The benefits of fiber are no secret. Plenty of research supports the positive effects fiber provides people, including overall metabolic health, insulin sensitivity, cardiovascular disease, colonic health, gut motility, and regulation of appetite. It can even enhance immune function. (1)(2) Still, fiber has its doubters who believe that the body does not absorb fiber but rather simply passes through it, disallowing its value to be gained
That’s where knowing the difference between soluble and insoluble fiber comes in. In late December 2024, Dr. Layne Norton contested the social media post by Dr. Shawn Baker, MD, who authored Carnivore Diet. Dr. Baker’s post stated, “If you eat a lot of fiber, much more of your nutrition just ends up in the toilet.”
Dr. Norton explains how this statement is not accurate as only insoluble fiber is not absorbed. Soluble fiber can be easily accessed and metabolized and helps regulate gut microbiota. (3)
[Related: What Is Visceral Fat and What Diet Combats It?]
No nutrition from fiber is completely erroneous.
—Dr. Layne Norton
Insoluble fiber is also beneficial, though. Since it helps keep people regular, it helps lessen the amount of time toxins in the body can interact with the intestinal lumen — the open space within the intestines that allows digested food to pass through. (4) It also helps “induce gut immunity, improve intestinal integrity and mucosal proliferation, and favor adhesion of probiotics and hence improve human health.” (5)
The massive amount of research and meta-analysis all points toward pursuing sufficient fiber in one’s diet for significant health benefits. A systemic review of 64 studies in January 2024 in Clinical Studies found that “dietary fiber from whole grains, cereals, and vegetables was associated with a reduced risk of all-cause mortality, while dietary fiber from nuts and seeds reduced the risk of cardiovascular-related death by 43%.” (6)
So when trying an elimination diet like the carnivore diet — called such because it eliminates fruits, veggies, and other fiber-providing foods — remember that the function of an elimination diet is to slowly add the removed nutritional elements back in to see what is tolerable.
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References
- Barber, T. M., Kabisch, S., Pfeiffer, A. F. H., & Weickert, M. O. (2020). The Health Benefits of Dietary Fibre. Nutrients, 12(10), 3209. https://doi.org/10.3390/nu12103209
- Anderson, J. W., Baird, P., Davis, R. H., Jr, Ferreri, S., Knudtson, M., Koraym, A., Waters, V., & Williams, C. L. (2009). Health benefits of dietary fiber. Nutrition reviews, 67(4), 188–205. https://doi.org/10.1111/j.1753-4887.2009.00189.x
- Guan, Z. W., Yu, E. Z., & Feng, Q. (2021). Soluble Dietary Fiber, One of the Most Important Nutrients for the Gut Microbiota. Molecules (Basel, Switzerland), 26(22), 6802. https://doi.org/10.3390/molecules26226802
- MATTSON, F. H., BENEDICT, J. H., & BECK, L. W. (1954). Composition of intestinal lumen lipides following the feeding of triglycerides, partial glycerides or free fatty acids. The Journal of nutrition, 52(4), 575–580. https://doi.org/10.1093/jn/52.4.575
- Baky, M. H., Salah, M., Ezzelarab, N., Shao, P., Elshahed, M. S., & Farag, M. A. (2024). Insoluble dietary fibers: structure, metabolism, interactions with human microbiome, and role in gut homeostasis. Critical reviews in food science and nutrition, 64(7), 1954–1968. https://doi.org/10.1080/10408398.2022.2119931
- Ramezani, F., Pourghazi, F., Eslami, M., Gholami, M., Mohammadian Khonsari, N., Ejtahed, H. S., Larijani, B., & Qorbani, M. (2024). Dietary fiber intake and all-cause and cause-specific mortality: An updated systematic review and meta-analysis of prospective cohort studies. Clinical nutrition (Edinburgh, Scotland), 43(1), 65–83. https://doi.org/10.1016/j.clnu.2023.11.005
Featured image via Shutterstock/Bruno D Andrea
