Oxalate content of legumes, nuts, and grain-based flours

Underutilized green leafy vegetables: frontier in fortified food development and nutrition

From the ancient period, Green leafy vegetables (GLV) are part of the daily diet and were believed to have several health beneficial properties. Later it has been proved that GLV has outstanding nutritional value and can be used for medicinal benefits. GLV is particularly rich in minerals like iron, calcium, and zinc. These are also rich in vitamins like beta carotene, vitamin E, K, B and vitamin C. In addition, some anti-nutritional elements in GLV can be reduced if it is grown properly and processed properly before consumption. Tropical countries have a wide variety of these green plants such as Red Spinach, Amaranth, Malabar Spinach, Taro Leaf, Fenugreek leaf, Bengal Gram Leaves, Radish Leaves, Mustard Leaves, and many more. This review focuses on listing this wide range of GLVs (in total 54 underutilized GLVs) and their compositions in a comparative manner. GLV also possesses medicinal activities due to its rich bioactive and nutritional potential. Different processing techniques may alter the nutritional and bioactive potential of the GLVs significantly. The GLVs have been considered a food fortification agent, though not explored widely. All of these findings suggest that increasing GLV consumption could provide nutritional requirements necessary for proper growth as well as adequate protection against diseases caused by malnutrition.

A Comprehensive Study on the Chemical Characterization and Neuroprotective Evaluation of Pracaxi Nuts Extracts Obtained by a Sustainable Approach

The Amazonian Pentaclethra macroloba (Willd.) Kuntze nuts contain a lipidic fraction with health-promoting effects, but little is known about the bioactivity of other constituents. In this study, the lipidic fraction obtained using supercritical fluid extraction (SFE) with CO2 was chemically characterized by using lipidomics techniques. The SFE-CO2 residue, named as pracaxi cake, was re-extracted by pressurized liquid extraction following a biorefinery approach. Using a response surface methodology and based on the extraction yield and different in vitro assays, two optimum conditions were obtained: 80% and 12.5% of ethanol at 180 °C. Under these conditions, extraction yield and different in vitro measurements related to neuroprotection were assessed. Chemical characterization of these extracts suggested the presence of triterpenoid saponins and spermidine phenolamides, which were not previously reported in pracaxi nuts. These results suggest that pracaxi oil extraction by-products are a valuable source of bioactive compounds with neuroprotective potential.

Secondary oxalate nephropathy and impact of high-dose vitamin C intake for COVID-19 prevention on a patient with Roux-en-Y gastric bypass: A case report

The current study is important in informing clinicians about the possibility of concurrent oxalate nephropathy caused by Roux-en-Y gastric bypass, high oxalate materials, and high-dose vitamin C intake for COVID-19 prevention.

Proximate composition, minerals, vitamins, phytochemical constituents and anti-nutrient profile of Beilschmiedia mannii seeds and Combretum racemosum leaves for soup preparation

Several vegetables are used in food preparation to improve the aroma, taste, appearance with less attention on the nutrient and anti-nutrient content. This study investigated the proximate, vitamins, minerals and anti-nutrients profile of Beilschmiedia manni seed and Combretum racemosum leaf. Proximate composition, vitamins, mineral analysis and anti-nutrient profile were determined using standard procedures. The proximate analysis revealed that C. racemosum contained high crude protein (19.18%), crude fat (22.20%) and energy value (449.11 kJ) but low carbohydrate (43.15%) compared to B. mannii with the high carbohydrate (64.25%) content. Phytochemical screening revealed the presence of active phytochemicals in both samples. Thiamine, riboflavin and niacin were significantly (p < 0.05) high in B. mannii compared to C. racemosum. The level of macro minerals in B. mannii seeds and C. racemosum leaves was in the order of K > Ph > Na > Mg > Ca. Beilschmiedia mannii seeds and C. racemosum leaves respectively contained 45.00 mg/100 g and 163.00 mg/100 g oxalate, 70.00 mg/100 g and 113.00 mg/100 g phytate, 58.00 mg/100 g and 209.00 mg/100 g of tannin. This study has revealed that B. mannii seeds and C. racemosum leaves are potential sources of essential nutrients, phytochemicals and could play important role in food enrichment, formulation of dietary supplements and in disease managements.

Potential of Continuous Electric Current on Biometrical, Physiological and Quality Characteristics of Organic Tomato

The tomato is one of the most important species in the food sector. For farmers, the increase in yield in greenhouse conditions by keeping a high quality of fruits represents a goal which is very difficult to achieve in these conditions. Therefore, the present study evaluates the influence that a continuous electric current might have on some biometrical, physiological and quality parameters of tomato fruits. The study was carried out in a greenhouse where tomato plants belonging to Qualitet F1 hybrid were treated with different continuous electric currents, under 5 DC sources, stabilized by the laboratory 0–30 V/0–5 A. During the research, the tomato plants were exposed to different electric current intensities or voltages on the plants or in the soil (T1-0.15 A; T2-0.30 A; T3-0.45 A; T4-1.5 V; T5-1.5 V-soil). The tomato plant samples were compared with an untreated control. In order to determine the influence of a continuous electric current, observations and determinations were made on tomato plants and fruits. The results highlighted significant differences between the treated and not treated plants, regarding the plant height, yield, firmness, acidity, total soluble solids, antioxidant activity, crude and dietary fibres, tannins, oxalates, saponins, α-amylase inhibitors, K, Mg, Fe and Zn content. Depending on the intensity of the electric current and the manner of application, the biometrical, physiological and quality parameters of tomato fruits were differently influenced. Both positive and negative influences were registered. More experiments are needed in order to establish a relation between the electric current intensity and the manner of application which can lead to better and higher tomato yields and quality in greenhouse conditions.

Revisiting Reduction of CO2 to Oxalate with First-Row Transition Metals: Irreproducibility, Ambiguous Analysis, and Conflicting Reactivity

Construction of higher C_≥2 compounds from CO₂ constitutes an attractive transformation inspired by nature's strategy to build carbohydrates. However, controlled C-C bond formation from carbon dioxide using environmentally benign reductants remains a major challenge. In this respect, reductive dimerization of CO₂ to oxalate represents an important model reaction enabling investigations on the mechanism of this simplest CO₂ coupling reaction. Herein, we present common pitfalls encountered in CO₂ reduction, especially its reductive coupling, based on established protocols for the conversion of CO₂ into oxalate. Moreover, we provide an example to systematically assess these reactions. Based on our work, we highlight the importance of utilizing suitable orthogonal analytical methods and raise awareness of oxidative reactions that can likewise result in the formation of oxalate without incorporation of CO₂. These results allow for the determination of key parameters, which can be used for tailoring of prospective catalytic systems and will promote the advancement of the entire field.

Oxalate nephropathy: a review

This review describes the clinical and pathological features of oxalate nephropathy (ON), defined as a syndrome of decreased renal function associated with deposition of calcium oxalate crystals in kidney tubules. We review the different causes of hyperoxaluria, including primary hyperoxaluria, enteric hyperoxaluria and ingestion-related hyperoxaluria. Recent case series of biopsy-proven ON are reviewed in detail, as well as the implications of these series. The possibility of antibiotic use predisposing to ON is discussed. Therapies for hyperoxaluria and ON are reviewed with an emphasis on newer treatments available and in development. Promising research avenues to explore in this area are discussed.

Is There Such a Thing as "Anti-Nutrients"? A Narrative Review of Perceived Problematic Plant Compounds

Plant-based diets are associated with reduced risk of lifestyle-induced chronic diseases. The thousands of phytochemicals they contain are implicated in cellular-based mechanisms to promote antioxidant defense and reduce inflammation. While recommendations encourage the intake of fruits and vegetables, most people fall short of their target daily intake. Despite the need to increase plant-food consumption, there have been some concerns raised about whether they are beneficial because of the various ‘anti-nutrient’ compounds they contain. Some of these anti-nutrients that have been called into question included lectins, oxalates, goitrogens, phytoestrogens, phytates, and tannins. As a result, there may be select individuals with specific health conditions who elect to decrease their plant food intake despite potential benefits. The purpose of this narrative review is to examine the science of these ‘anti-nutrients’ and weigh the evidence of whether these compounds pose an actual health threat.

Dietary Recommendations for Bariatric Patients to Prevent Kidney Stone Formation

Bariatric surgery (BS) is one of the most common and efficient surgical procedures for sustained weight loss but is associated with long-term complications such as nutritional deficiencies, biliary lithiasis, disturbances in bone and mineral metabolism and an increased risk of nephrolithiasis, attributed to urinary metabolic changes resultant from low urinary volume, hypocitraturia and hyperoxaluria. The underlying mechanisms responsible for hyperoxaluria, the most common among all metabolic disturbances, may comprise increased intestinal oxalate absorption consequent to decreased calcium intake or increased dietary oxalate, changes in the gut microbiota, fat malabsorption and altered intestinal oxalate transport. In the current review, the authors present a mechanistic overview of changes found after BS and propose dietary recommendations to prevent the risk of urinary stone formation, focusing on the role of dietary oxalate, calcium, citrate, potassium, protein, fat, sodium, probiotics, vitamins D, C, B6 and the consumption of fluids.

Antinutrients in Plant-based Foods: A Review

Modern society has easy access to a vast informational database. The pursuit of sustainable green and healthy lifestyle leads to a series of food choices. Therefore, it is of importance to provide reliable, comprehensive and up-to-date information about food content including both nutritional and antinutritional elements.

Nutrients are associated with positive effects on human health. Antinutrients, on the other hand, are far less popular for the contemporary man. They are highly bioactive, capable of deleterious effects as well as some beneficial health effects in man, and vastly available in plant-based foods. These compounds are of natural or synthetic origin, interfere with the absorption of nutrients, and can be responsible for some mischievous effects related to the nutrient absorption. Some of the common symptoms exhibited by a large amount of antinutrients in the body can be nausea, bloating, headaches, rashes, nutritional deficiencies, etc. Phytates, oxalates, and lectins are few of the well-known antinutrients.

Science has acknowledged several ways in order to alter the negative influence antinutrients exhibiting on human health. Mechanical, thermal and biochemical approaches act synergistically to provide food with lower antinutritional levels.

The purpose of this review was to synthesize the availability of antinutrients, clear their effect on the human body, and commemorate possible paths to disable them. This review provides links to the available literature as well as enables a systematic view of the recently published research on the topic of plant-based antinutrients.

Fe and Zn in vitro bioavailability in relation to antinutritional factors in biofortified beans subjected to different processes

The present work evaluated the effect of different processes in relation to mineral content and its bioavailability, as well as the effect of phytate and oxalate contents in biofortified beans. The following treatments were evaluated: raw beans (RB), cooked and oven-dried soaked beans (BOS), cooked and freeze-dried soaked beans (BFS), cooked and oven-dried beans without soaking (BOWS) and cooked and freeze-dried beans without soaking (BFWS). The mineral contents (mg per 100 g) varied between 3.56 and 5.80 (iron), 20.26 and 89.32 (calcium) and 1.56 and 2.38 (zinc). The oxalate content varied from 3.74 to 10.54 mg per 100 g. The total phytate content ranged from 1803.23 to 2.301 mg per 100 g. Regarding mineral bioavailability in Caco-2 cells, iron retention ranged from 8.89 to 17.85% and uptake was from 12.07 to 13.74 μg. On the other hand, the zinc retention was from 92.27 to 98.6% and uptake ranged from 24.68 to 36.26 μg. The different forms of bean processing can contribute to the mineral profile of this legume, in addition to increasing the bioavailability of some minerals, such as iron and zinc.

Changes in levels of phytic acid, lectins and oxalates during soaking and cooking of Canadian pulses

Raw and processed (soaked or cooked) seeds of peas, lentils, chickpeas, fava beans and common beans were studied for their contents of antinutritional factors (lectins, phytic acid, total and soluble oxalates), along with soybean as a control. Analysis of variance indicated that legume type, treatment and their interactive effects were significant on these antinutrients. The raw soybean seed was found to contain the highest levels of lectins (692.8 HU/mg), phytic acid (22.91 mg/g), total oxalate (370.5 mg/100 g) and soluble oxalate (200.7 mg/100 g) among all investigated seeds. Relatively high contents of lectins were detected in beans (87.69-88.59 HU/mg) and other pulses ranging from 2.73-11.07 HU/mg. Phytic acid in Canadian pulses varied slightly from 8.55-22.85 mg/g. Total oxalates were variable, ranging from 244.7-294.0 mg/100 g in peas, 168.6-289.1 mg/100 g in lentils, 241.5-291.4 mg/100 g in fava beans, 92.2-214.0 mg/100 g in chickpeas and 98.86-117.0 mg/100 g in common beans. Approximately 24-72% of total oxalate appeared to be soluble in all investigated pulses. Soaking the seeds in distilled water significantly decreased the contents of lectins (0.11-5.18%), total oxalate (17.40-51.89%) and soluble oxalate (26.66-56.29%), but had no impact on phytic acid. The cooking process was found to be more effective in reducing levels of all the investigated antinutritional factors, except phytic acid in common beans and soybean.

Phytate/calcium molar ratio does not predict accessibility of calcium in ready-to-eat dishes

BACKGROUND

Phytic acid (PA), a naturally occurring compound of plant food, is generally considered to affect mineral bioavailability. The aim of this study was to investigate the reliability of the PA/calcium molar ratio as a predictive factor of calcium accessibility in composed dishes and their ingredients.

RESULTS

Dishes were chosen whose ingredients were rich in Ca (milk or cheese) or in PA (whole-wheat cereals) in order to consider a range of PA/Ca ratios (from 0 to 2.4) and measure Ca solubility using an in vitro approach. The amounts of soluble Ca in composed dishes were consistent with the sum of soluble Ca from ingredients (three out of five meals) or higher. Among whole-wheat products, bread showed higher Ca accessibility (71%, PA/Ca = 1.1) than biscuits (23%, PA/Ca = 0.9) and pasta (15%, PA/Ca = 1.5), and among Ca-rich ingredients, semi-skimmed milk displayed higher Ca accessibility (64%) than sliced cheese (50%) and Parmesan (38%). No significant correlation between the PA/Ca ratio and Ca accessibility was found (P = 0.077).

CONCLUSION

The reliability of the PA/Ca ratio for predicting the availability of calcium in composed dishes is unsatisfactory; data emphasized the importance of the overall food matrix influence on mineral accessibility. © 2016 Society of Chemical Industry.

Studies on physico-chemical and cooking characteristics of rice bean varieties grown in NE region of India

Rice bean (Vigna umbellata) is grown in South and Southeast Asia, and the bean has gained importance due to its nutritional strength in terms of dietary fiber, quality protein and minerals. In current study, the nutritional and functional components, cooking and thermo-gravimetric properties of eleven rice bean varieties from NE India were investigated. Results revealed that the major nutrients among the varieties ranged as follows: 54.21-60.49% carbohydrates, 15.64-21.60% protein, 1.22-2.3% fat, 5.53-6.56% crude fibre, 3.34-3.8% ash; while the functional, anti-nutritional factors and mineral were present as 1189.32-1645.8 mg gallic acid equivalent (GAE)/100 g polyphenols, 205.38-432.14 mg/100 g phytic acid, 23.14-34.12 mg/100 g oxalate, 690.7-1589.5 mg/100 g saponins, 49.90-158.17 μg/100 g hydrocyanide, 111.51-168 calcium, 5.50-10.44 zinc, 3.72-8.37 iron. Principal component analysis revealed that varieties with higher calcium, iron and ash content had lower cooking time, swelling ratio, and cooked grain hardness. It is also revealed that varieties with higher weight loss at sixth stage in thermogravimetric graph had lower carbohydrate and higher protein content. Nagadal variety had higher fat, potassium, magnesium, calcium, sodium, iron, copper and chromium content and better cooking quality as compared to the other varieties. The study revealed that Nagadal variety was superior to other varieties with respect to mineral content, cooking and thermal properties and hence have better potential in the development of value added products.

Chronic dietary oxalate nephropathy after intensive dietary weight loss regimen

Background:

Hyperoxaluria has been associated with nephrolithiasis as well as acute and chronic kidney disease. We present a case of end stage renal failure caused by excessive dietary oxalate intake in a dietary weight loss regimen.

Case Presentation:

A 51-year-old Caucasian male with the past medical history of type 2 diabetes mellitus, gout, hypertension and morbid obesity was referred to the primary care clinic after being found pale and easily fatigued. The patient had lost 36 kg over a 7-month period by implementing exercise and intense dietary measures that included 6 meals of spinach, kale, berries, and nuts. Physical examination revealed a blood pressure of 188/93 mm Hg with sunken eyes and dry mucus membranes. Laboratory workup was notable for blood urea nitrogen of 122 mg/dL, creatinine of 12 mg/dL, and estimated glomerular filtration rate (eGFR) of 4.4 mL/min/1.73m2. Patient denied any history of renal disease or renal stones, or taking herbal products, non-steroidal anti-inflammatory drugs, antifreeze (ethylene glycol), or any type of "diet pills." Family history was unremarkable for any renal diseases. After failing intravenous fluid resuscitation, patient was started on maintenance hemodialysis. Abdominal imaging was consistent with chronic renal parenchymal disease with no evidence of nephrolithiasis. Renal biopsy revealed numerous polarized oxalate crystal deposition and diabetic nephropathy class IIA. At this point the patient was instructed to adopt a low oxalate diet. A 24-hour urine collection was remarkable for pH 4.7, citrate <50 mg, and oxalate 46 mg. Importantly, serum oxalate level was undetectable. Repeat renal biopsy 5 months later while patient was still on maintenance hemodialysis revealed persistence of extensive oxalate crystal deposition. Patient has been referred for evaluation for renal transplantation.

Conclusions:

Clinicians need to maintain a high index of suspicion for dietary hyperoxaluria as a potential etiology for acute or chronic kidney failure, particularly in patients pursuing intensive dietary weight loss intervention

Oxalate contents of commonly used Chinese medicinal herbs

Objective

To assess the total and soluble oxalate contents of commonly used Chinese medicinal herbs.

Methods

Twenty-two Chinese medicinal herbs were extracted in both acid and water prior to determination of total and soluble oxalate, respectively. Oxalate was assayed in herbal extracts using a well-established enzymatic procedure.

Results

Among the 22 medicinal herbs, there was significant variation in oxalate content; Houttuynia cordata contained the highest amount of soluble oxalate (2146 mg/100 g) and Selaginella doederleinii contained the lowest amount (71 mg/100 g).

Conclusion

The results indicated that different Chinese medicinal herbs, even from the same family, contain significantly different amounts of oxalate. In susceptible individuals, the use of medicinal herbs with the highest oxalate contents could increase risk of kidney stone formation.

Nutritional Management of Kidney Stones (Nephrolithiasis)

The incidence of kidney stones is common in the United States and treatments for them are very costly. This review article provides information about epidemiology, mechanism, diagnosis, and pathophysiology of kidney stone formation, and methods for the evaluation of stone risks for new and follow-up patients. Adequate evaluation and management can prevent recurrence of stones. Kidney stone prevention should be individualized in both its medical and dietary management, keeping in mind the specific risks involved for each type of stones. Recognition of these risk factors and development of long-term management strategies for dealing with them are the most effective ways to prevent recurrence of kidney stones.

Nephropathy in dietary hyperoxaluria: A potentially preventable acute or chronic kidney disease

Hyperoxaluria can cause not only nephrolithiasis and nephrocalcinosis, but also renal parenchymal disease histologically characterized by deposition of calcium oxalate crystals throughout the renal parenchyma, profound tubular damage and interstitial inflammation and fibrosis. Hyperoxaluric nephropathy presents clinically as acute or chronic renal failure that may progress to end-stage renal disease (ESRD). This sequence of events, well recognized in the past in primary and enteric hyperoxalurias, has also been documented in a few cases of dietary hyperoxaluria. Estimates of oxalate intake in patients with chronic dietary hyperoxaluria who developed chronic kidney disease or ESRD were comparable to the reported average oxalate content of the diets of certain populations worldwide, thus raising the question whether dietary hyperoxaluria is a primary cause of ESRD in these regions. Studies addressing this question have the potential of improving population health and should be undertaken, alongside ongoing studies which are yielding fresh insights into the mechanisms of intestinal absorption and renal excretion of oxalate, and into the mechanisms of development of oxalate-induced renal parenchymal disease. Novel preventive and therapeutic strategies for treating all types of hyperoxaluria are expected to develop from these studies.

Oxalate nephropathy and intravenous vitamin C

Oxalate nephropathy is a rare condition characterized by extensive calcium oxalate deposition in the renal tubules, resulting in kidney injury. There are primary forms of the disease that arise from genetic mutation causing overproduction of oxalate. More commonly, this condition is seen as a secondary phenomenon. The clinical presentation is nonspecific, with acute kidney injury and normal serologic study results. The characteristic finding on kidney biopsy is the presence of acute tubular injury associated with polarizable crystals in the tubular lumen and epithelial cytoplasm. We present a case of acute oxalate nephropathy in a patient with underlying systemic lupus erythematosus who recently received intravenous vitamin C.

Flow injection determination of carboxylate, phosphate, and sulfhydryl compounds using metal exchange complexation

The determination of carboxylate, phosphorous, and sulfhydryl compounds has been studied using flow injection by measuring the decrease in absorbance of the Fe(III)-salicylate complex due to preferential ligand interaction with ferric ion. Targeted compounds include polycarboxylates such as sodium citrate, sodium oxalate, and EDTA, anionic phosphorous compounds such as sodium monofluoroorthophosphate, sodium trimetaphosphate, and sodium hexametaphosphate, and sulfhydryl compounds such as cysteine, glutathione, and captopril. Initial flow injection optimization has focused on citrate based on its ability to replace salicylate ion in the Fe(III)-salicylate complex causing a decrease in absorbance at 525 nm proportional to the citrate concentration. Two flow injection analysis methods are developed. In the first method, offline reaction flow injection, sodium citrate dissolved in 100 μmol L(-1) Fe-salicylate is injected in a carrier solution of 100 μmol L(-1) Fe-salicylate. The decrease in peak area is linear over a range of 1.36-109 μmol L(-1) using a flow rate of 1 mL min(-1) and an injection volume of 100 μL. The effect of pH on the Fe-salicylate complex absorbance is studied from 1 to 3.5; pH 3 shows both a high and stable complex absorbance in the visible range which provided important potential selectivity over UV detection. The limit of detection is found to be less than 57 nmol L(-1) depending on the Fe(III)-salicylate concentration used. The second method is reverse flow injection using the sample as a flowing stream in which 3 mmol L(-1) Fe(III)-salicylate is injected and the decrease in the response with increased sample concentration was monitored. The commercially available pharmaceutical product (Citroma)(®) is used to assess the accuracy and precision of the two proposed methods as compared to a reference method.

Some Canadian-grown potato cultivars contribute to a substantial content of essential dietary minerals

Potato consumption provides significant dietary contributions to several essential minerals, but the effects of cultivar and planting site are not well-understood. The mineral content of 16 cultivars, grown at 5 locations, was measured using inductively coupled plasma-optical emission spectroscopy and evaluated on a per serving basis for percent recommended daily intake (% RDI), emphasizing some minerals where global deficiencies are common (calcium, iron, selenium, and zinc). Discriminant analysis showed that both genotype and growing location were important. Differences in mineral content occurred between cultivars at each site, specific cultivars at different sites, and collectively between sites. 'Freedom', 'Yukon Gold', and particularly the very stable mineral source 'Russet Burbank' contributed most to the % RDI for minerals. One serving per day of these cultivars provides a significant contribution to the % RDI for the macrominerals magnesium, phosphorus, and potassium and the trace minerals copper, iron, selenium, and zinc.

Calcium oxalate biomineralization by Piloderma fallax in response to various levels of calcium and phosphorus

Piloderma fallax is an ectomycorrhizal fungus commonly associated with several conifer and hardwood species. We examined the formation of calcium oxalate crystals by P. fallax in response to calcium (0.0, 0.1, 0.5, 1, and 5 mM) and phosphorus (0.1 and 6 mM) additions in modified Melin-Norkrans agar medium. Both calcium and phosphorus supplementation significantly affected the amount of calcium oxalate formed. More calcium oxalate was formed at high P levels. Concentrations of soluble oxalate in the fungus and medium were higher at low P levels. There was a strong positive linear relationship between Ca level and calcium oxalate but only under conditions of phosphorus limitation. Calcium oxalate crystals were identified as the monohydrate form (calcium oxalate monohydrate [COM] whewellite) by X-ray diffraction analysis. Prismatic, styloid, and raphide forms of the crystals, characteristic COM, were observed on the surface of fungal hyphae by scanning electron microscopy. P. fallax may be capable of dissolving hyphal calcium oxalate under conditions of limited Ca. The biomineralization of calcium oxalate by fungi may be an important step in the translocation and cycling of Ca and P in soil.

Food oxalate: factors affecting measurement, biological variation, and bioavailability

Food and nutrition professionals provide medical nutrition therapy for patients with kidney stones. If the stones contain oxalate or the patient has been diagnosed with hyperoxaluria, reduction of dietary oxalate may be appropriate. Differences in oxalate values for a single food may be due to analytical methods, and/or biological variation from several sources, including cultivar, time of harvest, and growing conditions. Bioavailability of food oxalate and, thus, urine oxalate, will also be affected by salt forms of oxalate, food processing and cooking methods, meal composition, and the presence of Oxalabacter formigenes in the patient's gut. Dietary advice for reducing urinary oxalate should include both reduction of dietary oxalate and simultaneous consumption of calcium-rich food or supplement to reduce oxalate absorption.

Enhanced kidney stone fragmentation by short delay tandem conventional and modified lithotriptor shock waves: a numerical analysis

PURPOSE

We evaluated the effectiveness of modified lithotriptor shock waves using computer models.

MATERIALS AND METHODS

Finite element models were used to simulate the propagation of lithotriptor shock waves in human renal calculi in vivo. Kidney stones were assumed to be spherical, homogeneous, isotropic and linearly elastic, and immersed in a continuum fluid. Single and tandem shock wave pulses modified to intensify the collapse of cavitation bubbles near the stone surface to increase fragmentation efficiency and suppress the expansion of intraluminal bubbles for decreased vascular injury were analyzed. The effectiveness of the modified shock waves was assessed by comparing the states of loading in the renal calculi induced by these shock waves to those produced by conventional shock waves.

RESULTS

Our numerical simulations revealed that modified shock waves produced marginally lower stresses in spherical renal calculi than those produced by conventional shock waves. Tandem pulses of conventional or modified shock waves produced peak stresses in the front and back halves of the renal calculi. However, the single shock wave pulses generated significant peak stresses in only the back halves of the renal calculi.

CONCLUSIONS

Our numerical simulations suggest that for direct stress wave induced fragmentation modified shock waves should be as effective as conventional shock waves for fragmenting kidney stones. Also, with a small interval of 20 microseconds between the pulses tandem pulse lithotripsy using modified or conventional shock waves could be considerably more effective than single pulse lithotripsy for fragmenting kidney stones.

Oxalate content of cereals and cereal products

Detailed knowledge of food oxalate content is of essential importance for dietary treatment of recurrent calcium oxalate urolithiasis. Dietary oxalate can contribute considerably to the amount of urinary oxalate excretion. Because cereal foods play an important role in daily nutrition, the soluble and total oxalate contents of various types of cereal grains, milling products, bread, pastries, and pasta were analyzed using an HPLC-enzyme-reactor method. A high total oxalate content (>50 mg/100 g) was found in whole grain wheat species Triticum durum (76.6 mg/100 g), Triticum sativum (71.2 mg/100 g), and Triticum aestivum (53.3 mg/100 g). Total oxalate content was comparably high in whole grain products of T. aestivum, that is, wheat flakes and flour, as well as in whole grain products of T. durum, that is, couscous, bulgur, and pasta. The highest oxalate content was demonstrated for wheat bran (457.4 mg/100 g). The higher oxalate content in whole grain than in refined grain cereals suggests that oxalic acid is primarily located in the outer layers of cereal grains. Cereals and cereal products contribute to the daily oxalate intake to a considerable extent. Vegetarian diets may contain high amounts of oxalate when whole grain wheat and wheat products are ingested. Recommendations for prevention of recurrence of calcium oxalate stone disease have to take into account the oxalate content of these foodstuffs.