General Info


Dietary fiber is not digested or absorbed in the body.

Dietary Origins

Foods that are rich in soluble fiber include apples, carrots, citrus fruits, grains such as barley, legumes, and oat bran and oatmeal, oats, onions, pears, squash, and sweet potatoes. Foods high in insoluble fiber include barley, flaxseeds, most other grains, potatoes, rice, rye, wheat bran, wheat cereals, whole-wheat breads, vegetables such as beets, brussels sprouts, cabbage, carrots, cauliflower, and turnips.


Dietary fiber is a general term that refers to a wide variety of compounds from plants that are resistant to the digestive enzymes produced in the body. Because dietary fiber is resistant to digestive enzymes, it is not broken down or absorbed, which means it does not provide calories or energy to the body. In general, dietary fibers are various forms of complex carbohydrates that have varying abilities to swell by absorbing water into their structural matrix. Fibers that can actually dissolve in water, such as pectin, gums, and fibersol, are referred to as soluble fiber. Insoluble fibers or roughage cannot dissolve in water but they can absorb water. This causes them to swell, making them good bulking agents, which speeds up transit time and improves elimination. Examples of insoluble fibers are cellulose, hemicelluloses, and lignins. Soluble fiber mixes with water, turning into a gel-like substance in the process as it passes through the gastrointestinal tract. Soluble fibers have a moderate cholesterol-lowering effect and they also slow the absorption of glucose from the intestines and help regulate blood sugar levels. When the non-digestible fibers reach the colon, anaerobic bacteria degrade them in a process called fermentation. This process produces byproducts known as short-chain fatty acids, which help maintain proper acid/base balance in the colon and may also play a role in the prevention of colorectal cancer. In general, high fiber diets are associated with significantly reduced risks of cancer, cardiovascular disease, and all causes of mortality. It is generally recommended that Americans should strive to achieve a total dietary fiber intake of 25 to 30 grams/day.

Toxicities & Precautions


There are no known toxicities or precautions associated with taking fiber.

Side Effects

Ingesting large amounts of fiber within a short period of time can cause some individuals to experience minor side effects such as gas, bloating and intestinal cramps. These symptoms may be avoided by always gradually increasing the amount of fiber in ones diet.

Functions in the Body

Dietary fiber

Dietary fiber contributes bulk to the intestinal content, in both wet weight and volume. As well as helping to speed up fecal transit time.

Fiber-rich diets

Fiber-rich diets generally help to improve the regulation of blood sugar.

Soluble fibers

Soluble fibers help regulate the metabolism of lipoproteins and cholesterol, which helps to lower LDL-cholesterol levels.

Soluble types of dietary fiber

Soluble types of dietary fiber are capable of binding to bile acids, and other toxic substances, which decreases the interaction of these compounds with the colonic tissues.

Symptoms & Causes of Deficiency

A lack of fiber is usually the result of poor food choices, which results in a diet that is deficient in fiber-containing foods. Consuming a diet lacking in fiber increases the risk of developing gastrointestinal problems such as constipation, diverticular disorders, and alterations in glycemic control. It may also be speculated that a deficiency in fiber may result in inability to manage weight, increased risk of hemorrhoids, and elevated cholesterol.