Key takeaways:
Eating a fiber-rich diet has many benefits, from preventing certain diseases to improving gut health.
There are two main types of fiber: soluble and insoluble.
While each type of fiber has different health benefits, both are important to include in your daily diet.
You’ve probably heard that fiber is good for your gut, but did you know its health benefits go far beyond that? It can help with everything from preventing diseases such as diabetes to helping you maintain a healthy weight.
Within the fiber family, there are two types: insoluble and soluble. And each has its own distinct superpowers.
Read below to learn more about the different types of fiber and their benefits, as well as how you can fit more fiber into your daily diet.
What is fiber?
Dietary fiber is a plant carbohydrate that your body can’t digest. Not being able to digest fiber is actually beneficiall for your health. Fiber travels through your digestive system while staying mostly intact. This helps move stool through your intestines and keep your bowel movements regular. Beyond this, research has shown it can:
Help you maintain a healthy weight
Support a healthy gut microbiome (the trillions of microbes, like bacteria and fungi)
Regulate your blood sugar
Lower your cholesterol levels
Reduce your risk of heart attacks, stroke, hypertension (high blood pressure), colon cancer, and type 2 diabetes
What’s the difference between soluble and insoluble fiber?
The two types of fiber are often found in the same foods, but they have slightly different roles in health.
What is soluble fiber?
Soluble fiber is a type of fiber that dissolves in water. Examples include psyllium powder (70% soluble fiber) which is commonly used as a fiber supplement, or guar gum and pectin, which are used to thicken food.
Here are a few of insoluble fiber’s benefits:
Feed gut bacteria: Certain soluble fibers, like oats and barley, are fermented by gut bacteria. This leads to the formation of short-chain fatty acids that protect the gut lining, improve immune function, and lower cholesterol.
Improve blood sugar and cholesterol: By mixing with digested food, gel-forming fiber (psyllium, oat, barley) slows down the absorption of sugar in the blood and removes cholesterol in the stool.
Regulate bowel function: Since gel-forming psyllium stays gelled throughout the gut it can soften hard stool and firm loose stools, helping with diarrhea and constipation.
Promote a healthy weight: Fibers that form gel can slow down food release from the stomach and help you feel full. They can also decrease the digestion and absorption of dietary fat.
Read more like this
Explore these related articles, suggested for readers like you.
What foods are rich in soluble fiber?
Some great sources of soluble fiber include:
| Total Fiber (per 100 g) | Soluble Fiber (per 100 g) | |
| Oats | 10.3 | 3.8 |
| Oranges | 1.8 | 1.1 |
| Peaches | 1.9 | 0.9 |
| Beetroot | 7.8 | 2.4 |
| Flaxseed | 22.33 | 12.18 |
| Psyllium fiber powder | 25 | 16.7 |
What is insoluble fiber?
On the other hand, insoluble fiber does not dissolve in water and is more fibrous. The skin of an apple or the wheat bran (outer shell of wheat) are examples of insoluble fiber.
This type of fiber can help with constipation or irregular bowel movements. Since insoluble fiber does not mix with water, it doesn’t absorb it like soluble fiber does and can’t help with diarrhea. But undigested insoluble fiber does increase stool bulk (volume) in the colon, which stimulates the colon. Insoluble fiber also stimulates the colon by irritating it and causing mucous and water formation, leading to stool passing faster.
Like soluble fiber, insoluble fiber may also help promote a healthy weight by increasing the sensation of fullness. This happens because insoluble fiber can increase the amount of time food stays in your stomach. Insoluble fiber also takes time to chew, signalling fullness. Insoluble fiber has also been linked to a lower risk of type 2 diabetes.
What foods are rich in insoluble fiber?
Some great sources of insoluble fiber include:
| Total Fiber (per 100 g) | Insoluble Fiber (per 100 g) | |
| Almonds | 11.2 | 10.1 |
| Broccoli (raw) | 3.29 | 3 |
| Apple (unpeeled) | 2 | 1.8 |
| Coconut (raw) | 9 | 8.5 |
| Wheat (whole-grain) | 12.6 | 10.2 |
| Lentils (raw) | 11.4 | 10.3 |
Keep in mind that most plant foods (fruits, vegetables, legumes, grains, nuts, and seeds) have both soluble and insoluble forms of fiber. For example, an apple’s skin is made up of mostly insoluble fiber (cellulose and hemicellulose), and its flesh is made up of mostly soluble fiber (pectin). So eating a diet rich in these foods will ensure you’re getting a healthy balance of both fibers.
How much fiber do you need in your daily diet?
There are no dietary recommendations for how much soluble vs. insoluble fiber you need per day. It’s more important to focus on making sure you’re getting enough fiber than focusing on the type.
The USDA Dietary Reference Intake recommendations for fiber for adults are:
Adults under the age of 50 should consume between 25 g (for females) and 38 g (for males) of fiber each day.
Most adults over the age of 50 should consume between 21 g (for females) and 30 g (for males) of fiber daily.
To understand what this looks like, some common foods and their approximate fiber content in a 1-cup serving include:
Oats = 8 g fiber
Popcorn = 1.2 g fiber
Black beans = 10 g fiber
Avocado = 10 g fiber
Cooked spinach = 4.3 g fiber
Raspberries = 8 g fiber
Keep in mind that the amount of fiber you would benefit from consuming each day will vary by age and health status. Most people need more fiber in their diets, but it is possible to have too much fiber.
The bottom line
There are two main types of fiber: insoluble fiber and soluble fiber. Each has unique benefits for your health, from improving gut health to lowering cholesterol. You can find both in most fruits, vegetables, whole grains, beans, or legumes. Try adding in a mix of soluble and insoluble fiber sources at each meal or snack time. And, remember to make sure you’re getting enough fiber in your diet, regardless of the type.
References
Akbar, A., et al. (2021). High fiber diet. StatPearls.
Anderson, J. W., et al. (2009). Health benefits of dietary fiber. Nutrition Reviews.
De Vries, J., et al. (2015). Effects of cereal fiber on bowel function: A systematic review of intervention trials. World Journal of Gastroenterology.
Dhingra, D., et al. (2011). Dietary fibre in foods: A review. Journal of Food Science and Technology.
El-Salhy, M., et al. (2017). Dietary fiber in irritable bowel syndrome (review). International Journal of Molecular Medicine.
Hervik, A. K., et al. (2019). The role of fiber in energy balance. Journal of Nutrition and Metabolism.
Holscher, H. D. (2017). Dietary fiber and prebiotics and the gastrointestinal microbiota. Gut Microbes.
Institute of Medicine. (2005). Dietary reference intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein, and amino acids. National Academies Press.
Koutsos, A., et al. (2015). Apples and cardiovascular health—Is the gut microbiota a core consideration? Nutrients.
McRorie, Jr., J. W. (2015). Evidence-based approach to fiber supplements and clinically meaningful health benefits, part 1. Nutrition Today.
McRorie, Jr., J. W. (2016). Understanding the physics of functional fibers in the gastrointestinal tract: An evidence-based approach to resolving enduring misconceptions about insoluble and soluble fiber. Journal of the Academy of Nutrition and Dietetics.
National Research Council (US) Committee on Diet and Health. (1989). Diet and health: Implications for reducing chronic disease risk. National Academies Press.
Phillips, M. M. (2020). Soluble and insoluble fiber. MedlinePlus.
Quagliani, D., et al. (2016). Closing America’s fiber intake gap. American Journal of Lifestyle Medicine.
Surampudi, P., et al. (2016). Lipid lowering with soluble dietary fiber. Current Atherosclerosis Reports.
Ursell, L. K., et al. (2012). Defining the human microbiome. Nutrition Reviews.
U.S. Department of Agriculture. (2019). Avocados, raw, all commercial varieties.
U.S. Department of Agriculture. (2019). [Historical record]: Black beans.
U.S. Department of Agriculture. (2019). [Historical record]: Organic rolled oats whole grain.
U.S. Department of Agriculture. (2019). Raspberries, raw.
U.S. Department of Agriculture. (2019). Snacks, popcorn, air-popped.
U.S. Department of Agriculture. (2019). Spinach, cooked, boiled, drained, without salt.
Ylönen, K., et al. (2003). Associations of dietary fiber with glucose metabolism in nondiabetic relatives of subjects with type 2 diabetes: The Botnia Dietary Study. American Diabetes Association.
Why trust our experts?
