Constipation – When lactose is fermented, it can produce methane gas. Methane gas slows down the time it takes food to travel through the gut. This can cause constipation. Diarrhea – Lactose intolerance can cause the volume of water in the colon to increase, which causes the volume of stool and liquid to increase.

Why does dairy cause constipation?

As it turns out, this reputation is well deserved. Mark Spielmann, RD, nutrition manager at La Rabida Children's Hospital in Chicago, says it's due to the high-fat and low-fiber content of many of these products. Dairy products made from milk can cause constipation in many individuals, particularly toddlers, he says.

Can lactose intolerance cause bowel problems?

The severity of symptoms can vary, depending on how much lactose you can tolerate and how much you have eaten ( 9 ). Bottom Line: Lactose intolerance can cause digestive problems. The main symptoms are bloating, gas, abdominal cramps and diarrhea.