As a dietitian, I often tell my clients that fiber is one of the most underrated superstars of a healthy diet. After reading this post, I think you’ll agree with me! Most people know it’s good for "keeping things moving," but fiber does so much more—especially when it comes to promoting a happy and healthy gut. Let’s explore what fiber is and why it’s so important for your digestive and overall health.
What Is Fiber?
Dietary fiber is a type of carbohydrate found in plant-based foods that your body can’t fully digest. Unlike other carbs, which are broken down into usable energy, fiber passes through your digestive system mostly intact. There are two main types of fiber: soluble fiber, which dissolves in water to form a gel-like substance, and insoluble fiber, which doesn’t dissolve and adds bulk to your stool. Both types play unique and essential roles in gut health.
What Does Fiber Do for Your Gut?
Nourishes Beneficial Gut Bacteria.
Fiber acts as food for the trillions of bacteria in your gut, also known as the gut microbiome. Specifically, prebiotic fibers act as a food source for beneficial bacteria, encouraging their growth and diversity. A diverse microbiome is linked to better digestion, stronger immunity, and even improved mental health.1
Supports Short-Chain Fatty Acid (SCFA) Production
When your gut bacteria feed on fiber, they produce short-chain fatty acids (SCFAs) like butyrate, acetate, and propionate. These SCFAs are powerhouses for gut health and perform the following functions:
Reduce inflammation: SCFAs help calm inflammation in the gut and throughout the body.2
Boost immunity: A well-fed microbiome supports a robust immune system.1-4
Strengthen the gut lining: SCFAs fortify the intestinal barrier, reducing the risk of leaky gut and keeping harmful substances out of your bloodstream.3
Supports Gut Barrier Function
To expand further, a healthy gut barrier (including a layer of epithelial cells, a mucus layer, and a layer of immune cells) is essential for preventing harmful pathogens from crossing into the bloodstream. Fiber plays a crucial role in maintaining this barrier. Research by Desai et al. (2016) highlights how a low-fiber diet can lead to the degradation of the colonic mucus barrier, increasing susceptibility to pathogens. Beneficial bacteria thrive on dietary fiber, using it to produce SCFAs that help keep the mucus layer intact and the gut lining strong.3
Improves Bowel Regularity
Fiber helps keep your digestive system running smoothly. Insoluble fiber, found in foods such as vegetables, whole grains, nuts, and legumes adds bulk to stool, making it easier to pass. Soluble fiber is found in foods like oats, beans, lentils, and fruit and absorbs water in the GI tract, creating softer stools. Together, they promote regular bowel movements and help prevent constipation.
Supports Healthy Digestion and Blood Sugar Stabilization
Soluble fiber slows the digestion and absorption of carbohydrates, helping to stabilize blood sugar levels and prevent energy spikes and crashes. It also increases the feeling of fullness after a meal and can keep you fuller for longer, which can support healthy weight management.5
Supports Cardiovascular Health
While not directly linked to gut health, fiber’s role in supporting cardiovascular health is too major to leave out of this list of benefits. Increased fiber intake has been shown to have a protective effect against cardiovascular disease through lowering total and LDL (“bad”) cholesterol. Specifically, soluble fiber binds to cholesterol in the digestive tract and helps remove it from the body before it can be absorbed into the bloodstream. This can reduce overall cholesterol levels and support heart health.6
Linked to Reduced Risk of GI Disorders and Cancers
Consuming enough fiber is associated with a lower risk of gastrointestinal disorders like gastroesophageal reflux disease, duodenal ulcers, diverticulitis, irritable bowel syndrome (IBS), and inflammatory bowel disease (IBD).3,5 Additionally, a high-fiber diet has been shown to reduce the risk of colon cancer.7 Fiber helps sweep the colon clean, removing potential carcinogens and, as already discussed, supports the growth of protective gut bacteria.
How Much Fiber Is Right for You?
According to the American Heart Association (AHA) and the United States Department of Agriculture (USDA), the recommended daily fiber intake is:
Women: 25 grams per day
Men: 38 grams per day
Children: A minimum of 14 grams per 1,000 calories consumed
Most people fall short of these recommendations, but incorporating a variety of whole foods from plant sources can help close the gap.
Who Can Benefit from a High-Fiber Diet?
Almost everyone can benefit from eating more fiber. Specific groups who may see significant improvements include:
Individuals with constipation or irregular bowel movements
People managing blood sugar levels, such as those with diabetes or insulin resistance
Those looking to improve heart health, as fiber helps in managing cholesterol levels
Anyone aiming for weight management, as fiber promotes satiety and can help reduce cravings
When Is a Low-Fiber Diet Appropriate?
While fiber is generally beneficial, there are times when a low-fiber diet may be necessary. This includes:
During flare-ups of digestive conditions, such as Crohn’s disease, diverticulitis, or ulcerative colitis
For individuals with strictures or bowel obstructions, as high-fiber foods may be harder to pass
After certain surgeries or treatments, especially those involving the digestive tract or abdominal area
If you’ve been advised to follow a low-fiber diet, work with a healthcare professional to ensure your nutritional needs are still being met.
Fiber-Rich Food Sources
To optimize the gut health benefits of fiber, focus on a variety of fiber-rich foods from all categories. Here are some examples:
Fruits: Apples (4g per medium apple), berries (8g per cup), pears (6g per medium pear), oranges (3g per medium orange), bananas (3g per medium banana)
Vegetables: Broccoli (5g per cup, cooked), carrots (3.5g per cup, chopped), leafy greens (1-2g per cup, raw), Brussels sprouts (4g per cup, cooked), zucchini (2g per cup, cooked)
Legumes: Lentils (15g per cup, cooked), chickpeas (12g per cup, cooked), black beans (15g per cup, cooked), kidney beans (13g per cup, cooked), edamame (8g per cup, cooked)
Whole Grains: Oats (4g per cup, cooked), quinoa (5g per cup, cooked), barley (6g per cup, cooked), brown rice (3.5g per cup, cooked), whole wheat bread (4g per slice)
Nuts and Seeds: Almonds (3.5g per ounce), chia seeds (10g per ounce), flaxseeds (8g per ounce), sunflower seeds (3g per ounce)
Need More Ideas:
Here are some high fiber recipes to try!
Breakfast: Banana Coffee Oatmeal Bake
Dinner: Miso Lime Shrimp Bowl
Snack: Simple Granola
Final Thoughts
Fiber isn’t just about digestion; it’s part of the foundation of overall health. By fueling your gut’s good bacteria, stabilizing blood sugar, and promoting regularity, fiber works behind the scenes to keep your gut—and your whole body—in tip-top shape. Next time you’re building a meal, think of fiber as your gut’s best friend. Your body will thank you!
References
1. Silva YP, Bernardi A, Frozza RL. The Role of Short-Chain Fatty Acids From Gut Microbiota in Gut-Brain Communication. Front Endocrinol (Lausanne). 2020;11:25. Published 2020 Jan 31. doi:10.3389/fendo.2020.00025
2. Morrison DJ, Preston T. Formation of short chain fatty acids by the gut microbiota and their impact on human metabolism. Gut Microbes. 2016;7(3):189-200. doi:10.1080/19490976.2015.1134082
3. Desai MS, Seekatz AM, Koropatkin NM, et al. A Dietary Fiber-Deprived Gut Microbiota Degrades the Colonic Mucus Barrier and Enhances Pathogen Susceptibility. Cell. 2016;167(5):1339-1353.e21. doi:10.1016/j.cell.2016.10.043
4. Parada Venegas D, De la Fuente MK, Landskron G, et al. Short Chain Fatty Acids (SCFAs)-Mediated Gut Epithelial and Immune Regulation and Its Relevance for Inflammatory Bowel Diseases [published correction appears in Front Immunol. 2019 Jun 28;10:1486. doi: 10.3389/fimmu.2019.01486]. Front Immunol. 2019;10:277. Published 2019 Mar 11. doi:10.3389/fimmu.2019.00277
5. Anderson JW, Baird P, Davis RH Jr, et al. Health benefits of dietary fiber. Nutr Rev. 2009;67(4):188-205. doi:10.1111/j.1753-4887.2009.00189.x
6. Soliman GA. Dietary Fiber, Atherosclerosis, and Cardiovascular Disease. Nutrients. 2019;11(5):1155. Published 2019 May 23. doi:10.3390/nu11051155
7. Bingham SA, Day NE, Luben R, et al. Dietary fibre in food and protection against colorectal cancer in the European Prospective Investigation into Cancer and Nutrition (EPIC): an observational study [published correction appears in Lancet. 2003 Sep 20;362(9388):1000]. Lancet. 2003;361(9368):1496-1501. doi:10.1016/s0140-6736(03)13174-1
