Increased amount and duration of tea consumption may be associated with decreased risk of renal stone disease

The Protective Role of Dietary Polyphenols in Urolithiasis: Insights into Antioxidant Effects and Mechanisms of Action

Urolithiasis is a common urological disease with increasing prevalence and high recurrence rates around the world. Numerous studies have indicated reactive oxygen species (ROS) and oxidative stress (OS) were crucial pathogenic factors in stone formation. Dietary polyphenols are a large group of natural antioxidant compounds widely distributed in plant-based foods and beverages. Their diverse health benefits have attracted growing scientific attention in recent decades. Many literatures have reported the effectiveness of dietary polyphenols against stone formation. The antiurolithiatic mechanisms of polyphenols have been explained by their antioxidant potential to scavenge free radicals and ROS, modulate the expression and the activity of endogenous antioxidant and prooxidant enzymes, regulate signaling pathways associated with OS, and maintain cell morphology and function. In this review, we first describe OS and its pathogenic effects in urolithiasis and summarize the classification and sources of dietary polyphenols. Then, we focus on the current evidence defining their antioxidant potential against stone formation and put forward challenges and future perspectives of dietary polyphenols. To conclude, dietary polyphenols offer potential applications in the treatment and prevention of urolithiasis.

Causal association between tea intake and risk for gout: a Mendelian randomization study

Background: Gout, an increasingly prevalent form of inflammatory arthritis, is caused by the accumulation of uric acid crystals in joints, resulting in severe pain, swelling and stiffness that adversely affect physical, mental and emotional wellbeing. The management of gout requires a combination of medication and lifestyle modifications. Recent studies suggest that tea intake may reduce the risk of developing gout; however, further research is needed to establish a causal relationship. Methods: In this study, we employed a bidirectional two-sample Mendelian randomization (MR) approach, utilizing genome-wide association study (GWAS) summary statistics, to investigate the causal association between increased tea intake and gout. We meticulously selected instrumental variables (IVs) based on rigorous criteria and employed five different MR methods. Heterogeneity was assessed using Cochran's Q statistic, and pleiotropy was evaluated using the MR Egger intercept and MR-PRESSO tests. Weak IVs were identified using F values. The Phenoscanner database was consulted to exclude single nucleotide polymorphisms associated with confounding factors or outcomes. Results: The study included one dataset related to tea intake (ukb-b-6066) and three datasets related to gout (ukb-b-12765, finn-b-M13_GOUT, and finn-b-GOUT_STRICT). Our forward MR analysis suggest a causal relationship between increased tea intake and reduced risk of gout in all three gout-related datasets [OR (95% CI): 0.9966 (0.9938-0.9993), p = 0.0167; 0.4842 (0.2683-0.8737), p-value = 0.0160; and 0.4554 (0.2155-0.9623), p = 0.0393, respectively]. The reveres MR showed increased risk of gout (ukb-b-12765) was significantly associated with low tea intake according to the IVW analysis [OR (95% CI): 0.0062 (0.0002-0.154), p = 0.0020]. However, this association was not observed in the Finn-b-M13_GOUT and Finn-b-GOUT_STRICT [OR (95% CI): 0.9992 (0.9909-1.0075), p = 0.8453 and OR (95% CI): 0.9996 (0.9932-1.0059), p = 0.8896, respectively]. No significant heterogeneity or potential pleiotropy was detected, and the possibility of weak IVs was also excluded. Conclusion: Our MR analysis suggest a causal relationship between genetically predicted tea intake and a decreased risk of gout. These findings underscore the potential advantages of increasing tea intake for preventing gout. However, further research is needed to validate these results and elucidate the underlying mechanisms.

Role, importance and assessment of dietary habits in urolithiasis patient

Urolithiasis, which prevalence is increasing, poses a risk for chronic kidney disease in patients. Dietary habits play a significant role in stone formation, growth and recurrence. Also, comorbidities and lifestyle changes are among the factors affecting stone formation. The next step should be to detect metabolic disorders, if any, with analyzes to be made after a detailed anamnesis, and to arrange the necessary treatment. Insufficient fluid intake is considered to be the main dietary risk factor for urolithiasis. A daily fluid intake of 2.5-3.0 L/day or diuresis of 2.0-2.5 L/day is recommended to prevent recurrence of kidney stones. Not all beverages are beneficial, and some may even increase the risk of stone formation. Dietary management, vitamins and supplements, physical activity are important components in reducing the risk of recurrent urolithiasis. A detailed dietary assessment is recommended as dietary habits affect the faith of the disease. In this review we evaluated the dietary approach of urolithiasis patients with and without comorbidities, the recommended daily fluid intake, vitamin supplementation, and relation of the urolithiasis with physical activity.

Association between tea intake and hospitalized nephrolithiasis in Chinese adults: A case–control study

Introduction and aim

Nephrolithiasis is one of the most common urological disorders worldwide. Tea is one of the most popular drinks worldwide. This study aimed to explore the association between tea intake and hospitalized nephrolithiasis in Chinese adults.

Methods

The patients and healthy participants were from the Shenyang sub-cohort of Tianjin Chronic Low-Grade Systemic Inflammation and Health Cohort Study. After selecting and matching by age (±1 year) and sex using the 1:2 ratio, 834 participants were included in this study. Of these, 278 patients had hospitalized nephrolithiasis and 556 were healthy controls. The tea intake was assessed using a validated self-administered food frequency questionnaire. Multivariate conditional logistic regression analysis was used to evaluate the association between tea intake and hospitalized nephrolithiasis.

Results

After adjustment, a higher frequency of tea intake was found to be negatively associated with the risk of hospitalized nephrolithiasis. Compared with participants who never drank tea, the odds ratio (95% confidence interval) [OR (95% CI)] for participants who drank ≥1 cup (180 mL) of tea per day was 0.418 (0.192–0.911) (P for trend = 0.013). Moreover, the adjusted OR (95% CI) for participants who drank ≥1 cup of green tea and black tea per day was 0.189 (0.069–0.520) (P for trend <0.001) and 1.248 (0.437–3.559) (P for trend = 0.654), respectively.

Conclusions

Increased tea intake was found to be associated with a lower risk of hospitalized nephrolithiasis among Chinese adults. This finding may assist in the prevention of hospitalized nephrolithiasis.

Diet and Stone Disease in 2022

Diet plays a central role in the development and prevention of nephrolithiasis. Although pharmacologic treatment may be required for some patients who are resistant to dietary measures alone, dietary modification may be sufficient to modulate stone risk for many patients. While there is no single specialized diet for stone prevention, several dietary principles and recommendations for stone prevention are supported by practice guidelines, including adequate fluid intake, modest calcium intake, low dietary sodium, and limited animal protein. In this review, we summarized the evidence supporting these dietary recommendations and reviewed the current literature regarding specific dietary components and comprehensive diets for stone prevention.

The chemistry, processing, and preclinical anti-hyperuricemia potential of tea: a comprehensive review

Hyperuricemia is an abnormal purine metabolic disease that occurs when there is an excess of uric acid in the blood, associated with cardiovascular diseases, hypertension, gout, and renal disease. Dietary intervention is one of the most promising strategies for preventing hyperuricemia and controlling uric acid concentrations. Tea (Camellia sinensis) is known as one of the most common beverages and the source of dietary polyphenols. However, the effect of tea on hyperuricemia is unclear. Recent evidence shows that a lower risk of hyperuricemia is associated with tea intake. To better understand the anti-hyperuricemia effect of tea, this review first briefly describes the pathogenesis of hyperuricemia and the processing techniques of different types of tea. Next, the epidemiological and experimental studies of tea and its bioactive compounds on hyperuricemia in recent years were reviewed. Particular attention was paid to the anti-hyperuricemia mechanisms targeting the hepatic uric acid synthase, renal uric acid transporters, and intestinal microbiota. Additionally, the desirable intake of tea for preventing hyperuricemia is provided. Understanding the anti-hyperuricemia effect and mechanisms of tea can better utilize it as a preventive dietary strategy.HighlightsHigh purine diet, excessive alcohol/fructose consumption, and less exercise/sleep are the induction factors of hyperuricemia.Tea and tea compounds showed alleviated effects for hyperuricemia, especially polyphenols.Tea (containing caffeine or not) is not associated with a higher risk of hyperuricemia.Xanthine oxidase inhibition (reduce uric acid production), Nrf2 activation, and urate transporters regulation (increase uric acid excretion) are the potential molecular targets of anti-hyperuricemic effect of tea.About 5 g tea intake per day may be beneficial for hyperuricemia prevention.

The Associations Between Tea and Coffee Drinking and Risk of Calcium-Oxalate Renal Stones

Findings regarding the association between tea and coffee consumption and oxalate-calcium stone are sparse and uncertain. The purpose of this study was to investigate the relations of tea and coffee with the risk of calcium oxalate stone formation. A total sample of 215 newly diagnosed patients with calcium oxalate stones and 215 controls matched for sex and age were recruited. Dietary intake of participants was assessed using a validated food frequency questionnaire over the preceding year and participants were asked to determine how many glasses of tea and cups of coffee they usually use. The associations between tea and coffee and kidney stone were examined using multivariable logistic regression. Compared with controls, cases had greater intake of tea (2.18±0.76 vs. 1.82±0.79 glasses/d) but lower intake of coffee (1.18±0.38 vs. 1.26±0.44 cups/week). After adjustment for potential confounders, compared with those who drank <2 glasses of tea/d, individuals with tea consumption of ≥4 glasses/d had greater risk for having calcium oxalate stone (OR= 2.73; 95 % CI: 1.50, 4.99). In the crude model, compared with coffee consumption for <1 cup/week, consumption of ≥1 cup/week was associated with a 38 % decrease in the risk of calcium oxalate stone. However, adjustment for potential confounders disappeared the significance (OR=0.81; 95 % CI: 0.48, 1.35). These results suggest that while high consumption of tea is associated with increased risk of calcium oxalate kidney stone, coffee drinking is not pertinent. However, due to low consumption of coffee in this population, our results should be interpreted cautiously.

Nutrition and Kidney Stone Disease

The prevalence of kidney stone disease is increasing worldwide. The recurrence rate of urinary stones is estimated to be up to 50%. Nephrolithiasis is associated with increased risk of chronic and end stage kidney disease. Diet composition is considered to play a crucial role in urinary stone formation. There is strong evidence that an inadequate fluid intake is the major dietary risk factor for urolithiasis. While the benefit of high fluid intake has been confirmed, the effect of different beverages, such as tap water, mineral water, fruit juices, soft drinks, tea and coffee, are debated. Other nutritional factors, including dietary protein, carbohydrates, oxalate, calcium and sodium chloride can also modulate the urinary risk profile and contribute to the risk of kidney stone formation. The assessment of nutritional risk factors is an essential component in the specific dietary therapy of kidney stone patients. An appropriate dietary intervention can contribute to the effective prevention of recurrent stones and reduce the burden of invasive surgical procedures for the treatment of urinary stone disease. This narrative review has intended to provide a comprehensive and updated overview on the role of nutrition and diet in kidney stone disease.

Tea and coffee consumption and the risk of urinary stones-a systematic review of the epidemiological data

OBJECTIVE

To explore the relationship between the consumption of coffee and tea with urolithiasis. We evaluated large epidemiological and small clinical studies to draw conclusions regarding their lithogenic risk.

METHODS

A systematic review was performed using the Medline and Scopus databases, in concordance with the PRISMA statement. English, French, and Spanish language studies regarding the consumption of caffeinated and decaffeinated coffee and tea, and the relationship to urinary stone disease were reviewed. Case reports and letters, unpublished studies, posters, and comments were excluded.

RESULTS

As per the inclusion criteria, 13 studies were included in the final review. Most studies, including four large prospective studies and one meta-analysis, reported a reduced risk of stone formation for coffee and tea. Caffeine has a diuretic effect and increases the urinary excretion of calcium, but if these losses are compensated for, moderate caffeine intakes may have little or no deleterious effects. Green and Herbal teas infused for short time had low oxalate content compared to black tea.

CONCLUSION

There is no evidence that moderate consumption of coffee raises the risk for stone formation in healthy individuals, provided the recommended daily fluid intake is maintained. The currently available literature supports in general a protective role for tea against the stone formation, mainly for green tea. However, heterogeneity of published data and lack of standardization needs to be addressed before final and clear conclusions can be given to patients and to the public in general.

Preprotection of Tea Polysaccharides with Different Molecular Weights Can Reduce the Adhesion between Renal Epithelial Cells and Nano-Calcium Oxalate Crystals

Crystal adhesion is an important link in the formation of kidney stones. This study investigated and compared the adhesion differences between nano-calcium oxalate monohydrate (COM) and human renal proximal tubule epithelial (HK-2) cells before and after treatment with tea polysaccharides (TPSs) TPS0, TPS1, TPS2, and TPS3 with molecular weights of 10.88, 8.16, 4.82, and 2.31 kDa, respectively. TPS treatment effectively reduced the damage of COM to HK-2 cells, thereby resulting in increased cell activity, decreased release of lactate dehydrogenase, cell morphology recovery, decreased level of reactive oxygen species, increased mitochondrial membrane potential, increased lysosomal integrity, decreased expression of adhesion molecule osteopontin and eversion of phosphatidylserine, and decreased crystal adhesion. Among the TPSs, TPS2 with moderate molecular weight had the best protective effect on cells and the strongest effect on the inhibition of crystal adhesion. Thus, TPS2 may be a potential anticalculus drug.

Caffeine intake and the risk of recurrent kidney stones in adults, an analysis of 2007-2014 National Health and Nutrition Examination Surveys

PURPOSE

The association between caffeine intake and the risk of recurrent kidney stones is unknown. We examined the association between caffeine intake and the risk of recurrent kidney stones in adults.

METHODS

Individuals with history of passing at least one kidney stone were included from 2007 to 2014 National Health and Nutrition Examination Survey. Recurrent kidney stones were defined using a standard questionnaire and structured dietary recalls were used to determine caffeine intake. The weighted logistic regression was used to assess the association between caffeine intake and the risk of recurrent kidney stones, and the non-linear relationship was explored with restricted cubic splines. Caffeine and dietary confounders (minerals and vitamins) were adjusted for total energy intake with residual model.

RESULTS

The multivariate-adjusted odds ratios (95% confidence intervals) of recurrent kidney stones for per-quartile increment in caffeine intake were 1.15 (1.01-1.31) overall, 1.11 (0.96-1.29) for white race individuals, 1.33 (1.09-1.63) for non-white race individuals, 1.15 (0.97-1.36) for men, 1.24 (1.01-1.53) for women, 1.54 (1.08-2.19) for non-overweight individuals, 1.11 (0.97-1.28) for overweight/obese individuals, 1.13 (0.99-1.29) for caffeine from coffee, and 0.90 (0.79-1.03) for caffeine from non-coffee sources. A linear relationship was found between caffeine intake and the risk of recurrent kidney stones overall and in subgroup analyses.

CONCLUSION

Compared with those who reported passing only one kidney stone, caffeine intake was independently and linearly associated with a higher risk of recurrent kidney stones in adults, especially for women, individuals of non-white race and non-overweight subjects. The increased risk may arise from caffeine from coffee.

Comparison of the adhesion of calcium oxalate monohydrate to HK-2 cells before and after repair using tea polysaccharides

Background: Kidney stone formation is closely related to renal epithelial cell damage and the adhesion of calcium oxalate crystals to cells. Methods: In this research, the adhesion of human kidney proximal tubular epithelial cells (HK-2) to calcium oxalate monohydrate crystals with a size of approximately 100 nm was studied. In addition, the inhibition of crystal adhesion by four tea polysaccharides (TPS0, TPS1, TPS2, and TPS3) with the molecular weights of 10.88, 8.16, 4.82, and 2.31 kDa, respectively were compared. Results: When oxalic acid-damaged HK-2 cells were repaired, cell viability increased. By contrast, reactive oxygen species level, phosphatidylserine eversion, and osteopontin expression decreased, thus indicating that tea polysaccharides have a repairing effect on damaged HK-2 cells. Moreover, after repairing the damaged cells, the amount of adherent crystals was reduced. The repair effect of tea polysaccharides is closely related to molecular weight, and TPS2 with the moderate molecular weight displayed the best repair effect. Conclusion: These results suggest that tea polysaccharides, especially TPS2, may inhibit the formation and recurrence of calcium oxalate kidney stones.