverse diet and rely less on milk.

This is a gradual process. An individual who was not lactose intolerant in youth may develop this intolerance with age.

2. Secondary Lactose Intolerance

This intolerance typically results from injury or illness. Common culprits include inflammatory bowel disease and celiac disease. Individuals who experience injury to their small intestine or who have a surgical procedure affecting the small intestine may also develop lactose intolerance. Once the underlying injury or disease is treated, lactose tolerance may return.

3. Congenital/Developmental Lactose Intolerance

Although it is exceedingly rare, lactose intolerance can be inherited. Defective gene transmission can cause the absence of lactase in a child.

Babies born with this condition will be intolerant to their mother’s breast milk. As soon as they ingest breast milk or formulas that contain dairy, they will have diarrhea. This condition needs to be identified and treated early on as it could be life-threatening.

Premature babies may develop lactose intolerance. This is because lactose production does not begin until at least the 34th week of pregnancy.

Is Lactose Intolerance Genetic or Environmental?

For some individuals, lactose intolerance can be an inherited trait. However, lactose intolerance is a recessive disorder. For a recessive disorder to show, two copies of the genes, known as alleles, have to be identical.

However, according to a Cornell University study, individuals whose ancestors came from places where dairy herds could not be safely raised, including extremely cold or extremely hot environments, typically lack the ability to digest milk after infancy.

As a result, there are high occurrences of lactose intolerance in individuals of African, Asian, and Hispanic descent. According to a report published by Science Daily, adults from Europe can drink milk since their ancestors lived in an area where dairy flourished. This allows them to pass on a gene that maintains lactose into adulthood.

What Are the Symptoms of Lactose Intolerance?

Symptoms of lactose intolerance typically develop within a few hours of consuming food or drink that contains lactose. These symptoms could include:

• A bloated stomach

• Diarrhea

• Stomach rumbling

• Gas

• Feeling sick

• Stomach cramps and pains

The severity of your symptoms will depend on how much lactose you have consumed. For some people, drinking a small glass of milk or having cheese on their sandwich is not enough to trigger their symptoms. Others cannot even ingest a tablespoon of milk in their tea or their coffee.

An individual experiencing what they believe to be symptoms of lactose intolerance should discuss it with their general practitioner before they eliminate dairy from their diet. A person might mistake irritable bowel syndrome or milk protein intolerance with lactose intolerance.

What Are the Risk Factors for Lactose Intolerance?


Premature babies or babies who have an immature digestive system run a high risk of showing lactose intolerance as the production of lactase doesn’t start until the 34th week of pregnancy. Some studies suggest that up to 40 percent of babies diagnosed with colic actually have some type of lactose intolerance.

Similarly, elderly individuals are at risk because people produce fewer lactase enzymes as they age. It is estimated that upward of 60 percent of adults have some degree of lactose intolerance.


Individuals from Mediterranean, Aboriginal, African, Asian, and Indian descent have a higher rate of lactose intolerance. For example, studies show that upwards of 70 percent of non-Caucasians in Australia are lactose intolerant.

Intestinal Injury

Injuries to the small intestine, be them from chemotherapy, persistent diarrhea, or trauma, may lead to temporary lactose intolerance. Once the condition or the trauma has been repaired, lactose tolerance may return.

Intestinal Disorders

Celiac disease, inflammatory bowel disease, and Crohn’s disease may all potentially damage the villi in the intestines that produces lactase. As a result, lactose intolerance can be a secondary effect of these conditions. If the villi heal, lactose tolerance resumes.

Were the Ancestors of Humans Lactose Tolerant or Intolerant?

The answer depends on what part of the world they were from. In many parts of the world, babies historically lose their ability to digest lactose shortly after they stop nursing.

The borders between regions where human ancestors could or could not digest lactose are not as demarcated as some would think. For example, in some parts of Europe, such as in the northern and eastern parts, human ancestors had lactose persistence. However, in southern Europe, they do not.

Something similar is seen in Africa. For example, the Tutsi of Rwanda can tolerate lactose. However, the Hutu, from the same part of the world, cannot tolerate lactose.

According to National Geographic, scientists have recently learned a lot about the human genome. The lactase gene, LCT, is turned on and off by neighboring segments of DNA. Based on their ancestry, different ethnic groups have different levels of lactase persistence.

All mammals shut down lactase production shortly after nursing. Prior to mankind raising livestock, lactase was useful after nursing. However, once societies started to raise milk-giving livestock, the body’s ability to adapt meant activating the lactase genes needed to absorb nutrients from milk into adulthood.

How Is Lactose Intolerance Diagnosed and Treated?

If your doctor suspects that you are lactose intolerant, they may encourage you to remove dairy from your diet. They can confirm their suspicion with one or both of the following tests:

Hydrogen Breath Test: You will drink liquid with high levels of lactose. If you are breathing out excessive amounts of hydrogen, your body is not digesting or absorbing lactose.

Lactose Tolerance Test: You will drink a liquid with a high level of lactose. After two hours, a blood test will be used to measure the levels of glucose in your bloodstream. If your glucose levels don’t rise, your body is not absorbing the lactose.

Treatment of lactose intolerance will vary depending on its reason. If there is an underlying condition, it needs to be addressed. Otherwise, your doctor will recommend a low lactose diet that could range from reducing lactose intake to eliminating lactose completely from your diet.

Lactose intolerance affects a good portion of the world's population. A person may develop lactose intolerance because of age, injury, or illness. Lactose intolerance can be treated by addressing the underlying condition or by making dietary changes and removing lactose from the diet.

If you suspect that you may be genetically predisposed to lactose intolerance, our Nutrition DNA Testing Kit can verify your suspicions so that you may seek further testing and treatment. Order your kit, or give us a call at 417.319.1047 if you have further questions.