Risk Of Incident Kidney Stones Research Articles

Association of serum bicarbonate with the development of kidney stones in patients with chronic kidney disease: a retrospective cohort study.

Epidemiological studies demonstrate an association between kidney stones and risk of chronic kidney disease (CKD) and CKD progression. Metabolic acidosis, as a consequence of CKD, results in a reduced urine pH which promotes the formation of some types of kidney stones and inhibits the formation of others. While metabolic acidosis is a risk factor for CKD progression, the association of serum bicarbonate with risk of incident kidney stones is not well understood. We used an Integrated Claims-Clinical dataset of US patients to generate a cohort of patients with non-dialysis-dependent CKD with two serum bicarbonate values of 12 to <22mmol/L (metabolic acidosis) or 22 to <30mmol/L (normal serum bicarbonate). Primary exposure variables were baseline serum bicarbonate and change in serum bicarbonate over time. Cox proportional hazards models evaluated time to first occurrence of kidney stones during a median 3.2-year follow-up. A total of 142 884 patients qualified for the study cohort. Patients with metabolic acidosis experienced post-index date kidney stones at greater frequency than patients with normal serum bicarbonate at the index date (12.0%vs 9.5%, P<.0001). Both lower baseline serum bicarbonate [hazard ratio (HR) 1.047; 95% confidence interval (CI) 1.036-1.057] and decreasing serum bicarbonate over time (HR 1.034; 95% CI 1.026-1.043) were associated with increased risk of kidney stone development. Metabolic acidosis was associated with a higher incidence of kidney stones and shorter time to incident stone formation in patients with CKD. Future studies may investigate the role of correcting metabolic acidosis to prevent stone formation.

Caffeine intake and the risk of incident kidney stones: a systematic review and meta-analysis

Kidney stone disease is increasingly common in the general population, with a high recurrence rate after stone removal. It has been proven that caffeine consumption can reduce the risk of diseases, such as stroke and dementia. However, the effect of caffeine intake on the incidence of kidney stones has not been determined. This systematic review and meta-analysis were performed to evaluate the association of caffeine intake with the risk of incident kidney stones. PubMed, Web of Science, Scopus, Cochrane and Google Scholar were searched using terms related to coffee, caffeine and kidney stones to find eligible articles up to December 2021. Articles with clear diagnostic criteria for kidney stone disease and the exact intake dose of caffeine were included. The incidence of kidney stone disease was the main outcome. Summarized risk estimates and 95% CIs for the highest and lowest categories of caffeine intake were calculated using a random effects model. Seven studies were included in the final meta-analysis, with 9707 cases of kidney stones and a total of 772,290 cohort members. Compared with the lowest category of caffeine intake, the pooled relative risk (RR) was 0.68 ([95% CI 0.61-0.75], I2 = 57%) for the highest category of caffeine intake. Subgroup analyses showed that caffeine intake had an inverse relationship with the incidence of kidney stones in all subgroups. This study suggests that a higher caffeine intake may be associated with a lower risk of incident kidney stones.

Higher Risk of Incident Kidney Stones in Patients with Metabolic Acidosis and CKD

Higher Risk of Incident Kidney Stones in Patients with Metabolic Acidosis and CKD

Editorial Comment: Fluid Intake and Dietary Factors and the Risk of Incident Kidney Stones in UK Biobank: A Population-based Prospective Cohort Study

Editorial Comment: Fluid Intake and Dietary Factors and the Risk of Incident Kidney Stones in UK Biobank: A Population-based Prospective Cohort Study

Mediterranean diet adherence and risk of incident kidney stones

Diet plays an important role in kidney stone formation. Several individual components have been associated with the risk of kidney stone formation, but there is limited evidence regarding the role of healthful dietary patterns. To prospectively study the association between adherence to the Mediterranean diet and the risk of incident kidney stones. We conducted a longitudinal study using 3 different cohorts: the Health Professionals Follow-up Study (n=42,902 men), the Nurses' Health Study I (n=59,994 women), and the Nurses' Health Study II (n=90,631 women). We assessed diet every 4 y using an FFQ and calculated adherence to a Mediterranean diet using the alternate Mediterranean diet score (aMED). A subgroup of 6077 participants provided ≥1 24-h urine sample, and urinary solute excretion was analyzed. We used Cox proportional hazards regression to examine the independent association between the aMED and incidence of kidney stones, adjusting for potential confounders. We used adjusted linear regression models to study the relation between aMED and urine composition. During 3,316,633 person-years of follow-up, 6576 cases of incident kidney stones were identified. For participants in the highest aMED score category, the risk of developing a kidney stone was between 13% and 41% lower compared with participants in the lowest score (pooled HR: 0.72, 95% CI: 0.59, 0.87; P value for trend<0.001). A higher aMED score was associated with higher urinary citrate, magnesium, oxalate, phosphate, uric acid, volume, and pH, and lower urinary sodium, resulting in lower supersaturation for calcium oxalate, calcium phosphate, and uric acid. Adherence to a Mediterranean diet is associated with a lower risk of developing a kidney stone.

Use of Proton Pump Inhibitors Increases Risk of Incident Kidney Stones

Proton pump inhibitors (PPIs) are widely prescribed and have effects on gut ion absorption and urinary ion concentrations. PPIs might therefore protect against or contribute to development of kidney stones. We investigated the association between PPI use and kidney stones. We performed a retrospective study using data from the Women's Veteran's Cohort Study, which comprised men and women, from October 1, 1999 through September 30, 2017. We collected data from 465,891 patients on PPI usage over time, demographics, laboratory results, comorbidities, and medication usage. Time-varying Cox proportional hazards and propensity matching analyses determined risk of PPI use and incident development of kidney stones. Use of histamine-2 receptor antagonists (H2RAs) was measured and levothyroxine use was a negative control exposure. PPI use was associated with kidney stones in the unadjusted analysis, with PPI use as a time-varying variable (hazard ratio [HR], 1.74; 95% CI, 1.67-1.82), and persisted in the adjusted analysis (HR, 1.46; CI, 1.38-1.55). The association was maintained in a propensity score-matched subset of PPI users and nonusers (adjusted HR, 1.25; CI 1.19-1.33). Increased dosage of PPI was associated with increased risk of kidney stones (HR, 1.11; CI, 1.09-1.14 for each increase in 30 defined daily doses over a 3-month period). H2RAs were also associated with increased risk (adjusted HR, 1.47; CI 1.31-1.64). We found no association, in adjusted analysis, of levothyroxine use with kidney stones (adjusted HR, 1.06; CI 0.94-1.21). In a large cohort study of veterans, we found PPI use to be associated with a dose-dependent increase in risk of kidney stones. H2RA use also has an association with risk of kidney stones, so acid suppression might be an involved mechanism. The effect is small and should not change prescribing for most patients.

Re: Antibiotic Use and Risk of Incident Kidney Stones in Female Nurses.

Re: Antibiotic Use and Risk of Incident Kidney Stones in Female Nurses.

Antibiotic Use and Risk of Incident Kidney Stones in Female Nurses

The intestinal microbiome may affect urinary stone disease by modulating the amount of oxalate absorbed from the intestine and subsequently excreted in urine. This study sought to explore the association between antibiotics, which alter the intestinal microbiota, and risk for urinary stone disease. Prospective cohort study. 5,010 women in the Nurses' Health Study (NHS) I and II who had collected 24-hour urine samples. Use of antibiotics during the age range of 40 to 49 (NHS II), 40 to 59 (NHS I), and 20 to 39 years (both cohorts). Incident symptomatic urinary stone disease; urine composition. Cause-specific hazards regression adjusted for age, body mass index, comorbid conditions, thiazide use, and dietary factors. Follow-up was censored at the time of asymptomatic kidney stones, cancer, or death. Cumulative use of antibiotics for a total of 2 or more months during the age range of 40 to 49 years (NHS II) and 40 to 59 years (NHS II) was associated with significantly higher risk for developing incident stones compared with no use (pooled HR, 1.48; 95% CI, 1.12-1.96). Similar results were found for the period of 20 to 39 years (pooled HR, 1.36; 95% CI, 1.00-1.84). Results were unchanged after excluding participants who reported urinary tract infection with their stone event or as the most common reason for antibiotic use. Urine composition was generally similar across antibiotic groups except for marginally lower urine pH and citrate values among those taking antibiotics for 2 or more months. Observational design; lack of information for type of antibiotic used; relatively large span of time between antibiotic use and urine collection. Use of antibiotics for more than 2 months in early adulthood and middle age is associated with higher risk for urinary stone disease in later life.

Plant and Animal Protein Intake and Risk of Incident Kidney Stones: Results from the Shanghai Men's and Women's Health Studies.

High animal protein intake is a risk factor for nephrolithiasis. Whether plant based sources of protein are associated with kidney stone risk is not well studied. We examined the association of animal and plant protein intake with the risk of incident kidney stones in Shanghai, China. Dietary intakes were obtained from a validated food frequency questionnaire at baseline. Self-reported stone events were ascertained at baseline and at followup visits. Multivariable Cox regression models were used to evaluate the associations of protein intake with the incident stone risk. During 319,211 and 696,950 person-years of followup 1,451 men and 1,202 women, respectively, reported incident stones. The average ± SD intake of animal and plant protein standardized to 2,000 kcal was 31.3 ± 13.7 and 48.4 ± 7.2 gm per day in women, and 30.8 ± 13.3 and 51.3 ± 7.6 gm per day, respectively, in men. On multivariable analysis participants in the highest quintiles of animal and nondairy animal protein intake showed an increased risk of incident stones compared to those in the lowest quintiles (HR 1.16, 95% CI 1.01-1.32, p=0.03 vs HR 1.14, 95% CI 1.01-1.30, p=0.04). Compared to the lowest quintile the highest intake quintiles of the animal-to-plant protein ratios and the nondairy animal-to-plant protein ratios were positively associated with stone risk (HR 1.17, 95% CI 1.03-1.33, p=0.02 and HR 1.20, 95% CI 1.06-1.36, p=0.005, respectively). No association was observed with plant protein intake (ptrend=0.14). In this population with a relatively low animal protein intake and a high plant protein intake, a greater animal protein intake was associated with a kidney stone risk. Increasing the proportion of plant protein relative to animal protein appeared protective against the risk.

Fluid Intake and Dietary Factors and the Risk of Incident Kidney Stones in UK Biobank: A Population-based Prospective Cohort Study

BackgroundFluid intake and diet are thought to influence kidney stone risk. However, prospective studies have been limited to small samples sizes and/or restricted measures. ObjectiveTo investigate whether fluid intake and dietary factors are associated with the risk of developing a first kidney stone. Design, setting, and participantsParticipants were selected from UK Biobank, a population-based prospective cohort study. Outcome measurements and statistical analysisCox proportional hazards models were used to investigate the association between fluid intake and dietary factors and the risk of a first incident kidney stone, ascertained from hospital inpatient records. Results and limitationsAfter exclusion, 439 072 participants were available for the analysis, of whom 2057 had hospital admission with an incident kidney stone over a mean of 6.1 yr of follow-up. For every additional drink (200 ml) consumed per day of total fluid, the risk of kidney stones declined by 13% (hazard ratio [HR] = 0.87, 95% confidence interval [CI] 0.85–0.89). Similar patterns of associations were observed for tea, coffee, and alcohol, although no association was observed for water intake. Fruit and fibre intake was also associated with a lower risk (HR per 100 g increase of fruits per day = 0.88, 95% CI 0.83–0.93, and HR per 10 g fibre per day = 0.82, 95% CI 0.77–0.87), whereas meat and salt intake was associated with a higher risk (HR per 50 g increase in meat per week = 1.17, 95% CI 1.05–1.29, and HR for always vs never/rarely added salt to food = 1.33, 95% CI 1.12–1.58). Vegetable, fish, and cheese intake was not associated with kidney stone risk. ConclusionsThe finding that high intake of total fluid, fruit, and fibre was associated with a lower risk of hospitalisation for a first kidney stone suggests that modifiable dietary factors could be targeted to prevent kidney stone development. Patient summaryWe found that higher intake of total fluid, specifically tea, coffee, and alcohol (but not water), and consumption of fruit and foods high in fibre are linked with a reduced likelihood of developing kidney stones.

Green tea intake and risk of incident kidney stones: Prospective cohort studies in middle-aged and elderly Chinese individuals.

To investigate the association between green tea intake and incident stones in two large prospective cohorts. We examined self-reported incident kidney stone risk in the Shanghai Men's Health Study (n=58054; baseline age 40-74years) and the Shanghai Women's Health Study (n=69166; baseline age 40-70years). Information on the stone history and tea intake was collected by in-person surveys. Multivariable Cox proportional hazards models were adjusted for baseline demographic variables, medical history and dietary intakes including non-tea oxalate from a validated food frequency questionnaire. During 319211 and 696950 person-years of follow up, respectively, 1202 men and 1451 women reported incident stones. Approximately two-thirds of men and one-quarter of women were tea drinkers at baseline, of whom green tea was the primary type consumed (95% in men, 88% in women). Tea drinkers (men: hazard ratio 0.78, 95% confidence interval 0.69-0.88; women: hazard ratio 0.8, 95% confidence interval 0.77-0.98) and specifically green tea drinkers (men: hazard ratio 0.78, 95% confidence interval 0.69-0.88; women: hazard ratio 0.84, 95% confidence interval 0.74-0.95) had lower incident risk than never/former drinkers. Compared with never/former drinkers, a stronger dose-response trend was observed for the amount of dried tea leaf consumed/month by men (hazard ratiohighest category 0.67, 95% confidence interval 0.56-0.80, Ptrend <0.001) than by women (hazard ratiohighest category 0.87, 95% confidence interval 0.70-1.08, Ptrend =0.041). Green tea intake is associated with a lower risk of incident kidney stones, and the benefit is observed more strongly among men.

Menopause and Risk of Kidney Stones

Metabolic changes due to menopause may alter urine composition and kidney stone risk but results of prior work on this association have been mixed. We examined menopause and the risk of incident kidney stones, and changes in 24-hour urine composition in the NHS (Nurses' Health Study) II. Using multivariate adjusted Cox proportional hazards models we prospectively analyzed 108,639 NHS II participants who provided information on menopause and kidney stones. We also analyzed 24-hour urine collections from 658 participants who performed a collection while premenopausal and a repeat collection after menopause. During 22 years of followup there were 3,456 incident kidney stones. The multivariate adjusted relative risk of an incident kidney stone in postmenopausal participants compared with premenopause was 1.27 (95% CI 1.08-1.46). On stratified analysis compared with premenopause the multivariate adjusted relative risk of natural and surgically induced menopause was 1.27 (95% CI 1.09-1.48) and 1.43 (95% CI 1.19-1.73), respectively. Among the 74,505 postmenopausal participants there was a total of 1,041 incident stone events. Compared with no hormone therapy neither current nor past use was significantly associated with kidney stone risk. Compared with premenopause the postmenopausal urine collections had lower mean calcium, citrate, phosphorus and uric acid, and higher mean volume. Postmenopausal status is associated with a higher risk of incident kidney stones. Natural menopause and surgical menopause are independently associated with higher risk. There are small but significant differences in urine composition between premenopausal and postmenopausal urine collections.

PD17-02 GREEN TEA INTAKE AND RISK OF INCIDENT KIDNEY STONES: A REPORT FROM THE SHANGHAI MEN’S AND WOMEN’S HEALTH STUDIES

You have accessJournal of UrologyStone Disease: Medical & Dietary Therapy I1 Apr 2018PD17-02 GREEN TEA INTAKE AND RISK OF INCIDENT KIDNEY STONES: A REPORT FROM THE SHANGHAI MEN’S AND WOMEN’S HEALTH STUDIES Xiang Shu, Hui Cai, Yong-Bing Xiang, Honglan Li, Loren Lipworth, Nicole Miller, Wei Zheng, Xiao-Ou Shu, and Ryan Hsi Xiang ShuXiang Shu More articles by this author , Hui CaiHui Cai More articles by this author , Yong-Bing XiangYong-Bing Xiang More articles by this author , Honglan LiHonglan Li More articles by this author , Loren LipworthLoren Lipworth More articles by this author , Nicole MillerNicole Miller More articles by this author , Wei ZhengWei Zheng More articles by this author , Xiao-Ou ShuXiao-Ou Shu More articles by this author , and Ryan HsiRyan Hsi More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2018.02.964AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Tea intake may increase kidney stone risk as a source of dietary oxalate, but as a fluid it may also decrease risk. Previous studies investigating the association of tea intake and risk of stones have had mixed results. However, these studies primarily evaluated black tea, which has the highest oxalate content among different tea types. Green tea has inhibitory, antioxidative effects on calcium urinary stone formation in animal models. Our study objective was to investigate the association of green tea and incident kidney stones in two large prospective cohorts in Shanghai, China. METHODS We examined self-reported incident kidney stone risk in the Shanghai Men's Health Study (N=58,054 men; baseline age range 40-74) and the Shanghai Women's Health Study (N =69,166 women; baseline age range 40-70 years) who had no history of nephrolithiasis at study enrollment. Information on kidney stone history and tea intake was collected by in-person surveys. Multivariable Cox proportional hazards models were adjusted for baseline demographic variables, medical history, smoking history, total energy intake, and dietary intakes of non-tea oxalate, protein, potassium, magnesium, dietary calcium, supplemental calcium and vitamin C assessed using a validated food frequency questionnaire. RESULTS During 319,211 and 696,950 person-years of follow-up, respectively, 1,451 men and 1,202 women reported incident kidney stones. Nearly two-thirds of men and approximately one in four women were self-reported current tea drinkers. Green tea was the primary type consumed in both genders (95% in men and 88% in women). Current tea drinkers had lower incident stone risk than never/former tea drinkers (Men: HR=0.88, 95% CI 0.83-0.94; Women: HR=0.93, 95% CI 0.88-0.99). Compared to never/former tea drinkers, green tea intake was associated with lower risk among both men (HR=0.78, 95% CI 0.69-0.89) and women (HR=0.84, 95% CI 0.74-0.95). Compared to never/former tea drinkers, a stronger dose-response trend was observed for the amount of dried tea leaf consumed/month in men (HR=0.85, 95% CI 0.73-0.99 for <100g; HR=0.82, 95% CI 0.70-0.96 for 100-150g; HR=0.67, 95% CI 0.56-0.80 for>150g; ptrend <0.001) than in women (HR=0.89, 95% CI 0.77-1.02 for <100g; HR=0.82, 95% CI 0.63-1.06 for 100-150g; HR=0.87, 95% CI 0.70-1.08 for >150g; ptrend=0.038). CONCLUSIONS Green tea intake is associated with lower risk of incident kidney stones among the middle-aged and elderly urban Chinese. The benefit of tea intake for reducing stone risk is observed more strongly in men than in women. © 2018FiguresReferencesRelatedDetails Volume 199Issue 4SApril 2018Page: e384 Advertisement Copyright & Permissions© 2018MetricsAuthor Information Xiang Shu More articles by this author Hui Cai More articles by this author Yong-Bing Xiang More articles by this author Honglan Li More articles by this author Loren Lipworth More articles by this author Nicole Miller More articles by this author Wei Zheng More articles by this author Xiao-Ou Shu More articles by this author Ryan Hsi More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Intake of Trace Metals and the Risk of Incident Kidney Stones

The association between the intake of trace metals and the risk of incident stones has not been longitudinally investigated. We performed a prospective analysis of 193,551 participants in the Health Professionals Follow-up Study, and the Nurses' Health Study I and II. During a followup of 3,316,580 person-years there was a total of 6,576 incident stones. We used multivariate regression models to identify associations of the intake of zinc, iron, copper and manganese with the risk of stones. In a subset of participants with 24-hour urine collections we examined the association between the intake of trace metals and urine composition. After multivariate adjustment total and dietary intakes of zinc and iron were not significantly associated with incident stones. A higher intake of manganese was associated with a lower risk of stones. The pooled HR of the highest quintile of total manganese intake compared with the lowest intake was 0.82 (95% CI 0.68-0.98, p = 0.02). Total but not dietary copper intake was marginally associated with a higher risk of stones (pooled HR 1.14, 95% CI 1.02-1.28, p = 0.01). There were no statistically significant associations of the total intake of manganese and copper with urinary supersaturation. Zinc and iron intake was not associated with a risk of stones. Copper intake may be associated with a higher risk in some individuals. Higher total manganese intake was associated with a lower risk of stones but not with traditional 24-hour urinary composite markers of stone risk. Further research is needed to elucidate the mechanisms by which manganese may reduce kidney stone formation.

Vitamin B6 intake and the risk of incident kidney stones.

Higher vitamin B6 intake might reduce urinary excretion of oxalate, one of the major determinants of risk for calcium oxalate kidney stones. Previous studies investigating the association between intake of vitamin B6 and risk of stones found conflicting results. We sought to investigate the association in three large prospective cohorts. We prospectively examined the association in the Health Professionals Follow-up Study (HPFS; n=42,919 men), Nurses' Health Study I (NHS I; n=60,003 older women), and Nurses' Health Study II (NHS II; n=90,629 younger women). Hazard ratios (HRs) and 95% confidence intervals (CIs) for incident stones across categories of total vitamin B6 intake (<3.0, 3.0-4.9, 5.0-9.9, 10.0-39.9, ≥40.0mg/day) were generated with Cox proportional hazards regression models adjusted for potential confounders. During 3,316,846 person-years of follow-up, 6576 incident kidney stones were confirmed. In univariate and multivariate analyses, there was no association between intake of vitamin B6 and incident stones. The HR for stones in the highest category compared with the lowest was 1.05 (95% CI 0.85, 1.30; p value for trend=0.61) for HPFS, 0.95 (95% CI 0.76, 1.18; p value for trend=0.42) for NHS I, and 1.06 (95% CI 0.91, 1.24; p value for trend=0.34) for NHS II. The pooled adjusted HR for the highest category compared with the lowest was 1.03 (95% CI 0.92, 1.15; p value for trend=0.60). Intake of vitamin B6 is not associated with risk of incident kidney stones.

Vitamin D Intake and the Risk of Incident Kidney Stones

Kidney stones are a common and painful condition. Longitudinal prospective studies on the association between the intake of vitamin D and the risk of incident kidney stones are lacking. We performed a prospective analysis of 193,551 participants in the Health Professionals Follow-up Study and Nurses' Health Study I and II. Participants were divided into categories of total (less than 100, 100 to 199, 200 to 399, 400 to 599, 600 to 999, 1,000 IU per day or greater) and supplemental (none, less than 400, 400 to 599, 600 to 999, 1,000 IU per day or greater) vitamin D intake. During a followup of 3,316,846 person-years there were 6,576 incident kidney stone events. Cox proportional hazards regression models were adjusted for age, body mass index, comorbidities, use of medications and intake of other nutrients. After multivariate adjustment there was no statistically significant association between vitamin D intake and risk of stones in the HPFS (HR for 1,000 or greater vs less than 100 IU per day 1.08, 95% CI 0.80, 1.47, p for trend = 0.92) and the NHS I (HR 0.99, 95% CI 0.73, 1.35, p for trend = 0.70), whereas there was a suggestion of a higher risk in the NHS II (HR 1.18, 95% CI 0.94, 1.48, p for trend = 0.02). Similar results were found for supplemental vitamin D intake. Vitamin D intake in typical amounts was not statistically associated with risk of kidney stone formation, although higher risk with higher doses than those studied here cannot be excluded.

Insights Into Nephrolithiasis From the Nurses' Health Studies.

To review the contributions of the Nurses' Health Study (NHS) I and NHS II to understanding the role of dietary factors, beverages, body size, and urinary factors in the development of kidney stones. We conducted a review of kidney stone-related publications of NHS I and NHS II between 1976 and 2016. Studies using NHS I and NHS II data have demonstrated the importance of many factors in kidney stone formation and were the first to report that higher dietary calcium was associated with a lower risk of incident kidney stones in women. Data from these cohorts were instrumental in emphasizing that nephrolithiasis is a systemic disease and suggesting that a kidney stone or shared risk factors may lead to hypertension, diabetes, and cardiovascular disease. Findings from the NHSs have changed the scientific understanding and the clinical practice of stone prevention and have been incorporated into widely consulted textbooks and the American Urological Association Medical Management of Kidney Stones guidelines.

Dietary Protein and Potassium, Diet-Dependent Net Acid Load, and Risk of Incident Kidney Stones.

Protein and potassium intake and the resulting diet-dependent net acid load may affect kidney stone formation. It is not known whether protein type or net acid load is associated with risk of kidney stones. We prospectively examined intakes of protein (dairy, nondairy animal, and vegetable), potassium, and animal protein-to-potassium ratio (an estimate of net acid load) and risk of incident kidney stones in the Health Professionals Follow-Up Study (n=42,919), the Nurses' Health Study I (n=60,128), and the Nurses' Health Study II (n=90,629). Multivariable models were adjusted for age, body mass index, diet, and other factors. We also analyzed cross-sectional associations with 24-hour urine (n=6129). During 3,108,264 person-years of follow-up, there were 6308 incident kidney stones. Dairy protein was associated with lower risk in the Nurses' Health Study II (hazard ratio for highest versus lowest quintile, 0.84; 95% confidence interval, 0.73 to 0.96; P value for trend <0.01). The hazard ratios for nondairy animal protein were 1.15 (95% confidence interval, 0.97 to 1.36; P value for trend =0.04) in the Health Professionals Follow-Up Study and 1.20 (95% confidence interval, 0.99 to 1.46; P value for trend =0.06) in the Nurses' Health Study I. Potassium intake was associated with lower risk in all three cohorts (hazard ratios from 0.44 [95% confidence interval, 0.36 to 0.53] to 0.67 [95% confidence interval, 0.57 to 0.78]; P values for trend <0.001). Animal protein-to-potassium ratio was associated with higher risk (P value for trend =0.004), even after adjustment for animal protein and potassium. Higher dietary potassium was associated with higher urine citrate, pH, and volume (P values for trend <0.002). Kidney stone risk may vary by protein type. Diets high in potassium or with a relative abundance of potassium compared with animal protein could represent a means of stone prevention.

Total, Dietary, and Supplemental Vitamin C Intake and Risk of Incident Kidney Stones

Previous studies of vitamin C and kidney stones were conducted mostly in men and either reported disparate results for supplemental and dietary vitamin C or did not examine dietary vitamin C. Prospective cohort analysis. 156,735 women in the Nurses' Health Study (NHS) I and II and 40,536 men in the Health Professionals Follow-up Study (HPFS). Total, dietary, and supplemental vitamin C intake, adjusted for age, body mass index, thiazide use, and dietary factors. Incident kidney stones. During a median follow-up of 11.3 to 11.7 years, 6,245 incident kidney stones were identified. After multivariable adjustment, total vitamin C intake (<90 [reference], 90-249, 250-499, 500-999, and ≥1,000mg/d) was not significantly associated with risk for kidney stones among women, but was among men (HRs of 1.00 [reference], 1.19 [95% CI, 0.99-1.46], 1.15 [95% CI, 0.93-1.42], 1.29 [95% CI, 1.04-1.60], and 1.43 [95% CI, 1.15-1.79], respectively; P for trend = 0.005). Median total vitamin C intake for the 500- to 999-mg/d category was ∼700mg/d. Supplemental vitamin C intake (no use [reference], <500, 500-999, and ≥1,000mg/d) was not significantly associated with risk for kidney stones among women, but was among men (HR, 1.19 [95% CI, 1.01-1.40] for ≥1,000mg/d; P for trend = 0.001). Dietary vitamin C intake was not associated with stones among men or women, although few participants had dietary intakes > 700mg/d. Nutrient intakes derived from food-frequency questionnaires, lack of data on stone composition for all cases. Total and supplemental vitamin C intake was significantly associated with higher risk for incident kidney stones in men, but not in women.

Treatment effect, adherence, and safety of high fluid intake for the prevention of incident and recurrent kidney stones: a systematic review and meta-analysis.

The objective of this systematic review and meta-analysis were to evaluate the effectiveness of high fluid intake for the prevention of incident and recurrent kidney stones, as well as its adherence and safety. A literature search was performed encompassing 1980 through July 2014. Studies that reported relative risks, odds ratios, or hazard ratios comparing the risk of kidney stone events in patients with high vs inadequate fluid intake were included. Pooled risk ratios (RRs) and 95 % confidence intervals (CIs) were calculated using a random-effect, generic inverse variance method. Nine studies [2 randomized controlled trials (RCTs) with 269 patients; 7 observational studies with 273,685 individuals] were included in the meta-analysis. Pooled RRs of kidney stones in individuals with high-fluid intake were 0.40 (95 % CI 0.20-0.79) and 0.49 (0.34-0.71) in RCTs and observational studies, respectively. High fluid intake was significantly associated with reduced risk of recurrent kidney stones: RRs 0.40 (95 % CI 0.20-0.79) and 0.20 (0.09-0.44) in RCTs and observational studies, respectively. Adherence and safety data on high fluid intake treatment were limited; 1 RCT reported no withdrawals due to adverse events. This analysis demonstrated a significantly reduced risk of incident kidney stones among individuals with high fluid consumption. High fluid consumption also reduced the risk of recurrent kidney stones. Furthermore, the magnitude of risk reduction was high. Although increased water intake appears to be safe, future studies on its safety in patients with high risk of volume overload or hyponatremia may be indicated.