Alternative Names

Insoluble vs. soluble fiber; Fiber - soluble vs. insoluble

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

Hensrud DD. Diet and nutrition. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 13.

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.

Saint-Cyr M, Waldrop SW, Krebs NF. Nutritional requirements. In: Kliegman RM, St. Geme JW, Blum NJ, et al, eds, Nelson Textbook of Pediatrics. 22nd ed. Philadelphia, PA: Elsevier; 2025:chap 60.