Gallstone disease, primarily composed of solidified cholesterol and bile pigments, is the most common digestive disorder necessitating hospitalization in Western countries (1, 2). The majority of individuals afflicted with gallstones do not manifest any symptoms, with a mere 2–4% of cases resulting in severe symptoms such as acute abdominal pain (3). Beyond typical presentations, gallstones rarely cause mechanical obstruction syndromes, including Bouveret syndrome (gastric outlet obstruction due to impacted stones) or gallstone ileus (small bowel obstruction secondary to stone migration) (4). Globally, the prevalence of gallstones has been documented to be approximately 6% in the 21st century (5). An epidemiological study of the United States population found that the prevalence of cholelithiasis increased from 7.4 to 13.9% over a period of nearly 30 years from 1988 to 2020 (6). This significant increase underscores the imperative for effective prevention strategies, as the burden that gallstones impose on healthcare systems is considerable (7). A rational and holistic diet has been demonstrated to be one of the most efficacious measures for the prevention of gallstone disease (8, 9).

Dietary fiber is a pivotal nutrient in the prevention of various chronic diseases, with the potential to regulate gut microbial ecology and metabolism, thereby impacting human health (10–12). Nevertheless, the correlation between dietary fiber intake and gallstone formation remains to be extensively studied. A recently conducted case–control study, incorporating a sample of 531 participants, has revealed a correlation between dietary fiber intake and the risk of gallstone formation (13). However, the correlation between dietary fiber intake and gallstones among the adult population of the United States remains unclear. Furthermore, extant investigations have exclusively concentrated on diminutive cohorts of a few hundred individuals, consequently lacking substantial, large-scale data to substantiate their findings. Additionally, the dose–response relationship between dietary fiber intake and gallstone risk remains uncertain. In light of the observed study gaps, we hypothesized that there exists a correlation and a dose–response trend between dietary fiber intake and gallstones in the United States population.

This study utilized the NHANES database, a nationally representative, large-scale, continually updated dataset, for a comprehensive analysis of the cross-sectional association between dietary fiber intake and gallstone prevalence. The findings were further delineated through stratified analyses, subgroup analyses, and restricted cubic spline analyses, which yielded more nuanced associations between dietary fiber intake and gallstones.

In this study, we analyzed the most recent NHANES data from 2017 to 2023, and for the first time, we found a nearly linear inverse association between dietary fiber intake and gallstones among United States adults. A significant discrepancy was also observed in the dietary fiber intake of patients with gallstones in comparison to those without gallstones. The inverse correlation between dietary fiber intake and gallstones was found to be statistically significant in specific subgroups, including men, Hispanic individuals, those with less than a high school diploma, individuals with alcohol consumption, and those with a diagnosed history of diabetes.

This study addressed a significant research gap in the extant literature on this subject, as it is the first to examine the relationship between dietary fiber and gallstone formation in a population-based sample in the United States. The primary conclusion of the study was that for every additional 1 g of dietary fiber consumed, there was a 2% reduction in the risk of gallstone prevalence. This finding aligns with previous research that has also demonstrated a inverse correlation between the intake of dietary fiber (both soluble and insoluble) and the prevalence of gallstones (13). The antioxidant activity of dietary fiber is a globally recognized phenomenon (27–29). A significant benefit of the antioxidant-rich, anti-inflammatory diet that has been demonstrated in a multitude of studies is its potential to contribute to a reduction in the prevalence of gallstones among American adults (30–32). It is noteworthy that ultra-processed foods frequently exhibit a paucity of dietary fiber and have recently been demonstrated to be associated with unfavorable gallstone outcomes (33–35). The preceding findings, whether primary or secondary in nature, provide direct or indirect confirmation of the preventive effect of adequate dietary fiber intake on gallstone disease, thereby providing substantial support for the primary findings of this study.

In subgroup analyses, the sensitive populations for the relationship between dietary fiber and gallstones were identified as men, Hispanics, those with less than high school education, alcohol consumers, and diabetics. The persistent identification of women as a risk factor for gallstones may obscure the protective effect of dietary fiber on gallstones in women (2, 36). Consequently, it is plausible that the relationship between dietary fiber and gallstones is only significant in men. The NHANES survey demonstrated that Hispanics exhibited a higher prevalence of gallstones compared to non-Hispanics (205/1717 (11.94%) vs. 766/7556 (10.14)), suggesting that environmental, cultural, dietary, and genetic factors contribute to the variation in gallstone prevalence (37, 38). This observation lends further support to the hypothesis that these factors may play a role in the increased sensitivity to gallstones observed in Hispanic populations. Furthermore, a correlation has been observed between diabetes, alcohol consumption, and gallstone formation, indicating that individuals with diabetes and those who consume alcohol are more likely to benefit from a diet high in fiber (24, 39–41). It is evident that there is an absence of substantial evidence to substantiate the internal logic of the identification of these sensitive populations. The subgroup findings (e.g., Hispanic individuals) should be interpreted as hypothesis-generating due to potential type I error from multiple testing. Large cohort studies or epidemiological research in specific populations are imperative to validate our findings.

Despite the absence of a definitive understanding of the underlying mechanisms, previous research reports offer valuable insights into the potential impact of dietary fiber intake on gallstone disease. A primary rationale for this phenomenon pertains to the protective function of dietary fiber, which promotes peristalsis within the gastrointestinal tract and enhances intestinal flora (42–44). The improvement of human gut bacteria has been demonstrated to have a positive effect on the biotransformation of bile salts, thus effectively preventing gallstones at source (45–47). Conversely, the proliferation of specific detrimental intestinal microbiota (especially Desulfovibrionales) has also been observed to promote the development of gallstones (48). It has been ascertained that dietary fiber is subject to fermentation by the gut microbiota present within the colon, thereby yielding significant quantities of short-chain fatty acids (e.g., acetate, propionate, and butyrate) (49). These acid metabolites represent pivotal intermediate stages in the body’s more profound metabolism and have the capacity to regulate bile acid metabolism by modulating the gut microbiota. For instance, sodium butyrate has been demonstrated to modulate bile acid metabolism in conjunction with intestinal microflora, thus providing a potential therapeutic intervention for cholesterol gallstones (50). To summarize, the examination of the preventative mechanisms of dietary fiber in relation to the development of gallstones and its impact on the underlying pathophysiology remains in its initial stages. In order to substantiate these findings, it is imperative that large-scale randomized controlled trials and in-depth fundamental mechanistic studies are conducted in the future.

However, it is important to note that the study was subject to certain limitations. Firstly, the reports of dietary fiber intake and gallstone disease were derived from self-recall and may be subject to bias. Secondly, the cross-sectional design inherently limits causal inference; our findings demonstrate an association rather than establishing causality. Thirdly, although we adjusted for major known confounders (including diabetes, hypertension, BMI, and lifestyle factors), we acknowledge the absence of data on dyslipidemia (e.g., serum LDL/HDL cholesterol), hypertriglyceridemia, hematological disorders, and detailed dietary patterns (e.g., ketogenic, high-fat, or low-carbohydrate diets) in our models. These factors may influence gallstone pathogenesis through bile cholesterol saturation, hemolytic effects on bilirubin metabolism, or dietary interactions with fiber. While NHANES provides triglyceride measurements for subsets, comprehensive dyslipidemia diagnosis and hematologic disease data were unavailable for our full cohort across cycles. Our study did not evaluate holistic dietary patterns (e.g., Western diets) due to the nutrient-specific focus on fiber. Future studies incorporating these clinical variables would strengthen causal inference.

In summary, the present study demonstrated, for the first time, an inverse correlation between dietary fiber intake and gallstone disease in an adult population in the United States. However, residual confounding and the observational design preclude definitive causal conclusions. Large-scale multi-center clinical trials and epidemiological studies are imperative to validate this finding. Ensuring adequate dietary fiber intake may be a plausible initiative to protect patients from gallstones. Specifically, whole grains with high levels of dietary fiber (such as oatmeal or oats), nuts and seeds (such as chia seeds or flax seeds), and cruciferous vegetables (including broccoli or Brussels sprouts) are worthy of consideration.