Ask the doctor: What are the differences between soluble and insoluble fiber?

Q. I enjoyed your article on diverticular disease and the fiber content of various foods. However, could you make some distinctions between soluble and insoluble fiber? Some fiber makes me feel very bloated.

A. Dietary fiber, sometimes referred to as roughage, consists of the indigestible parts of plant foods. As you note, there are two kinds. Soluble fiber dissolves in water; insoluble does not. Both are important for healthy digestion; both can help prevent not only diverticulitis and constipation but also heart disease, obesity, and diabetes.