Fiber And Diabetes

There has been a lot of attention on the importance of fiber in weight loss, digestion and in overall health. More recently, information about the important role that fiber plays in the regulation of blood glucose has also become an important consideration in developing the best possible nutritional program for those with diabetes or the risk of developing diabetes.

In studies of men with a risk for the development of type 2 diabetes, researchers identified different mechanisms by which fiber was determined to assist in reducing risks. These included reducing the oxidative stress that occurs in a high fat, high carbohydrate diet which, in turn, decreased the action of proinflammatory genes in the body. They noted that a meal that included high levels of natural fibers, including that from fruit, prevented the spike in plasma lipoplysccharides that were seen for up to five hours after eating the high carbohydrate, high fat diets. Finally, they noted that high fat, high carbohydrate diets without fiber interfered with insulin and lead to an increase in insulin resistance and a decrease in insulin sensitivity. 1

Understanding Fiber

Fiber is a naturally occurring plant product and is found in carbohydrates along with sugar and starch.  Unlike sugar and starch, the fiber component of the carbohydrate cannot be digested by the body so it is not absorbed from the digestive system into the blood. There are actually two different types of fiber, one that can be partially broken down and one that remains largely intact through the system. Soluble fiber can be partially dissolved by the enzymes of the digestive system to form a thick gel like material.

The fiber that remains intact through the digestive system is known as insoluble fiber. Historically insoluble fiber was thought to have little effect on the prevention of diabetes or the regulation of blood glucose levels. More recent studies have shown that insoluble fiber may actually play a very important role. Research into the consumption of whole grains, which are high in insoluble fiber, has shown a positive effect on weight loss, increased performance of the gastrointestinal tract, reduction in obesity and the prevention of coronary heart disease. 2

Insoluble fiber assists in moving waste material through the gastrointestinal tract and promoting the elimination of wastes from the body on a regular basis. It may also work to help regulate or modulate the release of specific hormones in the lining of the gut that have been linked to increased insulin resistance in cells. In addition, the foods that contain insoluble fibers, specifically whole grains and legumes, are also excellent sources of many of the trace minerals and nutrients that important to a balanced diet.

Soluble fiber does break down somewhat in the digestive tract. It forms a gel-like material that contains roughly 20-200 percent its own volume in water. This liquid-gel combination traps sugars, starches and the larger macromolecules of fat, preventing them from being absorbed readily and quickly through the intestinal walls. In addition the gel also traps bacteria that begin a fermentation process, releasing specific chemicals and also helping to break down the food more effectively in the digestive system. The lining of the intestines also becomes coated with the partially digested soluble fiber, further limiting rapid uptake of the glucose from the digested material. As the thick gel-like soluble fiber mass passes through the digestive system the entire system becomes regulated and large blood glucose spikes immediately after eating are less likely to occur.

Effects of Fiber In The Diet

Adding fiber to your diet can help in lowering the risk for developing prediabetes, gestational diabetes or type 2 diabetes as it has an effect on hunger and satiation. In a study comparing a high insoluble fiber intake at breakfast with a low fiber cereal, it was found that people that consumed the low fiber cereal had a higher subjective appetite before the next meal. In addition those that consumed the high fiber cereal consumed less total energy at the meal and also had a lower total energy intake at the next meal. The high fiber cereal group also had lower plasma glucose ratings both before and after the next meal.3 In this study the cereal was provided as a breakfast with tests done in 4 hours or just before and after the lunch meal.

Fiber is instrumental in providing a feeling of satiation that can last for several hours after a meal. The fiber adds bulk to the digestive system, slows down the gastric emptying and regulates the movement of the digestive material which all contributes to feelings of being full and satiated. This in turn decreases the signals from the intestine that triggers feelings of hunger and helps to decrease the craving for high carbohydrate “snacks” that are often experienced by those with diabetes or prediabetes.

Women should consume between 21 and 25 grams and males slightly more at 30 to 38 grams.  Ideally fiber should be from natural food sources and not specific fiber supplements as trace minerals and nutrients from high fiber foods are not found in the supplements.

Good Sources Of Fiber

While most foods that are high in fiber are low on the glycemic index and therefore considered to be low in carbohydrates, there are exceptions. Adding fiber to the diet by consuming specific foods in place of high carbohydrate, high fat and high protein foods can be a good option for most diabetics. As with any dietary change it is important to discuss any concerns with your doctor prior to dramatically changing a diet.

Good sources of dietary fiber include

  • Whole wheat products (breads, crackers, pastas, cereals)
  • Fresh fruits
  • Fresh vegetables
  • Beans and peas
  • Brown rice
  • Whole gains (quinoa, oats, rye, buckwheat, millet)
  • Sprouted grains

Other fruits and vegetables can also be great sources of fiber but may have increased levels of starches and sugars.  When consuming fruits and vegetables it is beneficial to eat them raw and with the peel whenever appropriate. Good sources of fiber from fruits and vegetables can be found in raspberries, pears, apples, strawberries, beans, nuts, artichokes, peas, broccoli, greens and corn


1 Ghanim, H., Chaudhuri, A., & Dandona, P. (2010). Associations Between Dietary Fiber and Inflammation, Hepatic Function, and Risk of Type 2 Diabetes in Older Men: Potential Mechanisms for the Benefits of Fiber on Diabetes Risk . Diabetes Care , 44.

2 Kaline, K., Bornstein, S. R., Bergmann, A., et al (2007). The Importance and Effect of Dietary Fiber in Diabetes Prevention with Particular Consideration of Whole Grain Products. Thieme eJournals .

3 Hamedani, A., Akhavan, T., & Samra, R. A. (2008). Reduced energy intake at breakfast is not compensated for at lunch if a high-insoluble-fiber cereal replaces a low-fiber cereal. American Society for Nutrition , 1343-1349.

This article was originally published July 12, 2012 and last revision and update of it was 9/10/2015.