Symptoms and causes of Lactose Intolerance

Those suffering from Lactose Intolerance often experience the following symptoms after eating milk or dairy products:

  • Diarrhea
  • Gas
  • Stomach pain
  • Nausea
  • Vomiting

The causes of the symptoms of Lactose Intolerance

The symptoms are caused by the fact that the body produces too little lactase, which essentially breaks down lactose to make it usable for the body.

If the lactose in the small intestine isn't fully broken down, doctors refer to this as Lactose Malabsorption. The small intestine simply cannot absorb these large lactose molecules, so the lactose remains in the intestine, where it binds with water - thus triggering diarrhea. If the lactose finally moves from the large intestine to the small intestine, bacteria will then attack the lactose. This produces gases such as methane and hydrogen, which explains the significant flatulence that so many experience after eating dairy products. The larger intestinal lining also expands the intestine and leads to contractions which can trigger severe pain.

In particular, milk contains so much lactose that the consumption of a larger amount causes problems even in people without Lactose Intolerance. The more lactose is absorbed, the more lactase the body needs in order to utilize the milk sugar. Many people suffer from a lactase deficiency when they drink a glass of milk at once; in this case, the mechanisms described in small intestine and large intestine begin, although there is actually no true Lactose Intolerance.

Causes of Lactose Intolerance

Depending on the cause of the Lactose Intolerance, doctors differentiate between three variants:

1.) Primary Lactose Intolerance

The most common cause of lactase deficiency is genetics. For many people, the body loses the ability to form the enzyme lactase after the first few years of life. This process usually begins between the ages of 5 and 20 years. Many men and women who are suffering from a primary lactose intolerance still have lactase – just in smaller quantities. This means most people with Lactose Intolerance can tolerate small amounts of milk sugar.

2.) Secondary Lactose Intolerance

In the case of secondary Lactose Intolerance, affected individuals can no longer tolerate milk sugar as a result of a disease such as Celiac or Crohn's Disease. In such cases, Lactose Intolerance is often temporary - if the intestine has the opportunity to regenerate, it also regenerates the enzyme lactase. Secondary Lactose Intolerance is often associated with Fructose Malabsorption, as well. 

In some cases, the intestinal flora can also be altered after an antibiotic cure in such a way that those affected only have a temporary lactose intolerance. 

3.) Congenital Lactose Intolerance

In extremely rare cases, children are born with with alactasia, a condition that refers to a complete absence of lactase in the body. These individuals suffer from very early Lactose Intolerance, which leads to severe diarrhea just a few days after birth. There is a risk of malnutrition and dehydration for these affected infants, and they must be fed lactose-free milk so they can develop normally.

Further reading:

What is Lactose Intolerance?

Diagnosing Lactose Intolerance

Treatment and therapy for Lactose Intolerance