Correction on the prior post. Bran is an insoluble fiber..........it does absorb water.....and lots of it. Just pour some bran in a bowl and pour some milk or water into it and watch what happens in a few minutes!!!! No more liquid to be seen. It is very important to drink plenty of liquid when you have a bowl of all bran.
"There are two types of fiber: soluble and insoluble. Soluble fiber is viscous (or thick) and forms a gel in water. It includes components such as pectins and gums found in beans, some fruits and vegetables, oats, psyllium and barley. Research indicates that soluble fibers help lower blood cholesterol levels and may play a role in regulating the body's use of glucose (a type of sugar)."
"Insoluble fiber does not dissolve in water. Major components of insoluble fiber are cellulose, hemicellulose and lignon. Foods including wheat bran, whole grains and vegetables are some of the best sources of insoluble fiber. Insoluble fiber retains water in the gastrointestinal tract (or GI tract), thus increasing bulk and aiding in waste elimination. Since these different types of fiber serve different functions, it is important to make sure we have enough of both in your daily diet."