A common problem that some people have is constipation. Some of us are just more prone to it. Water is paramount. Drinking 2 litres a day is recommended. After that there is the usual health advice of eating several portions of fruit and vegetables every day. After that if you still have a problem in that department, you could try linseeds. You can sprinkle them on porridge, or other cereal or in yoghurt or on salads. After trying various dietary changes, I found linseeds to be the most effective for maintaining regularity!
NOTE – I am not a medic. Please consult your doctor for medical advice.