A new study analyzing U.S. health data over two decades found that adults who consumed more dietary fiber had a lower risk of stroke and were more likely to survive if they experienced one.
Investigators identified genetic evidence supporting a potential causal relationship between high fiber intake and reduced risk of small vessel stroke, a common subtype.
In the analysis, the investigators used data from over 39,000 adults who participated in the National Health and Nutrition Examination Survey spanning 1999 to 2018. Investigators compared dietary fiber intake with stroke occurrence, adjusting for age, sex, income, body mass index, smoking, alcohol use, diabetes, hypertension, and other health factors.
In fully adjusted models, individuals with the highest fiber intake—over 18.3 g per day—were 29% less likely to report having had a stroke compared with those consuming less than 10.9 g daily. The association remained consistent across subgroups defined by age, sex, and other risk factors.
The investigators also examined mortality among 1,453 stroke survivors. Those in the highest fiber group had a 32% lower risk of all-cause mortality over a median follow-up of 6.9 years. The survival benefit showed a dose-response pattern, with higher fiber intake linked to better outcomes.
To explore whether the relationship might be causal, the investigators conducted a Mendelian randomization analysis. They used genetic variants associated with fiber intake to estimate its effect on stroke risk, minimizing bias found in observational studies.
The genetic analysis, using data from large biobanks in the United States and Europe, didn't find a causal link between fiber intake and major ischemic stroke subtypes such as large artery or cardioembolic strokes. However, a significant causal association was observed for small vessel stroke. Individuals with genetic markers tied to higher fiber intake had a lower risk of this stroke type.
Fiber may influence stroke risk through several mechanisms. It is known to reduce cholesterol, lower inflammation, improve insulin sensitivity, and support a healthier gut microbiome—all of which contribute to cardiovascular health, noted researchers.
While the findings aligned with current dietary guidelines promoting fiber intake, the investigators noted that more clinical trials are needed to determine whether increasing fiber directly prevents stroke. They also highlighted that the majority of U.S. individuals fall short of the recommended daily fiber intake—over 90% don't meet guidelines.
The authors declared no conflicts of interest.
Source: Stroke