Diarrhea is a common side effect of treatment for many types of cancer. It is when you experience loose, watery, or unformed stool (poo) that may happen 3 or 4 times a day. Some people may experience stomach upset such as gas (air in the digestive system) or bloating (swelling of the lower belly caused by gas. Focus on foods that are low in insoluble fibre (have more soluble fibre), lactose, fat, caffeine and spices (chili, cayenne, curry). Talk to your health care team about anti-diarrhea medication.