Introduction

Stone disease, or urolithiasis, is characterized by the formation of calculi within the urinary tract. Stone disease is a major global health issue, although prevalence varies from 1% to 20% across populations because of complex interactions between factors such as geography, climate, genetics, lifestyle, and importantly diet [1]. Recent studies indicate a worldwide increase in urolithiasis prevalence, largely driven by dietary changes and the rising incidence of metabolic conditions such as obesity [2–4]. Therefore, dietary factors have a fundamental influence on formation of urinary stones. Diet affects the composition of the urine and may contribute to the supersaturation of the stone-forming salt, thereby influencing the risk of stone formation [5,6].

Urolithiasis can result in a range of consequences, from mild discomfort such as renal colic, to long-term complications such as hypertension, hydronephrosis and chronic kidney disease [5–7]. Additionally, urolithiasis may contribute to psychological distress, including anxiety and depression, and to economic and lifestyle challenges, such as increased medical expenses and reduced work productivity [8,9]. Consequently, urolithiasis places a significant financial burden on national healthcare systems. For example, in the United Kingdom, the cost of treating this condition is comparable to the combined expenditure for bladder and prostate cancer [10]. In the United States, the annual healthcare costs associated with urolithiasis management are projected to reach $30 billion by 2030 [11]. Therefore, a thorough understanding of the key factors contributing to urolithiasis is essential for developing effective and targeted prevention strategies and health-related interventions. This understanding is particularly important for modifiable risk factors, such as dietary habits, for which modifications could be essential in reducing the prevalence of urolithiasis.

Despite the multifaceted burden of urolithiasis, there is a scarcity of large and reliable population-level studies of the relation between dietary habits and the prevalence of urolithiasis and renal colic-like pain symptoms. Indeed, experts emphasize that high-quality research should rely on surveys conducted within representative populations to ensure robust findings [12]. Moreover, there is a particularly pronounced lack of such data for Central and Eastern Europe. The distinct cultural, regional, and ethnic characteristics of the Slavic population pose challenges in directly comparing findings with those from Western European or American populations [13]. Therefore, regional assessments are essential for drawing accurate conclusions, deepening the understanding of urolithiasis, and identifying key contributing factors, particularly dietary patterns that may differ from those of other populations. Given these considerations, we aimed to provide a comprehensive analysis of the associations between urolithiasis, renal colic-like pain symptoms, and dietary factors, including body weight, in a population-representative sample of adults aged 18 years and older from all regions of Poland.

Methods

This study builds upon data from the POLSTONE study, a population-based, cross-sectional epidemiological investigation assessing the prevalence of urolithiasis and renal colic symptoms in Poland. The POLSTONE study’s conceptual framework, design, methodology, and data collection are detailed [14,15]; thus, only a brief summary is provided here. The Research Ethics Committee of Jagiellonian University Medical College in Krakow, Poland approved this study (118.6120.94.2023), which is also registered with ClinicalTrials.gov (NCT06176469). Before participation, all individuals provided informed consent and were thoroughly briefed on the study’s duration, the nature of data collection, data storage protocols, investigator details, and research objectives.

Results

Urolithiasis

Respondents who self-reported being overweight or obese had a higher prevalence of urolithiasis compared with persons who did not report these conditions (p < 0.001, Table 1). Considering BMI, the highest prevalence of urolithiasis was observed in individuals with obesity, reaching 15.27%, whereas the lowest prevalence (10.76%) was found for the normal-weight group (p < 0.001, Table 1).

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Table 1. Association of urolithiasis with body weight.

https://doi.org/10.1371/journal.pone.0333733.t001

We observed a higher prevalence of urolithiasis in respondents who consumed beef, pork, dark bread, legumes, soy products, nuts, spinach, strawberries, fruit juices, soda, coffee, instant meals (e.g., Chinese soups), and fast food dishes compared with persons who did not report consuming one or more of these products (p < 0.01, S1 Table). Conversely, a lower prevalence of urolithiasis was observed for respondents who consumed poultry, processed meat (cold cuts, sausages, frankfurters, pâtés, canned meats), diary, white bread and tea compared with individuals who did not report consuming one or more of these products (p < 0.05, S1 Table). We did not find associations between prevalence of urolithiasis and consumption of cereal products, fresh fruits, fresh vegetables, cocoa, chocolate, and highly processed sweets.

Multivariate regression analysis confirmed an increased risk of urolithiasis associated with the consumption of beef, legumes, soy products, soda, coffee, and fast food dishes (Table 2). The highest risk was observed for fast food consumption, whereby eating fast food daily nearly tripled the risk of urolithiasis (OR = 2.847) compared with not ever consuming fast food. Conversely, the model indicated a decreased risk of urolithiasis associated with consuming poultry, spinach, strawberries, tea, and instant meals (e.g., Chinese soups) (Table 2). The greatest risk reduction was observed for poultry consumption, as eating poultry once a week reduced the risk of urolithiasis by 59.6% (OR = 0.404) compared with not consuming poultry.

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Table 2. Multivariate logistic regression analysis of dietary habits and urolithiasis.

https://doi.org/10.1371/journal.pone.0333733.t002

Renal colic-like pain symptoms

Similar to urolithiasis, respondents who self-reported being overweight or obese had a higher prevalence of renal colic-like pain symptoms compared with persons who did not report these conditions (p < 0.001, Table 3). Considering BMI, the highest prevalence of renal colic-like pain symptoms was observed for obese individuals (48.05%), whereas the lowest prevalence (40.74%) was found for the normal-weight group (p < 0.001, Table 3).

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Table 3. Association of renal colic-like pain symptoms with body weight.

https://doi.org/10.1371/journal.pone.0333733.t003

We observed a higher prevalence of renal colic-like pain symptoms in respondents who consumed beef, pork, poultry, processed meat (cold cuts, sausages, frankfurters, pâtés, canned meats), white bread, dark bread, legumes, soy products, highly processed sweets, spinach, strawberries, fruit juices, soda, coffee, instant meals (e.g., Chinese soups), and fast food dishes, compared with individuals who did not report consuming one or more of these products (p < 0.01, S2 Table). Conversely, a lower prevalence of renal colic-like pain symptoms was observed for respondents who consumed cereal products, fresh fruits, and tea compared to those who did not report consuming one or more of these products (p < 0.05, S2 Table). We did not find associations between prevalence of renal colic-like pain symptoms and consuming diary, fresh vegetables, nuts, cocoa, and chocolate.

Multivariate regression analysis confirmed an increased risk of renal colic-like pain symptoms associated with the consumption of processed meat (cold cuts, sausages, frankfurters, pâtés, canned meats), legumes, soy products, fruit juices, soda, instant meals (e.g., Chinese soups), and fast food dishes (Table 4). The highest risk was observed for fast food consumption, whereby eating fast food daily increased the risk of renal colic-like pain symptoms by 64.5% (OR = 1.645) compared with not consuming fast food at all. Interestingly, our model did not identify any foods associated with a decreased risk of renal colic-like pain symptoms.

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Table 4. Multivariate logistic regression analysis of dietary habits and renal colic-like pain symptoms.

https://doi.org/10.1371/journal.pone.0333733.t004

Discussion

This study is the first analysis from Central and Eastern Europe to specifically identify associations between the prevalence of urolithiasis, renal colic-like pain symptoms, and diet, including body weight. Notably, the analysis included a population-representative sample of men and women aged 18 and older from all geographical regions of Poland, ensuring appropriate representation of both urban and rural areas. Our findings indicate that urolithiasis and renal colic-like pain symptoms correlated with body weight, as defined by BMI, and multiple dietary factors. These data are crucial because specific dietary adjustments can significantly contribute to reducing urolithiasis prevalence [21], beyond the general recommendation of a well-balanced diet that includes all food groups as the most beneficial approach [22–24].

Our results indicate that being overweight or obese was associated with the highest prevalence of urolithiasis and renal colic symptoms. Siener et al. explained that overweight and obesity significantly increase the risk of stone formation because of higher urinary excretion of promoters, but not inhibitors, of calcium oxalate stone formation [25]. In a recent systematic review and meta-analysis, Emami et al. examined the link between obesity and the risk of kidney stone formation [26]. The analysis included 15 observational studies published between 2005 and 2022. Results showed that people with obesity had a 1.35 times greater risk of developing kidney stones compared with persons without obesity (95% CI: 1.20–1.52, p < 0.001). Regionally, the association was particularly pronounced in North America and Europe, where the risk was significantly higher than in Asia. Additionally, in a cross-sectional survey-based study in China, Chen et al. demonstrated that individuals with metabolically healthy obesity still had an elevated risk of kidney stones; thus, obesity alone, even in the absence of metabolic abnormalities, can contribute to stone formation [27].

Conversely, we also found that underweight individuals had a higher prevalence of urolithiasis and renal colic-like pain symptoms compared with persons having normal weight. Low body weight may predispose individuals to nutritional deficiencies and electrolyte imbalances, such as hypokalemia [28]. These abnormalities cause metabolic disturbances such as reduced urine output and increased urinary ammonium excretion due to hypophosphaturia and diarrhea with hyperchloremic acidosis which promote kidney stone formation, mainly of ammonium urate. Additionally, malnourished individuals, particularly those with anorexia nervosa, are at risk of developing refeeding syndrome, a condition characterized by severe electrolyte shifts during nutritional rehabilitation [29]. In a population-based retrospective cohort study, Denburg et al. found that young women with anorexia nervosa had more than a threefold higher risk of developing urolithiasis compared with their unexposed counterparts [30]. Although the association between low body weight and urolithiasis is well-documented in the context of eating disorders such as anorexia nervosa, there are only limited studies specifically focused on underweight individuals who do not have eating disorders. Therefore, our study is the first population-based analysis to reliably document the relation between underweight status and the occurrence of urolithiasis or renal colic-like pain symptoms. Finally, our findings further support the conclusion that maintaining a healthy body weight is an important factor in preventing both urolithiasis and renal colic-like pain symptoms.

The intake of animal protein contributes to a high purine load, which leads to increased uric acid production and excretion, factors associated with a higher risk of kidney stone formation [31,32]. High protein intake is also linked to an increased acid load, which elevates urinary calcium levels while reducing urine pH and citrate excretion [33]. Restricting animal protein intake is one of the general preventive measures for urolithiasis outlined in the European Association of Urology Guidelines on Urolithiasis [21]. Our study confirmed that high meat consumption, particularly beef, was strongly correlated with the prevalence of both urolithiasis and renal colic-like pain symptoms. However, an interesting finding from our multivariate analysis showed that poultry consumption appeared to have a protective effect on urolithiasis, although this effect was not observed for renal colic-like pain symptoms. The observed differences in the effects of various meats on urolithiasis may be attributed to several factors, including their purine content, which influences uric acid metabolism, and their impact on urinary pH and citrate excretion. Poultry has a different amino acid profile compared with beef and other meat types, which could influence urinary stone risk factors [34]. However, there are limited studies of the relation between the amino acid composition of different meats and their direct effects on urolithiasis. The specific effects of different meat types on urinary pH and citrate levels may also differ, potentially influencing their association with urolithiasis [35]. In a study by Best et al., persons who consumed poultry had higher urine pH and lower urinary oxalate levels compared with persons who consumed beef [35]. Consequently, the mechanisms of the protective effect of poultry consumption on urolithiasis that we observed is only a hypothesis. Nevertheless, our study underscores the fact that different types of meat have different effects on urolithiasis. Therefore, additional research should be focused on the specific impact of different types of meat on urolithiasis, instead of treating meat consumption as a single category. As experts have suggested, the source of protein matters because various protein types may influence urolithiasis risk differently [31].

In our study, the consumption of grain products (e.g., rice, pasta, cereals, groats, oatmeal) was inversely correlated with renal colic-like pain symptoms and not significantly correlated with urolithiasis. However, the prevalence of urolithiasis was higher among persons who consumed dark bread, and the prevalence of renal colic-like pain symptoms was higher in individuals who consumed both dark and white bread. This finding aligns with the results of Shabani et al., who identified bread consumption as an independent risk factor for urolithiasis [36]. To explain why bread has effects on urolithiasis and renal colic-like pain symptoms different from other grain products, we can consider several potential factors that focus on the unique characteristics of bread consumption compared with other grain-based foods such as rice, pasta, or cereals. Alkay et al. suggested that the fermentation process involved in making bread, especially sourdough, might influence the bioavailability of certain minerals such as magnesium, potassium, and calcium [37]. Bread’s fermentation process can decrease the levels of phytates, compounds that inhibit mineral absorption, which could result in different mineral absorption dynamics compared with non-fermented grain products like pasta and rice. Moreover, bread, especially when consumed in large quantities, may impact citrate excretion differently from other grains [38]. Citrate is a natural inhibitor of stone formation, and although whole grains might support higher citrate levels due to their magnesium and fiber content, bread and other processed grains might have a less favorable effect on urinary citrate excretion. Finally, in terms of combined nutrient intake, bread is often consumed with other foods like butter, spreads, and meats; these foods can increase caloric density and potentially exacerbate conditions like obesity or metabolic syndrome, which are risk factors for urolithiasis. Grains like rice or oats, which are often eaten as part of a more balanced meal (e.g., with vegetables or lean proteins), may not have the same impact. Therefore, the effect of bread may be multifaceted.

Legumes, soy products, nuts, spinach, and strawberries are rich in oxalate products. In our study, we observed higher prevalence of both urolithiasis and renal colic symptoms in respondents consuming these products. Therefore, our study supports previous findings that high intake of oxalate rich products may induce higher oxalate urine concentration and stone formation of calcium oxalate stones [39]. Nevertheless, an interesting observation emerged from our multivariate analysis. Spinach consumption (specifically ‘once a week’) and strawberry consumption (specifically ‘every day’) were associated with a protective effect against urolithiasis. These discrepancies may be attributed to other factors that may have a protective impact. The oxalate content of spinach can vary significantly based on variety, growth conditions, and season. For instance, Kawazu et al. analyzed 213 spinach varieties and found oxalate levels ranging from 0.76% to 1.8% of fresh weight [40]. This variability suggests that not all spinach consumption contributes equally to oxalate intake. The impact of dietary oxalate on kidney stone formation also depends on oxalate bioavailability and absorption. Although spinach is high in oxalates, the actual absorption can be influenced by other dietary components. For example, consuming calcium-rich foods alongside oxalate-rich foods can reduce oxalate absorption by forming insoluble complexes in the gut [41]. Strawberries, despite containing oxalates, are rich in antioxidants, fiber, and vitamin C. These compounds may contribute to overall kidney health and potentially offset the risks associated with oxalate content. Finally, moderation has a crucial influence. Consuming spinach once a week and strawberries daily, as noted in our study, may provide health benefits without significantly increasing the risk of stone formation. This idea aligns with findings of Salgado et al. who reported that moderate intake of oxalate-containing foods, especially when balanced with other dietary factors, does not substantially elevate kidney stone risk [42]. The protective effect observed might also reflect the benefits of a balanced diet rather than the isolated impact of specific foods [43].

The European Association of Urology Guidelines on Urolithiasis recommend maintaining a generous intake of fluids for the prevention of stone recurrence, with a strong preference for water as the primary fluid source [21]. Indeed, a high intake of fluids containing added sugars is linked to an increased prevalence of urolithiasis [44]. Carbohydrates can alter urine composition by elevating uric acid, calcium, and oxalate, key contributors to kidney stone formation [45]. Fructose is proposed as a key factor mediating the increased risk of kidney stone formation associated with soda consumption [31]. Notably, fruit juices and sugar-sweetened beverages are particularly high in sugars. In our study, respondents who consumed fruit juices or sugar-sweetened beverages had a higher prevalence of both renal colic symptoms and urolithiasis compared with persons who did not consume those items. Importantly, fruit juice consumption emerged as an independent risk factor for renal colic symptoms, whereas sugar-sweetened beverage intake was an independent risk factor for both renal colic symptoms and urolithiasis. The analysis of data from 194,095 participants in the Health Professionals Follow-Up Study, and Nurses’ Health Study I and II by Ferraro et al., with a median follow-up of more than eight years, also indicated significant positive associations with the risk of stone formation for sugar-sweetened cola and sugar-sweetened non-cola, confirming our results [46]. Regarding tea and coffee, the literature presents conflicting findings. Ferraro et al. reported an inverse association between tea and coffee intake and the risk of urolithiasis [46]. This protective effect is suggested to stem from the diuretic properties of these beverages, which may at least partially counteract their hypercalciuric effects [47]. Our findings support the protective effect of tea; individuals who reported tea consumption had a lower prevalence of both urolithiasis and renal colic-like pain symptoms. Moreover, tea consumption was an independent protective factor for urolithiasis. In contrast, in our study coffee consumption was associated with a higher prevalence of both conditions, and coffee was an independent risk factor for urolithiasis. Several factors may help explain this negative association. First, it is important to consider that the method of coffee preparation and consumption can influence its health effects. For instance, unfiltered coffee contains compounds like cafestol and kahweol, which may raise cholesterol levels, a risk factor for stone formation [48]. Additionally, adding sugar or high-fat dairy products could contribute to metabolic changes that increase stone risk. Further, coffee has diuretic properties, potentially leading to increased urine output. If coffee consumption is not balanced with adequate water intake, it might result in dehydration, concentrating urine and promoting stone formation. Finally, genetic predispositions, underlying health conditions, and variations in diet can modify how coffee affects an individual’s stone risk. For example, certain populations might metabolize coffee differently, influencing its impact on kidney stone formation [49].

Fast food and processed products are often high in added sugars and calories and are commonly associated with poor dietary habits. Moreover, these foods typically contain excessive amounts of sodium that can increase urinary calcium excretion and contribute to kidney stone formation. Indeed, our initial findings confirmed that dietary sodium, particularly from added salt, plays a significant role in stone formation [14]. The National Institute of Diabetes and Digestive and Kidney Diseases recommends minimizing the consumption of processed and fast foods as a preventive measure against urolithiasis [50]. Consistent with these concerns, our findings revealed a strong correlation between fast food consumption and both renal colic symptoms and urolithiasis. Notably, daily fast food intake nearly triples the risk of developing urolithiasis. For these reasons, limiting fast food consumption should be considered a key dietary strategy for kidney stone prevention.

A main limitation of our study is its reliance on self-reported data without clinical verification, which may affect accuracy, as noted by Coyne et al. [51]. This introduces a potential recall bias, as participants may not accurately remember or report past symptoms or diagnoses. Some respondents may have misunderstood questions (for example, confusing renal colic–like pain with other conditions), and the survey length limited the inclusion of all relevant factors. Importantly, dietary recommendations can vary depending on stone type, but obviously we could not identify specific stone compositions. Lastly, we do not know whether our findings can be generalized beyond the Central and Eastern European population that we studied, as cultural, socioeconomic, and healthcare system differences may influence the prevalence and perception of these conditions.

Conclusions

This study presents the first comprehensive, population-based assessment of urolithiasis, renal colic-like pain symptoms, and dietary patterns, including body weight, in Central and Eastern Europe. Our findings indicate that both conditions are influenced by body weight and various dietary factors. These insights may inform health improvement programs and educational campaigns in Poland aimed at reducing the burden of urolithiasis and renal colic-like pain symptoms.

Supporting information

Acknowledgments

The authors are indebted to the study participants.