The Guardian of Gut Balance: The Microecological Game Between Dietary Fiber and Gut Bacteria
As dietary fiber intake decreases, stool volume decreases accordingly. Professor Yin Nanmin once conducted an experiment. He selected five male students and deprived them of any dietary fiber for the first week, ate 12 grams daily for the second week, and 32 grams daily for the third week. He then measured the stool volume of each student. The results showed that as dietary fiber intake increased, stool volume also increased. Moreover, the interval between bowel movements was also affected by dietary fiber intake. During the week without dietary fiber, even students who did not usually experience constipation developed constipation.
Recently, many researchers have reported that dietary fiber has many functions besides preventing constipation. Generally, each gram of matter in the large intestine contains about 1 billion microorganisms, with approximately 100 species and 100 trillion microorganisms in the entire large intestine. Dietary fiber that cannot be digested in the stomach and small intestine enters the large intestine and has a significant impact on the gut microbiota. Gut microorganisms are divided into harmful and beneficial bacteria. Moreover, the types and quantities of gut microorganisms change with age. During lactation, beneficial bifidobacteria are absolutely dominant, but after weaning, the gut microbiota becomes almost identical to that of adults.
As people approach old age, the number of Bifidobacteria in their intestines decreases, while Escherichia coli and other bacteria increase. Additionally, harmful bacteria such as *Pericarpium ferruginosa* (putrefactive bacteria), which were rare in youth, also increase. This increase in harmful bacteria like *Pericarpium ferruginosa* is a result of aging, negatively impacting the body and accelerating the aging process. The gut microbiota naturally changes depending on the food we eat. Ingesting dietary fiber increases Bifidobacteria in the gut, which are beneficial for bowel movements and boosting the body's immunity. Colorectal cancer is a cancer that occurs in the colon and rectum. Excessive fat intake increases the risk of colorectal cancer. Previously, colorectal cancer was not common in Japan, but with the Westernization of diets and lifestyles, the incidence of this disease has increased. Eating more dietary fiber can help prevent colorectal cancer.
In addition, insufficient dietary fiber intake can easily lead to other diseases, including tooth decay, anemia-related heart disease, arteriosclerosis, gallstones, diabetes, duodenal ulcers, appendicitis, colon polyps, and hemorrhoids. Recently, obesity has become a major problem in Japan, but eating more fiber-rich foods can effectively prevent it. While fruits and vegetables are often the first things that come to mind when thinking about fiber-rich foods, the fiber in grains, tubers, and legumes, which are consumed in large quantities, is also very important. Furthermore, seaweed and mushrooms, which are popular in Japan, are also rich in dietary fiber.