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Bioavailability of soluble oxalate from spinach eaten with and without milk products
Abstract
Leafy vegetables such as spinach (Spinacia oleracea) are known to contain moderate amounts of soluble and insoluble oxalates. Frozen commercially available spinach in New Zealand contains 736.6+/-20.4 mg/100g wet matter (WM) soluble oxalate and 220.1+/-96.5mg/100g WM insoluble oxalate. The frozen spinach contained 90mg total calcium/100g WM, 76.7%of this calcium was unavailable as it was bound to oxalate as insoluble oxalate. The oxalate/calcium (mEq) ratio of the frozen spinach was 4.73. When frozen convenience food is grilled there is no opportunity for the soluble oxalates to be leached out into the cooking water and discarded. Soluble oxalates, when consumed, have the ability to bind to calcium in the spinach and any calcium in foods consumed with the spinach, reducing the absorption of soluble oxalate. In this experiment 10 volunteers ingested 100g grilled spinach alone or with 100g additions of cottage cheese, sour cream and sour cream with Calci-Trim milk (180 g) and finally, with 20g olive oil. The availability of oxalate in the spinach was determined by measuring the oxalate output in the urine over a 6-hour and 24-hour period after intake of the test meal. The mean bioavailability of soluble oxalate in the grilled spinach was 0.75+/-0.48% over a 6-hour period after intake and was 1.93+/-0.85% measured over a 24-hour period. Addition of sour cream and Calci-Trim milk reduced the availability of the oxalate in the spinach significantly (P<0.05) in both the 6-hour and 24-hour collection periods.
... The addition of food ingredients containing a high calcium content to foods containing high soluble oxalate contents has been shown to significantly reduce the soluble oxalate content of the final product [9]. Baking taro leaves with milk [10,11] and with spinach leaves [12] has also been shown to be effective. The addition of four different calcium salts during the preparation of a green juice made from spinach leaves was also very effective at reducing the soluble oxalate content of the final juice [12]. ...
... Baking taro leaves with milk [10,11] and with spinach leaves [12] has also been shown to be effective. The addition of four different calcium salts during the preparation of a green juice made from spinach leaves was also very effective at reducing the soluble oxalate content of the final juice [12]. The preparation of pesto and a juice from fat hen also offers the possibility of reducing the soluble oxalate of the final product by the addition of calcium-containing ingredients. ...
... It is interesting to note that the addition of a food source of calcium (dry powdered Parmesan cheese) to the pesto increased the insoluble oxalate content and, thus, decreased the available soluble oxalate, whereas the addition of calcium chloride to the juice had little effect. The addition of Parmesan cheese to the pesto mix had a similar effect as the addition of milk to taro leaves [10,11] and spinach leaves [12], while the addition of calcium chloride during the preparation of juice from fat hen leaves was not as effective as the addition of calcium chloride during the processing of rhubarb stems [9]. In this present experiment, it is possible that the addition of the other ingredients containing high fiber contents during the preparation of juice from fat hen leaves may have had the effect of reducing the overall soluble oxalate contents of the juice. ...
The total, soluble, and insoluble oxalate contents of fresh and wok-fried fat hen (Chenopodium album) leaves were extracted and measured using High pressure liquid chromatography. The total oxalate content of the raw leaves was 1112.4 mg/100 g dry matter (DM), and the levels were significantly reduced by boiling (682.8 mg/100 g DM) or cooking the leaves in a wok (883.6 mg/100 g DM). The percentages of soluble oxalate contents in the total oxalates of the raw and boiled leaves were similar (mean 75%), while the proportion of soluble oxalate content in the wok-fried leaves was reduced to 53.4% of the total, giving a significant increase in the insoluble oxalate content of the wok-fried leaves. The percentage of insoluble calcium in the total calcium was significantly reduced (p < 0.05) when the leaves were boiled, but the insoluble oxalate content significantly increased (67.2%) in the wok-fried leaves when compared to the content of the original raw leaves. Processing the cooked leaves into pesto or extracting the juice gave final products that contained significantly reduced total and soluble oxalate contents. The addition of calcium chloride to the juice caused a very small reduction in the soluble oxalate content in the juice.
... The addition of food ingredients containing a high calcium content to foods containing high soluble oxalate contents has been shown to significantly reduce the soluble oxalate content of the final product [9]. Baking taro leaves with milk [10,11] and with spinach leaves [12] has also been shown to be effective. The addition of four different calcium salts during the preparation of a green juice made from spinach leaves was also very effective at reducing the soluble oxalate content of the final juice [12]. ...
... Baking taro leaves with milk [10,11] and with spinach leaves [12] has also been shown to be effective. The addition of four different calcium salts during the preparation of a green juice made from spinach leaves was also very effective at reducing the soluble oxalate content of the final juice [12]. The preparation of pesto and a juice from fat hen also offers the possibility of reducing the soluble oxalate of the final product by the addition of calcium-containing ingredients. ...
... It is interesting to note that the addition of a food source of calcium (dry powdered Parmesan cheese) to the pesto increased the insoluble oxalate content and, thus, decreased the available soluble oxalate, whereas the addition of calcium chloride to the juice had little effect. The addition of Parmesan cheese to the pesto mix had a similar effect as the addition of milk to taro leaves [10,11] and spinach leaves [12], while the addition of calcium chloride during the preparation of juice from fat hen leaves was not as effective as the addition of calcium chloride during the processing of rhubarb stems [9]. In this present experiment, it is possible that the addition of the other ingredients containing high fiber contents during the preparation of juice from fat hen leaves may have had the effect of reducing the overall soluble oxalate contents of the juice. ...
The total, soluble and insoluble oxalate contents of fresh and wok-fried fat hen (Chenopodium album) leaves were extracted and measured using HPLC chromatography. The total oxalate content of the raw leaves was 1112.4 mg/100 g dry matter (DM), and the levels were significantly reduced by boiling (682.8 mg/100 g DM) or cooking the leaves in a wok (883.6 mg/100 g DM). The percentages of soluble oxalate contents in the total oxalates of the raw and boiled leaves were similar (mean 75%), while the proportion of soluble oxalate content in the wok-fried leaves were reduced to 53.4% of the total, giving a significant increase in the insoluble oxalate content of the wok-fried leaves. The percentage of insoluble calcium in the total calcium was significantly reduced (P < 0.05) when the leaves were boiled but the insoluble oxalate content significantly increased (67.2%) in the wok-fried leaves when compared to the content of the original raw leaves. Processing the cooked leaves into pesto or extracting the juice gave final products that contained significantly reduced total and soluble oxalate contents. The addition of calcium chloride to the juice made a very small reduction in the soluble oxalate content in the juice.
... Boiling and soaking may reduce the soluble oxalate content of foods (Oscarsson & Savage, 2007) because the soluble oxalate that leaches into the water is discarded in European cooking. Addition of extra calcium to oxalate rich foods can decrease the soluble oxalate and, hence, reduce the uptake of oxalate (Albihn & Savage 2001;Brogren & Savage 2003). The absorption of soluble oxalates into the body poses problems as it has no metabolic use in the tissues so must be excreted by the kidneys; this can lead to the development of kidney stones. ...
... A number of foods contain high level of oxalates including spinach, rhubarb, beets, nuts, chocolate, wheat bran, black tea and strawberries (Charrier et al., 2002;Brogren & Savage, 2003;Savage et al., 2003). Oxalic acid levels are higher in plants than in meat and dairy products, which can be considered as oxalate-free when planning a low oxalate diet. ...
... In general, the concentration of oxalates varies widely in plants. Some cultivars of spinach contain oxalate in the range of 700-900 mg/100 g fresh weight (FW) (Brogren & Savage, 2003;Morrison & Savage, 2003), while other cultivars can have around 1700 mg/100 g FW (Savage et al., 2000) (Appendix 1). ...
... Jaworska (2005b) reported that the soluble oxalate content of spinach was 59-81% of the total oxalate content while Savage et al. (2000) reported that spinach grown in New Zealand contained 80-87% soluble oxalate. High dietary soluble oxalate can bind to calcium from other foods consumed at the same time forming insoluble oxalates and reducing absorption of calcium from the intestine (Brogren and Savage, 2003;Morrison and Savage, 2003;Taylor and Curhan, 2004;Siener et al., 2006). Conversely if high amounts of soluble oxalates are absorbed from the small intestine, stone formation in the kidney may occur due to combination with calcium as the oxalates are excreted (Noonan and Savage, 1999). ...
... The high fat content in palak paneer was due to the addition of paneer, which contained 44% fat. It has been suggested that oil or fat in a food could bind to calcium in the gastrointestinal tract, resulting in less calcium being available to bind to soluble oxalate leading to more oxalate being absorbed by the body (Brogren and Savage, 2003). However the consumption of spinach with olive oil did not change the output of urinary oxalate, indicating that the fat content of the test meal had no effect on the absorption of oxalate from the digestive tract (Brogren and Savage, 2003). ...
... It has been suggested that oil or fat in a food could bind to calcium in the gastrointestinal tract, resulting in less calcium being available to bind to soluble oxalate leading to more oxalate being absorbed by the body (Brogren and Savage, 2003). However the consumption of spinach with olive oil did not change the output of urinary oxalate, indicating that the fat content of the test meal had no effect on the absorption of oxalate from the digestive tract (Brogren and Savage, 2003). In contrast, Finch et al. (1981) showed that the mean bioabsorption of oxalates was higher (8.5-9%) in the case of peanut and chocolate, which contained high levels of fat compared to spinach which contain low levels of fat and resulted in a 1.5% absorption of oxalates. ...
... High levels of calcium, magnesium and iron decrease the bioavailability of oxalates because of formation of insoluble oxalate salts (Hanson et al., 1989). Addition of foods high in calcium decreases the content of soluble oxalates (Brogren & Savage, 2003). Recently, it was found that silver beet leaves cooked in tap water contained 1783 ± 187 mg total oxalate 100 g )1 dry matter (DM) and 342 ± 48 mg soluble oxalate 100 g )1 DM, while silver beet leaves cooked in standard milk contained 1912 ± 36 mg total oxalate 100 g )1 DM and only 102 ± 13 mg soluble oxalate 100 g )1 DM (Simpson et al., 2009). ...
... The percentage of total calcium bound as calcium oxalate ranged from 26% to 63% of the total calcium content of the test meals (Table 3). This is lower than the value (76.7%) previously reported by Brogren & Savage (2003) for grilled spinach. In the case of the yoghurt meal, 161.5 mg of calcium was supplied from the yoghurt and the silver beet leaves therefore an excess of calcium was supplied, which could have bound to the free oxalate ion (C 2 O 4 2) ) in the test meals. ...
... The individual reference blank values ranged from 2.8 to 18.9 mg per 6 h (mean 6.35 ± 1.24 mg per 6 h) and increased to a mean of 10.89 ± 0.96 mg per 6 h after ingestions of stir-fried silver beet leaves. However, the mean urinary output of total oxalates over 6 h after consumption of stir-fried silver beet leaves is low when compared to the mean urinary output reported for grilled spinach (14.0 ± 3.7 mg per 6 h) (Brogren & Savage, 2003). The absorption of soluble oxalates decreased when yoghurt was added to the food, and these results are supported by a study carried out by Brogren & Savage (2003) feeding spinach and calcium sources (milk and sour cream) as test meals. ...
Silver beet (Beta vulgaris var. cicla) leaves contain oxalates, and the addition of yoghurt, a food rich in calcium, to stir-fried leaves was investigated as a way of reducing the soluble oxalate content. Fourteen participants ingested 115 g stir-fried silver beet leaves with or without standard yoghurt and low-fat yoghurt, respectively. Stir-fried silver beet leaves contained 209.1 ± 0.1 mg of total oxalates per meal fresh weight (FW) and 109.2 ± 0.1 mg of soluble oxalates per meal FW. The proportion of soluble oxalates was reduced from 52% to a mean of 30% of the total oxalates when standard yoghurt or low-fat yoghurt was added. The mean absorption of oxalate was determined by measuring the output of oxalate in the urine over a 6-h period following ingestion of the meals. The mean absorption of oxalate from stir-fried silver beet leaves was 2.41%, which reduced to 1.10% and 0.89% when consumed with standard yoghurt and low-fat yoghurt, respectively.
... Before ensiling and after 120 days of maturation, the physical properties for fleig score (Alçiçek and Özkan, 1997), Weende analysis (DM, CP, EE, ash) (Bulgurlu and Ergül, 1978), volatile fatty acids (VFA) (Hard and Horn, 1987), total oxalate, insoluble and soluble oxalate analysis (Brogren and Savage, 2003) were performed for the silages, and Fleig scores were determined (Kılıç, 1986). ...
... Oxalate analyses of rumen fluids, blood samples and feed materials (Table 4) were conducted using high-performance liquid chromatography for total oxalate and insoluble oxalate. Soluble oxalate is determined as total oxalate-insoluble oxalate (Brogren and Savage, 2003). Blood Ca analyses were made with an autoanalyzer (Roche/Hitachi 912 Autoanalyzer, Roche Diagnostics GmbH, Germany) and feed Ca analyses were performed with a spectrometer (AAS, THERMO Solar AA Series spectrometer). ...
This study was carried out to eliminate the toxic effect of soluble oxalate in sugar beet pulp (SBP) by ensiling and adding Ca during ensiling and to determine the effects of the obtained silage on sheep. The study was based on two experiments. For the first experiment, the laboratory silages were prepared as SBP alone with the addition of molasses and straw at different levels of dry matter and Ca. After fermentation for 120 days, the Fleig scores, physical properties, Weende analysis, and oxalate analysis were performed. This laboratory trial showed that the content of the soluble oxalate could be reduced to nontoxic levels by ensiling and adding Ca. For the second experiment, SBP silage with 30% dry matter (DM) and 45 mg/kg SBP were prepared according to the results of the first experiment. This silage was fed to 36 sheep divided into six groups. During the experiment, blood samples and rumen fluid was collected every 14 days during the experiment, and the body weights were controlled. The results of this experiment showed that the soluble oxalate amount of SBP decreased to a tolerable level by the rumen. Thus, ensiling SBP with barley straw, molasses, urea, and di-calcium phosphate (DCP), as a calcium source, showed that soluble oxalate levels of SBP could be reduced levels below the toxic levels, and added to sheep ratio as 60%.
... octreotide, orlistat, mycophenolate) [4][5][6][7][8][9][10][11]. Additionally, ethylene glycol (antifreeze) ingestion or high intake of vitamin C, along with dietary deficiency of magnesium or calcium, has also been known to cause hyperoxaluria and oxalate crystal formation [12][13][14]. ...
... Lastly, this case is unique because of the patient's large daily consumption of water and calcium, and low consumption of vitamin C, which have all been shown to be significant factors in calcium oxalate deposition [13,14]. In an attempt to find the cause of this patient's susceptibility to diet-induced secondary oxalate nephropathy, we came upon a study that showed mice with greater levels of the cryopyrin protein initiated a larger inflammatory response leading to greater renal injury when given an oxalate-rich diet [20]. ...
... Recently, reported levels of total, soluble and insoluble oxalates were in the ranges of: 329.6-1764.7, 266.5-736.6 and 40.2-1400.1 mg/100 g fresh weight (FW) (Akhtar, Israr, Bhatty, & Ali, 2011;Brogren & Savage, 2003;Ghosh Das & Savage, 2013;Noonan & Savage, 1999;Savage, Martensson, & Sedcole, 2009;Savage et al., 2000). Soluble oxalates in plant foods are found bound to Na + , K + and NH 4+ and insoluble oxalates are commonly bound to Ca 2+, Mg 2+ and Fe 2+ (Savage et al., 2000). ...
... Studies have found that soluble oxalate levels decreased when foods with high levels of calcium were consumed along with foods containing high levels of soluble oxalates. The addition of calcium from milk during the cooking process, or calcium salts during manufacturing, was also able to convert the soluble oxalates into insoluble oxalates (Brogren & Savage 2003;Faudon & Savage 2014;Oscarsson & Savage, 2007;Savage, Charrier, & Vanhanen, 2003;Simpson, Savage, Sherlock, & Vanhanen, 2009). ...
Highlights
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Spinach leaf contains high levels of total and soluble oxalates.
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Addition of soluble calcium salts makes small changes to the pH of the homogenate.
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Calcium salts significantly reduce the soluble oxalate content of spinach homogenates.
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Calcium carbonate was the least effective at reducing soluble oxalate content.
Abstract
Spinach (Spinacia oleracea L.) is often used as a base vegetable to make green juices that are promoted as healthy dietary alternatives. Spinach is known to contain significant amounts of oxalates, which are toxic and, if consumed regularly, can lead to the development of kidney stones. This research investigates adding 50 to 500 mg increments of calcium carbonate, calcium chloride, calcium citrate and calcium sulphate to 100 g of raw homogenates of spinach to determine whether calcium would combine with the soluble oxalate present in the spinach. Calcium chloride was the most effective additive while calcium carbonate was the least effective. The formation of insoluble oxalate after incubation at 25°C for 30 minutes is a simple practical step that can be incorporated into the juicing process. This would make the juice considerably safer to consume on a regular basis.
Keywords
Spinach; Soluble oxalate; Calcium salts, pH
... A much higher reduction in oxalates can be obtained if a high-calcium product, such as milk, is added during vegetable processing (Brogren andSavage 2003, Savage et al. 2009). Water with a high calcium content can play a similar role. ...
... The results given in Table 3 show that the percentage of bound calcium depended on the species, but technological and culinary processing did not significantly affect this parameter. According to Brogren and Savage (2003), as much as 77% of calcium in spinach was bound in insoluble oxalates, while Oscarsson and Savage (2007) stated that differences in the amounts of bound calcium in taro leaves depended on their age. ...
The oxalate content of beetroot, carrot, celeriac and parsnip after freezing by traditional and modified methods (the latter resulting in a convenience food product), and after the preparation of frozen products for consumption was evaluated. The highest content of total and soluble oxalates (105 and 82 mg 100 g -1 fresh matter) was found in beetroot. The lowest proportion (55%) of soluble oxalates was noted in celeriac; this proportion was higher in the remaining vegetables, being broadly similar for each of them. Blanching brought about a significant decrease in total and soluble oxalates in fresh vegetables. Cooking resulted in a higher loss of oxalates. The level of oxalates in products prepared for consumption directly after freezing approximated that before freezing. Compared with the content before freezing, vegetables prepared for consumption by cooking after frozen storage contained less oxalates, except for total oxalates in parsnip and soluble oxalates in beetroot and celeriac. The highest ratio of oxalates to calcium was found in raw beetroot; it was two times lower in raw carrot; five times lower in raw celeriac; and eight times lower in raw parsnip. These ratios were lower after technological and culinary processing. The percentage of oxalate bound calcium depended on the species; this parameter was not significantly affected by the procedures applied. The true retention of oxalates according to Judprasong et al. (2006) was lower than retention cal-culated taking its content in 100 g fresh matter into account.
... Alimentos com elevada quantidade de oxalatos, como o espinafre e a carambola (180-730 mg/100g) não são recomendados para pessoas com tendência a formação de cálculos renais e com outros problemas relacionados a estes tipos de sais, como a artrite, o reumatismo e a gota [25,26] . Brogren & Savage [27] investigaram os teores de fatores antinutrientes em espinafre comercializados na Nova Zelândia e encontram elevados níveis de oxalatos, sendo 736,6±20,4 mg/100g de oxalato solúvel e 220,1±96 mg/100g de oxalato insolúvel. ...
Os alimentos, além de apresentarem substâncias nutritivas essenciais para o desenvolvimento do organismo, podem também conter uma variedade de fatores antinutricionais, como os inibidores de proteínas, oxalatos, taninos, nitritos, dentre outros, assim denominados, devido ao fato de interferirem na absorção de nutrientes, podendo acarretar danos à saúde quando ingeridos em altas quantidades. Assim, esse artigo tem como objetivo discutir as possíveis consequências dos fatores antinutricionais em alimentos, assim como os efeitos do processamento sobre essas substâncias e apresentar estudos biológicos sobre os mesmos.
... Oxalate is better absorbed from black tea or coffee, especially instant coffee (which have a high content of oxalate [223]), when they are consumed in the absence of added milk compared with, for example, tea containing a little milk [224], presumably because the calcium in the milk precipitates the oxalate released from the tea and makes it less available for intestinal absorption. Similarly, oxalate is better absorbed from spinach consumed without the addition of any dairy produce than when served with creamed spinach [225]. Even under normal gastric conditions of pH ($2), any CaOx crystals that are formed in this way and ingested might not all be redissolved within the period of time that they remain in the stomach [132]. ...
The formation of stones in kidney, urinary bladder, or urinary tract, also known as urolithiasis, is a multifactorial disease caused by the accumulation of crystalline deposits in the urine, which poses a great threat to human health. Kidney stones occur as a result of increased supersaturation of the urine causes the dissolved salts and minerals to precipitate, which leads to nucleation, and crystal entities are then accumulated in the renal system. According to stone composition, most urinary stones can be classified as calcium oxalate, struvite, and uric acid stones. Calcium oxalate stones are the most common type of kidney stones and about 80% of urinary stones are composed of calcium oxalate. This review was undertaken to gain an understanding of the mechanisms involved in the formation of kidney stones considering calcium oxalate (CaOx) and struvite crystallization. The classical nucleation and growth theory in aqueous solution and the primary causes that promote crystallization and those that inhibit crystal growth were discussed to understand kidney stone-formation. Several factors may contribute to an increased risk of kidney stone-formation have been discussed in detail.
... The studies to reduce oxalate risk in taro corm by using different sources of calcium are scarce. However some studies have been conducted on spinach (Spinacia oleracea) (Brogren & Savage, 2003, Bong, et al. 2017, raw taro leaves (Savage & Dubois, 2006). ...
... Cooking at 45 minute at 15 psi pressure reduced the total, soluble and insoluble content of all vegetables (silverbeet leaf, silverbeet stem, New Zeland spinach, Spinach, Rhubarb stalk, Beetroot, Broccoli, Carrot, Parsnip) Savage et al. (2000). Freezing followed by grilling reduces the availability of calcium as 76.7% of calcium was bound to oxalate to insoluble oxalate form (Brogren and Savage, 2003). Similarly, the oxalate content of spinach pasta was found to contained highest amount of total (91.8 mg/100g wet weight) and soluble oxalate (53.8 mg/100g wet weight (Liebman and Okombo, 2009). ...
... 4,5 These cases explain why most research on high-oxalate food crops has focused on the amount of soluble oxalate that they contain. [6][7][8][9] Spinach belongs to the Chenopodiaceae family, with a domestic species (Spinacia oleracea L.) and two well-known wild species (S. turkestanica and S. tetrandra) worldwide. 10 Previous studies have discussed the main origins of the spinach, which is commonly cultivated in Central Asia, particularly in Iran. ...
Background:
Oxalic acid is a prevalent antinutrient compound in the human diet, found in large quantities in spinach. On the other hand, spinach is one of the most valuable leafy vegetables in its nutritional and economic values, make it always considered by vegetable producers. So, improving the nutritional value of the spinach through the adjustment of oxalate accumulation is one of the primary purposes of spinach breeding programs. To better understanding, this process acquires inclusive knowledge of the central biosynthetic patterns of oxalic acid based on the major precursor, and the final product of the oxalate is critical.
Results:
We found two central biosynthetic patterns related to the maximum accumulation of oxalate and the one related to the minimum concentration of oxalate. In addition to these three pathways, we also developed a general model using variations of the mentioned compounds among all the studied genotypes.
Conclusion:
Among the obtained patterns, we found a unique type of spinach with high-oxalate accumulation that can be suitable to achieve the desired plant. This noticeable type of spinach has the highest ratio of insoluble to soluble oxalate. It is also accumulated so much with ascorbic acid compared to other types. Our findings in this study also indicate a faint role of ascorbic acid as a precursor to oxalate production in spinach and possibly confirming the significant role of glyoxylate as the most critical precursor in this plant. This article is protected by copyright. All rights reserved.
... Earlier studies have reported a reduction in soluble oxalates in spinach (Brogren and Savage, 2003) and taro (Oscarsson and Savage, 2007) from 49 to 73% when cooked with a milky product. Consuming purslane with a calcium rich food such as milk or sour cream would allow a reduction in the absorption of soluble oxalate since calcium binds with soluble oxalate forming insoluble oxalates which will not be absorbed in the gastrointestinal tract. ...
... Notwithstanding these results, it should be noted that the oxalate content of a food does not necessarily correlate with its bioavailability as minerals such as calcium (28), magnesium (29), and other cations reduce its absorption from the digestive tract (30). The formulas analyzed in this study had highly variable calcium; thus, the potential for oxalate absorption from each formula should be assessed with this in mind. ...
Objectives:
Patients requiring oral and/or enteral nutrition support, delivered via nasogastric, gastric, or intestinal routes, have a relatively high incidence of calcium oxalate (CaOx) kidney stones. Nutrition formulas are frequently made from corn and/or or soy, both of which contain ample oxalate. Excessive oxalate intake contributes to hyperoxaluria (>45 mg urine oxalate/d) and CaOx stones especially when 1) unopposed by concomitant calcium intake, 2) gastrointestinal malabsorption is present, and/or 3) oxalate degrading gut bacteria are limiting or absent. Our objective was to assess the oxalate content of commonly used commercial enteral nutrition formulas.
Methods:
Enteral nutrition formulas were selected from the formulary at our clinical inpatient institution. Multiple samples of each were assessed for oxalate concentration with ion chromatography.
Results:
Results from 26 formulas revealed highly variable oxalate concentration ranging from 4-140 mg oxalate/L of formula. No definitive patterns for different types of formulas (e.g., flavored vs. unflavored, high protein vs. not) were evident. CV for all formulas ranged from 0.68 to 43% (mean±SD 19 ± 12%; median 18%).
Conclusions:
Depending on the formula and amount delivered, patients requiring nutrition support could obtain anywhere from 12-150 mg oxalate/d or more and are thus at risk for hyperoxaluria and CaOx stones.
... Several studies have shown that co-ingestion of foods containing calcium, e.g. milk (rich source of calcium), reduces oxalate bioavailability (Brogren and Savage, 2003). Addition of calcium from milk or from other food sources of calcium reduced the concentration of soluble oxalate that was available for absorption in the small intestine (Radek and Savage, 2008). ...
... However, Morris and Ellis (1985) mentioned that a [phytate]: [calcium] molar ratio > 0.24 will diminish calcium absorption. In addition, phytate was found to increase available soluble oxalate, which can bind calcium, resulting in a reduction of calcium absorption (Brogren & Savage, 2003). The molar ratio of [oxalate]: [calcium] has been reported as hazardous when it is > 2.0 (Israr, Frazier, & Gordon, 2013); the inhibitory effect of phytate on iron absorption is dose-dependent (Gibson et al., 2010) and can occur at a very low phytate concentration. ...
Cassava, rice, and banana flours were used individually to replace wheat flour in cereal-legume-based composite flours. The proximate composition, mineral content, antinutritional effect, mineral molar ratios, and aflatoxin level were investigated. Replacing wheat flour with rice flour significantly (P < 0.05) improved protein, fat, potassium, and phosphorus content in samples. The molar ratios of phytate or oxalate to minerals (calcium and zinc) in all composite flours were lower than the reported critical values, except phytate to iron. However, all samples, except full replacement by rice flour, might not provide adequate zinc bioavailability when the effect of calcium and phytate on zinc absorption was collectively considered. Although all composite flours were contaminated with aflatoxins, only the control composed of wheat flour did not meet the EU regulatory threshold
(4.0 μg/kg) for total aflatoxins. The findings showed that nutritional properties and aflatoxin content of composite flours can be improved by replacement with local crops.
... Table beet, a vegetable crop grown for both its roots and leaves, is considered by the National Kidney Foundation to be a food high in oxalic acid (Council on Renal Nutrition, 2009). Potential health associations of oxalic acid (synonymous in this article with oxalate) are decreased bioavailability of other nutrients and increased risk of kidney stone formation in those predisposed to the disease (Brogren and Savage, 2003;Holmes et al., 2001;Morris et al., 2007;Nakata and McConn, 2006;Robertson and Nordin, 1969). Many commonly consumed food crops contain oxalate such as spinach (Spinacia oleracea), beet, tea (Camellia sinensis), and chocolate. ...
Oxalic acid (C 2 O 42– ) is a compound of interest as a result of its relationship with kidney stone formation and antinutritive properties. Because table beet [ Beta vulgaris ssp. vulgaris (garden beet group)] is considered a high oxalate food, breeding to decrease oxalic acid levels is an area of interest. In this study, a field trial was conducted over 2 years for 24 members of the Chenopodiaceae using two different planting dates to determine if variation exists for both total and soluble oxalic acid levels in roots and leaves. Total and soluble oxalic acid was extracted from homogenized root core and leaf tissue samples and a colorimetric enzymatic assay was used to determine total and soluble oxalic acid levels. Mean values ranged from 722 to 1909 mg/100 g leaf tissue and 553 to 1679 mg/100 g leaf tissue for total and soluble oxalate levels, respectively. Beet cultivar Forono and swiss chard [ B. vulgaris ssp. vulgaris (leaf beet group)] cultivar Burpee's Fordhook Giant Chard produced the respective highest and lowest soluble and total oxalic acid leaf levels. Swiss chard cultivars produced 38% less total oxalate compared with table beet cultivars based on overall means. Root soluble oxalate values ranged from 103 to 171 mg/100 g root tissue and total values ranged from 95 to 142 mg/100 g root tissue. Significant variation for both total and soluble oxalic acid levels were detected, indicating progress could be made toward breeding for lower oxalic acid levels in table beet. However, gains in oxalic acid nutritional quality may be limited because it would take a substantial decrease in levels for table beet to be reclassified as a low oxalate food.
... The gut is under a constant burden of LPS and periodic burden of CaOx. Foods such as spinach contain 400-900 mg of oxalate; for example, 100 g of New Zealand spinach is reported to have 736 mg of soluble oxalate and 220 mg of CaOx (37)(38)(39). Most of the oxalate absorbed is excreted in the urine, but 10% or less is secreted back into the intestine (40). ...
PurposeA number of hyperoxaluric states have been associated with calcium oxalate (CaOx) deposits in the kidneys. In animal models of stone disease, these crystals interact with circulating monocytes that have migrated into the kidney as part of innate immunity. Similarly, macrophages surround CaOx crystals in kidneys of patients excreting high levels of oxalate. We investigate the effect of this exposure and subsequent human immunological response in vitro.Materials and methodsPrimary human monocytes were collected from healthy donors and exposed to CaOx, potassium oxalate, and zinc oxalate (ZnOx). Cytokine production was measured with a multiplex ELISA. Quantitative reverse transcription-polymerase chain reaction was done to validate the mRNA profile expression. M1 macrophage phenotype was confirmed with immunofluorescence microscopy.ResultsBoth primary monocytes and THP-1 cells, a human monocytic cell line, respond strongly to CaOx crystals in a dose-dependent manner producing TNF-α, IL-1β, IL-8, and IL-10 transcripts. Exposure to CaOx followed by 1 h with LPS had an additive effect for cytokine production compared to LPS alone, however, LPS followed by CaOx led to significant decrease in cytokine production. Supernatants taken from monocytes were previously exposed to CaOx crystals enhance M2 macrophage crystal phagocytosis. CaOx, but not potassium or ZnOx, promotes monocyte differentiation into inflammatory M1-like macrophages.Conclusion
In our in vitro experiment, human monocytes were activated by CaOx and produced inflammatory cytokines. Monocytes recognized CaOx crystals through a specific mechanism that can enhance or decrease the innate immune response to LPS. CaOx promoted M1 macrophage development. These results suggest that monocytes have an important role promoting CaOx-induced inflammation.
... However, this minimal processing does not allow for the reduction of potentially toxic anti-nutrients, such as oxalates, in these juices. Green juices often contain spinach, which is known to contain high levels of oxalates (Brogren & Savage, 2003;Vanhanen & Savage, 2015). To some extent, the oxalate contents of green juices containing spinach are moderated by the other plant materials added to the mixture. ...
Plant foods contain a surprising number of different toxins. A few well-known plants, including some grown in Thailand are known to contain high levels of oxalates however, some plants have not yet been fully investigated. A few plants have become fashionable to promote health because they contain antioxidants but some of these plants will contain oxalates as well. In many cases there is little published data to confirm the oxalates levels of these plants. If plant leaves are boiled before they are consumed this allows soluble oxalate to be leached out and discarded in the cooking water. This means that the cooked food contains considerably lower levels of soluble oxalates than the original raw plants. Cooking in a wok generally concentrates the oxalate contents as much of the cooking water is removed as steam. However, during cooking some of the soluble oxalates can combine with free calcium in the food and be converted to insoluble oxalates; these are not absorbed in the digestive tract. The preparation of juices using fruit or vegetables are being promoted as healthy alternatives, this poses further problems, as they may be prepared from raw vegetable leaves, such as spinach, which contain high levels of oxalates. These juices are not cooked so the oxalate concentration is not reduced during their preparation. Recent research has shown that the addition of calcium salts to these juices can considerably reduce the soluble oxalate content of the drink prepared without changing the taste.
... Therefore, the consumption of 324 mg of C. ambrosioides can provide the amount of oxalic acid (5 g) set as the minimal lethal dose for an adult (a level difficult to reach through the diet). However, it should be noted that the bioavailability of ingested oxalate is estimated to be less than 15% and is influenced by a number of food composition and physiological related factors (Brogren and Savage, 2003;Kristanc and Kreft, 2016a;Liebman and Al-Wahsh, 2011). ...
Wild edible plants (WEPs) are part of the cultural and genetic heritage of different regions of the world. In times of famine and scarcity, these sources of nutrients and health-promoting compounds have received high importance mainly in rural and suburban areas. Although currently underutilized, WEPs are still consumed traditionally by different communities and are gaining relevance in today's society. However, these foods lack recognition as significant contributors to the human diet in developed areas. This review describes the nutritional value of WEPs from the North-eastern region of Portugal and points out those containing potentially toxic compounds. Several retrieval strategies are presented with the aim of promoting the (re)use, production, commercialization and conservation of WEPs (wild harvested plants and crop wild relatives), and their importance for social, economic and agro-ecological development is highlighted.
... The later can be associated with enteric hyperoxaluria from fat malabsorption, e.g., in patients with Roux-en-Y gastric bypass surgery (2), jejunoileal bypass surgery (3), Crohn's disease (4), sprue (5) or taking medications such as orlistat that cause fat malabsorption (6). Other potential culprits for excessive oxalate absorption include either excessive dietary intake of oxalate or its substrate (vitamin C) or dietary deficiency of calcium or magnesium (1,7). Diagnosis of dietary hyperoxaluria is based on the following criteria: First, one should rule out other potential causes of hyperoxaluria, i.e., primary hyperoxaluria (hereditary), and enteric hyperoxaluria (fat malabsorption). ...
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
... Published values for acid-extracted oxalate contents of spinach range from 217.90 to 2677.00 mg/100 g FW (average 1078.13 AE 24.90 mg/100 g FW) and water-extracted oxalate contents range from 105.10 to 2287.00 mg/100 g FW (average 799.63 AE 12.38 mg/100 g FW) (Noonan and Savage, 1999;Savage et al., 2000;Brogren and Savage, 2003;Savage and Mårtensson, 2010;Akhtar et al., 2011;Ghosh Das and Savage, 2013). The values range widely because the data were obtained from spinach grown in many different countries and climates and also under different irrigation and fertilising regimes. ...
... It is possible that liquid calcium preparations or dairy products might be more effective than calcium in solid or pill form, since it would be predicted that a liquid preparation might mix more effectively with food, allowing the calcium to bind oxalate more ef fi ciently. Milk or milk products have been shown to reduce oxalate absorption from tea [ 68 ] and from spinach [ 69 ] . ...
Calcium oxalate is the major component of 70–80 % of renal calculi. Both of these components have both dietary and endogenous sources. Oxalate is found in many plant foods but is particularly rich in certain foods such as spinach, certain nuts, green leafy vegetables, and fruits. Hyperoxaluria occurs in 18 % of kidney stone patients, and treatment has been to reduce intake of oxalate-containing foods or co-ingesting calcium-containing foods or supplements in an attempt to have calcium and oxalate bind together to stay in the gastrointestinal tract. Oxalate absorption occurs all along the intestinal tract and recently shown to be transported from the bloodstream into the lumen of the gastrointestinal tract (i.e., secreted). Small intestine and proximal colon are thought to be the secretory portion, and the distal colon is thought to absorb oxalate into the body. This may prove to be an important mechanism to reduce systemic levels of oxalate in future studies. The intestinal bacterium,Oxalobacter formigenes, has been shown to degrade oxalate from dietary foodstuffs and is found less commonly in stone-forming patients. There are any other oxalate-degrading bacteria, but many of these do not rely solely on oxalate as their main food source. There is much room for investigation in this area as only a small amount of the complete intestinal flora can be identified using traditional microbiologic techniques. Probiotic preparations involving many different types of bacteria have met with limited success in clinical trials to reduce hyperoxaluria. There are many subtypes ofO. formigenesand it is unknown which would be the best to recolonize kidney stone patients. Enteric hyperoxaluria increases the bioavailability of oxalate in patients with extensive small-bowel resection or enteric bypass surgery for obesity. Primary hyperoxaluria is a rare genetic disorder whereby the defective liver enzyme peroxisomal AGT1 results in a failure to convert glyoxylate to glycine or glycolate resulting in an increased conversion to oxalate. Treatment is challenging and typically requires a combined hepatic and renal transplantation.
... Thus, oxalate is better absorbed from black tea or coffee, especially instant coffee (all of which have a high content of oxalate [62]), when they are consumed in the absence of added milk compared with, for example, tea containing a little milk [63], presumably because the calcium in the milk precipitates the oxalate released from the tea and makes it less available for intestinal absorption. Similarly, oxalate is better absorbed from spinach consumed without the addition of any dairy produce than when served with it, such as in creamed spinach [64]. It has been calculated that, even under normal gastric conditions of pH (~2), any CaOx crystals that are formed might not all be redissolved within the period of time that they remain in the stomach [43]. ...
This review describes the various dietary regimens that have been used to advise patients on how to prevent the recurrence of their calcium-containing kidney stones. The conclusion is that although there is some general advice that may be useful to many patients, it is more efficacious to screen each patient individually to identify his/her main urinary, metabolic, nutritional, environmental, and lifestyle risk factors for stone-formation and then tailor specific advice for that particular patient based on the findings from these investigations. If the patient can be motivated to adhere strictly to this conservative approach to the prophylactic management of their stone problem over a long time period, then it is possible to prevent them from forming further stones. This approach to stone management is considerably less expensive than any of the procedures currently available for stone removal or disintegration. In the UK, for each new stone episode prevented by this conservative approach to prophylaxis it is calculated to save the Health Authority concerned around £2000 for every patient treated successfully. In the long term, this accumulates to a major saving within each hospital budget if most stone patients can be prevented from forming further stones and when the savings are totalled up country-wide saves the National Exchequer considerable sums in unclaimed Sick Pay and industry a significant number of manpower days which would otherwise be lost from work. It is also of immense relief and benefit to the patients not to have to suffer the discomfort and inconvenience of further stone episodes.
... A number of commonly eaten foods such as silver beet, spinach, rhubarb, nuts, multi-grain flours, chocolate, black tea and parsley contain high levels of total and soluble oxalate (Zarembski & Hodgkinson, 1962; Fasett, 1973; Brinkely, McGuire, Gregory, & Pak 1981; Noonan & Savage, 1999: Savage, Vanhanen, Mason, & Bush, 2000 Hönow & Hesse, 2002; Chai & Liebman, 2005; Siener, Hönow, Seidler, Voss, & Hesse, 2006). Brogen and Savage, (2003) showed that many green leafy vegetables commonly grown in the Indian sub-continent such as spinach, purple and green amaranth and colocasia, also contain very high levels of oxalates, while a range of other commonly eaten vegetables and spices such as coriander, curry leaves, dill and fenugreek contain moderate levels of oxalates. Savage et al. (2000) reported values for a range of other common European vegetables that were usually cooked before eating. ...
... In this case, oxalate nephropathy occurred following six weeks' consumption of a juicing diet that contained large amounts of spinach. Spinach, a common constituent of juicing diets, is known to contain high levels of oxalate, with fresh or frozen spinach contents reported to range from 320 to 1260 mg/100 g wet matter (WM) [3,4,[8][9][10] and higher levels are being reported in fresh, summer-grown plants [9]. Many other vegetables, such as celery, cucumber and parsley also contain moderate levels of oxalates [11]. ...
Background: Juicing is a popular health trend where green juice is prepared from a range of common vegetables. If spinach is included in the mix then the juice may contain significant quantities of oxalates and these are not safe to consume regularly in large amounts as they predispose some people to kidney stone formation.
Methods: Green juice, prepared from spinach and other common vegetables using a high speed blender that produced a juice containing all the original fiber of the processed raw vegetables, was compared with a juice produced using a masticating juicer, where the pulp containing most of the fiber was discarded in the process. The oxalate contents of both juices were measured using HPLC chromatography.
Results: Two juices were prepared using each processing method, one juice contained a high level of spinach, which resulted in a juice containing high levels of total, soluble and insoluble oxalates; the other was a juice mixture made from the same combination of vegetables but containing half the level of spinach, which resulted in a juice containing considerably (P
... Oxalic acid forms water-soluble salts with Na + , K + and NH 4 + ions; it can also form insoluble oxalates by binding with Ca 2+ , Fe 2+ and Mg 2+ . The consumption of a food containing high levels of calcium [12], the addition of calcium during cooking [13] [14] or the addition of calcium salts during the manufacture of a food are alternative ways to convert soluble oxalates into insoluble oxalates. Insoluble oxalates will not be absorbed in the digestive tract and their formation reduces the bioavailability of oxalate consumed in the diet [14]. ...
Rhubarb (Rheum rhabarbarum) juice was used to make a Japanese soft mitsumame-type dessert sweet. The dessert was prepared from extracted rhubarb juice, which was cooked with sugar, agar and guar gum, then allowed to set in sweet moulds. The total, soluble and insoluble oxalates were determined in the ingredients and the final products using HPLC chromatography. To reduce the soluble oxalate content of the dessert while retaining the colour and taste of the final product, increments of CaCl2 and CaCO3 were added to the test dessert mixes. The addition of CaCl2 reduced the pH from 3.55 ± 0.03 to pH 3.09 ± 0.02 while addition of CaCO3 increased the pH from 3.55 ± 0.03 to 4.96 ± 0.01. In both cases, the incremental addition of calcium reduced the soluble oxalate content of the sweets by converting it to insoluble oxalate.
... The oxalate content of food can vary considerably between plants of the same species, due to differences in climate, soil quality, state of ripeness, or even which part of the plant is analyzed. Variations also may be caused by the different methods used for measuring oxalate in food [13]. The objective of this study was to use the methods to measure the total oxalate content and soluble oxalate content of common edible mushrooms that are regularly used as food and are sometimes taken in larger amounts, so that reliable advice can be given to people who have to consider the possible adverse effects of consuming mushrooms which may contain high levels of available oxalates. ...
Total, soluble, insoluble oxalate and mineral content of 20 edible mushrooms were measured using spectroscopic and enzymatic methods. Total oxalate content ranged from 45 (Hericium erinaceus) to 104 (Morchella conica), mg/100 g dry matter (DM), while the soluble oxalate levels ranged from 34 (Lactaius delicious) to 65 (Phellinus florida) mg/100g DM but not detected in Hericium erinaceus, Sparassis crispa, Geastrum arinarius, Boletus edulis, Helvella crispa, and Ganoderma lucidum respectively and very low in Lactaius delicious (34), Russula brevepis (35), and Cantharellus clavatus (37) mg/100g DM. The Ca, P, K and Mg content showed range of 1.35-12.56 mg/g for Ca, 1.22-3.82 mg/g for P, 15.4-25.4 mg/g for K and 1.19-4.71 mg/g for Mg. Overall, the percentage of soluble oxalate content of the selected mushrooms ranged from 34 to 65% of the total oxalate content which suggests that, the selected edible mushrooms presents no risk to people liable to kidney stone formation while other foods like some spices and vegetables can supply significant amounts of soluble oxalates and therefore should be used in moderation as good vegetable, which might be important for human nutrition.
... The distribution of oxalates in plants is also very variable. Some green leafy vegetables such as spinach, purple and green amaranth and colocasia contain very high oxalate levels [8]. ...
Total and soluble oxalate content levels were measured in thirteen selected vegetables purchased from a local market in Surin Province in the northeast of Thailand. Total oxalate contents of the leaves, shoots and roots of the fresh vegetables ranged from 249.5 ± 12.1 to 7597.9 ± 77.6 mg oxalate/100g dry matter (DM) while soluble oxalate content ranged from 205.0 ± 2.3 to 2677.6 ± 19.0 mg oxalate/100 g DM. Very high levels of total oxalates were found in three of the selected Thai vegetables, Polygonum odoratum (7597.9 ± 77.6 mg/100g DM), Piper aurantaucum (7026.6 ± 76.9 mg/100g DM) and Limnophila aromatica (6179.0 ± 23.6 mg/100g DM). However, the soluble oxalate content of L. aromatica was low and the highest soluble oxalate contents of fresh vegetables were found in P. odoratum, P. auran-tuacum and Neptunia oleracea at 2677.6 ± 19.0, 2152.2 ± 65.3 and 1640.8 ± 3.4 mg/100g DM, respectively. Boiling the vegetables reduced the soluble oxalate content between 30.4 and 65.0%. The insoluble oxalate levels increased in eleven of the cooked vegetables while small decreases were observed in L. aromatica and N. oleracea.
... Items in Western diets that significantly increase urinary oxalate excretion include spinach, rhubarb, beets, nuts, chocolate, tea, wheat bran, and strawberries [6] . The bioavailability of ingested oxalate is influenced by other ingested items [32] . Oxalate content of various diets, its relation to nephrolithiasis, and guide-lines for oxalate intake have been reported [13][14][15][33][34][35][36][37] . ...
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.
... In the absence of severe symptoms, patients should be instructed to immediately remove any plant debris from the mouth by wiping with a wet cloth, rinsing the mouth with water to flush out the crystals, then drinking a full glass of milk or ingesting another calcium-containing food or supplement (Yuen 2001). The calcium is thought to limit absorption of soluble oxalates by forming insoluble calcium salts (Hossain 2003;Brogren and Savage 2003). Cold items such as popsicles, ice cream, or ice chips may provide symptomatic relief for the local irritation. ...
Although the taro plant, Colocasia esculenta, is commonly consumed throughout Asia, Africa, the Pacific Islands, and the Caribbean, its consumption is less common in North America. Exposure to raw or improperly prepared taro is associated with oropharyngeal irritation and swelling and, rarely, airway obstruction. Although cases of toxicity in countries where taro is a staple have been reported, cases in North America have not been described. Here, two cases of oral irritation and swelling in BC residents who ate raw taro leaf, were reported to the British Columbia Drug and Poison Information Centre (BC DPIC) and triggered an investigation involving a regional health authority and the Canadian Food Inspection Agency. Investigators found that the vendor, a chain of ethnic supermarkets, offered no point of sale preparation instructions. The vendor responded initially by posting instructional signage and later by voluntary product withdrawal. Analysis of BC DPIC records between 1 November 2011 and 20 December 2013 identified 11 cases of symptomatic taro exposure, five to the leaf and six to the corm. The two index cases and subsequent investigation illustrate how new foods or foods in unfamiliar contexts may present as calls to a poison control centre and that prevention requires collaboration among public and corporate stakeholders.
Key words: taro, food safety, poison control, health protection
Rhubarb petioles are usually cooked for a tasty and well-liked dessert, but they contain high levels of oxalates known to be potent toxins. This work aimed to study on oxalate bioaccessibility of a food containing high oxalates using an in vitro digestion system. Cooking rhubarb petioles with water, trim or standard milk significantly (p < 0.05) reduced oxalate contents of the mixture by dilution (total oxalate mean raw 902.7 mg/100 g fresh weight, mean cooked 454.3 mg/100 g fresh weight). Total reduction of soluble oxalate amounts cooked with trim and standard milk were 65.9 % and 74.5 %, respectively when compared to those in the raw petioles. In the intestinal segment, significantly lower amounts of soluble oxalates (lower 8 % - 36 %) are available for absorption compared to those measured by the chemical extraction. A standard serving of boiled rhubarb contains high levels of soluble oxalate which is significantly reduced by 70.3 % when it is cooked with milk. Overall, the data suggests that less soluble oxalates available for absorption in the in vitro digestion than those reported by chemical extractions. Cooking a food containing high oxalates, especially rhubarb stalks, with milk would be an effective way to reduce soluble oxalate intakes for people suffering from kidney stone.
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.
Background:
Numerous studies acknowledged the importance of an adequate vegetable consumption for human health. However, current methods to estimate vegetable intake are often prone to measurement errors due to self-reporting and/or insufficient detail. More objective intake biomarkers for vegetables, using biological specimens, are preferred. The only concentration biomarkers currently available are blood carotenoids and vitamin C, covering total fruit and vegetable intake. Identification of biomarkers for specific vegetables is needed for a better understanding of their relative importance for human health. Within the FoodBAll Project under the Joint Programming Initiative "A Healthy Diet for a Healthy Life", an ambitious action was undertaken to identify candidate intake biomarkers for all major food groups consumed in Europe by systematically reviewing the existent literature. This study describes the review on candidate biomarkers of food intake (BFIs) for leafy, bulb, and stem vegetables, which was conducted within PubMed, Scopus and Web of Science for studies published through March 2019.
Results:
In total, 65 full-text articles were assessed for eligibility for leafy vegetables, and 6 full-text articles were screened for bulb and stem vegetables. Putative BFIs were identified for spinach, lettuce, endive, asparagus, artichoke, and celery, but not for rocket salad. However, after critical evaluation through a validation scheme developed by the FoodBAll consortium, none of the putative biomarkers appeared to be a promising BFI. The food chemistry data indicate that some candidate BFIs may be revealed by further studies.
Conclusion:
Future randomized controlled feeding studies combined with observational studies, applying a non-targeted metabolomics approach, are needed in order to identify valuable BFIs for the intake of leafy, bulb, and stem vegetables.
Green juices are an example of a modern food innovation that has developed partly by itself in response to general nutritional advice in the media imploring people to consume more fruits and vegetables. Unfortunately, the risks of developing acute oxalate nephropathy is high following the consumption of some green juices and fruit juices. This study investigates the occurrence and levels of oxalates in green juices made from common fruit and vegetables available in New Zealand. The influence of the type of juicer used to prepare the juices, and the use of treatments and/or additions to reduce the oxalate content of these mixed juices, was also investigated. A Design of Experiments multi-factor approach was used to investigate the extraction of oxalates from a green juice. Fresh spinach samples were juiced in a high speed blender and the oxalate contents were extracted using seven levels of pH, eight levels temperature and six extraction times. A statistically significant quadratic model with an overall level of significance of P < 0.0002 was achieved by using 20 experimental runs performed over one day. The optimum conditions for extracting all the oxalate from the model green spinach juice was at pH 0.93, with a temperature of 65°C and at any time greater than 15 minutes. The least amount of oxalic acid was extracted at pH 4.59 with a temperature of 25°C. To investigate the levels of oxalates found in homemade green juices, five green juice recipes containing between three and nine ingredients were made. Fresh spinach was the common component, and ranged from 20.1% to 37.9% w/w. The oxalate content ranged from 90.34 to 152 and 13.0 to 82.85 mg/100 g fresh weight (FW) for total and soluble oxalates, respectively. The percentage of soluble oxalate varied from 11.9 to 67.8%. The juices were made using a masticating juicer (MJ), which separates out a waste pulp fraction that is normally discarded. This fraction contained large amounts of oxalic acid, 134.6 to 348.09 mg/100 g FW in total. The waste pulp also had a higher concentration of minerals of all 11 minerals present, apart from Al, compared to the green juice. It is proposed there is an interaction between the oxalate, calcium and the pulp fraction of the green juice. A 200 g glass of green juice containing a mix of apple, celery and spinach, contained 165.7 mg of soluble oxalate; this is a considerable amount of soluble oxalate to ingest. In the home, juicing commonly uses two basic types of juicer, a high speed blender (HSB) or a masticating juicer (MJ); the MJ separates out a pulp fraction while the HSB does not. High and low spinach containing juices were made using both juicers. The MJ had a concentrating effect during processing, resulting in 528.41 mg total oxalate/100 g FW compared to the HSB, at 369.47mg total oxalic acid/100 g FW. They both produced green juices that had similar ratios of soluble oxalate, for both the high and low spinach juices. A significant amount of the oxalate and minerals were separated out into the waste pulp fraction from the juice made using the MJ. The waste pulp contained 238.10 to 55.67 mg total oxalate/100 g FW and 61.7 to 74.7% of the calcium content of the original spinach leaves. Two strategies to lower the soluble oxalate content of green juices were investigated; direct addtion of a food grade calcium salt, and soaking the raw materials used to make the fresh green juice. Four calcium salts tested. Calcium chloride was the most effective, reducing the soluble oxalate by 98.3% after the addtion of 500 mg/100 g to the fresh juice. Fresh spinach leaves were soaked in either tap water, a 1% w/v/ NaCl or a 1%w/v CaCl solution, prior to processing into a juice. The tap water and 1% w/v NaCl showed no loss of soluble oxalate but the 1% w/v CaCl treatment showed a 50% reduction in soluble oxalate and a 28.% increase in insoluble oxalate. This treatment had the added benefit of increasing the bioavailabilty of calium in the soaked spinach leaves. This study has shown that there are high levels of oxalate in green juices and, if consumed, this could pose a risk for diet induced nephropathy.
https://hdl.handle.net/10182/10512
Purpose of review:
Urolithiasis is a very common condition, which can be accompanied by serious complications. Diagnosis, treatment, and prevention are of great cost for the national health systems. Many studies have been published about the role of diet in both stone formation and prevention. The aim of this review is to summarize the most recent developments that correlate diet to lithiasis.
Recent findings:
Recurrent stone formers should undergo metabolic evaluation and stone chemical analysis. Current evidence propose difference approaches based on the metabolic disorder that is diagnosed. Diet could have a detrimental role in the prevention of recurrences. Prevention advises include increased fluid uptake, vegetables and fruit intake but decreased sugar, salt, and meat consumption.
Summary:
The analysis of the food contents and their role to lithogenesis prevention are of great importance. Modifying diet to prevent stones could help many people who suffer from lithiasis to avoid recurrence and the consequences. Furthermore, the cost for diagnosis and treatment could be significantly reduced. Therefore, the field of dietary factors in lithogenesis should be further investigated.
This study was carried out to determine the effect of blanching time on selected mineral contents of four frequently consumed GLVs in South western, Nigeria. Fluted pumpkin (Telfairia occidentalis), feather cockscomb (Celosia argentea) and spinach (Amaranthus cruentus) which are usually excluded and Water leaf (Talinum triangulare) which is allowed in the diets of patients with Chronic Renal Failure (CRF) were subjected to 10, 30 and 60 minutes blanching times. Four samples were generated from each vegetable species: sample A (unblanched raw vegetable), sample B (blanched vegetable for 10 minutes), sample C (blanched vegetable for 30 minutes) and sample D (blanched vegetable for 60 minutes). Calcium, magnesium, potassium, phosphorus and sodium content of the vegetables were determined according to AOAC method and Phosphorus by the Vanodo-molybdate method. Data were analysed using ANOVA and Duncan Multiple Range test at p<0.05. The result showed that increase in blanching time significantly increased the calcium while the potassium and sodium content of all the vegetables significantly reduced with 10 minutes blanching (p<0.05). Blanching for 30 minutes or more had significant reducing effect on the magnesium and phosphorus concentrations of the GLVs. Thirty minutes blanching time had significant reducing effects on the mineral contents of the vegetables except for calcium content which increased with increase in blanching time. The GLVs could be recommended for patients suffering from CRF provided they are blanched for 30 minutes. © 2017, Ibadan Biomedical Communications Group. All rights reserved.
It appears that reducing the risk of cardiovascular disease (CVD) may also be the ideal diet and lifestyle program to reduce the risk of kidney stones. Comprehensive lifestyle changes and healthy-heart parameters have synergistic impacts on reducing recurrent or incident nephrolithiasis as observed either in randomized trials from Parma, Italy, or from the observational cohort analysis when utilizing the Dietary Approaches to Stop Hypertension (DASH) program in the USA. Hypertension, dyslipidemia, weight and waist gain and accelerated large amounts of weight loss (bariatric surgery, diet, etc.), glucose intolerance/diabetes, and metabolic syndrome increase stone risk, but a higher potassium to sodium intake ratio, increased dietary magnesium, reduced animal protein, and normalizing dietary calcium and increased fluid intake could lower risk. Soluble dietary oxalates are more concerning compared to insoluble forms. A variety of dietary supplements also appear to impact risk. Arguably the best-known supplemental source of increased oxalate is from high dosages (>1,000–1,500 mg/day) of plain vitamin C (ascorbic acid), and calcium ascorbate or buffered vitamin C may cause less profound changes in oxalate. Vitamin C may lower serum uric acid and gout risk by also creating a higher urinary uric acid load in some individuals, which could also theoretically increase uric acid stone risk. Some cranberry concentrate supplements for urinary tract infection (UTI) have unusually high oxalate concentrations and need to be tested for this compound. Vitamin B6 (pyridoxine hydrochloride and potentially pyridoxal-5-phosphate) shifts oxalate metabolism toward the production of glycine at dosages of 50–100 mg per day and could be beneficial in some oxalate stone formers apart from those with primary hyperoxaluria type I. Higher dosages (300 mg or more) could also cause a sensory peripheral neuropathy. A probiotic or Oxalobacter formigenes and other intestinal bacterial may also play a role in reducing oxalate levels. Calcium supplements in excess appear to increase the risk of stone disease, especially calcium carbonate, and calcium citrate is an alternative for those with a history of oxalate stones, but supplementation also increases constipation risk with age. Vitamin D has a controversial impact on stone risk, but megadosing is never prudent. Omega-3 fatty acids supplements via anti-inflammatory effects could reduce stone risk, and omega-6 has some preliminary similar benefits, but inosine dietary supplementation is known to increase uric acid levels and stone disease. A variety of other CAM options are discussed in this chapter. What if healthcare professionals in urology could have some role in helping patients improve the quality and quantity of their life via comprehensive lifestyle recommendations for stone disease risk reduction? It appears that this is no longer a question, but a reality.
A tremendous surge of public interest in natural therapies has been reported in the past several decades in both developing and developed countries. Furthermore, edible wild-growing plants whose use had long been associated with poverty and famine have also gained in popularity among people in developed countries. An important fraction of herbal products evade all control measures and are generally perceived as safe. However, this may not always be true. It is important to recognize that some plants are not associated with acute toxicity but rather produce more insidious problems, which develop only with long-term exposure. In this review, we continue a systematic analysis of the subacute and chronic toxicity associated with the use of herbal preparations. The hepato-, neuro-, nephro- and immunotoxicity of plant species that either grow natively or are cultivated in Europe are discussed in some detail. The basic concepts regarding the molecular mechanisms implicated in their nonacute toxicity and their pathophysiological, clinical and epidemiological characteristics are included. Among others, we discuss the hepatotoxicity of pyrrolizidine alkaloids, the nephrotoxicity of aristolochic acid, the lathyrism associated with neurotoxin swainsonine, thiamine depletion and thyroid dysfunction of herbal cause, and finally address also the immunosuppressive effects of cannabinoids.
This chapter describes the various general and specific dietary regimens that can be used to advise patients on how to prevent the recurrence of their calcium- and uric acid-containing kidney stones. The conclusion is that although there is some general advice that may be useful to most patients, it is more efficacious to screen the patient in order to identify his/her main urinary, metabolic, nutritional, environmental, and lifestyle risk factors for stone formation and then tailor specific advice for that patient on the basis of the findings from these detailed investigations. If the patient can be motivated to adhere strictly over a long time period to this conservative approach to the prophylactic management of their stone problem, then it is possible to prevent their forming further stones. Although this approach to stone management may be relatively expensive in the short term, it is not as expensive as any of the procedures currently available for stone removal or disintegration and in the long term may save health authorities considerable sums within their hospital budgets. It will also be of considerable benefit to the patient not to have to suffer the discomfort and inconvenience of further stone episodes and would save the Exchequer considerable sums in unclaimed sick pay and industry a significant number of days lost from work.
Oxalic acid, is present in different ionic forms in plants, in the form the acid, oxalate ion or salts, dependent on pH.
This has a profound effect on the potential toxicity of the oxalates. Acute oxalate toxicity most commonly causes renal pathology.
Insoluble oxalates, in the form of crystals (raphides) are used as an anti-herbivory protective mechanism by plants by causing physical damage to the lips, tongue and palate.
Endogenous synthesis of oxalate, linked to inherited enzyme and/or vitamin deficiencies may lead to renal pathology as well.
Oxalates are of importance in veterinary toxicology. The first and most important reason is that absorbed soluble oxalates cause serious primary nephropathy and kidney shut down by severely damaging the renal tubular epithelium. The second reason is that highly irritating insoluble calciumoxalate raphides form in certain plants as protection against herbivory and may cause alarming signs if the plants are eaten, or in the case of those with a nettle action, touched. The reason for preferential gastric absorption is linked to the specific conditions required for the reaction of calcium with oxalic acid. For the insoluble calcium oxalate to form, an alkaline environment in required. Therefore the acidic environment favors the absorption of oxalic acid before the formation of the insoluble salts as in ruminants. These two syndromes are discussed in this chapter. In summary, in the veterinary situation, Ca-oxalate raphide intoxication is rare, but it is prudent to be aware of it in coming to a diagnosis of sudden acute mouth irritation in humans and diverse species of animals.
Purslane (Portulaca oleracea L.) is a rich source of important nutrients such as minerals and antioxidants. In addition, its edible tissues contain high levels of omega-3 fatty acids which are recommenced for a healthy diet. Raw leaves, stems and buds have been reported to contain high levels of oxalate and, therefore, they are not recommended for regular consumption for people who have a tendency to form kidney stones. In this study the fresh leaves, stems and buds contained respectively 23.45±0.45, 5.58±0.18 and 9.09±0.12 g total oxalates kg-1 fresh weight. The stems and buds contained a mean of 75.0% soluble oxalates while the leaves contained only 27.5% soluble oxalates. Boiling the leaves, stems and buds resulted in a loss of soluble oxalates from the tissue which resulted an overall 27% reduction in total oxalate in the tissues. Pickling the whole plant resulted in a loss of soluble oxalates from the tissue by leaching into the vinegar, resulting in a reduction of total oxalate content of the pickled tissue by 16%. Larger leaves contained 40% more total oxalates than the small leaves while the oxalate content of the stems ranged between 4.9 and 6.2 g total oxalates kg-1 fresh weight. The leaves contained 33% soluble oxalate while in contrast the stems contained a mean of 67% soluble oxalates. Overall, the results of this experiment confirm that cooking and pickling purslane reduces the soluble oxalate content of the processed tissue. Reduction in the soluble oxalate concentration of the tissue will reduce the potential of this high oxalate containing plant to increase urinary oxalate output which could then lead to an increased incidence of kidney stones. This is particularly important as purslane has a number of positive nutritional attributes which suggest that it should be part of a healthy diet.
Oxalic acid (C2O42–) is a compound of interest as a resultof its relationship with kidney stone formation and antinutritiveproperties. Because table beet [Beta vulgaris ssp. vulgaris(garden beet group)] is considered a high oxalate food, breedingto decrease oxalic acid levels is an area of interest. In thisstudy, a field trial was conducted over 2 years for 24 membersof the Chenopodiaceae using two different planting dates todetermine if variation exists for both total and soluble oxalicacid levels in roots and leaves. Total and soluble oxalic acidwas extracted from homogenized root core and leaf tissue samplesand a colorimetric enzymatic assay was used to determine totaland soluble oxalic acid levels. Mean values ranged from 722to 1909 mg/100 g leaf tissue and 553 to 1679 mg/100 g leaf tissuefor total and soluble oxalate levels, respectively. Beet cultivarForono and swiss chard [B. vulgaris ssp. vulgaris (leaf beetgroup)] cultivar Burpee's Fordhook Giant Chard produced therespective highest and lowest soluble and total oxalic acidleaf levels. Swiss chard cultivars produced 38% less total oxalatecompared with table beet cultivars based on overall means. Rootsoluble oxalate values ranged from 103 to 171 mg/100 g roottissue and total values ranged from 95 to 142 mg/100 g roottissue. Significant variation for both total and soluble oxalicacid levels were detected, indicating progress could be madetoward breeding for lower oxalic acid levels in table beet.However, gains in oxalic acid nutritional quality may be limitedbecause it would take a substantial decrease in levels for tablebeet to be reclassified as a low oxalate food.
The total, soluble and insoluble oxalate contents of eleven indigenous fruits and vegetables commonly consumed in Surin Province in the northeast of Thailand were determined using high-performance chromatography. The fresh food samples were purchased in local markets and harvested growing wild in the local district. Four of the studied vegetables contained no detectable levels of oxalate. The remaining seven plant foods had total oxalate contents ranging from 4.6 to 2056.4 mg oxalate/100 g fresh weight (FW) while soluble oxalate content ranged from 51.3 to 1238.1 mg oxalate/100 g FW. Four of these foods contained no detectable levels of soluble oxalate. As all of these foods are consumed raw or only lightly cooked so there is little scope to reduce the intake of soluble oxalates in the three of the other foods, two of which, the fruits of Phyllanthus emblica Linn and flowers of Musa sapientum Linn., contain very high levels of soluble oxalates (1238.1 ± 31.4, 230.6 ± 1.6 mg/100 g FW, respectively). A juice prepared by extracting Indian gooseberry fruits produced a tart drink, which contained 1160.6 mg ± 18.4 soluble oxalate/100 ml.
Oxalate, malate, citrate, and succinate contents of tropical root crops were determined by HPLC. Water extraction gave soluble oxalates, and extraction with acid gave total oxalates. The difference between them equaled the amount of calcium oxalate. Total calcium was determined by atomic absorption, and free calcium (calcium not present as calcium oxalate) was readily calculated. Taro (Colocasia esculenta) leaves, from edible and nonedible cultivars (because of their acrid nature), showed no differences in their amounts of total oxalate or of calcium oxalate. This showed that acridity of taro leaves was not due solely to calcium oxalate raphides present. Stems of giant swamp taro (Cyrtosperma chamissonis), elephant foot yam (Amorphophallus campanulatus), skin of giant taro (Alocasia macrorrhiza), and taro leaves contained about 400 mg/100 g fresh weight of calcium oxalate, about 10 times the amount present in sweet potato, cassava, taro Colocasia and Xanthosoma, and yam. The free calcium content was 0-20 mg/100 g fresh weight and would be adequate for all root crops, except taro Xanthosoma.
Oxalates occur as end products of metabolism in a number of plant tissues; some leafy plants and some root crops contain markedly high levels of soluble and insoluble oxalates. When consumed these oxalates can bind calcium and other minerals. Measurement of oxalate content in vegetables commonly consumed in New Zealand shows that cooking reduces the oxalate content of the food by leaching losses into the cooking water. Roots and brassicas grown in New Zealand appear to contain relatively low levels of oxalates. Leafy vegetables such as silverbeet and NZ spinach appear to approach and exceed levels found in rhubarb stalks, although New Zealand silverbeet stems contain lower levels.
Oxalic acid and its salts occur as end products of metabolism in a number of plant tissues. When these plants are eaten they may have an adverse effect because oxalates bind calcium and other minerals. While oxalic acid is a normal end product of mammalian metabolism, the consumption of additional oxalic acid may cause stone formation in the urinary tract when the acid is excreted in the urine. Soaking and cooking of foodstuffs high in oxalate will reduce the oxalate content by leaching. The mean daily intake of oxalate in English diets has been calculated to be 70-150 mg, with tea appearing to contribute the greatest proportion of oxalate in these diets; rhubarb, spinach and beet are other common high oxalate-content foods. Vegetarians who consume greater amounts of vegetables will have a higher intake of oxalates, which may reduce calcium availability. This may be an increased risk factor for women, who require greater amounts of calcium in the diet. In humans, diets low in calcium and high in oxalates are not recommended but the occasional consumption of high oxalate foods as part of a nuritious diet does not pose any particular problem.
An experimental model which allowed a differentiation between endogenously-and exogenously-derived urinary oxalate was used to assess the effect of olestra ingestion on oxalate absorption and excretion. Seventeen healthy subjects participated in three oxalate load (OL) tests separated by at least one week and administered in the following order: OL-1, potato with fat (potato chips); OL-2, potato with olestra (olestra-containing potato chips); and OL-3, potato without fat (boiled potatoes). The three experimental treatments provided similar levels of carbohydrate. Oxalate loads, ingested immediately after consumption of the potato chips/boiled potatoes, consisted of 180 mg unlabeled oxalic acid and 14.3 mg 13C2-oxalic acid. Twenty-four hour urine samples were collected the day before the OL tests and timed urine samples were collected during the 48 h post-oxalate ingestion period. Endogenously-derived oxalate did not differ between treatments. Oxalate absorption for OL-1 (10.5 %) and OL-2 (10.2 %) was lower (P<0.05) than for OL-3 (13.2 %). The presence of fat or olestra depresses total oxalate absorption.
100 g of spinach a day was added to the hospital diet of fifty-four patients with suspected malabsorption. Hyperoxaluria was found in thirty-eight patients; all of them had steatorrhoea. No patient with steatorrhoea had a urinary oxalate excretion of less than 40 mg a day. Ten other patients had hyperoxaluria, but the faecal fat determinations were regarded as unreliable in almost all and malabsorption could not be confirmed. It is suggested that in clinical practice determination of urinary oxalate after an oral load of oxalate could replace faecal fat determination in most patients with suspected malabsorption.
To investigate the possibility of measuring urinary oxalate output instead of faecal fat excretion as an outpatient screening test for steatorrhoea, we determined 24 hour urinary oxalate and five day faecal fat excretion before and during an oral load of sodium oxalate 600 mg daily (oxalate 4.44 mmol), in 32 patients with suspected malabsorption on a diet containing oxalate 30 mg (0.33 mmol), fat 50 g (180 mmol), and calcium 1 g (25 mmol). Nineteen patients proved to have steatorrhoea (mean faecal fat 62 mmol/24 h, range 19--186 mmol) of varying aetiologies. On the diet alone, urinary oxalate was raised in only nine of these patients (mean 0.25 mmol/24 h, range 0.08--0.59 mmol) (normal less than 0.20). By contrast, when the diet was supplemented with oral sodium oxalate, all 19 patients with steatorrhoea had hyperoxaluria (mean 0.91 mmol/24 h, range 0.46--1.44 mmol) (normal less than 0.44). There was a significant positive linear relationship between urinary oxalate and faecal fat when the 32 patients were on the high oxalate intake (r = 0.73, P less than 0.001), but not when they were on the low oxalate intake. Mean percentage absorption of orally administered oxalate was 5.8 +/- 0.99% (+/- 1 SD) in normal subjects and 14.7 +/- 6.0% (P less than 0.002) in patients with steatorrhoea. Measurement of urinary oxalate output during oral sodium oxalate loading appears to be a reliable and convenient screening test for steatorrhoea.
Intestinal absorption of oxalate was assessed indirectly from the increase in renal oxalate excretion following the oral administration of 5 mmol of stable oxalate. When sodium oxalate alone was given without divalent cations to patients in the fasting state, the urinary oxalate increased promptly (within 2 hours). The increase was more prominent and sustained in those with ileal disease (ileal resection or jujunoileal bypass); thus, 35 per cent of the orally administered oxalate eventually appeared in the urine in the group with ileal disease, 8 per cent in the group with stones (renal and absorptive hypercalciurias) and 9 per cent in the control group. This hyperexcretion of oxalate could be largely, but not totally, ameliorated by the concurrent oral administration of divalent cations. Although urinary oxalate decreased significantly following the oral administration of calcium or magnesium, hyperoxaluria persisted in most patients. The results suggested that the hyperabsorption of oxalate in ileal disease cannot be accounted for solely by an increased absorbable oxalate pool associated with calcium-fatty acid complexation. Moreover, although urinary oxalate decreased, urinary calcium increased concurrently when either calcium or magnesium was given. Thus, there was no significant change or increase in the urinary state of saturation with respect to calcium oxalate.
Clinical studies suggest that steatorrhoea can be associated with excessive absorption of dietary oxalate. We examined the influence of bile salts, Ca++, and long-chain fatty acid on the absorption of oxalate and water by rat intestine in vivo. Absorption was measured under steady-state conditions during single-pass infusions. Each intestinal segment served as its own control. In jejunum, 10 mM taurocholate, the principal salt in rat bile, depressed absorption of oxalate and water. Absorption was not depressed further by Ca++ or linoleic acid. In ileum, 10 mM taurocholate did not inhibit absorption. Linoleic acid, 2 mM, depressed absorption of both oxalate and water. In colon 10 mM taurocholate decreased absorption. Net water transport was depressed further when linoleic acid was added to the infusion, but oxalate absorption was enhanced. Ca++ negated these effects of linoleic acid. It is concluded that long-chain fatty acids may enhance the absorption of oxalate from the rat colon. This observation may be relevant to understanding hyperoxaluria in patients with steatorrhoea.
We extended the study of oxalate bioavailability by testing 7 additional food items: brewed tea, tea with milk, turnip greens, okra, peanuts and almonds. Nine normal subjects ingested a large serving of each of these items. The bioavailable oxalate was calculated from the increment in urinary oxalate during 8 hours after ingestion and bioavailability was determined as the percentage of total oxalate content in a given food item represented by bioavailable oxalate. Brewed tea and tea with milk, with a high oxalate content, had a low bioavailable oxalate level (1.17 and 0.44 mg. per load) because of the low oxalate availability (bioavailability of 0.08 and 0.03%). Turnip greens, with a satisfactory oxalate bioavailability (5.8%), had a negligible effect on urinary oxalate excretion, since oxalate content was relatively low (12 mg. per load). Okra, with a moderate oxalate content (264 mg. per load) had a negligible bioavailable oxalate (0.28 mg. per load). Only peanuts and almonds provided a moderate increase in oxalate excretion (3 to 5 mg. per load) due to the modest oxalate content (116 and 131 mg. per load) and oxalate bioavailability (3.8 and 2.8%). Thus, the ability of various oxalate-rich foods to augment urinary oxalate excretion depends not only on oxalate content but on the bioavailability.
The absorbability of calcium from spinach was compared with the absorbability of Ca from milk in 13 healthy adults in a randomized cross-over design in which the test meal of either milk or spinach had 200 mg of Ca labeled with 45Ca. Absorption was measured by the standard double-isotope method in which both the test food and the miscible Ca pool are labeled with different Ca tracers. Measurement of both Ca and oxalate in our test spinach revealed a very slight stoichiometric excess of oxalate; hence it is likely that all of the spinach Ca was effectively bound. Absorption was higher from milk in every case, with the mean absorption from milk averaging 27.6% and from spinach, 5.1%. The mean within-subject difference between Ca absorption from milk and from spinach was 22.5 +/- 9.5% (P less than 0.0001). These results conclusively establish that spinach Ca is much less readily available than milk Ca.
Summary Enteric hyperoxaluria and oxalate urolithiasis in patients with ileal resection seem to be caused by intestinal hyperabsorption of oxalate. The mechanism responsible for hyperabsorption of oxalate is not known. Intestinal transport of oxalic acid was therefore examined by an in vitro technique in rat intestine. Oxalic acid was absorbed by a mechanism of simple passive diffusion. The rate of absorption decreased from the colon to the duodenum (colon>ileum>jejunum>duodenum). Bile acids enhanced oxalic acid absorption in the large and small intestine and increased extracellular space; calcium, however, markedly decreased mucosal-serosal transport of oxalic acid. Cholestyramine known to reduce oxalate excretion in hyperuxaluria associated with ileal resection did not directly affect absorption of oxalic acid, but decreased the enhanced absorption of oxalic acid induced by bile acids. The results suggest that the beneficial therapeutic effect of cholestyramine in hyperuxaluria is rather mediated by its bile acid binding activity than by direct binding of oxalic acid.
1. The short-term effects of different intakes of calcium and oxalic acid on the urinary excretion of these substances was studied in eight normal men and eight men with a history of calcium-containing renal stones.
2. The effect of dietary oxalate on urine oxalate depended partly upon the calcium intake. Thus, on a normal calcium intake an increase in oxalate intake caused an increase in oxalate excretion that corresponded to 3·6% of the additional dietary oxalate; on a low calcium diet, however, the increase corresponded to 8·1%.
3. A decrease in daily calcium intake from 1000 to 250 mg caused a fall in calcium excretion averaging 150 mg/day in the patients and 60 mg/day in the controls but this was accompanied by average rises of 10 and 7 mg/day respectively in oxalate excretion, with the result that the calcium oxalate activity products remained almost unchanged.
4. A decrease in oxalate as well as calcium intake resulted in a fall in calcium excretion that was not accompanied by a rise in oxalate excretion, and there was a statistically significant fall in the calcium oxalate activity product in both the patients and normal subjects.
1. Seventeen healthy controls and 63 patients with idiopathic calcium stone disease of the urinary tract were investigated for urinary calcium and oxalate excretion and for [14C]oxalate intestinal absorption.
2. Under comparable controlled dietary intake a significant increase in calcium excretion was found in patients with stone disease. Oxalate excretion and [14C]oxalate intestinal absorption were mildly but not significantly increased. When patients with stone disease were subdivided into normocalciuric and hypercalciuric subjects, oxalate excretion and [14C]oxalate absorption were significantly increased in the latter. There was a significant direct relationship between calcium excretion and both oxalate excretion and [14C]oxalate absorption.
3. [14C]Oxalate absorption increased significantly in 22 stone-formers when dietary calcium was changed from normal to low.
4. The kinetics of [14C]oxalate intestinal absorption showed that the main difference between normocalciuric and hypercalciuric subjects occurred within the first 6 h after the oxalate-labelled meal.
5. These results confirm that mild hyperoxaluria is a frequent feature of idiopathic calcium stone disease even when patients and controls are studied under controlled dietary conditions. Our data are consistent with the hypothesis that hyperoxaluria is secondary to calcium hyperabsorption and is upper intestinal in origin.
The ability of 7 "oxalate-rich" foods to enhance urinary oxalate excretion was measured in 8 normal volunteers. The analyzed value for oxalate was high for spinach (1,236 mg.), moderate for chocolate (126 mg.) and tea (66 mg.), and for low vegetable juice, cranberry juice, pecans, and orange juice (2 to 26 mg.). The urinary oxalate increased by 29.3 mg. during eight hours after ingestion of spinach. However, it rose by less than 4.2 mg. from consumption of other food items. The bioavailable oxalate (per cent of total appearing in urine) was much less from food items of high or moderate oxalate content (spinach and chocolate) than from standard solutions of sodium oxalate (2.4 to 2.6 versus 6.5 to 7.3 per cent). Thus, only spinach among food items tested was capable of causing hyperoxaluria in normal subjects.
1. Urinary composition was studied in nine healthy adults on unrestricted diet and low-oxalate diet with and without individual oxalate-rich foods.
2. Urine oxalate was constant on the low-oxalate and constant high-oxalate diets and only fluctuated greatly on unrestricted diet.
3. Urine oxalate was mainly due to dietary oxalate which accounts for up to two-thirds of urinary oxalate.
4. Urine oxalate was unaffected by urine volume.
5. Varying percentages of dietary oxalate were absorbed depending on the nature of the foodstuff.
6. Although tea was the main source of dietary oxalate in some people it, like strawberries, did not represent a real risk factor. Chocolates, peanuts, beetroot, rhubarb and spinach were considered as high-risk foods.
7. Calcium oxalate crystalluria at 4°C was increased significantly when the oxalate-rich foods were taken. When urine was examined at 37°C no increase in crystalluria was found.
Dietary restriction of oxalate intake has been used as therapy to reduce the risk of recurrence of calcium oxalate kidney stones. Although urinary oxalate is derived predominantly from endogenous synthesis, it may also be affected by dietary intake of oxalate and calcium. The risk of increasing urinary oxalate excretion by excessive consumption of dietary oxalate is greatest in individuals with a high rate of oxalate absorption, both with and without overt intestinal disease. Although oxalate-rich foods enhanced excretion of urinary oxalate in normal volunteers, the increase was not proportional to the oxalate content of the food. Only eight foods--spinach, rhubarb, beets, nuts, chocolate, tea, wheat bran, and strawberries--caused a significant increase in urinary oxalate excretion. Restriction of dietary calcium enhances oxalate absorption and excretion, whereas an increase in calcium intake may reduce urinary oxalate excretion by binding more oxalate in the gut. This review of the literature indicates that initial dietary therapy for stone-forming individuals can be limited to the restriction of foods definitely shown to increase urinary oxalate. The effects of oxalate-restricted diets on urinary oxalate should be evaluated by means of laboratory analyses of urine composition. Subsequent long-term therapy can be recommended if beneficial results are obtained from oxalate restriction at an appropriate calcium intake.
To investigate the influence of dietary intake on urinary oxalate excretion in calcium renal-stone formers.
Dietary intake was monitored by using the dietary-record method in 60 idiopathic stone formers. The patients collected their urine for 24 h at home and their urinary oxalate excretion rate was determined. The relationship between the daily intake of various nutrients and urinary oxalate excretion was examined by both monovariate and multivariate analyses.
By monovariate analysis, the intake of carbohydrate, total protein and fat were significantly correlated with urinary oxalate excretion, but the intake of calcium and body surface area were not. In addition, the intake of total protein was highly correlated with that of fat. By multivariate analysis, the intake of carbohydrate and fat were significantly related to urinary oxalate excretion, and the intake of calcium was inversely correlated with urinary oxalate excretion, but the intake of total protein showed no significant correlation.
The intake of carbohydrate and fat was positively and the intake of calcium was inversely correlated with urinary oxalate excretion in stone formers and, taken together, these findings suggested that fat plays an important role in urinary oxalate excretion and that protein has a minimal effect.
An experimental model that allowed differentiation between endogenously and exogenously derived urinary oxalate was used to assess the effect of different forms and doses of ingested calcium on oxalate absorption and excretion. In replication 1 (R-1), subjects participated in three oxalate load (OL) tests: baseline (OL alone), calcium carbonate (OL with concomitant calcium carbonate ingestion), and calcium citrate malate (CCM) (OL with concomitant CCM ingestion). The calcium salts each provided 300 mg elemental Ca. OLs consisted of 180 mg unlabeled and 18 mg 1,2[13C2]oxalic acid. In R-2, subjects participated in four OL tests: baseline (OL alone) and OLs administered concomitantly with 100, 200, or 300 mg Ca. Timed urine samples after the OL were collected at 2-h intervals for the initial 6 h and samples were pooled into 9-h aliquots for the remaining 18 h of the 24-h period. In R-1, 24-h mean exogenous oxalate decreased (P < 0.05) after the OL from 36.2 mg (baseline) to 16.1 mg (after calcium carbonate) and to 14.3 mg (after CCM) whereas endogenous oxalate remained relatively constant. Mean 24-h oxalate absorption decreased significantly from that at the time of the baseline treatment (18.3%) after both calcium carbonate (8.1%) and CCM (7.2%) treatments. In R-2, mean 24-h oxalate absorption was significantly lower after 200 (5.9%) and 300 (7.6%) mg Ca than after 100 mg Ca (9.1%) and the OL alone (11.3%). Concomitant meal ingestion significantly decreased oxalate absorption in the absence of dietary calcium but not in association with the 300-mg Ca treatment. The overall data provide definitive evidence that dietary calcium can reduce oxalate absorption and excretion. Calcium carbonate and CCM were equally effective in this regard and a minimum of 200 mg elemental Ca maximized this effect in conjunction with an oxalic acid intake of 198 mg.
The amount of oxalate ingested may be an important risk factor in the development of idiopathic calcium oxalate nephrolithiasis. Reliable food tables listing the oxalate content of foods are currently not available. The aim of this research was to develop an accurate and reliable method to measure the food content of oxalate.
Capillary electrophoresis (CE) and ion chromatography (IC) were compared as direct techniques for the estimation of the oxalate content of foods. Foods were thoroughly homogenized in acid, heat extracted, and clarified by centrifugation and filtration before dilution in water for analysis. Five individuals consuming self-selected diets maintained food records for three days to determine their mean daily oxalate intakes.
Both techniques were capable of adequately measuring the oxalate in foods with a significant oxalate content. With foods of very low oxalate content (<1.8 mg/100 g), IC was more reliable than CE. The mean daily intake of oxalate by the five individuals tested was 152 +/- 83 mg, ranging from 44 to 352 mg/day.
CE appears to be the method of choice over IC for estimating the oxalate content of foods with a medium (>10 mg/100 g) to high oxalate content due to a faster analysis time and lower running costs, whereas IC may be better suited for the analysis of foods with a low oxalate content. Accurate estimates of the oxalate content of foods should permit the role of dietary oxalate in urinary oxalate excretion and stone formation to be clarified. Other factors, apart from the amount of oxalate ingested, appear to exert a major influence over the amount of oxalate excreted in the urine.
It is believed that soluble oxalate has higher bioavailability than insoluble oxalate. Oca (Oxalis tuberosa) is moderately high in oxalate and contains oxalate in soluble form only. We estimated the bioavailability of oxalate in oca based on the urinary excretion of oxalate after oxalate loading with oca to estimate the bioavailability of oxalate in oca. We also clarified whether bioavailability differs in various oxalate loads from the same food source and studied the effect of an additional calcium source on the bioavailability of oxalate from oca.
Four men and 4 women ingested 50, 100 and 150 gm. oca as well as 100 gm. oca with 100 gm. sour cream. Oxalate was measured in a 6-hour urine sample from each volunteer.
The mean bioavailability of oxalate from oca plus or minus standard deviation was 1.44% +/- 1.31% during the 6-hour period after intake. There was no significant difference in oxalate bioavailability among oxalate intake levels in this study, although oca consumption with sour cream significantly decreased the uptake of oxalate (p <0.01). The variation in bioavailability among individuals was high in our study.
The bioavailability of oxalate in oca appears to be similar to that in spinach. However, bioavailability varies among individuals and depends on other constituents of a combined meal.
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Bioavailability of soluble oxalate from tea and the effect of consuming milk with tea
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