Effect of two sports drinks on urinary lithogenicity

Current Dietary and Medical Prevention of Renal Calcium Oxalate Stones

Kidney stones refer to abnormal crystal formation that occurs in the kidney. Among a variety of components of kidney stones, calcium oxalate (CaOx) is the most common type. Despite many efforts to investigate the pathogenesis of CaOx stones, the pathogenesis remains an issue of debate. With high occurrence and recurrence, individuals with stone formation are prone to frequently consult a doctor and to be hospitalized, and the treatment of kidney stones poses a heavy burden on the patients. Concerns should be focused not only on treatment but also on prevention. Herein, we reviewed the studies on prevention methods of CaOx stones through diet, lifestyle, and medication extending until the current time frame. As hyperoxaluria is the most common metabolic disorder among CaOx stone formations, we also included several studies on the treatment and prevention of hyperoxaluria. Our objective was to outline the effective methods to prevent renal CaOx stone formation.

Effect of a high-citrate beverage on urine chemistry in patients with calcium kidney stones

A well-accepted strategy to prevent kidney stones is to increase urine volume by increasing oral intake of fluids, especially water, to lower supersaturation of the relevant, relatively insoluble salts, and thereby lower the risk of precipitation. Randomized controlled trials have shown that this strategy works. It is inexpensive, safe, and intuitively attractive to patients. However, although any beverage can increase urine volume, and citrus juices can increase urine citrate content and pH, no beverage other than water has been clearly shown by randomized controlled trial to prevent kidney stones. We designed an innovative, palatable, low-calorie, high alkali citrate beverage to prevent kidney stones, called Moonstone. One packet of Moonstone powder, mixed in 500 ml of water, contains 24.5 meq of alkali citrate. We administered one packet twice a day to ten calcium stone formers. Moonstone resulted in an increase in mean 24-h urine citrate and urine pH, and a decrease in supersaturation of calcium oxalate in calcium stone formers compared to an equal volume of water. These changes, comparable to those seen in a prior study of a similar amount of (potassium-magnesium) citrate, will likely be associated with a clinically meaningful reduction in kidney stone burden in patients with calcium stones. The effect to increase urine pH would also be expected to benefit patients with uric acid and cystine stones, groups that we hope to study in a subsequent study. The study preparation was well tolerated and was selected as a preferred preventative strategy by about half the participants. Moonstone is an alternative, over-the-counter therapy for kidney stone prevention.

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.

What roles do alkali metal ions play in the pathological crystallization of uric acid?

Na+ and K+ regulate the crystal growth of uric acid dihydrate by kink blocking and rough growth mechanisms.

PycnoRacer®, a fitness drink including Pycnogenol®, improves recovery and training in the Cooper test

BACKGROUND

This study evaluates the effects of training (on running distance measured with a Cooper test) in 3 weeks in non-professional athletes using PycnoRacer®, a fitness drink (FD) including Pycnogenol® during the training period.

METHODS

Pycnogenol® has been used in preclinical conditions and prevention. PycnoRacer® is a liquid combination of Pycnogenol® (15 mg), L-leucine (0.6 g), L-arginine (0.3 g), L-isoleucine (0.3 g), and L-valine (0.3 g). Two comparable groups (one using the FD) were formed: 60 training athletes were requested to drink one bottle 4 times/day, while 65 controls did not use PycnoRacer® or other comparable sports drinks. All subjects had a strong athletic background and advanced knowledge of the procedures of the tests. Two daily training sessions were completed. The sessions consisted in warming up and running a Cooper test.

RESULTS

125 subjects completed the three weeks according to plans. There were nine dropouts due to logistical or working problems. Subjects using the FD improved on average by 18.83% (range 12-23%) in their running distance with training. The difference with controls was significant (P<0.05) at 3 weeks (controls improved on average by 8.9%; range 3-17.4%). The difference between the two groups was on average 9.93% (P<0.05). A comparable increase in VO2max was observed in the groups. In the FD group the increase was on average by 10.05 mL/kg/min compared to 4.95 mL/kg/min in controls, with a difference of 5.1 mL/kg/min (P<0.05). A VAS score showed comparable values. Lower values (concerning muscular pain and cramps) were observed in FD subjects (P<0.05) at the end of the 3 weeks of training. The level of plasma free radicals (PFR) values after the last Cooper test was significantly lower at 3 weeks in the FD group (P<0.05). No intolerance problem was observed by subjects using the FD.

CONCLUSIONS

In conclusion, the use of PycnoRacer® improved training, running distance, VO2max and PFR decreasing muscular pain and cramps.

The role of fluid intake in the prevention of kidney stone disease: A systematic review over the last two decades

OBJECTIVE

The incidence of kidney stone disease (KSD) is rising worldwide; hence, more focus must be directed toward its etiology and risk factors. Increasing fluid intake is recommended as the most ideal prevention; yet, there is inconsistent evidence surrounding optimum volumes and types of fluid that affect stone formation. This review aimed to analyze the published literature on fluid intake and types of fluid consumed and their impact on KSD prevention.

MATERIAL AND METHODS

Papers were acquired from databases: MEDLINE, EMBASE, PubMed, CINAHL, and Cochrane Library. Included English language studies that involved adults consuming beverages along with a standardized diet in relation to KSD. Those failing to control dietary factors were excluded.

RESULTS

After an initial search of 1099 papers, 9 (541 participants) were included in the final review. Six varieties of water and ten different types of juices were investigated. Higher fluid intake was associated with increased urine output and reduced stone formation. Water with high calcium content seemingly increased the rate of calcium oxalate (CaOx) stone formation. The relative supersaturation of CaOx in urine was decreased with grapefruit, apple, orange juices, and sodas, whereas cranberry juice increased it. Plum juice and the energy drink Gatorade had no effect on stone formation.

CONCLUSION

Fluids low in calcium seem to reduce the risk of KSD. Certain varieties of fluid, such as grapefruit, apple, and orange juices reduce urine CaOx saturation, with a subsequent reduction in stone formation. Findings from this review could contribute to primary prevention for those at risk of KSD.

Effect of increasing doses of cystine-binding thiol drugs on cystine capacity in patients with cystinuria

Appropriate dosing of cystine-binding thiol drugs in the management of cystinuria has been based on clinical stone activity. When new stones form, the dose is increased. Currently, there is no method of measuring urinary drug levels to guide the titration of therapy. Increasing cystine capacity, a measure of cystine solubility, has been promoted as a method of judging the effects of therapy. In this study, we gave increasing doses of tiopronin or D-penicillamine, depending on the patients' own prescriptions, to ten patients with cystinuria and measured cystine excretion and cystine capacity. The doses were 0, 1, 2, 3 g per day, given in two divided doses, and administered in a random order. Going from 0 to 1 g/day led to an increase in cystine capacity from - 39.1 to 130.4 mg/L (P < 0.009) and decreased 24 h cystine excretion from 1003.9 to 834.8 mg/day (P = 0.039). Increasing the doses from 1 to 2 to 3 g/day had no consistent or significant effect to further increase cystine capacity or decrease cystine excretion. Whether doses higher than 1 g/day have additional clinical benefit is not clear from this study. Limiting doses might be associated with fewer adverse effects without sacrificing the benefit of higher doses if higher doses do not offer clinical importance. However, trials with stone activity as an outcome would be desirable.

Uric acid nephrolithiasis: An update

Uric acid nephrolithiasis appears to increase in prevalence. While a relationship between uric acid stones and low urinary pH has been for long known, additional association with various metabolic conditions and pathophysiological basis has recently been elucidated. Some conditions such as diabetes and metabolic syndrome disease, excessive dietary intake, and increased endogenous uric acid production and/or defect in ammoniagenesis are associated with low urinary pH. In addition, the phenomenon of global warming could result in an increase in areas with greater climate risk for uric acid stone formation. There are three therapeutic steps to be taken for management of uric acid stones: identification of urinary pH profiles, assessment of urinary volume status, and identification of disorders leading to excessive uric acid production. However, the most important factor for uric acid stone formation is acid urinary pH, which is a prerequisite for uric acid precipitation. This article reviews recent insights into the pathophysiology of uric acid stones and their management.

Water and other fluids in nephrolithiasis: State of the art and future challenges

Adequate hydration, as to maintain urinary volume over 2 L/day, has long been considered as the cornerstone medical prescription for preventing nephrolithiasis. However, scientific evidence about what kind of water stone formers should drink and about the effects of other beverages on urinary stone risk factors is sometimes unclear. Moreover, the recommendation that water therapy prevents kidney stone recurrence relies on only one randomized controlled trial, even if more epidemiologic and basic science studies seem to support this assumption. Therefore, in this review we analyze current evidence that support water therapy in nephrolithiasis and we highlight the possible effects of different types of water and other beverages on lithogenic risk, giving some practical recommendations for what stone formers should be advised to prevent recurrence.

Randomised clinical trial: Polyethylene glycol 3350 with sports drink vs. polyethylene glycol with electrolyte solution as purgatives for colonoscopy--the incidence of hyponatraemia

BACKGROUND

Polyethylene glycol 3350 plus sports drink (PEG-SD) is a hypo-osmotic purgative commonly used for colonoscopy, though little safety data are available.

AIM

To evaluate the effect of PEG-SD on serum sodium (Na) and other electrolytes compared with PEG-electrolyte solution (PEG-ELS).

METHODS

We performed a single center, prospective, randomised, investigator-blind comparison of PEG-ELS to PEG-SD in out-patients undergoing colonoscopy. Laboratories were obtained at baseline and immediately before and after colonoscopy. The primary endpoint was development of hyponatraemia (Na <135 mmol/L) the day of colonoscopy. Changes in electrolyte levels were computed as the difference between the lowest value on the day of colonoscopy and baseline. Purgative tolerance and efficacy were assessed.

RESULTS

A total of 389 patients were randomised; 364 took purgative and had baseline and day of colonoscopy labs (180 PEG-SD, 184 PEG-ELS). The groups were well matched except for a higher fraction of women and Blacks in PEG-ELS. Seven patients (3.9%) in PEG-SD and four patients (2.2%) in PEG-ELS developed hyponatraemia (OR = 1.82, 95% CI: 0.45-8.62, P = 0.376). Changes in electrolytes from baseline were small but significantly worse with PEG-SD for sodium, potassium and chloride (P = 0.001, 0.012, 0.001, respectively). Preparation completion, adverse events, and overall colon cleansing were similar between the groups, but PEG-ELS had more excellent preparations (52% vs. 30%; P = 0.001).

CONCLUSIONS

Greater, but very modest, electrolyte changes occur with PEG-SD. Hyponatraemia is infrequent with both purgatives. A significant increase in hyponatraemia was not identified for PEG-SD vs. PEG-ELS, but the sample size may have been inadequate to identify a small, but clinically important difference. ClinicalTrials.gov identifier NCT01299779.

Optimum nutrition for kidney stone disease

We summarize the data regarding the associations of individual dietary components with kidney stones and the effects on 24-hour urinary profiles. The therapeutic recommendations for stone prevention that result from these studies are applied where possible to stones of specific composition. Idiopathic calcium oxalate stone-formers are advised to reduce ingestion of animal protein, oxalate, and sodium while maintaining intake of 800 to 1200 mg of calcium and increasing consumption of citrate and potassium. There are few data regarding dietary therapy of calcium phosphate stones. Whether the inhibitory effect of citrate sufficiently counteracts increasing urine pH to justify more intake of potassium and citrate is not clear. Reduction of sodium intake to decrease urinary calcium excretion would also be expected to decrease calcium phosphate stone recurrence. Conversely, the most important urine variable in the causation of uric acid stones is low urine pH, linked to insulin resistance as a component of obesity and the metabolic syndrome. The mainstay of therapy is weight loss and urinary alkalinization provided by a more vegetarian diet. Reduction in animal protein intake will reduce purine ingestion and uric acid excretion. For cystine stones, restriction of animal protein is associated with reduction in intake of the cystine precursor methionine as well as cystine. Reduction of urine sodium results in less urine cystine. Ingestion of vegetables high in organic anion content, such as citrate and malate, should be associated with higher urine pH and fewer stones because the amino acid cystine is soluble in more alkaline urine. Because of their infectious origin, diet has no definitive role for struvite stones except for avoiding urinary alkalinization, which may worsen their development.

Noncitrus alkaline fruit: a dietary alternative for the treatment of hypocitraturic stone formers

BACKGROUND AND PURPOSE

Fruits and vegetables are natural suppliers of potassium, bicarbonate, or bicarbonate precursors such as citrate, malate and others-hence, possessing potential effects on citraturia. We aimed to compare the acute effects of a noncitrus (melon) fruit vs citric ones (orange and lime) on citraturia and other lithogenic parameters.

PATIENTS AND METHODS

Two-hour urine samples were collected from 30 hypocitraturic stone-forming patients after an overnight fast and 2, 4, and 6 hours after the consumption of 385 mL (13 oz) of either freshly squeezed orange juice (n=10), freshly blended melon juice (n=10), or freshly squeezed lime juice (n=10). Urinary citrate, potassium, pH, and other lithogenic parameters were determined and net gastrointestinal alkali absorption (NGIA) was calculated. Potential renal acid load (PRAL) and pH from juices were determined.

RESULTS

Significant and comparable increases of mean urinary citrate were observed in all groups, whereas mean urinary potassium, pH, and NGIA were significantly increased only after consumption of melon and orange juices. The pH of melon juice was higher and the PRAL value was more negative compared with orange juice, indicating a higher alkalinity.

CONCLUSIONS

These findings suggested that melon, a noncitrus source of potassium, citrate, and malate, yielded an increase in urinary citrate excretion equivalent to that provided by orange, and hence represents another dietary alternative for the treatment of hypocitraturic stone-formers. Despite its low potassium content, lime also produced comparable increases in citraturia possibly because of its high citric acid content.

Clinical review. Kidney stones 2012: pathogenesis, diagnosis, and management

CONTEXT

The pathogenetic mechanisms of kidney stone formation are complex and involve both metabolic and environmental risk factors. Over the past decade, major advances have been made in the understanding of the pathogenesis, diagnosis, and treatment of kidney stone disease.

EVIDENCE ACQUISITION AND SYNTHESIS

Both original and review articles were found via PubMed search reporting on pathophysiology, diagnosis, and management of kidney stones. These resources were integrated with the authors' knowledge of the field.

CONCLUSION

Nephrolithiasis remains a major economic and health burden worldwide. Nephrolithiasis is considered a systemic disorder associated with chronic kidney disease, bone loss and fractures, increased risk of coronary artery disease, hypertension, type 2 diabetes mellitus, and the metabolic syndrome. Further understanding of the pathophysiological link between nephrolithiasis and these systemic disorders is necessary for the development of new therapeutic options.

Dietary habits in women with recurrent idiopathic calcium nephrolithiasis

Background

Nutrition has been widely recognized to influence the risk of kidney stone formation. Therefore the aim of our study was to assess: a) whether usual diet of women with idiopathic calcium nephrolithiasis (ICN) living in Parma (Northern-Italy) is different compared to healthy controls, b) how their diet differs from Italian National guidelines and c) whether it is related to nephrolithiasis clinical course.

Methods

143 women with recurrent ICN (mean age 43 ± 13 ys) and 170 healthy women (mean age 42 ± 11 ys) were enrolled. All women completed a food frequency questionnaire for the last 60-days and a 3-day dietary diary analysed with a dedicated software.

Results

Stone formers showed a higher consumption of sausages, ham, meat and sweets than healthy controls (43.1% vs 11.1%, 29.4% vs 13.9%, 21.6% vs 4.2%, 66.7% vs 18.1%, p < 0.001). The 3-day diary analysis showed an intake of calories, carbohydrates, lipids and non-discretionary sodium about 10% higher than healthy controls (p < 0.001). Finally, after dividing the population into 3 age groups (≤30, 31-40, > 40 years), the differences described above were amplified in the class ≤30 years, where nephrolithiasis presented a more serious course (shorter recurrence interval, greater stone-rate). In this age group the intake of fruit and vegetables was notably lower than guideline recommendations.

Conclusions

We conclude that the usual diet of women with recurrent ICN is different from controls and characterized by low intake of fruits and vegetables and higher consumption of simple sugars and foods with high protein and salt content. This dietary imbalance could play a role in the ICN pathogenesis, especially in younger women.

This work was financed by grants from Italian Ministry of University and Research as part of a larger project about the prevention of kidney stones (PRIN 2005063822) and by Fondazione per la Ricerca Scientifica Termale (FoRST). No potential conflict of interest relevant to this paper was reported.

Effect of diet orange soda on urinary lithogenicity

Studies have shown that certain beverages decrease urinary lithogenicity by increasing urine citrate excretion. Diet Sunkist Orange soda had the highest concentration of citrate and total alkali content among 12 diet sodas previously assayed. We studied the effect of Diet Sunkist Orange soda consumption on urinary chemistry. Nine healthy men and women ages 26-54 years completed the study. During the control period, subjects drank 36 oz of water for 3 days in addition to their own, self-selected diet and recorded a food diary. During the study period, the subjects drank three 12-oz cans of Diet Sunkist Orange soda a day instead of water, and replicated their diets from the control period. In each period, the subjects performed 24-h urine collections on days 2 and 3. Urine chemical analysis was performed, including urinary citrate levels and pH. Diet Sunkist Orange soda increased urinary citrate excretion by 60 mg/day, which was not statistically significant (95% CI -75 to 195, P value 0.34). There was no significant change in pH from the control period to the study period (pH: 6.29-6.21; 95% CI: -0.09 to 0.25, P = 0.30). Urine volumes and creatinine excretions were not significantly different between the control and study periods. Despite the relatively high citrate and total alkali content of Diet Sunkist Orange soda, the volume consumed in this study (36 oz per day) did not provide sufficient potential base to significantly alter urine composition in healthy subjects with normocitraturia. The effect of Diet Sunkist Orange soda on urinary chemistry in patients with hypocitraturia and nephrolithiasis is not likely to have a clinically significant effect to prevent calcium or uric acid stones.

Lifestyle recommendations to reduce the risk of kidney stones

Kidney stones are increasingly common in wealthy industrialized countries. The most frequent form (80%) is idiopathic calcium stone disease. Eating habits and lifestyle have a direct effect on the lithogenic urinary risk factors and the pathogenesis of this condition. A diet characterized by a high intake of fluids, fruits, and vegetables; a low consumption of salt and protein; and a balanced intake of calcium, fats, and carbohydrates constitutes an efficacious approach to the prevention and treatment of this illness. A correct body weight, regular exercise, and a reduction in stressful life events are also useful preventive actions.

Dietary therapy for patients with hypocitraturic nephrolithiasis

Citrate is an inhibitor of urinary stone formation. Clinical and in vitro data suggest that increasing urine citrate levels will decrease the precipitation of calcium stones. Historically, low urinary citrate has been treated with oral potassium citrate or sodium citrate supplementation, but recent studies have shown the potential of dietary interventions to raise urine citrate levels. Dietary therapy with commercial or homemade beverages is attractive to patients who would prefer nonpharmacological intervention. To date, several drinks have shown promise but no single beverage has been found to consistently raise urine citrate levels in a reproducible fashion. Further research is necessary to develop the ideal dietary therapy for hypocitraturic calcium nephrolithiasis.

Update on the pathophysiology and management of uric acid renal stones

Idiopathic uric acid nephrolithiasis appears to be increasing in prevalence. While it has long been known that low urine pH is associated with uric acid stones, only recently has the pathophysiological basis for this disease emerged. Excessively acidic urine is the decisive risk for uric acid lithogenesis, and patients with diabetes and the metabolic syndrome often hold the company of low urine pH. While association does not imply causation, interesting insights have been made regarding insulin's influence on acid-base physiology. We review recent evidence from both the molecular and clinical realms to underline the importance of [H+] in the development and treatment of uric acid nephrolithiasis.

Citrate, malate and alkali content in commonly consumed diet sodas: implications for nephrolithiasis treatment

PURPOSE

Citrate is a known inhibitor of calcium stone formation. Dietary citrate and alkali intake may have an effect on citraturia. Increasing alkali intake also increases urine pH, which can help prevent uric acid stones. We determined citrate, malate and total alkali concentrations in commonly consumed diet sodas to help direct dietary recommendations in patients with hypocitraturic calcium or uric acid nephrolithiasis.

MATERIALS AND METHODS

Citrate and malate were measured in a lemonade beverage commonly used to treat hypocitraturic calcium nephrolithiasis and in 15 diet sodas. Anions were measured by ion chromatography. The pH of each beverage was measured to allow calculation of the unprotonated anion concentration using the known pK of citric and malic acid. Total alkali equivalents were calculated for each beverage. Statistical analysis was done using Pearson's correlation coefficient.

RESULTS

Several sodas contained an amount of citrate equal to or greater than that of alkali and total alkali as a lemonade beverage commonly used to treat hypocitraturic calcium nephrolithiasis (6.30 mEq/l citrate as alkali and 6.30 as total alkali). These sodas were Diet Sunkist Orange, Diet 7Up, Sprite Zero, Diet Canada Dry Ginger Ale, Sierra Mist Free, Diet Orange Crush, Fresca and Diet Mountain Dew. Colas, including Caffeine Free Diet Coke, Coke Zero, Caffeine Free Diet Pepsi and Diet Coke with Lime, had the lowest total alkali (less than 1.0 mEq/l). There was no significant correlation between beverage pH and total alkali content.

CONCLUSIONS

Several commonly consumed diet sodas contain moderate amounts of citrate as alkali and total alkali. This information is helpful for dietary recommendations in patients with calcium nephrolithiasis, specifically those with hypocitraturia. It may also be useful in patients with low urine pH and uric acid stones. Beverage malate content is also important since malate ingestion increases the total alkali delivered, which in turn augments citraturia and increases urine pH.