The Definition of Crude Fiber in Food

Often there is much confusion about the difference between dietary fiber (soluble fiber) and crude fiber, or what is now referred to as insoluble fiber. Most crude fiber contains one-seventh to one-half dietary fiber.

Components of Crude Fiber

• Crude fiber is determined by laboratory analysis and is mainly composed of lignin, which is found in the tissues of plants and cellulose---basically a plant's skeleton.

Laboratory Analysis of Crude Fiber

• In layman's terms, analysis of crude fiber in the laboratory involves oven-drying the fiber to be analyzed after exposing it to a series of sulfuric acid and sodium hydroxide solutions. What's left is crude fiber: a mixture of insoluble fibers that have no nutritional value.

Do We Need Crude Fiber?

• Insoluble or crude fiber is expelled by the body and aids in maintaining regular intestinal peristalsis (bowel) movements. In short, most people need some crude fiber in their diets.

Sources of Crude Fiber

• Excellent sources of crude fiber, or insoluble fiber, include: vegetables like leafy greens, whole grains like whole wheat and rye, and beans such as kidney beans and black beans.

Irritable Bowel Syndrome

• While most doctors and nutritionists recommend eating a diet that is high in both soluble and insoluble fiber, many suggest that those suffering from irritable bowel syndrome not eat insoluble fiber on an empty stomach.