Soluble vs. insoluble fiber
Insoluble vs. soluble fiber; Fiber - soluble vs. insoluble
Dietary fiber is the part of food that is not affected by the digestive process in the body. Only a small amount of fiber is metabolized in the stomach and intestine, the rest is passed through the gastrointestinal tract and makes up a part of the stool. There are two types of dietary fiber, soluble and insoluble. Soluble fiber retains water and turns to gel during digestion. It also slows digestion and nutrient absorption from the stomach and intestine. Soluble fiber is found in foods such as oat bran, barley, nuts, seeds, beans, lentils, peas, and some fruits and vegetables. Insoluble fiber appears to speed the passage of foods through the stomach and intestines and adds bulk to the stool. It is found in foods such as wheat bran, vegetables and whole grains. Fiber is very important to a healthy diet and can be a helpful aid in weight management. One of the best sources of fiber comes from legumes, the group of food containing dried peas and beans.
Information
There are 2 different types of fiber -- soluble and insoluble. Both are important for health, digestion, and preventing diseases.
- Soluble fiber attracts water and turns to gel during digestion. This slows digestion. Soluble fiber is found in oat bran, barley, nuts, seeds, beans, lentils, peas, and some fruits and vegetables. It is also found in psyllium, a common fiber supplement. Some types of soluble fiber may help lower risk of heart disease.
- Insoluble fiber is found in foods such as wheat bran, vegetables, and whole grains. It adds bulk to the stool and appears to help food pass more quickly through the stomach and intestines.
References
Ella ME, Lanham-New SA, Kok K. Nutrition. In: Feather A, Waterhouse M, eds. Kumar and Clarke's Clinical Medicine. 10th ed. Philadelphia, PA: Elsevier; 2021:chap 33.
Iturrino JC, Lembo AJ. Constipation. In: Feldman M, Friedman LS, Brandt LJ, eds. Sleisenger and Fordtran's Gastrointestinal and Liver Disease. 11th ed. Philadelphia, PA: Elsevier; 2021:chap 19.
Maqbool A, Parks EP. Shaikhkhalil A, Panganiban J, Mitchell JA, Stallings VA. Nutritional requirements. In: Kliegman RM, St. Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM, eds. Nelson Textbook of Pediatrics. 21st ed. Philadelphia, PA: Elsevier; 2020:chap 55.
Version Info
Last reviewed on: 7/30/2022
Reviewed by: Michael M. Phillips, MD, Emeritus Professor of Medicine, The George Washington University School of Medicine, Washington, DC. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
