Lactose intolerance: How does it happen?
Diagnosis of lactose intolerance
Lactose intolerance – where does the intolerance come from?
Lactose intolerance affects millions of people worldwide—but few know exactly how it develops. Why can some people tolerate dairy products without any problems, while others experience discomfort after just one sip of milk?
Types of lactose intolerance
Primary lactose intolerance (genetic)
This is the most common form of lactose intolerance worldwide. It develops naturally with age:
- Babies can usually digest lactose well because breast milk contains lactose.
- With increasing age, many people experience a decrease in the production of the enzyme lactase (which breaks down lactose).
The result: lactose can no longer be digested properly, leading to symptoms such as flatulence, abdominal pain, or diarrhea. This form is genetic and permanent—it affects many people in Asia, Africa, and South America, for example. It is somewhat less common in Central Europe.
Secondary lactose intolerance
This form does not arise from predisposition, but as a result of other diseases or intestinal damage.
- E.g. after gastrointestinal infections, celiac disease, Crohn’s disease, or antibiotic treatment.
- The small intestine is then temporarily damaged and produces too little lactase.
The good news is that secondary lactose intolerance is often curable if the underlying condition is treated or cured.
Congenital (inborn) lactose intolerance
This form occurs very rarely and must be treated strictly throughout life.
- Affects newborns from birth—they cannot tolerate breast milk.
- Genetically determined congenital lactase deficiency.
Diagnosis of forms of lactose intolerance
There are several tests available to diagnose lactose intolerance. You can find out more about the tests here: Diagnosis lactose intolerance
If you want to specifically test whether you have a genetic lactose intolerance, i.e. primary lactose intolerance, you can take a special test for this.
Genetic Test
This test is only relevant for primary lactose intolerance. The test involves analyzing either a cheek swab or a blood sample in the laboratory. It looks for a specific genetic mutation (polymorphism in the LCT gene) that is responsible for the natural decline in lactase. If the genetic mutation is present, primary lactose intolerance is likely. If the genetic mutation is not present, primary lactose intolerance is very unlikely. Nevertheless, secondary intolerance may still be present. Important: A positive genetic test does not automatically mean that you have symptoms—only that you are predisposed to them.
