BERKELEY, CA (UroToday.com) - Urolithiasis is a common nephrologic disorder whose prevalence is increasing, likely due to lifestyle factors, including diet and obesity. Because urolithiasis is a complex disease, an understanding of the epidemiology, particularly of the interactions among different factors, may help lead to measures that reduce the risk of stone formation. Diet plays an important role in the pathogenesis of urolithiasis, and changes in dietary habits have likely contributed to the substantial increases in urolithiasis observed over the past several decades.
National surveys in Japan conducted in 1955, 1965, 1975, 1985, 1995, and 2005 have demonstrated changes in the profile and incidence of urolithiasis among the Japanese population. We conducted the sixth nationwide survey of urolithiasis in cooperation with the Japanese Society on Urolithiasis Research and the Japanese Urological Association in 2005 to evaluate chronological trends of urolithiasis in Japan. These surveys all revealed that the incidence of urolithiasis differs by region and that regions with high or low incidence are fixed. However, previous studies did not investigate the association between food intake and incidence of urolithiasis by region. In the present study, we evaluated urolithiasis incidence and nutrition data for each of 12 predefined geographic regions using information obtained from the aforementioned Japanese national surveys to clarify the association between regional variations in urolithiasis incidence and nutrition intake.
To clarify the association between regional variations in urolithiasis incidence and nutrition intake, we evaluated associated data from Japanese national surveys. The incidence of urolithiasis in 12 regions of Japan was calculated from 2005 patient data obtained from 430 hospitals (n = 92,797). Nutrition intake data were obtained from the National Health and Nutrition Survey. We examined the association between urolithiasis incidence and average intake of various types of food or nutrients by region. Continuing surveys in Japan reveal fixed variations in urolithiasis incidence among geographic regions. The national average of patients with urolithiasis was estimated as 203.1 per 100,000 citizens.
We analyzed the association between urolithiasis incidence and data from the 2002 National Health and Nutrition Survey for each region (as collected by the Japanese Ministry of Health, Labour and Welfare). Regarding food, intakes of total, animal food, and vegetable food were not correlated by region with the incidence of urolithiasis. Intake of fruit correlated negatively with the incidence of urolithiasis (r = -0.72, p = 0.008) while intake of eggs (r = 0.537, p = 0.072) and sugar (r = 0.475, p = 0.119) tended to be positively correlated with incidence. The intake of the other foods, including cereals, rice and wheat, vegetables, seafood, and meat, showed no correlation with the incidence of urolithiasis.
Regarding nutrients, total energy was not related to the incidence of urolithiasis by region. Intake of protein, lipid, or carbohydrate, as well as proportions of fat, carbohydrate, and animal protein, to total energy input showed no correlation with incidence. Intake of potassium (r = -0.500, p = 0.098), vitamin K (r = 0.562, p = 0.057), and pantothenic acid (r = -0.560, p = 0.058) tended to be negatively correlated with incidence while the other nutrients showed no correlation. These data are useful as a basis for investigating risk and nutritional factors associated with urinary tract stones. However, this study compared the incidence of urolithiasis with the regional average consumption of nutrients and found that while the variation in nutrient intake per person is large, the variation in average consumption between regions is small. This is a limitation of the study.
The composition of urine is influenced by dietary intake, and several dietary factors have been proposed for modifying the risk of urolithiasis. Food characteristics may also influence local variations in urolithiasis incidence. Since dietary factors play an important role in kidney stone formation, dietary modification can also influence the risk of stone recurrence. Thus, results of epidemiologic studies implicating a relationship among various nutrients and stone incidence can be applied in the clinical setting with the goal of reducing the likelihood of stone formation. Nevertheless, randomized trial data are lacking for most dietary interventions.
Written by:
Takahiro Yasui, MD as part of Beyond the Abstract on UroToday.com. This initiative offers a method of publishing for the professional urology community. Authors are given an opportunity to expand on the circumstances, limitations etc... of their research by referencing the published abstract.
Department of Nephro-urology, Nagoya City University Graduate School of Medical Sciences
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