my stomach hurts

Digestion should be the natural process of an exquisitely complex system that converts food into the materials needed for life: vitamins, minerals, fats, amino acids (proteins), and sugars (carbohydrates).

From the average person’s point of view, it is a relatively easy, even unremarkable process, something you take for granted. But from a medical viewpoint it is truly fascinating.

Much happens between the time you eat a piece of food and the time the waste products leave your body. Most people are concerned only with the two parts of the digestive system that require some active participation on their part – the food going in and the waste coming out. The steps between these two poles are involuntary, and you probably don’t pay a lot of attention to them, or need to, as long as things are working well.

Elimination itself is fairly straightforward. Eating causes the colon to contract, beginning the process of peristalsis: contraction followed by relaxation, over and over again along the tube, moving things down to the exit. Between thirty to sixty minutes after eating (depending on various factors, such as how much was in the intestinal tract to begin with), a person will normally feel the urge to have a bowel movement.

About 60% of the fecal mass is made up of water, although this figure can vary widely. When you have diarrhea, for example, the percentage of water is much higher. About 30% of a normal stool consists of dead bacteria, which gives feces its characteristic odor. The rest is made up of indigestible fiber, fats (such as cholesterol), inorganic salts, live bacteria, dead cells and mucus from your intestinal lining, and protein.