What Is Viscous Fiber?

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In chemistry, viscosity is a term used to describe how well a liquid flows. Your blood can be measured in terms of viscosity, as can intravenous, or IV, solutions a doctor might recommend to rehydrate you. While you might tend to think of fiber sources as tough outer coverings, such as the crunchy portion of a celery stick, viscous fiber is the type that forms a fluid, gel-like paste in your stomach. Also known as soluble fiber, viscous fiber helps keep your blood glucose levels steady.


Scientists divide fiber types into viscous and insoluble fiber. Each name can tell a researcher what to expect as far as physiological outcome. For example, insoluble fiber is not broken down in your body, which adds bulk to your stool. Viscous fibers are characterized by their ability to form a liquid or gel solution when combined with water in your digestive system. This is because viscous fibers bind with fatty acids in your stomach to create the paste. Examples of sub-sets of viscous fibers include pectins, such as those found in apples; beta-glucans; guar gum; and mucilages, such as psyllium husk.

Whole Food Sources

By incorporating whole food sources of viscous fiber in your diet, you can experience several health benefits, including prolonging the amount of time it takes for your stomach to empty, which can help keep your blood sugar steady. Food sources include oat bran, dried beans, nuts, barley, flaxseed, oranges, apples and carrots.


In addition to getting viscous fiber from natural food sources, you also can take soluble fiber supplements to improve your blood sugar control and bowel regularity. Examples of viscous fiber supplements include those that contain pectin, guar gum and psyllium. Taking these types of viscous fiber supplements can help lower your low-density lipoprotein, or LDL, cholesterol, which is known as the “bad” form of cholesterol because it contributes to heart disease.


While fiber supplementation can help you maintain normal blood glucose levels, excess fiber supplementation is associated with the risk of stomach problems, ranging from intestinal discomfort to blockages. For this reason, it is preferred that you obtain your viscous fiber from whole food sources. You also will want to slowly increase your viscous fiber intake because eating too much fiber too soon can lead to gastrointestinal side effects such as gas and diarrhea.