There are several reasons why the intestinal tract works slower as we get older. If there are sclerotic processes in the blood-vessels in the heart and brain, then they are also inevitable in blood-vessels elsewhere, such as in the abdominal cavity, and this affects the speed of intestinal peristalsis. Older people are also less physically active. They tend to have dental issues, so coarser, fibre-dense foods, which nourish good intestinal bacteria, are eaten less. These foods are called prebiotics, and they are necessary for bacteria to feed, live, multiply and secrete the substances that we need. If problems are persistent, then a person ought to supplement with fibre and probiotics.