You will learn that fiber goes far beyond bran. Before you load your grocery cart with bran products, there are important things you need to learn about dietary fiber in general. Lettuce and cucumbers are low in fiber. These are gums, mucilages, pectins, lignin, cellulose and hemicelluloses. Both are important for health.
Some foods are better sources of one form than the other.
For example, soluble fiber accounts for half of the fiber in oat bran but only a fifth of the fiber in wheat bran. Insoluble Fiber Insoluble fiber is a coarse, chewy material that will not dissolve in water. It is what we think of as roughage. This stimulates the intestinal muscles, thus helping to pass the stool and relieve constipation. By speeding up the movement of food through the intestine, insoluble fiber reduces pressure in the intestine.