Final answer:
Non-fermentable or insoluble fiber does not dissolve in water and is not easily metabolized by intestinal bacteria, providing bulk and aiding peristalsis to prevent constipation. It's found in foods such as whole wheat, bran, and beans. Insoluble fiber plays a crucial role in digestive health.
Step-by-step explanation:
Fibers that are not really dissolved in water and not easily metabolized by intestinal bacteria are called non-fermentable or insoluble fiber. This type of dietary fiber consists of non-starch polysaccharides such as cellulose, and other plant components. Insoluble fiber does not dissolve in water, but it plays a crucial role in maintaining digestive health by absorbing water to add bulk to feces, thus facilitating peristalsis and easing defecation. While some forms like resistant starches can be fermented in the colon, generally, insoluble fiber is inert to digestive enzymes in the upper gastrointestinal tract.
By stimulating peristalsis, insoluble fiber helps keep food wastes moving through the digestive tract, which may help prevent or alleviate constipation. Good sources of insoluble fiber include whole wheat, wheat bran, beans, and potatoes. In addition to providing bulking, dietary fibers can also impact the absorption of other nutrients and chemicals, consequently affecting overall gastrointestinal health.