Fiber in Laboratory Rodent Diets

The roles of dietary fiber and the gut microbiota in mediating health and disease have been investigated heavily in recent decades. What constitutes fiber varies somewhat depending on the group or body providing the definition but most broadly it is carbohydrates and lignin that are resistant to digestion by host enzymes.

Grain-based diets are relatively rich in fiber. Neutral detergent fiber (NDF) provides a fairly accurate estimate of the insoluble fiber in grain-based diets. NDF in natural ingredient rodent diets is typically 12-15% but can be greater depending on the specific formula. While measurements of soluble fiber in the ingredients are less certain, we estimate that grain-based diets contain around 2-5% soluble fiber.

Within a grain-based diet, fiber is a constituent of the ingredients in a diet, not an ingredient itself, so the ability to manipulate fiber content in grain-based rodent chow diets is very limited.

To adjust fiber levels precisely, we typically start with a purified diet that allows us to easily isolate and manipulate nutritional variables, then add the fiber(s) of choice. The highly refined ingredients in purified diets predominately consist of one nutrient per ingredient which makes fiber adjustments possible.

Common objectives of fiber adjusted diets include:

Modulating the composition and/or function of the gut microbiota
Reducing inflammation
Increasing short chain fatty acids
Combatting obesity, metabolic dysfunction, and/or MASLD/MASH.

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Fiber in Laboratory Animal Diets

Common Dietary Starting Points

Diet Code	Rationale
TD.130343	Contains no polysaccharides other than cellulose. As described in Desai 2016.
TD.00278	Contains no cellulose or other fiber source. Originally developed to reduce fecal output following gastrointestinal surgeries.
AIN-76A, AIN-93G, AIN-93M	Well-known diets with defined composition. Diets contain 5% cellulose. Corn starch may provide some resistant starch.
High fat diets such as TD.88137 , TD.06414	Investigate the role of fiber in the development of obesity, atherosclerosis, and MASLD/MASH.

Fiber Sources

We stock cellulose, pectin, inulin, and high amylose corn starch. You may choose to provide another source of fiber, such as those listed below, as a customer supplied ingredient.

Chitin
Lignin
Oat Fiber

Fructo-oligosaccharides
Galacto-oligosaccharides
Xylo-oligosaccharides

What is a "low" or "high" fiber rodent diet?

There is no single definition of a low or high fiber diet and it is going to depend on the overall context of the diet. The Dietary Reference Intakes (DRIs), developed and published by the Institute of Medicine, are reference values used to plan and assess nutrient intakes for healthy people. The Adequate Intake (AI) for dietary fiber is 14 g/1,000 kcal (NAP 2005).

For perspective, a natural ingredient rodent diet may be ~40-50 g fiber/1,000 kcal whereas the AIN-93G diet has ~13 g fiber/1,000 kcal.
Typical inclusion rates for pectin and inulin are up to 10% but can be higher; however, gastrointestinal disturbances may result.
Refer to the tables below for a selection of reported fiber outcomes based on different fiber sources.

Pectin Studies

Inclusion Rate	Outcomes	Reference
3.1%	Decreased liver weight, increased cecal propionic and total SCFAs	Jakobsdottir, G., Xu, J., Molin, G., Ahrné, S., & Nyman, M. (2013). High-fat diet reduces the formation of butyrate, but increases succinate, inflammation, liver fat and cholesterol in rats, while dietary fibre counteracts these effects. PloS one, 8(11), e80476.
3.3%, 6.7%, and 10%	Dose dependently decreased food intake and body weight gain	Adam, C. L., Williams, P. A., Garden, K. E., Thomson, L. M., & Ross, A. W. (2015). Dose-dependent effects of a soluble dietary fibre (pectin) on food intake, adiposity, gut hypertrophy and gut satiety hormone secretion in rats. PloS one, 10(1), e0115438.
5%	Decreased fasting blood glucose. Increased cecal acetic, propionic, butyric acids	Wu, C., Pan, L. L., Niu, W., Fang, X., Liang, W., Li, J., Li, H., Pan, X., Chen, W., Zhang, H., Lakey, J. R. T., Agerberth, B., de Vos, P., & Sun, J. (2019). Modulation of Gut Microbiota by Low Methoxyl Pectin Attenuates Type 1 Diabetes in Non-obese Diabetic Mice. Frontiers in immunology, 10, 1733.
5%	Decreased weight loss in DSS induced colitis	Lim, B. O., Lee, S. H., Park, D. K., & Choue, R. W. (2003). Effect of dietary pectin on the production of immunoglobulins and cytokines by mesenteric lymph node lymphocytes in mouse colitis induced with dextran sulfate sodium. Bioscience, biotechnology, and biochemistry, 67(8), 1706–1712.
5%	Increased bacterial 16S rRNA but decreased diversity	Drew, J. E., Reichardt, N., Williams, L. M., Mayer, C. D., Walker, A. W., Farquharson, A. J., Kastora, S., Farquharson, F., Milligan, G., Morrison, D. J., Preston, T., Flint, H. J., & Louis, P. (2018). Dietary fibers inhibit obesity in mice, but host responses in the cecum and liver appear unrelated to fiber-specific changes in cecal bacterial taxonomic composition. Scientific reports, 8(1), 15566.
10%	Increased cecal acetate and propionate	Howard, E. J., Meyer, R. K., Weninger, S. N., Martinez, T., Wachsmuth, H. R., Pignitter, M., Auñon-Lopez, A., Kangath, A., Duszka, K., Gu, H., Schiro, G., Laubtiz, D., & Duca, F. A. (2024). Impact of Plant-Based Dietary Fibers on Metabolic Homeostasis in High-Fat Diet Mice via Alterations in the Gut Microbiota and Metabolites. The Journal of nutrition, 154(7), 2014–2028.
10%	Prevented high fat induced weight gain. Improved glucose tolerance and decreased fatty liver.	Bray, J. K., Chiu, G. S., McNeil, L. K., Moon, M. L., Wall, R., Towers, A. E., & Freund, G. G. (2018). Switching from a high-fat cellulose diet to a high-fat pectin diet reverses certain obesity-related morbidities. Nutrition & metabolism, 15, 55.

Inulin Studies

Inclusion Rate	Outcomes	Reference
2.5%	Increased cecal butyrate	Hutchinson, N. T., Wang, S. S., Rund, L. A., Caetano-Silva, M. E., Allen, J. M., Johnson, R. W., & Woods, J. A. (2023). Effects of an inulin fiber diet on the gut microbiome, colon, and inflammatory biomarkers in aged mice. Experimental gerontology, 176, 112164.
5%	Increased cecal acetate, butyrate, and total SCFAs	Matt, S. M., Allen, J. M., Lawson, M. A., Mailing, L. J., Woods, J. A., & Johnson, R. W. (2018). Butyrate and Dietary Soluble Fiber Improve Neuroinflammation Associated With Aging in Mice. Frontiers in immunology, 9, 1832.
5%	Increased fecal SCFAs	Tan, S., Caparros-Martin, J. A., Matthews, V. B., Koch, H., O'Gara, F., Croft, K. D., & Ward, N. C. (2018). Isoquercetin and inulin synergistically modulate the gut microbiome to prevent development of the metabolic syndrome in mice fed a high fat diet. Scientific reports, 8(1), 10100.
6.6-17.7%	Preserved gut mass and reduced adiposity	Chassaing, B., Miles-Brown, J., Pellizzon, M., Ulman, E., Ricci, M., Zhang, L., Patterson, A. D., Vijay-Kumar, M., & Gewirtz, A. T. (2015). Lack of soluble fiber drives diet-induced adiposity in mice. American journal of physiology. Gastrointestinal and liver physiology, 309(7), G528–G541.
7%	Reduced body weight and hepatic fat accumulation	Weitkunat, K., Stuhlmann, C., Postel, A., Rumberger, S., Fankhänel, M., Woting, A., Petzke, K. J., Gohlke, S., Schulz, T. J., Blaut, M., Klaus, S., & Schumann, S. (2017). Short-chain fatty acids and inulin, but not guar gum, prevent diet-induced obesity and insulin resistance through differential mechanisms in mice. Scientific reports, 7(1), 6109.
10%	Increased cecal crypt depth	Liu, T. W., Cephas, K. D., Holscher, H. D., Kerr, K. R., Mangian, H. F., Tappenden, K. A., & Swanson, K. S. (2016). Nondigestible Fructans Alter Gastrointestinal Barrier Function, Gene Expression, Histomorphology, and the Microbiota Profiles of Diet-Induced Obese C57BL/6J Mice. The Journal of nutrition, 146(5), 949–956.
10%	Increased proliferation of intestinal stem cells, crypt depth, and colon length	Corrêa, R. O., Castro, P. R., Fachi, J. L., Nirello, V. D., El-Sahhar, S., Imada, S., Pereira, G. V., Pral, L. P., Araújo, N. V. P., Fernandes, M. F., Matheus, V. A., de Souza Felipe, J., Dos Santos Pereira Gomes, A. B., de Oliveira, S., de Rezende Rodovalho, V., de Oliveira, S. R. M., de Assis, H. C., Oliveira, S. C., Dos Santos Martins, F., Martens, E., … Vinolo, M. A. R. (2023). Inulin diet uncovers complex diet-microbiota-immune cell interactions remodeling the gut epithelium. Microbiome, 11(1), 90.
10%	Reduced weight gain and fat mass in HFD	Drew, J. E., Reichardt, N., Williams, L. M., Mayer, C. D., Walker, A. W., Farquharson, A. J., Kastora, S., Farquharson, F., Milligan, G., Morrison, D. J., Preston, T., Flint, H. J., & Louis, P. (2018). Dietary fibers inhibit obesity in mice, but host responses in the cecum and liver appear unrelated to fiber-specific changes in cecal bacterial taxonomic composition. Scientific reports, 8(1), 15566.
10%	Increased fecal SCFAs	Mistry, R. H., Gu, F., Schols, H. A., Verkade, H. J., & Tietge, U. J. F. (2018). Effect of the prebiotic fiber inulin on cholesterol metabolism in wildtype mice. Scientific reports, 8(1), 13238.
20%	Reduced HFD induced weight gain and adiposity, prevented dysglycemia	Zou, J., Chassaing, B., Singh, V., Pellizzon, M., Ricci, M., Fythe, M. D., Kumar, M. V., & Gewirtz, A. T. (2018). Fiber-Mediated Nourishment of Gut Microbiota Protects against Diet-Induced Obesity by Restoring IL-22-Mediated Colonic Health. Cell host & microbe, 23(1), 41–53.e4.

Resistant Starch (Hylon VII) Studies

Inclusion Rate	Outcomes	Reference
20%	Prevented hypertension. Increased cecal and portal blood acetate and butyrate	Ganesh, B. P., Nelson, J. W., Eskew, J. R., Ganesan, A., Ajami, N. J., Petrosino, J. F., Bryan, R. M., Jr, & Durgan, D. J. (2018). Prebiotics, Probiotics, and Acetate Supplementation Prevent Hypertension in a Model of Obstructive Sleep Apnea. Hypertension (Dallas, Tex. : 1979), 72(5), 1141–1150.
20%	Reduced colonic epithelial cell proliferation	Le Leu, R. K., Hu, Y., Brown, I. L., & Young, G. P. (2009). Effect of high amylose maize starches on colonic fermentation and apoptotic response to DNA-damage in the colon of rats. Nutrition & metabolism, 6, 11.
53.4%	Reduced appearance of age-related retinal lesions	Weikel, K. A., Fitzgerald, P., Shang, F., Caceres, M. A., Bian, Q., Handa, J. T., Stitt, A. W., & Taylor, A. (2012). Natural history of age-related retinal lesions that precede AMD in mice fed high or low glycemic index diets. Investigative ophthalmology & visual science, 53(2), 622–632.
53.4%	Prevented features of age-related macular degeneration	Rowan, S., Jiang, S., Korem, T., Szymanski, J., Chang, M. L., Szelog, J., Cassalman, C., Dasuri, K., McGuire, C., Nagai, R., Du, X. L., Brownlee, M., Rabbani, N., Thornalley, P. J., Baleja, J. D., Deik, A. A., Pierce, K. A., Scott, J. M., Clish, C. B., Smith, D. E., … Taylor, A. (2017). Involvement of a gut-retina axis in protection against dietary glycemia-induced age-related macular degeneration. Proceedings of the National Academy of Sciences of the United States of America, 114(22), E4472–E4481.
54.2%	Reduced severity and delayed onset of seizures	Michetti, C., Ferrante, D., Parisi, B., Ciano, L., Prestigio, C., Casagrande, S., Martinoia, S., Terranova, F., Millo, E., Valente, P., Giovedi', S., Benfenati, F., & Baldelli, P. (2023). Low glycemic index diet restrains epileptogenesis in a gender-specific fashion. Cellular and molecular life sciences : CMLS, 80(12), 356.