Q: What is the difference between soluble and insoluble fiber?

A: Dietary fiber is that non-nutritious portion of plant foods that passes through the bowels undigested. There are two types of fiber—soluble and insoluble. Soluble fiber dissolves in liquid, forming a thick gel that absorbs elements as it moves through the digestive tract. Insoluble fiber is a rougher fiber that helps "sweep clean" the intestines and inactivates intestinal toxins.

• Soluble fiber sources—flax seed, psyllium, apple pectin, & guar gum
• Insoluble fiber sources—flaxseed, pure cellulose, wheat germ, & oat bran

It is best to get a balance of soluble and insoluble fiber. The best way to do that is to eat a variety of fiber-rich foods. The best forms of "mixed" fibers are unrefined cereal grains (oats, brown rice, whole wheat), peas, beans, squash, apples, and berries. Flax seed is an excellent fiber source because it is 50% soluble and 50% insoluble fiber.