Updated: Mar 28, 2021
There are two kinds of dietary fiber - soluble and insoluble. We will focus on the insoluble fiber that we encounter in our foods, that stringy substances in our fruits and vegetables. Fiber is indigestible and cannot be absorbed by the human body. But that doesn't make it worthless in our diet. On the contrary, it has so many functions. For example, fiber scrubs our guts as it passes through (like a brush cleaning our house of stuck-on dirt). It also bulks our stool making it easier to pass. Most importantly, it feeds the 'good' bacteria in our gut that regulate more of our body's functions than we could ever imagine.
There is limited space in our gut for bacteria. We can determine the dominant population of bacteria by what we eat. When we eat whole grains and fiber from whole plants, we feed the 'good' bacteria and they outgrow and outnumber the 'bad' bacteria. 'Bad' bacteria are so named because their byproducts when the they feed on the food in our gut is usually toxic to the human host. Such toxicity includes cancer causing chemicals, inflammation, ulcerative colitis, irritable bowel syndrome, and other discomforts. The byproducts from the 'good' bacteria are not harmful to the human host. Benefits from 'good' bacteria help in mood stabilization and better overall health. Even your stool and other body secretions will not smell as badly when your whole plant fiber intake is adequate.
The importance of an intentional increase of fiber in our diet cannot be overstated. A whole plant diet will definitely guarantee an adequate amount of daily fiber intake.
Grandma said "eat your vegetables". Now you know why.