Is soluble fiber really soluble in the same way, say that sugar is? To me, soluble fiber sounds an awful lot like an oxymoron, since fiber and soluble seem contradictory.
Fiber is actually indigestible. It was once thought that since it is indigestible, it is useless, but now it is known that insoluble fiber helps prevent colon cancer, by adding bulk to the feces and promoting more rapid defecation. Soluble fiber is broken down into fatty acids by intestinal bacteria that is absorbed by the body.