# Dietary fiber

Dietary fiber is the plant carbohydrate your gut enzymes cannot break down. It comes in two main types. Soluble fiber (like pectin, beta-glucan, and inulin) dissolves in water and forms a thick gel. Insoluble fiber (like cellulose and lignin) adds bulk to stool and speeds its passage. In your colon, gut microbes ferment soluble fiber, including members of Bacteroidetes and Firmicutes. They turn it into short-chain fatty acids (SCFAs): acetate, propionate, and butyrate. Butyrate is the main fuel for your colon-lining cells. It also blocks histone deacetylase enzymes, which calms NF-κB inflammatory signals. Propionate goes to your liver to help control sugar production. Acetate travels around your body and tunes appetite through the GPR41 and GPR43 receptors. All of this matters for aging. Higher SCFA output eases the slow, chronic inflammation of aging ('inflamm-aging'). And SCFA-making microbes decline as you age. Dose-response analyses of many studies (Yao et al. 2023) show that each extra 10 g of fiber a day links to about 10% lower all-cause death and 13% lower heart death. Reynolds et al. 2019 (Lancet) found the biggest benefit at 25 to 29 g a day. But these links are observational, and trial evidence on hard outcomes is still limited.

## Sources

- Reynolds AN, Mann J, Cummings J, et al.. (2019). Carbohydrate quality and human health: a series of systematic reviews and meta-analyses. The Lancet. https://doi.org/10.1016/s0140-6736(18)31809-9
- Yao F, Ma J, Cui Y, et al.. (2023). Dietary intake of total vegetable, fruit, cereal, soluble and insoluble fiber and risk of all-cause, cardiovascular, and cancer mortality: systematic review and dose-response meta-analysis of prospective cohort studies. Frontiers in Nutrition. https://doi.org/10.3389/fnut.2023.1153165
- Vinelli V, Biscotti P, Martini D, et al.. (2022). Effects of Dietary Fibers on Short-Chain Fatty Acids and Gut Microbiota Composition in Healthy Adults: A Systematic Review. Nutrients. https://doi.org/10.3390/nu14132559

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_Canonical: https://longevity-switzerland.com/en/glossary/dietary-fiber · Part of Longevity Cities · Updated 2026-06-22_