Constipation

Hard, infrequent stools, incomplete bowel motions, stomach discomfort, bloating, and excessive straining are all signs of constipation. Despite being a far less common symptom than diarrhea, it might still be a sign of lactose intolerance.

In the colon, bacteria convert undigested lactose to methane gas. Methane may make it harder for food to pass through the gut efficiently, which can cause constipation in certain people. Only people with irritable bowel syndrome and bacterial overgrowth have so far been subject to studies on methane's constipating effects. Even though it has been noted as a symptom, constipation is not typically linked to lactose intolerance. Other factors that contribute to constipation include dehydration, a diet low in fiber, certain drugs, irritable bowel syndrome, diabetes, hypothyroidism, Parkinson’s disease and hemorrhoids.