Getting Enough Fiber on the Gluten-Free Diet
Getting adequate dietary fiber is especially important for people following the gluten-free diet.
The benefits of fiber include:1
Normalizes bowel movements. Fiber increases the weight and size of your stool and softens it. A bulky stool is easier to pass so there’s less chance of constipation. If you have loose or watery stools, fiber will absorb the water and add bulk. Some people on the gluten-free diet may have trouble with constipation due to inadequate fiber in their diet.1
Helps maintain bowel health. Fiber lowers the risk of developing hemorrhoids (swollen veins in the region of the anus) and diverticular disease (small, bulging pouches in the intestines). Researchers are studying how certain fermenting fibers may help prevent diseases in the colon.
Lowers cholesterol levels. Soluble fiber found in beans, gluten-free oats and oat bran, and flaxseed may help lower total blood cholesterol levels. These fibers lower low-density lipoprotein, or "bad," cholesterol levels, reducing the risk of heart disease.
Helps control blood sugar levels. Soluble fiber can help people, particularly those with diabetes, improve their blood sugar levels by slowing the absorption of sugar. A healthy diet that includes insoluble fiber, as well, may also reduce the risk of developing type 2 diabetes.
Aids in reaching a healthy weight. High-fiber foods take longer to chew so your body has time to tell you when you're no longer hungry. This leads to less overeating. A high-fiber diet increases the volume (or visual size) of a meal and lingers longer in your body so you stay full for longer. High-fiber diets also tend to have fewer calories for the same volume of food.
Aids in shaping the healthy bacteria in your gut. Fiber feeds the healthy bacteria in your gut (your microbiome) which, in turn, leads to a healthier body.
What is Fiber?
Fiber is the portion of a plant (made up of carbohydrate and lignin) inside the cell wall that is not digested by humans. It moves through our digestive system creating bulk and preventing constipation.1 There are two kinds of dietary fiber, soluble and insoluble.
Soluble fiber (dissolves in water): helps lower cholesterol, specifically low-density lipo-protein cholesterol (LDL), to aid in heart health.1 It is found in whole grains as well as in many fruits, vegetables, nuts, seeds, and legumes, such as beans, soybeans, and peanuts.2
Insoluble fiber (does not dissolve in water): is not digested, but it adds bulk to the stool and can be very helpful to treat constipation.2 It is found in whole grains, nuts and seeds, as well as in many vegetables.
Many fibrous foods such as whole grains, fruits, vegetables, nuts and seeds have a combination of both soluble and insoluble fiber.
Why Should I Eat Gluten-Free Whole Grains?
Eating whole grains is good for us because they are high in fiber, low in fat, contain protein, and are rich in B vitamins.
Many gluten-containing grain products, such as whole grain breads and cereals, are made from whole grains, such as whole wheat and/or barley. They are typically high in fiber, vitamins and minerals.
This is not necessarily the case with gluten-free grain products which are often prepared with refined (low fiber) flours and grains (rice and rice flour, corn and corn flour, potato starch and tapioca starch). These ingredients are processed to produce foods that are similar in texture and taste to gluten-containing products. Many gluten-free products are also not enriched with vitamins and minerals (learn more about enrichment below).
A study done on the fiber content of gluten-free vs. gluten-containing cereals found that out of 85 gluten-free cereals, 26 cereals contained lower amounts of fiber than their gluten-containing counterpart.3 That is almost 1 in 4 cereals!
Fortunately, manufacturers today are beginning to use more gluten-free whole grains in their products. By substituting the most common gluten-free grains and starches (white rice, potato and corn) with some of the gluten-free whole grains such as quinoa, brown rice, and millet, and high-fiber gluten-free breads and crackers, the nutrient content of your diet vastly improves.1
Tips for Adding Whole Gluten-Free Grains to Your Diet
Drink water! Fiber without water can be constipating. Make sure you drink more water as you add whole gluten-free grains, or any fiber, to your diet.
Look for the word “whole” in the ingredients list. Example: “whole grain brown rice” or “whole quinoa.”
Look for at least 2 grams of fiber per serving on the Nutrition Facts panel. Whenever possible, choose products that list 3 grams of fiber or more per serving (3 grams is considered high fiber).
Rotate these high fiber gluten-free grains into your diet. Select several at a time and keep them ready to use. Don’t rely on just one as your new wheat substitute since each one is high in certain vitamins and minerals, but not all.
Consume at least one-half of your grains each day as whole grains. The US Department of Agriculture and the Whole Grains Council both recommend that at least three 1-oz. servings (48 grams of whole grain; this is different from fiber) or half of the grains we consume daily should be whole grains.6
What Else Should I Know About Fiber?
As the bacteria in the colon break down fiber, it ferments, which can cause gas. Slowly increase the amount of fiber you are eating so your intestines have time to adjust to the increased fiber load.
Space your fiber intake through the day so you are not eating it all at once.
Be sure to drink plenty of water (6-8 cups) as you add more fiber to your diet.
Eating too much fiber can bind with minerals like zinc, iron, calcium, copper, magnesium and selenium in your foods or supplements and keep them from being fully absorbed. Typically, however, this is not a common problem among people on the gluten-free diet.
- Aim for comfortable, well-formed bowel movements without straining.
A Quick Word About Legumes
What Are Legumes?9
- Legumes are plants with a pod. To be specific, pulses are the edible seeds of legumes and they include:
- Dry peas
- Dry beans
- They do not include fresh green beans or fresh peas.
- While soybeans and peanuts are related to legumes, they are different because they have a much higher fat content.
Why Are Legumes So Important in the Gluten-Free Diet?
Eating legumes with gluten free grains, nuts or seeds provides high quality, complete protein. A complete plant-based protein is equal to animal protein. Among many other vitamins and minerals, legumes are high in potassium which regulates our fluid balance and blood pressure. Legume (or pulse) flour, such as chickpea flour, adds nutrition, fiber and good taste to gluten-free baked goods.
- Higgins, L. Whole Grains = Nutritional Gold. In Real Life with Celiac Disease: Troubleshooting and Thriving Gluten-Free. Dennis M, Leffler D, eds. AGA Press. Bethesda, MD, 2010.
- Simpson S. Constipation. In Real Life with Celiac Disease: Troubleshooting and Thriving Gluten-Free. Eds. Dennis M, Leffler D. AGA Press. Bethesda, MD, 2010.
- Thompson T. Folate, iron, and dietary fiber contents of the gluten-free diet. J Am Diet Assoc. 2000;100(11):1389-1396.
- Thompson, T., M. Dennis, L. A. Higgins, A. R. Lee, and M. K. Sharrett. Gluten-free diet survey: Are Americans with coeliac disease consuming recommended amounts of fibre, iron, calcium and grain foods? J Hum Nutr Diet. 2005;18(3):163-169.
- Dennis M, Kupper C, Lee AR, Sharrett MK, Thompson T. Celiac Disease Toolkit. American Dietetic Association, 2011.
- Make Half Your Grains Whole Grains. MyPlate. U.S. Department of Agriculture. myplate.gov. Accessed April 5, 2022.
- What Counts as a Serving? Whole Grains Council. wholegrainscouncil.org. Accessed April 5, 2022.
- How Much Dietary Fiber Should I Eat? U.S. Department of Agriculture. ask.usda.gov. Accessed April 5, 2022.
- What are Pulses? The Global Pulse Confederation. pulses.org. Accessed April 5, 2022.
- General Product Warning: Check Your Lentils (including certified gluten-free lentils) for Foreign Grain. Gluten-Free Watchdog. Dec 2016. glutenfreewatchdog.org. Accessed April 5, 2022.
Revision Date: April 5, 2022
Editors: Melinda Dennis, MS, RD, LDN;
with assistance from Megan Azzola, Dietetic Intern, 2022