Sources

Last updated: September 6, 2026

Formulas & recommendations

• Institute of Medicine (2005). Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. National Academies Press. The Adequate Intake values and the 14 g per 1,000 kcal basis.
• U.S. Dietary Guidelines for Americans 2020-2025, which adopt the IOM values.
• FDA Daily Value for dietary fiber (28 g), used on Nutrition Facts labels.
• 21 CFR 101.81, Health claims: soluble fiber from certain foods and risk of coronary heart disease. Sets the daily intake levels behind the claim: 7 g or more of soluble fiber from psyllium seed husk, 3 g or more of beta-glucan from whole oats or barley.

Fiber supplements

• U.S. National Institutes of Health, Office of Dietary Supplements. Dietary Supplement Label Database (dsld.od.nih.gov). Supplement Facts panels as filed by manufacturers; the source of every product figure in our supplement comparison.
• McRorie JW Jr, McKeown NM (2017). “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 117(2):251-264.
• van der Schoot A, Drysdale C, Whelan K, Dimidi E (2022). “The Effect of Fiber Supplementation on Chronic Constipation in Adults: An Updated Systematic Review and Meta-Analysis of Randomized Controlled Trials.” American Journal of Clinical Nutrition 116(4):953-969.

Intake surveys

• Quagliani D, Felt-Gunderson P (2017). “Closing America’s Fiber Intake Gap: Communication Strategies From a Food and Fiber Summit.” American Journal of Lifestyle Medicine 11(1):80-85. The source of the finding that about 5% of the population meets fiber recommendations.

Food composition data

• USDA FoodData Central (api.nal.usda.gov/fdc): total dietary fiber and household serving values (SR Legacy), as published in standard clinical fiber tables.

Soluble and insoluble fiber analyses

• Anderson JW, Bridges SR (1988). “Dietary fiber content of selected foods.” American Journal of Clinical Nutrition 47(3).
• Marlett JA (1992). “Content and composition of dietary fiber in 117 frequently consumed foods.” Journal of the American Dietetic Association 92(2).
• Li BW, Andrews KW, Pehrsson PR (2002). “Individual sugars, soluble, and insoluble dietary fiber contents of 70 high consumption foods.” Journal of Food Composition and Analysis 15(4).