DEAR DOCTOR K:
As I’ve entered my 70s, I’ve noticed that my eating and bowel habits have changed. Is this normal?
Well, I could tell you what it says in the medical textbooks, or I could speak from personal experience. The answer would be the same: It sure is normal.
Aging most definitely affects our eating and bowel habits. The human digestive system — our gastrointestinal (GI) tract, or “gut” — is a series of hollow organs linked to form a long, twisting tube. It begins at the mouth and winds down through the esophagus, stomach, small intestine and colon. These organs break down food into components that the body can absorb and use for energy. What’s left is expelled by an efficient disposal system. Here is an illustration of the GI tract:
The food you eat travels a winding 30-foot pathway known as the gastrointestinal tract or the alimentary canal. Along the way the mucosa, or the surface layer of cells lining the gastrointestinal tract, produces digestive enzymes and juices that help break down food to be absorbed into the bloodstream.
Here are some age-related changes you may have noticed:
The MOUTH. As we age, the number and sensitivity of our taste buds decline. Our chewing muscles also weaken and we begin to lose teeth. The food we swallow next enters the tube that leads from the throat to the stomach, called the esophagus.
The ESOPHAGUS. Food does not simply drop down the esophagus; it is pushed down by coordinated contractions of the muscles in the esophagus wall. Unlike the muscles of our arms and legs, we don’t will these muscles to move. When they are stimulated by the presence of a lump of chewed food, they just automatically squeeze the food downward.
Unfortunately, the muscles of the esophagus weaken as we age. They contract less vigorously around food after swallowing, and this can make swallowing more difficult.
Weakened muscles in the esophagus also can cause a second problem. Muscles at the bottom of the esophagus, where it enters the stomach, normally squeeze down hard after food passes through. This keeps stomach acid from squirting back up into the esophagus. When those muscles become weaker with age, it can contribute to acid reflux.
The STOMACH AND SMALL INTESTINE. The stomach is a storage and processing facility where food is prepared for digestion. The stomach produces acid, which helps break down food. As we age, the stomach produces less acid. This doesn’t usually interfere with digestion. And it may make acid reflux and “heartburn” less of a problem.
But lower levels of stomach acid can lead to vitamin B12 deficiency. That’s because stomach acid helps the small intestine absorb vitamin B12 in food. Lower levels of stomach acid also can lead to an overgrowth of bacteria in the small intestine.
The COLON. The final stage of digestion happens in the colon, or large intestine. Just as happens in the esophagus, muscles in the wall of the colon squeeze the waste downward. Moving one’s bowels may be the most frequent GI challenge associated with aging. In general, people have more trouble having regular bowel movements after they reach age 65. Weakness and poor coordination of the muscles of the colon are a major reason for this.
Although our gut ages along with the rest of us, and that can contribute to some of the infirmities of growing older, there are effective treatments. We’ll discuss these in future columns.