In a world of flashy diets and quick fixes, sometimes what matters is simply what you eat most days. A major new umbrella review in Clinical Nutrition, pulling together evidence from more than 17 million people, shows how much fiber might matter in the long run.
The review
The review examined the links between fiber intake and a wide range of conditions, from heart disease to diabetes to cancers. Across the strongest studies, higher fiber intake was linked to lower risks of cardiovascular disease, type 2 diabetes, stroke, diverticular disease, colorectal cancer, ovarian cancer, and premature death, even after adjusting for lifestyle and other dietary factors. The numbers vary by condition, but the pattern never really changes direction. In many cases, the review found dose–response relationships: as fiber intake increased, risk tended to decrease. Some meta-analyses even showed benefits for precancerous conditions like colorectal adenomas. Importantly, across the population groups studied, the review found no major harms associated with higher fiber intake.
Umbrella reviews sit at the top of the evidence pyramid. Instead of looking at one study, or even one meta-analysis, they evaluate many meta-analyses at once, re-checking their quality, statistical strength, and consistency. The convergence of evidence, from so many large studies, strengthens confidence in the findings.
In this case, the review doesn’t assume every association is equal; it tested them rigorously, ranking each one by the credibility of the evidence. Authors note that not all included meta-analyses were of equal quality, and some results showed considerable heterogeneity, meaning the strength of evidence varies across different health outcomes. Despite the strict criteria, the associations presented in this article reached the highest level of certainty.
What does this mean for everyday life?
The review reflects what happens when people regularly eat foods naturally rich in fiber: fruits, vegetables, legumes, whole grains, nuts and seeds, as it didn’t evaluate supplements or powders. Eating these fiber-rich foods regularly, replacing refined foods, is enough to make a difference.
Fiber doesn’t behave like other nutrients. It resists digestion, feeds the gut microbiome, and helps maintain regular digestion. But it also appears to influence several physiological pathways: better cholesterol balance, improved insulin sensitivity, stabilized blood sugar, reduced inflammation. The authors note that these biological effects of fiber documented in previous research are consistent with the protective patterns observed.
The evidence doesn’t promise a guarantee and the researchers are careful not to claim causation, as umbrella reviews rely heavily on observational data, which can’t rule out every confounding factor. But given the scale of data, the consistency of the findings, and the lack of major downsides, fiber-rich eating emerges as one of the smartest, most affordable strategies for long-term health we currently have.
The takeaway
In a world full of complicated nutrition advice, the takeaway from this review is very simple: People who eat more dietary fiber tend to have better health outcomes and lower risk of many major diseases.
Reference
- Veronese, N., Gianfredi, V., Solmi, M., Barbagallo, M., Dominguez, L. J., Mandalà, C., … & Fontana, L. (2025). The impact of dietary fiber consumption on human health: An umbrella review of evidence from 17,155,277 individuals. Clinical Nutrition, 51, 325-333. https://doi.org/10.1016/j.clnu.2025.06.021
Lecturer at the Sociology Department, University of Barcelona