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Soluble vs. insoluble fiber

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.

Alternative Names

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

References

Lembo AJ. Constipation. In: Feldman M, Friedman LS, Brandt LJ, eds. Sleisenger and Fordtran's Gastrointestinal and Liver Disease. 10th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 19.

Parks EP, Maqbool A, Shaikhkhalil A, Groleau V, Dougherty KA, Stallings VA. Nutritional requirements. In: Kliegman RM, Stanton BF, St. Geme JW, Schor NF, eds. Nelson Textbook of Pediatrics. 20th ed. Philadelphia, PA: Elsevier; 2016:chap 44.

Threapleton DE, Greenwood DC, Evans CE, et al. Dietary fibre intake and risk of cardiovascular disease: systematic review and meta-analysis. BMJ. 2013;347:f6879. PMID: 24355537 www.ncbi.nlm.nih.gov/pubmed/24355537.

Wallig MA, Keenan KP. Nutritional toxicologic pathology. In: Haschek WM, Rousseaux CG, Wallig MA, eds. Haschek and Rousseaux's Handbook of Toxicologic Pathology. 3rd ed. Waltham, MA: Elsevier Academic Press; 2013:chap 36.

Review Date 6/21/2018

Updated by: Michael M. Phillips, MD, Clinical Professor of Medicine, The George Washington University School of Medicine, Washington, DC. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.