Dietary fiber is a type of carbohydrate just like sugars and starches (see Carbs, Protein and Fats – Their Effect on Glucose Levels). This sometimes can be confusing for people living with diabetes. Carbohydrate is the macronutrient that has the biggest impact on glucose. So, does fiber have any effect on your glucose levels?

The short answer is no. Fiber does not raise glucose levels because it is not digested by the body.

Fiber is the structural portion of fruits, vegetables, grains, nuts, and legumes that cannot be digested or absorbed by your body. Therefore, fiber does not provide calories nor glucose for energy. 

So if fiber does not provide glucose to the body for energy, why should we eat it? There are two types of fiber: insoluble and soluble. Insoluble fiber keeps your digestive tract working well. Whole wheat bran is an example of this type of fiber. Soluble fiber can help lower your cholesterol levels and help with steady glucose levels. Oatmeal is an example of this type of fiber. Common sources of fiber are wheat, corn, or oat bran; legumes (cooked dried peas and beans); nuts; and vegetables and fruits.

So how much fiber should I eat? Research suggests the average person should eat between 20-35 grams of fiber each day. Most Americans eat about half that amount. A study in the New England Journal of Medicine showed that people with diabetes who ate 50 grams of fiber a day — particularly soluble fiber — were able to manage their glucose levels easier than those who ate less fiber.

Fiber adds “bulk” to your meals, helping you to feel full and satisfied after you eat. Other fibers have a laxative effect on the digestive system.

Some ways to increase the fiber content of your meals:

  • Dietary fiber is listed under the Total Carbohydrate on the Nutrition Facts Label. High fiber foods are those with 5 grams or more per serving, and good sources of fiber are foods with 2-1/2 to 5 grams per serving.
  • Look for whole-grain bread that contains 3 grams of fiber per serving and whole-grain crackers that contain at least 2 grams of fiber per serving.
  • Leave the skin on your fruits and vegetables
  • Substitute brown rice for white rice and whole-wheat pasta instead of white pasta.

Be sure to increase your fiber intake slowly (3-5gms per day) over several weeks and remember to drink plenty of water each day to avoid constipation.

Although this content is reviewed by Joslin Diabetes Center healthcare professionals, it is not intended to replace the medical advice of your doctor or healthcare provider. Please consult your healthcare provider for advice about a specific medical condition.