How does the human body make feces? What are the components of feces?

　　In order to survive, humans must obtain nutrients from food to maintain the body's metabolism. When we eat food, it enters the body's digestive system, where the small intestine absorbs 90% of the water in the food and absorbs the nutrients our body needs from the food we have just ingested. The rest is undigested food, which passes through the large intestine, where it turns the undigested food into feces.

　　The colon mainly absorbs the remaining water from the undigested food, although the bacteria in the colon perform more digestion, and the final product that is excreted from the body is a solidified mass of feces. There are three main components of feces: water, bacteria, and undigested dietary fiber, of which 75% is water, 25-54% of the solids are live, dead, harmless and disease-causing bacteria, and incompletely digested dietary fiber.

　　Why does feces have a strong, irritating odor?

　　The most disgusting is the peculiar odor of feces, which is the result of the activity of intestinal microorganisms. Feces releases a large number of volatile gases, the most common ones being carbon dioxide, oxygen, hydrogen and methane, but the source of the bad odor is indole and fecal odorants, which are formed by the action of intestinal bacteria on the amino acid tryptophan, which is present in most diets.

　　Of these volatile compounds, fecal odoriferin has a strong odor that causes people to wince and wince when they inhale it.

　　Why do we feel disgusted by feces?

　　The bacteria in human feces can cause terrible diseases such as cholera, food poisoning and diarrhea, and in addition to our body's natural defense barriers (skin and complex immune system), we have a behavioral immune system that prevents us from approaching potentially infectious objects, such as feces.

　　The "aversion response" is one of the basic emotions of many species, and most bodily secretions and excretions put us at risk of contracting diseases, and aversion is considered a mechanism to avoid disease or to stimulate health care emotions. As evolution and natural selection occurred, those animals and species that managed to stay away from pathogens survived and completed their evolution. In humans, the aversive response occurs involuntarily, without any conscious decision to "feel disgusted," and therefore, when encountering an objectionable irritant such as feces, it leads to more hygienic habits and attempts to avoid disease infection.

　　Disease avoidance behavior is not unique to humans, even lobsters will stay away from other sick lobsters!

　　Have we learned the aversion response?

　　Disgust as an emotion has attracted a great deal of interest from many scientists, and various brain studies have shown that there is significant brain activity in the anterior insula and amygdala regions of the brain when we are confronted with stimuli that produce disgust.

      It is as if we are naturally disgusted by our own excrement because of the danger it poses to human health, the volatile components of feces, the pathogenic bacteria in feces, and the foul odor that creates a generalized aversion response as part of a strategy to avoid disease.

　　Disgust is a strong universal emotional response, but it occurs at different intensities; sometimes we feel sick, but some things may make you feel even sicker. In addition, in some cases you may tolerate things that others find disgusting, e.g., a mother of an infant is far less disgusted by her child's feces than by the feces she sees on the street, and in that case the mother's disgust with her child's feces is actually greatly reduced.

　　Similarly, we are more disgusted by the sight of someone else's feces than we are by our own feces because we are aware that other people's feces can bring new pathogens; this subconscious makes us "shudder" more than witnessing our own feces in the toilet!

　　In fact, we should be thankful that the body develops an aversion to feces, which is a disgusting trigger, so we usually stay away from feces and the disease-causing bacteria it carries. In short, people's aversion to feces doesn't always have a negative effect, and thankfully, the body's wonderful digestive and behavioral immune systems help humans survive safely!