But while it’s encouraging to see more people interested in fiber, scientists remind us that how much we eat is only part of the story. The type of fiber, how our gut microbes use it, and our individual gut health also matter, and these nuances are not always reflected in current dietary guidelines.
How fiber nourishes our gut and our health
When we consume dietary fiber, our gut bacteria break it down, producing short-chain fatty acids (SCFAs) such as butyrate and propionate. These molecules nourish intestinal cells and play an important role in regulating inflammation and immune responses.
This is evident from recent research by Stanford University SCFAs can also modulate gene expression, influencing cell proliferation and cancer control via epigenetic mechanisms. “We found a direct link between eating fiber and modulation of gene function that has anti-cancer effects.says professor Michael Snyder, author of the study.
These findings add to a growing body of evidence linking a high-fiber diet to a lower risk of obesity, diabetes and certain cancers – all through the metabolic activity of the gut microbiota.
Dietary guidelines may need a microbiome update
As Professor Yolanda Sanz explains: “Until now, these were guidelines and recommendations for a healthy diet […] have not considered what microbiome research contributes.”
In fact, the standard daily intake of 20 to 35 grams of fiber was established decades ago, based primarily on its effect on bowel movements. Today, experts like Patrick Veiga point out that higher intakes can help prevent chronic diseases – from cardiovascular disease to diabetes and cancer – but the evidence is still emerging and most people barely reach 20 grams per day.
“Fiber recommendations are still based on stool data from decades ago,says Veiga.Today we suspect that more than the recommended intake might be needed to better prevent chronic diseases – but we don’t yet have enough data to confirm this.”
But as research into the gut microbiome continues, scientists are realizing it the story of fiber is not just about quantity, but also about quality and individual response.
Although increasing fiber intake is generally beneficial, not all fibers behave the same.
As Professor Sanz notes: “Fiber is an umbrella term for a diverse group of substances. Different types behave differently, and not everyone benefits from them the same.”
For example, in people with inflammatory bowel disease (IBD), β-fertility (a type of fiber found in foods such as chicory root and Jerusalem artichoke) can help promote the production of SCFAs and support colon repair. However, their effects depend on the composition of the individual’s microbiota and whether the disease is in remission or active. In some patients, certain fibers may worsen symptoms instead of relieving them.
Overall, these insights suggest that future nutritional advice could integrate not only how much fiber we need, but also how our microbiota respond to different types of fiber. reinforcing the importance of personalized nutritional approaches rather than one-size-fits-all recommendations.
A positive trend – if we follow the science, and not the hype
The popularity of fibermaxxing reflects a positive shift: people are recognizing the value of fiber for digestion and overall health. But instead of focusing solely on hitting a number, scientists encourage us to:
- Increase fiber intake gradually,
- Diversify fiber sources (fruits, vegetables, legumes, whole grains, nuts and seeds),
- Stay hydratedAnd
- Pay attention to individual tolerance and intestinal health.
Because ultimately Nourishing our gut microbiota is about balance and diversityno extremes.
As research continues to discover how dietary fiber shapes our microbiome and impacts long-term health, one message is clear: Making fiber a daily habit is one of the most powerful – and simple – ways to support our well-being from the inside out.
References:
Sanz Y, Cryan JF, Deschasaux-Tanguy M, et al. The gut microbiome connects nutrition and human health. Nat Rev Gastroenterol Hepatol. 2025; 22(8):534-555. two: 10.1038/s41575-025-01077-5.
Nshanian, M., Gruber, J.J., Geller, B.S et al. Short-chain fatty acid metabolites propionate and butyrate are unique epigenetic regulatory elements linking nutrition, metabolism and gene expression. Night Metab 7, 196–211 (2025). Doi: 10.1038/s42255-024-01191-9
Armstrong HK, Bording-Jorgensen M, Santer DM, et al. Unfermented β-fructan fiber fuels inflammation in certain patients with inflammatory bowel disease. Gastroenterology. 2023;164(2):228-240. doi:10.1053/j.gastro.2022.09.034
Shin A, Kashyap PC. Promote or prevent? Gut microbial function and immune status may determine the effect of fiber in inflammatory bowel disease. Gastroenterology. February 2023; 164(2):182-184. doi:10.1053/j.gastro.2022.11.022
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