Dietary fiber is found in plant foods. Fiber cannot be digested by humans. It has no calories because the body cannot absorb it.
Soluble fiber attracts water and turns to gel during digestion.
This slows digestion and the rate of nutrient absorption from the stomach and intestine. It is found in oat bran, barley, nuts, seeds, beans, lentils, peas, and some fruits and vegetables. Insoluble fiber is found in foods such as wheat bran, vegetables and whole grains. It appears to speed the passage of foods through the stomach and intestines and adds bulk to the stool. Dietary fiber provides a feeling of fullness and adds bulk in the diet.