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Is Dietary Fiber Healthy? Digestion, Benefits, And Downsides

Dietary fiber is a plant-based carbohydrate found in fruits, vegetables, legumes, and whole grains. Nuts and seeds are also great sources of fiber. Also known as roughage, fiber is the part of a plant that can't be completely broken down by the digestive tract. 

An image of a female dietitian in her office talking to a male patient about the health benefits of fresh vegetables.

Fiber is an essential part of a healthy diet. After all, fiber foods promote regular and productive bowel movements that remove toxins from your body. Thus, fiber supports overall health. But studies suggest it may also help prevent or fix several disease states and medical conditions. Conversely, low-fiber intake is associated with many health problems.1a

How Fiber Moves Through the Digestive Tract 

When fiber and other foods reach the stomach, they're mixed with gastric juices that begin the digestive process.  This partially  digested food then passes to your small intestine where most of digestion occurs. 

As dietary fiber cannot be broken down by the digestive system, the small intestine moves it into the colon (large intestine). Good bacteria eats (ferments) some of this fiber to produce beneficial postbiotic metabolites. The rest is excreted out of the rectum as stool.  

A 3-d transparent illustration of a female body with internal organs, highlighting the intestines.

Importance of Eating Fiber Foods

The United States Department of Agriculture (USDA) recognized the importance of eating fiber foods when they created their famed "food pyramid" in 1992. Of all the food groups listed on this pyramid, guess which ones have the highest number of servings daily? That's right. Fiber Foods. 

The USDA food pyramid, updated and renamed "MyPyramid" in 2005,  recommended eating:

4-5 servings of vegetables

4-5 servings of fruit

4-8 servings of whole grains 

These guidelines ensure you get enough fiber in your diet every day. 

However, the USDA recently changed the pyramid to a plate icon, showing how much of the plate should contain fruits, vegetables, whole grains, protein, and dairy respectively. But it still gives a strong message; namely, fiber foods are an essential part of your diet.

An image of the My Plate Logo showing designations for fruits, vegetables, grains, protein, and dairy.

How Much Fiber Do I Need?

And just how much fiber do you need? Well, experts recommend that you eat a high-fiber diet, i.e., 25 grams of fiber per day for women and 35 grams for men.1b To ensure you get enough nutrition, you should also eat a variety of plant based foods, including fruits, vegetables, and whole grains. 

Sadly, most Americans are not getting enough fiber. In fact, research suggests that the average American consumes just 16-17 grams of fiber per day.2 That's about half the recommended fiber intake. Clearly most of us need to eat more high fiber foods more often. 

An image of an attractive fit woman in her fifties eating a healthy salad.

Soluble and Insoluble Fiber

There are two types of fiber -- soluble and insoluble -- and each play important roles in your health. Most fiber foods contain both types but tend to be richer in one or the other.

These fibrous foods not only aid digestion and proper bowel function, but they also feed the good bacteria in your lower colon. Soluble and insoluble fiber are both necessary parts of a healthy diet. Let's discuss each one.

Soluble Fiber

Soluble fiber dissolves in water and gastrointestinal juices to form a gel-like substance in the colon, which is then fermented by bacteria. (This is what typically causes the gas and bloating you experience after meals.) 

Though soluble fiber dissolves in water, it offers many health benefits. For instance, studies suggest that soluble fiber binds with cholesterol and glucose (sugar) slowing or preventing absorption into the bloodstream. It may also help lower blood pressure. This can help prevent type 2 diabetes and heart disease.4,5  

Because soluble fiber helps you feel fuller longer, it may prevent overeating, thereby assisting with  weight control. It also supports a healthy gut. 

In addition, research indicates that the postbiotics supplements and their metabolites made from bacterial fermentation of soluble fiber provide a variety of health benefits. This is especially true for the short-chain fatty acid butyrate. 

An image of a female eating oatmeal with raspberries and blueberries with almonds on the side.

Foods High In Soluble Fiber

Foods that are high in soluble fiber include:


  • Black beans
  • Oatmeal
  • Avocado
  • Brussels sprouts
  • Oranges
  • Broccoli
  • Chia seeds
  • Flax seeds


Insoluble Fiber

Unlike soluble fiber, insoluble fiber passes through the digestive system relatively intact. Once in the colon, this fiber absorbs water that bulks up the stool for easier passage.  


As it moves through the digestive tract, insoluble fiber aids digestion and helps remove toxins from the system.  This may support overall health and even help prevent certain bowel issues and diseases. It also promotes regular bowel movements and helps prevent constipation. 


Insoluble fiber can also help you lose weight. How? Well...because it's not digested, this type of dietary fiber is calorie-free.  Plus, insoluble fiber stays in your digestive system longer than other foods, thus minimizing the need to overeat. 

An image of a full shopping bag with fresh fruits and vegetables, cheese, bread, and a vegetable beverage.

Foods High in Insoluble Fiber

Insoluble fiber rich foods include:


  • Walnuts
  • Almonds
  • Flax seeds
  • Cocoa
  • Spinach
  • Radishes
  • Berries
  • Beans


Benefits Of Fiber  

Research studies suggest that there are many benefits of dietary fiber, including:


  1. Weight control. Dietary fiber may increase after-meal satiety and decrease hunger. Also, an increase in dietary fiber is associated with a 10% decrease in calorie intake. (This is because the calories from fiber are not absorbed but leave the body as excrement.) Fiber can also help regulate blood glucose levels, aiding weight management.6


  1. Improved digestive and bowel health. As previously mentioned, fiber helps remove toxins from the digestive system via the rectum. (Dietary fiber may reduce the risk of inflammatory bowel disease, while a  low fiber diet may contribute to this disease.) 7 An adequate fiber intake may also increase good bacteria, helping digestive health. 


  1. Reduced risk of coronary heart disease, stroke, type 2 diabetes, and colorectal cancer.8


  1. Improved immune function. Good intestinal bacteria is largely responsible for the health of our immune system, and a high-fiber diet appears to support the growth and maintenance of these bacteria.9


  1. Better blood sugar control. Many clinical research studies suggest plant-based foods may lower glucose levels, increase insulin sensitivity, and aid blood sugar management. Getting enough fiber, then, may cut down on the risk of developing type 2 diabetes. Indeed, studies show an association of a  high fiber diet with a 20% to 30% reduced risk of type 2 diabetes. Further, this effect was mainly observed with insoluble fiber intake.10


An image of a stethoscope with glucose meter to check blood glucose levels, lancet, tape measure, green vegetables, and oranges in a glass bowl.

How To Get More Fiber In Your Diet

As you can see, the benefits of dietary fiber go beyond These benefits go beyond digestive health. But how do you add more fiber to your diet? Let's start with high fiber foods. 

The best type of dietary fiber comes in high-fiber non-starchy vegetables, leafy greens, and low-sugar fruits. These foods slow glucose absorption and increase satiety (feeling of fullness), which can help prevent overeating and indirectly aid weight management.

Aim to get at least 25 grams of fiber per day if you're a woman and 35 grams if you're a man. Keeping track of grams of dietary fiber can be difficult. But there is an easier way. Simply fill half your plate with high fiber foods (mostly non-starchy vegetables) at each meal. 

High-Fiber Foods To Enjoy

The best high-fiber foods include: 

  • Navy beans (9.6 grams of fiber per ½ cup cooked)
  • Chia seeds (8.3 grams per 2 tablespoons)
  • Raspberries (8 grams per 1 cup)
  • Collard greens (7.6 grams per 1 cup cooked and chopped)
  • Flax Seeds (5.6 grams per 2 tablespoons)
  • Broccoli (5.1 grams per 1 cup cooked and chopped)
  • Almonds (3.8 grams per ¼ cup roasted)
  • Cocoa powder ( 4 grams per 2 tablespoons unsweetened)

Be sure to increase your fluid intake when eating fiber, as this is necessary to bulk up your stool for  regular easy-to-pass bowel movements. 

Do You Need Fiber Supplements?

It is better to eat a wide variety of plant foods than it is to take fiber supplements. This is because supplements don't provide the nutrients that foods high in fiber do. Fiber supplements may be necessary, though, if you suffer from constipation, diarrhea, or irritable bowel syndrome. 

Be sure to check with your doctor before taking fiber supplements.

An image of a woman's hand pouring a powdered orange drink mix into a clear glass of water.

Dangers Of Eating Too Much Fiber 

Fibrous foods contain vitamins, minerals, and other nutrients that the body needs for health. However, eating a lot of fiber can mess with your digestive tract and lead to a host of unpleasant gastrointestinal symptoms, such as gas, bloating, and stomach cramps.

High-fiber intake can also be dangerous for those suffering from certain medical conditions can you experience all the health benefits of a high-fiber diet without all those negative digestive symptoms?


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1- United States Department of Agriculture (USDA). Dietary Guidelines for Americans 2020-2025. Accessed Mar 17, 2021.

1a- Zelman K. Fiber: How Much Do You Need? Nourish by WebMD. Reviewed by Jennifer Robinson, MD on Apr 07, 2016. Accessed Feb 18, 2021.

2- King DE, Mainous AG 3rd, Lambourne CA. Trends in dietary fiber intake in the United States, 1999-2008. J Acad Nutr Diet. 2012 May;112(5):642-8. doi: 10.1016/j.jand.2012.01.019. Epub 2012 Apr 25. PMID: 22709768.

3- 5- Makki K, Deehan EC, Walter J, Bäckhed F. The Impact of Dietary Fiber on Gut Microbiota in Host Health and Disease. Cell Host Microbe. 2018 Jun 13;23(6):705-715. doi: 10.1016/j.chom.2018.05.012. PMID: 29902436.

4- Aller R, de Luis DA, Izaola O, La Calle F, del Olmo L, Fernandez L, Arranz T, Hernandez JM. Effect of soluble fiber intake in lipid and glucose levels in healthy subjects: a randomized clinical trial. Diabetes Res Clin Pract. 2004 Jul;65(1):7-11. doi: 10.1016/j.diabres.2003.11.005. PMID: 15163472.

5- Khan K, Jovanovski E, Ho HVT, Marques ACR, Zurbau A, Mejia SB, Sievenpiper JL, Vuksan V. The effect of viscous soluble fiber on blood pressure: A systematic review and meta-analysis of randomized controlled trials. Nutr Metab Cardiovasc Dis. 2018 Jan;28(1):3-13. doi: 10.1016/j.numecd.2017.09.007. Epub 2017 Oct 7. PMID: 29153856.

6- Howarth NC, Saltzman E, Roberts SB. Dietary fiber and weight regulation. Nutr Rev. 2001 May;59(5):129-39. doi: 10.1111/j.1753-4887.2001.tb07001.x. PMID: 11396693.

7- Day AS, Davis R, Costello SP, Yao CK, Andrews JM, Bryant RV. The Adequacy of Habitual Dietary Fiber Intake in Individuals With Inflammatory Bowel Disease: A Systematic Review, Journal of the Academy of Nutrition and Dietetics, 2021, ISSN 2212-2672,

8- The Lancet. (2019, January 10). High intake of dietary fiber and whole grains associated with reduced risk of non-communicable diseases. ScienceDaily. Retrieved February 18, 2021 from

9- Harvard T.H. Chan School of Public Health. Nutrition and Immunity. Accessed Feb 18, 2021. perfectly optimized content goes here!

10- Weickert MO, Pfeiffer AFH. Impact of Dietary Fiber Consumption on Insulin Resistance and the Prevention of Type 2 Diabetes. J Nutr. 2018 Jan 1;148(1):7-12. doi: 10.1093/jn/nxx008. PMID: 29378044.

11- Tarantino O. 43 Best High-Fiber Foods For a Healthy Diet. Eat This, Not That! Oct 5, 2017. Accessed Feb 18, 2021.

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