Overall, the digestive (muscular) system is less affected by aging than most other parts of the body. The muscles of the esophagus contract less forcefully, but the movement of food through the esophagus is not affected. Food is emptied from the stomach slightly more slowly, and the stomach cannot hold as much food because it is less elastic. The muscles that support the digestive system have “over strength”, they are more powerful than needed when young. But nature did so intentionally. These muscles can work against gravity even when in an upside down position. The strength of these muscles slowly decreases but due to the leftover power there is no negative impact. But the speed of contractions also decreases which is responsible for a slower moving.
The digestive tract produces less lactase, an enzyme the body needs to digest milk. As a result, older people are more likely to develop intolerance of dairy products (lactose intolerance). People with lactose intolerance feel bloated or have gas or diarrhea after they consume milk products. Reducing intake of milk containing products must be actively promoted when this happens.
In the large intestine, materials move through a little more slowly. In some people, this slowing contributes to constipation. During passing the liquid re-absorption continues and this contributes to a harder content.
The liver becomes smaller because the number of cells decreases. Less blood flows through it, liver enzymes that help the body process drugs and other substances work less efficiently. As a result, the liver is less able to help remove drugs and other substances from the body. The effects of drugs—intended and unintended—last longer. As mentioned before the intake of long-term drugs exhausts the body and organs and prevents proper uptake of the needed active ingredients. This is a matter of concern for future delivery systems of drugs during aging and long-term use.