Many people ask this question “Can lactose intolerance cause constipation”? The answer is no, lactose intolerance does not normally cause constipation.
Some people get bowel symptoms such as diarrhoea when they drink milk. They don’t have the ability to digest lactose in the milk. This condition is called lactose intolerance. It is different from cow’s milk allergy that is caused by hypersensitivity to proteins in the milk.
Lactose is a carbohydrate or sugar found in milk. We need an enzyme called lactase to digest this carbohydrate in the digestive system. The lactase enzyme is secreted in the small intestine. It breaks the lactose sugar into galactose and glucose that can be absorbed by the small intestine.
Constipation is not a symptom of lactose intolerance. I will explain why.
If you have lactose intolerance, the sugar in the milk passes the small bowel without digestion. It cannot be absorbed by the intestine. So, it passes to the large bowel. There are millions of bacteria in the large bowel. They ferment a portion of the lactose and produce gas. Excessive gas production causes stomach upset and tummy pain.
The unfermented portion of the lactose retains water in the large bowel. It acts as an osmotic laxative that is a substance given to relieve constipation. To be clear, it causes loose motions or diarrhoea.
So, diarrhoea, abdominal pain and excess wind are the symptoms of lactose intolerance. Constipation is not a symptom.
Drinking large amounts of cow’s milk can cause constipation. However, it is not related to lactose intolerance.
People with lactose intolerance may have the following symptoms also:
- Bloating
- Rumbling sound in the abdomen
- Nausea and vomiting
- Foamy stools
People with irritable bowel syndrome may also have similar symptoms. In addition, they can have constipation also. Sometimes the irritable bowel syndrome is misdiagnosed as lactose intolerance.
Bottom line:
If you get constipation after drinking milk, don’t think you are intolerant to lactose. It is due to the high calcium content of the milk. Lactose intolerance doesn’t cause constipation.