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Effect of Different Cooking Methods on Vegetable Oxalate Content

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Abstract

Approximately 75% of all kidney stones are composed primarily of calcium oxalate, and hyperoxaluria is a primary risk factor for this disorder. Nine types of raw and cooked vegetables were analyzed for oxalate using an enzymatic method. There was a high proportion of water-soluble oxalate in most of the tested raw vegetables. Boiling markedly reduced soluble oxalate content by 30-87% and was more effective than steaming (5-53%) and baking (used only for potatoes, no oxalate loss). An assessment of the oxalate content of cooking water used for boiling and steaming revealed an approximately 100% recovery of oxalate losses. The losses of insoluble oxalate during cooking varied greatly, ranging from 0 to 74%. Because soluble sources of oxalate appear to be better absorbed than insoluble sources, employing cooking methods that significantly reduce soluble oxalate may be an effective strategy for decreasing oxaluria in individuals predisposed to the development of kidney stones.

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... It is found in blueberries, blackberries, tangerines and plums, and in vegetables as spinaches, beets and quinoa [23][24][25][26]. Besides, legumes and nuts also have great content of OAA [27]. Due to its bioenergetic, antiinflammatory and neurogenetic properties, OAA has been postulated as a possible treatment for AD [28]. ...
... At present, there is a growing number of studies with different methodological approaches related to antioxidant consumption and cognitive deterioration [27]; most controlled clinical trials include observational cross-sectional design studies and some prospective community cohorts [52][53][54][55][56]. In turn, there is variability in the source of vitamin administered, where some studies assess the daily consumption of vitamins through diet, while other studies use vitamin supplements. ...
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... O oxalato, frequentemente encontrado em vegetais, não pode ser metabolizado pelos humanos e é excretado na urina. Segundo Chai & Liebman [23] , cerca de 75% de todos os cálculos renais são compostos, principalmente, de oxalato de cálcio e a hiperoxalúria é um dos principais fatores de risco para esta doença porque o oxalato origina de uma combinação de absorção de oxalato da dieta e sintetizados endogenamente. A restrição da ingestão de oxalato na dieta tem sido sugerida como um tratamento para prevenir a nefrolitíase recorrente em alguns pacientes. ...
... Sabe-se que o tratamento térmico, dentre outras funções, é um método bastante utilizado para redução e/ ou inativação de substâncias indesejáveis em alimentos. Desse modo, vários estudos [17,23,45,46] têm sido realizados para avaliar o efeito da temperatura nos teores dos fatores antinutricionais em produtos alimentícios. [17] estudaram o efeito da extrusão na biodisponibilidade do cálcio e de fatores antinutricionais em sementes de amaranto. ...
... Chai & Liebman [23] avaliaram o efeito de diferentes métodos de cozimento em vegetais no conteúdo de oxalato e observaram que a fervura promoveu uma maior redução no teor de oxalato (30-87%) e foi mais eficaz do que cozinhar (5-53%) e do que o forneamento (usado apenas para a batata, sem perda de oxalato). Os autores afirmam que o emprego de métodos de cozimento reduzem significativamente o oxalato e pode ser uma estratégia eficaz para diminuir oxalúria em indivíduos com predisposição para o desenvolvimento de pedras nos rins. ...
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... Twelve research articles out of 66 papers with soluble oxalate contents suitably analysed from fresh materials of at least three vegetable species were selected. The datasets covered 23 families and 88 species, but the data shown in Table 1 include only 14 families and 76 species as some sets included few species per family [1,[6][7][8][9][10][11][12][13][14][15][16]. Table 1 lists oxalate content group means and ranges by vegetable family, edible parts and gives vegetable species with the highest values for that vegetable family. ...
... [6] (ion chromatography-conductivity detector), Savage et al. [7] (ion chromatography-UV-Vis detector), Gupta et al. [8] (titration with potassium permanganate), Savage and Martensson [9] (ion chromatography-UV-Vis detector), Kumari et al. [10] (titration with potassium permanganate), Siener et al. [11] (ion chromatography-enzymatic reaction-amperometric detection), Chai and Liebman [12] (enzymatic degradation), Jimidar et al. [13] (capillary electrophoresis), Gupta et al. [14] (titration with potassium permanganate), Judprasong et al. ...
... Stir frying and pressure cooking with oil, spices and salts reduced total oxalate content by 23-42% on a dry matter basis [37]. In contrast, baking and roasting showed negligible effects on oxalate content [12,15]. Extrusion of cereal bran at 140°C reduced oxalate by up to 37%, while there was only about a 10% reduction by extrusion at 115°C [38]. ...
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Information on food composition including types and contents of nutrients and anti-nutrients is important for food and nutrition research. There is satisfactory information on established nutritive elements for various food groups. However, literature on anti-nutrient component generally scattered and scanty on few major food groups and commonly consumed plant parts. A better understanding of both the positive and negative qualities of vegetable component would help develop better evidence-based promotion and appropriate dietary strategies. This paper reviews seven types of anti-nutrient elements in vegetables: oxalates, phytates, nitrates, tannins, glucosinolates, saponins and alkaloids and their effects, mechanisms, content and processing methods. A total of 360 research papers were systematically identified and 123 were selected with acceptable anti-nutrient data. Vegetable families and plant parts with highest content of each anti-nutrient were identified, with the Leguiminosae family having highest content of phytate, tannins and saponins, and leafy vegetables having high oxalate. The simplest food processing methods to reduce anti-nutrients in vegetables are boiling and removal of certain plant parts. While consumption of vegetables with anti-nutrients do not normally cause adverse effects in the general population, future research to determine nutrient bioavailability based on diets will help increase awareness and improve recommendations on plant food intake.
... Absorbed dietary oxalates are believed to contribute to calcium oxalate kidney stone formation [53]. Insoluble oxalates, on the other hand, are excreted in the feces [54]. Due to their effects on nutrient absorption and possible role in kidney stone formation, oxalates are considered by some to be 'antinutrients'. ...
... Leaves (spinach, beet greens) are reported to have far greater oxalate content than stalks (rhubarb) or roots (beets, carrots). A distinction should be made between total oxalate, soluble and insoluble oxalate, as excess soluble oxalate has more of an effect on bioavailability and kidney stone formation [54]. Chai and Liebman reported fresh spinach to contain an average of 1145 mg/100 g fresh weight (FW) total oxalate, 803 mg being in the soluble form, and 343 mg being insoluble oxalate [54]. ...
... A distinction should be made between total oxalate, soluble and insoluble oxalate, as excess soluble oxalate has more of an effect on bioavailability and kidney stone formation [54]. Chai and Liebman reported fresh spinach to contain an average of 1145 mg/100 g fresh weight (FW) total oxalate, 803 mg being in the soluble form, and 343 mg being insoluble oxalate [54]. Another group found spinach to contain 978 mg/100 g FW of total oxalate, 543 mg of that being soluble oxalate [55]. ...
Article
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Plant-based diets are associated with reduced risk of lifestyle-induced chronic diseases. The thousands of phytochemicals they contain are implicated in cellular-based mechanisms to promote antioxidant defense and reduce inflammation. While recommendations encourage the intake of fruits and vegetables, most people fall short of their target daily intake. Despite the need to increase plant-food consumption, there have been some concerns raised about whether they are beneficial because of the various 'anti-nutrient' compounds they contain. Some of these anti-nutrients that have been called into question included lectins, oxalates, goitrogens, phytoestrogens, phytates, and tannins. As a result, there may be select individuals with specific health conditions who elect to decrease their plant food intake despite potential benefits. The purpose of this narrative review is to examine the science of these 'anti-nutrients' and weigh the evidence of whether these compounds pose an actual health threat.
... EXTRACTION OF TOTAL AND SOLUBLE OXALIC ACID. Oxalic acid extraction and measurement were performed similarly to the methods described by Chai and Liebman (2005). Leaves were ground in an industrial blender in a ratio of 3 g water to 1 g bulked leaf tissue for 2 min. ...
... These values were more than double those reported by Savage et al. (2000), although this may have been the result of differences in leaf maturity and environmental conditions. Total oxalate values for swiss chard were comparable to those observed by Chai and Liebman (2005). There was 38% less total oxalate in swiss chard cultivars than in beet cultivars based on overall means. ...
... The range for root soluble oxalate was 103 to 171 mg/100 g root tissue. These values are, on average, three times larger than values of raw beet root reported by Savage et al. (2000) and over two times larger than values reported by Chai and Liebman (2005) on raw beet root. Levels are smaller than those for pickled beet root reported by Kasidas and Rose (1980). ...
Article
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.
... In the use of foods of plant origin, the identification of compounds considered as "antinutrients" must also be considered due to their adverse effects. One of these compounds is oxalate, which is present in chaya [37][38][39]. Excessive consumption of oxalates is contraindicated due to their ability to generate insoluble complexes with minerals such as calcium (Ca 2+ ), iron (Fe 2+ ), and magnesium (Mg 2+ ) by promoting their accumulation [38]. In this sense, many strategies such as soaking, steaming, boiling, or cooking have been reported to reduce the oxalate concentration from foods. ...
... Our results showed a significant decrease in the oxalate content in the different formulations of cookies in comparison with the chaya flour, indicating that the baking temperature has an important role in decreasing this antinutritional component. Similar results reported a decrease of 30% and 87% in the total oxalate content of boiling vegetables compared with that of baked or steamed vegetables [39]. ...
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Chaya and amaranth are Mexican traditional foods with a high nutritional value. Many studies have demonstrated the individual beneficial effect of each. However, there is no evidence of the use of these foods on the formulation of functional foods. This study evaluated the effect of replacing 5-20% of wheat flour with chaya and amaranth flours to generate four different formulations of cookies. Proximal analysis, total polyphenols and oxalate content, antioxidant activity, fatty acid profile, and sensory analysis were performed on the cookies. The results of the chemical composition showed that all cookies have a high protein content (9.21-10.10%), an adequate amount of fiber (5.34-6.63%), and a balanced ratio of unsaturated-saturated fatty acids (70:20), and they contain PUFAs (50.4-53.2 g/100 g of fatty acids), especially α-linolenic and oleic acids. All formulations presented antioxidant activity (2540 ± 65.9 to 4867 ± 61.7 Trolox equivalents (μmoles/100 g)) and polyphenols (328-790 mg/100 g); in particular, quercetin was identified in their composition. Results of the sensory analysis indicated that incorporation of chaya and amaranth flour in cookies does not affect the acceptability of the products. The inclusion of traditional foods, such as chaya and amaranth, in cookies enhances their nutritional value and increases the content of bioactive compounds associated with health effects.
... Most of studied samples had a significative loss of total oxalates (17%-48%) characterized by the loss of soluble oxalates into cooking water (around 31% to 48%), while Suaeda torreyana S. Watson had the most important loss of these compounds (76%). On the other hand, insoluble oxalates remained in a higher amount in the food matrix (losses of 6% to 35% only), or even had an increase of this component as in Portulaca oleracea L. These findings were consistent with different studies [31,32], which found that boiling reduced the total oxalate of vegetables by leaching a high amount of soluble oxalate into the cooking water, while the insoluble oxalate remained in the food matrix or had moderate losses. These last studies had reported an increase (between 25% and 40%) of insoluble oxalate after boiling of vegetables as potatoes [32], silver beet steams (Beta vulgaricus v. cicla), and parsnip (Peucadenum sativum) [31]. ...
... On the other hand, insoluble oxalates remained in a higher amount in the food matrix (losses of 6% to 35% only), or even had an increase of this component as in Portulaca oleracea L. These findings were consistent with different studies [31,32], which found that boiling reduced the total oxalate of vegetables by leaching a high amount of soluble oxalate into the cooking water, while the insoluble oxalate remained in the food matrix or had moderate losses. These last studies had reported an increase (between 25% and 40%) of insoluble oxalate after boiling of vegetables as potatoes [32], silver beet steams (Beta vulgaricus v. cicla), and parsnip (Peucadenum sativum) [31]. The decreases of total oxalate after boiling in this study is significant because total oxalate in vegetable foods is inversely correlated with the calcium bioavailability [31,33]. ...
Article
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The consumption of vegetables in Mexico includes a wide variety of plants that grow naturally as weeds in the fields. The intake of these vegetables is very important in the Mexican diet because these plants supply an important input of nutrients and compounds such as fiber, vitamins, minerals, and antioxidants. Thus, the plants may be universally promoted as healthy. However, there is little information about these vegetables of popular consumption, especially in terms of the nutritional changes caused by boiling. To determine the influence of boiling on five plants of popular consumption in Mexico, the nutritional composition (proximal analysis, dietary fiber, and oxalates), antioxidant compounds (ascorbic acid, phenolics), antioxidant activity (measured by ABTS and DPPH assays), and physicochemical characteristics (water retention capacity, viscosity, color, and SEM) were evaluated. The boiling affected the nutritional composition of plants, mainly soluble compounds as carbohydrates (sugars and soluble fiber), ash, ascorbic acid, and phenolic compounds and caused changes in food hydration and color. Therefore, it is recommended that these plants be consumed raw or with short boiling times and included the cooking water in other preparations to take advantage of the nutrients released in the food matrix. In the future, to complete studies, 3 to 5 min of cooking should be considered to minimize undesirable modifications in terms of the vegetables’ composition.
... Traditionally, dietary oxalate intake has been associated with the pathophysiology of kidney stone disease risk (Crivelli et al., 2021), and a relationship between dietary oxalates and kidney stone formation has been observed in human studies (Curhan, Willett, Knight & Stampfer, 2004). In relation to oxalate content, it is important to take into consideration that soluble oxalates have a greater impact on bioavailability and the risk of stone formation than insoluble oxalate (Chai & Liebman, 2005). Thus spinaches contain an average of 1145 mg total oxalate/100 g fresh weight, with 803 mg being soluble oxalate (Petroski & Minich, 2020). ...
... A boiling process for 12 min resulted in a reduction between 30% and 87% of soluble oxalates. Whereas, in steam cooking the reduction in oxalates is around 42% to 46% (Chai & Liebman, 2005). Similarly, with soaking a loss of oxalate content between 40.5% and 76.9%, can be achieved (Akhtar, Israr, Bhatty & Ali, 2011). ...
Article
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The intake of foods derived from plants has been proposed as an useful strategy in the prevention of several chronic diseases. However, plants also possess a group of substances known as antinutrients, which may be responsible for deleterious effects related to the absorption of nutrients and micronutrients, or exert beneficial health effects. This review compiles scientific evidence regarding the physiological impact of some antinutrients (lectins, goitrogens, phytates and oxalates) in the human health, their negative effects and the culinary and industrial procedures to reduce their presence in foods. It can be concluded that, the effects of antinutrients on human health could change when consumed in their natural food matrix, and after processing or culinary treatment. Accordingly, some of these compounds could have beneficial effects in different pathological conditions. Future research is required to understand the therapeutic potential of these compounds in humans.
... The negative effect of oxalates on calcium absorption increases when the molar ratio of total oxalate: calcium is major than 9:4 and this occurs in spinach and rhubarb [145]. Chai and Liebman [146] suggested that the boiling method is effective in reducing total oxalate (soluble and insoluble) content in spinach and rhubarb stalks compared to steaming (Table 7). a Values are expressed as mean ± SD; data from [146]. ...
... Chai and Liebman [146] suggested that the boiling method is effective in reducing total oxalate (soluble and insoluble) content in spinach and rhubarb stalks compared to steaming (Table 7). a Values are expressed as mean ± SD; data from [146]. ...
Article
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This article reviews physicochemical aspects of calcium absorption from foods. Notable differences are observed between different food products in relation to calcium absorption, which range from <10% to >50% of calcium in the foods. These differences can be related to the interactions of calcium with other food components in the food matrix, which are affected by various factors, including fermentation, and how these are affected by the conditions encountered in the gastrointestinal tract. Calcium absorption in the intestine requires calcium to be in an ionized form. The low pH in the stomach is critical for solubilization and ionization of calcium salts present in foods, although calcium oxalate complexes remain insoluble and thus poorly absorbable. In addition, the rate of gastric transit can strongly affect fractional absorption of calcium and a phased release of calcium into the intestine, resulting in higher absorption levels. Dairy products are the main natural sources of dietary calcium in many diets worldwide, which is attributable to their ability to provide high levels of absorbable calcium in a single serving. For calcium from other food products, lower levels of absorbable calcium can limit contributions to bodily calcium requirements.
... The concentrations of phytates, oxalates, tannins and Cynogenic glyconides in S. alternata are 5.37 mg/100g, 2.95 mg/100g, 4.29 mg/100g and 7.53 mg/100g respectively shown in Figure 2. Cynogenic glyconides has the highest value while oxalate has the least value. High value of oxalate in human diet can increase the risk of renal calcium absorption and has been implicated as a source of kidney stones [8]. Whereas high value of tannin in foods interferes with protein absorption and digestive enzymes [3]. ...
Article
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Plant leaves play an essential part in health service as source of medicines. Since ancient age, plants are exploited as medicinal source. Various medicinal plants and their purified constituents have exposed helpful therapeutic potentials. The present study revealed the nutritional and antinutritional content of S. alternata which are known to possess the active medicinal chemical constituents. S. alternata has high content of the following essential minerals; Calcium, and Sodium with the following concentrations; 15.82 ± 0.01mg/100g and 10.55 ± 0.01 mg/100g, respectively. While relative amount of Potassium (5.89 ± 0.03mg/100g), Phosphorus (3.97 ± 0.02mg/100g) and Magnesium (6.29 ± 0.02mg/100g) were found to be present in the sample. The presence of Phytochemicals; Saponins, Alkaloids, Flavonoids Tannins and Hydrogen cyanide were evaluated to be 5.23± 0.01 mg/100g, 5.54 ± 0.0102mg/100g, 31.60 ± 0.0202mg/100g, 12.59 ± 0.0102mg/100g and 10.11 ± 0.0102mg/100g respectively. Anti-nutritional factors were recorded, thus; Phytate (5.37 ± 0.02 mg/100g), Oxalate (2.95 ± 0.01 mg/100g), Tannin (4.29 ± 0.01 mg/100g) and Cynogenic glyconide (7.53 ± 0.01 mg/100g). The presence of these phytochemicals and minerals point to the medicinally and nutritionally potent and should be used in the pharmaceutical industries for the formulation of drugs. All the anti-nutrient concentrations found exceeded the acceptable levels for human and animal consumption. However, the levels of anti-nutrients can be reduced through traditional processing techniques such as boiling, steaming, and cooking to make it safer for drugs development.
... The antinutritional composition of tomato fruits was determined by following different methods: the phytate content was measured according to the method described by Lucas and Markaka [35]; the tannins were determined using the method of Ogawa and Yazaki [36]; the oxalate content was measured using the methods of Chai and Liebman [37] and Umogbai et al. [38], and the results were calculated according to Attalla et al. [39] and Chai and Liebman [40]; the saponins content were measured according to AOAC, 1990 [41]; the trypsin inhibitors were determined as described by Korsinczky et al. [42] and calculated according to Lukanc et al. [43]; the α-amylase inhibitors were measured as described by Barrett and Udani [44]. ...
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The tomato is one of the most important species in the food sector. For farmers, the increase in yield in greenhouse conditions by keeping a high quality of fruits represents a goal which is very difficult to achieve in these conditions. Therefore, the present study evaluates the influence that a continuous electric current might have on some biometrical, physiological and quality parameters of tomato fruits. The study was carried out in a greenhouse where tomato plants belonging to Qualitet F1 hybrid were treated with different continuous electric currents, under 5 DC sources, stabilized by the laboratory 0–30 V/0–5 A. During the research, the tomato plants were exposed to different electric current intensities or voltages on the plants or in the soil (T1-0.15 A; T2-0.30 A; T3-0.45 A; T4-1.5 V; T5-1.5 V-soil). The tomato plant samples were compared with an untreated control. In order to determine the influence of a continuous electric current, observations and determinations were made on tomato plants and fruits. The results highlighted significant differences between the treated and not treated plants, regarding the plant height, yield, firmness, acidity, total soluble solids, antioxidant activity, crude and dietary fibres, tannins, oxalates, saponins, α-amylase inhibitors, K, Mg, Fe and Zn content. Depending on the intensity of the electric current and the manner of application, the biometrical, physiological and quality parameters of tomato fruits were differently influenced. Both positive and negative influences were registered. More experiments are needed in order to establish a relation between the electric current intensity and the manner of application which can lead to better and higher tomato yields and quality in greenhouse conditions.
... Despite the high oxalate content in some foods, it is important to mention that different processes have been identified to reduce the oxalate content, e.g., soaking, steaming, boiling, or cooking. 25 Chai and Liebman 25 reported that boiling decreased the total oxalate content of vegetables by 30% and 87% compared with that of baked or steamed vegetables. ...
Article
Objective There is no enough information on the classification of oxalate content in several foods, particularly in ethnic foods, to recommend their consumption in subjects with urolithiasis (UL). The objective of the present study was to generate reliable information on the oxalate content and antioxidant activity in different foods and classify them by very low, low, medium, high and very high oxalate content and antioxidant activity. Methods The oxalate content of 109 foods including ethnic foods was assessed by an enzymatic assay, and the antioxidant activity was measured by the oxygen radical absorbance capacity to determine the oxalate/antioxidant activity ratio. Oxalate consumption was then evaluated in 400 subjects with overweight and obesity using 24-h dietary recalls. Results The main foods with high oxalate content were raw spinach, huanzontle, purslane, chard, almond, and toasted and sweetened roasted amaranth. The highest antioxidant activity was found in strawberries, all types of chocolates, roselle, morita peppers, and pinolillo. Subjects with overweight or obesity exceed the dietary oxalate daily intake recommendation. Conclusions The classification of foods by their oxalate content and antioxidant activity will be very useful to generate nutritional recommendation in different diseases, mainly UL.
... value recorded against CSCT40 compared with control value). This is in tandem with the report ofChai and Liebman (2005), Massey, (2007), Jack (2013)and Augustine and Anitha (2014) which indicated there was a significant loss of oxalate in almost all the test vegetablesviz, red swiss chard, spinach, rhubarb, beets, carrots, Brussels sprouts, broccoli, potato and green leafy vegetables subjected to boiling which ranged from 30 to 87%.Nonetheless, toasting of castor seed at 40 min level appeared to be more efficient method in reducing its oxalate content followed by autoclaving at 30 min level.It is expedient that tannins in any plant materials to be used for animal feed be made to undergo a process of reduction because these substances are astringent, bitter plant polyphenols that either bind and precipitate or shrink proteins and interfere with iron absorption through a complex formation with iron when it is in the gastrointestinal lumen which decreases the bioavailability of iron (King-Thom et al., 1998 and Praveen and Kumud, 2012).In this work, tannin values in all the treatments are significantly different (p< 0.05) from one another. It is highest in control castor seed sample, 10.54±0.06 and least in 60 minutes boiled samples, 5.78±0.03. ...
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The anti-nutritional values in raw, autoclaved, boiled, fermented, soaked and toasted castor oil seeds (Ricinus communis L.) collected from Ado-Ekiti metropolis, Nigeria were 3CSCA30 and CSCA40) for autoclaving; 40, 50 and 60 min (CSCB40, CSCB50 and CSCB60) for boiling; 48, 72 and 96 h (CSCF48, CSCF72 and CSCF96) for fermenting; 48, 72 and 96 h(CSCS48, CSCS72 and CSCS96) for soaking and 20, 30 and 40 min (CSCT20, CSCT30 and CSCT40) for toasting. The raw sample which served as control was tagged CSCR00. The 15 processed and the raw samples were decorticated, after the wet samples (except toasted) had been sundried for four days, ground and then representative samples were taken to the laboratory for anti-nutrients determination according to AOAC (2006), Abeza et al., (1968), Reddy et al., (1982) and Wang et al., (1996) (tannin, oxalate, phytate and lectin respectively). Samples exhibited significant difference (p˂0.05) compared to the control sample and among one another in terms of all the parameters examined. There was reduction in phytate, oxalate, tannin and lectin with increase in temperature of all the treatment methods adopted. Owing to the drastic reduction in virtually all the parameters examined, castor seed sample autoclaved for 30 min (CSCA30) was considered best level among others. It was therefore recommended for fish feed formulation.
... Oxalic acid and oxalates are common in plant foods, and the largest amounts are found in rhubarb, spinach, mangold, and purslane [88]. Oxalic acid may be present as insoluble calcium or magnesium oxalate crystals or as soluble sodium or potassium oxalate. ...
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Objective: To provide an overview of nutrients and compounds, which influence human intestinal iron absorption, thereby making a platform for elaboration of dietary recommendations that can reduce iron uptake in patients with genetic haemochromatosis. Design: Review. Setting. A literature search in PubMed and Google Scholar of papers dealing with iron absorption. Results: The most important promoters of iron absorption in foods are ascorbic acid, lactic acid (produced by fermentation), meat factors in animal meat, the presence of heme iron, and alcohol which stimulate iron uptake by inhibition of hepcidin expression. The most important inhibitors of iron uptake are phytic acid/phytates, polyphenols/tannins, proteins from soya beans, milk, eggs, and calcium. Oxalic acid/oxalate does not seem to influence iron uptake. Turmeric/curcumin may stimulate iron uptake through a decrease in hepcidin expression and inhibit uptake by complex formation with iron, but the net effect has not been clarified. Conclusions: In haemochromatosis, iron absorption is enhanced due to a decreased expression of hepcidin. Dietary modifications that lower iron intake and decrease iron bioavailability may provide additional measures to reduce iron uptake from the foods. This could stimulate the patients' active cooperation in the treatment of their disorder and reduce the number of phlebotomies.
... However, no direct evidence has shown that acridity is caused by mechanical puncturing of the skin and several studies suggest that the raphides do not cause acridity (Moy et al., 1979;Paull et al., 1999;Pohl, 1964). Evidence that acridity is due not to the raphides but to a factor on the raphides includes the following: (i) Acridity is lost with cooking and after extraction with methanol, ethanol, distilled water, and water/detergent mixtures with intact raphides remaining (Akpan & Umoh, 2004;Bradbury & Nixon, 1998;Chai & Liebman, 2005;Moy et al., 1979;Payne et al., 1941;Pedler & Warden, 1888;Saha & Hussain, 1983;Tang & Sakai, 1983;Tsai et al., 2006); (ii) there is no strong relationship between acridity and raphide number or amount of calcium oxalate extracted (Halloway et al., 1989;Moy et al., 1979;Payne et al., 1941); (iii) species that have pointed raphides can have very low or no acridity (Bradbury & Nixon, 1998;Ledbetter & Porter, 1970); (iv) the slowness of the acridity response at low concentrations does not suggest mechanical injury; (v) wide variation in sensitivity to taro acridity is not consistent with mechanical penetration; (vi) fewer raphide bundles are often found in the more acrid taro cultivars (Moy et al., 1979); and (vii) treatment of purified acrid raphides with protease leads to rapid loss of acridity with no change in raphide morphology (Paull et al., 1999). An alternate possibility is that chemical irritants or allergens occur on the surface of the raphides (Bradbury & Nixon, 1998;Konno et al., 2014;Nixon, 1987;Paull et al., 1999;Suzuki et al., 1975;Tang & Sakai, 1983), and the raphides play a synergist role as carriers (Konno et al., 2014). ...
Article
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Calcium oxalate raphide crystals are found in bundles in intravacuolar membrane chambers of specialized idioblasts cells of most plant families. Aroid raphides are proposed to cause acridity in crops such as taro (Colocasia esculenta (L.) Schott). Acridity is irritation that causes itchiness and pain when raw/insufficiently cooked tissues are eaten. Since raphides do not always cause acridity and since acridity can be inactivated by cooking and/or protease treatment, it is possible that a toxin or allergen‐like compound is associated with the crystals. Using two‐dimensional (2D) gel electrophoresis and mass spectrometry (MS) peptide sequencing of selected peptides from purified raphides and taro apex transcriptome sequencing, we showed the presence on the raphides of peptides normally associated with mitochrondria (ATP synthase), chloroplasts (chaperonin ~60 kDa), cytoplasm (actin, profilin), and vacuole (V‐type ATPase) that indicates a multistage biocrystallation process ending with possible invagination of the tonoplast and addition of mucilage that may be derived from the Golgi. Actin might play a crucial role in the generation of the needle‐like raphides. One of the five raphide profilins genes was highly expressed in the apex and had a 17‐amino acid insert that significantly increased that profilin's antigenic epitope peak. A second profilin had a 2‐amino acid insert and also had a greater B‐cell epitope prediction. Taro profilins showed 83% to 92% similarity to known characterized profilins. Further, commercial allergen test strips for hazelnuts, where profilin is a secondary allergen, have potential for screening in a taro germplasm to reduce acridity and during food processing to avoid overcooking. All edible Aroids cause allergic type responses (acridity) thought to be caused by the sharp calcium oxalate raphide crystals. We have shown that raphide‐associated proteins could guide biomineralization, and the profilins found are potential allergens.
... Oxalate reduction during boiling could be due to its solubility in boiling water, facilitated by the breakage of cells to leak soluble oxalates into the cooking water. Boiling was reported to remarkably lower the soluble oxalate content by 30-87% than steaming (5-53%) in red and green Swiss chard leaves, spinach, and rhubarb stalks (39). Boiling in water also reduced total oxalates in Thai vegetables significantly by 16-79%, also in Mexican vegetables (40) and in chard (Beta vulgaris), watercress (Nasturtium nasturtium-aquaticum), spinach (Spinacia oleracea), and purslane (Portulaca oleracea L.) (38). ...
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Different household cooking techniques (boiling, steaming, stir frying, and microwave) were tested on the changes of targeted phenolic compounds, antioxidant property (ferric reducing-antioxidant power (FRAP) activity), α-glucosidase activity, antinutritive compounds, and sensory properties in commonly consumed traditional leafy vegetables in Southern Africa, the non-heading Chinese cabbage ( Brassica rapa L. subsp. chinensis ) and African nightshade ( Solanum retroflexum Dun). Stir frying increased kaempferol-3- O -hydroxyferuloyl-trihexoside, kaempferol-dihexoside, sinapoyl malate, rutin, and isorhamnetin- O -dihexoside in Chinese cabbage leaves, followed by steaming. Similarly, stir frying increased kaempferol-3- O -rutinoside, chlorogenic acid, caffeoylmalic acid, and quercetin-3- O -xylosyl-rutinoside in nightshade, followed by steaming. Biomarkers, sinapoyl malate (Chinese cabbage) and caffeoylmalic acid (nightshade), separated the stir frying from the other cooking techniques. Steaming and stir-frying techniques significantly increased the FRAP activity; whereas boiling and microwaving reduced the tannin, oxalate, and phytate contents in both leafy vegetables and steroidal saponins in nightshade. Stir-fried nightshade leaf extract showed the most effective inhibition against α-glucosidase activity, with an IC 50 of 26.4 μg ml ⁻¹ , which was higher than acarbose, a synthetic compound (positive control; IC 50 69.83 μg ml ⁻¹ ). Sensory panelists preferred the stir-fried Chinese cabbage and nightshade leaves, followed by steamed, microwaved, and boiled vegetables.
... Thus, it is necessary to disseminate information to potential consumers about the forms of preparation that reduce or eliminate calcium oxalate from the leaves of taioba so that the presence of this compound does not become an obstacle to popularization. In this sense, the form of preparation of the leaf of the taioba used in the Dom Helder settlement (boiled) is precisely the most effective way to reduce calcium oxalate in conventional vegetables 75 . ...
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This study aims to provide a simple framework to identify wild food plants with potential for popularization based on local knowledge and perception. To this end, we also characterized the distribution of this knowledge in the socio-ecological system. We developed the study in the rural settlement Dom Hélder Câmara in northeastern Brazil. The species with the greatest potential for popularization considering the attributes accessed from local knowledge and perception were Psidium guineense Sw., Genipa americana L., Xanthosoma sagittifolium (L.) Schott and Dioscorea trifida L.f. However, the high variation in local knowledge on wild food plants suggests that species that are not frequently cited can also be promising. The absence of age or gender-related knowledge patterns indicates that studies for prospecting wild food plants in similar socioecological contexts need to reach the population as a whole, rather than focusing on a specific group.
... 62.5 ml is taken to be heated until almost boiling. Followed by titration using KMnO 4 4 5). ...
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Kimpul tuber is a source of carbohydrates that have high levels of oxalate, therefore it is necessary to reduce oxalate levels, several methods have been used to reduce oxalate levels, high levels of oxalate are caused by the sap or mucus in the taro. The process of decreasing oxalate levels by physical and chemical means has been carried out but has not yet obtained optimal results for low oxalate levels, therefore a fermentation process is carried out to obtain optimal results, which is recommended for 71mg / 100gr. Use of taro is one of the foods used to replace rice or other types of carbohydrates, but taro has a low-calorie level so it is safe for those who have diabetes. In this study, the fermentation process was carried out for 48 and 72 hours to get a perfect process by involving the microbes saccharomyces cerevisiae and rhizopus oryzae. The results of this study indicated that the levels of oxalate produced were 54 mg/100gr in the 72-hour fermentation process using 0.2% / liter rhizopus orizae.
... Although these are calcium-rich vegetables, they are also high in oxalic acid, and calcium bioavailability appears to be only ~5% (Heaney, Weaver, and Recker 1988;Mangels 2014). However, steaming and especially boiling (and discarding the water) can considerably reduce oxalic acid content (by ~30-80%) (Massey 2007;Chai and Liebman 2005). Thus, more human studies assessing bioavailability with different cooking methods would be helpful in this field (Heaney, Weaver, and Recker 1988). ...
... However, a prospective cohort study reported only a modest positive association between dietary oxalate intake and the risk for incident stone formation [139]. Several reasons could be responsible for these inconsistencies, including the use of food frequency questionnaires, which are prone to errors, to evaluate dietary oxalate intake in large cohort studies, the daily variation in the oxalate ingestion and the variability of the oxalate content due to growth conditions, preparation and processing of food [59,[140][141][142]. Therefore, studies using diets strictly controlled in their oxalate and nutrient content and the use of comprehensive data on the oxalate content of raw and processed foods are required. ...
Article
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The prevalence of kidney stone disease is increasing worldwide. The recurrence rate of urinary stones is estimated to be up to 50%. Nephrolithiasis is associated with increased risk of chronic and end stage kidney disease. Diet composition is considered to play a crucial role in urinary stone formation. There is strong evidence that an inadequate fluid intake is the major dietary risk factor for urolithiasis. While the benefit of high fluid intake has been confirmed, the effect of different beverages, such as tap water, mineral water, fruit juices, soft drinks, tea and coffee, are debated. Other nutritional factors, including dietary protein, carbohydrates, oxalate, calcium and sodium chloride can also modulate the urinary risk profile and contribute to the risk of kidney stone formation. The assessment of nutritional risk factors is an essential component in the specific dietary therapy of kidney stone patients. An appropriate dietary intervention can contribute to the effective prevention of recurrent stones and reduce the burden of invasive surgical procedures for the treatment of urinary stone disease. This narrative review has intended to provide a comprehensive and updated overview on the role of nutrition and diet in kidney stone disease.
... Oxalate and phytate levels have been observed to decrease after processing. In peas, reductions in phytate were observed after thermal processing [21,22], while reductions in oxalate have been observed in several fruits and vegetable after processing [23][24][25]. ...
Article
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Ackee (Blighiasapida) fruit has a nutritional composition comparable to other commonly consumed fruits although its consumption is limited by the presence of anti-nutrients. This study investigated the effect of processing on some anti-nutrients (oxalate and phytate) as well as on ascorbate, carotenoids and phenolic compounds in ackee arils. Changes in physicochemical (pH, titratable acidity, brix and color) were also analyzed. Ackee fruit was cut into arils and cooked for 15 min either by boiling in water at 100°C or steamed or fried in oil at 180°C. The unprocessed ackee aril had a pH, titratable acidityand brix of 5.79, 0.52% and 2.70, respectively. Significant changes in these physicochemical properties were only observed in the boiled arils while the highest change in color was observed in the steam fruits. Significant reductions in ascorbate levels of 49.27, 32.86 and 56.29% were observed after boiling, steaming and frying, although these processing methods did not significantly affect carotenoid and phenol levels. The levels of the anti-nutrients reduced significantly with oxalate reducing by 22.37, 26.67 and 37.42% and phytate levels reducing by 62.50, 66.67 and 54.17%, after boiling, steaming and frying, respectively.
... However, the leaves and roots of chard have reported the presence of oxalates and nitrates, substances that represent an antinutritional factor since they subtract micronutrients during the digestive process in humans and contribute to the formation of kidney stones. [217,218] Antithrombotic activity of extracts derived from chaya leaves Currently, there are limited studies in the scientific literature that indicate the antithrombotic effect of chaya leaf extracts, which will be presented in this section. Although the exact mechanism by which the chaya has this activity is not known, in this investigation, due to the scientific advances achieved in this topic, it is suggested that it may be due to the secondary metabolites present in the leaves, which have been discussed in the previous sections. ...
Article
Cardiovascular diseases are the leading cause of death worldwide. The most common underlying pathologies of cardiovascular disorders are thromboembolic diseases. The antithrombotic therapy prevents the formation of thrombi or dissolves the previously constituted ones. However, it presents a high rate of accidents such as gastric bleeding and cerebrovascular embolisms. Thus, the use of herbal medicine has become a viable option for the treatment of such diseases. Reports of traditional Mayan and Nigerian medicine indicate that the Cnidoscolus aconitifolius (Mill.) I.M. Johnst, knowed as Chaya by Mayas in Yucatán, is used as a blood thinner. Currently, there are limited scientific reports that support the antithrombotic activity of the chaya, among which its cardioprotective, anticoagulant and fibrinolytic effect has been reported. However, the exact mechanism by which the chaya exerts these effects is not yet known. Due to the ethnobotanical reports of traditional medicine and existing scientific studies, it is possible to suggest that chaya extracts exert a biological effect on various platelet, coagulant and fibrinolytic enzymes of the blood hemostatic system. This review will analyze the content of secondary metabolites present in Cnidoscolus aconitifolius (Mill.) I.M. Johnst leaf extracts, in order to propose the possible antithrombotic mechanisms of chaya.
... 30,31 Students, parents and food providers at school canteens should be informed that boiling or steaming vegetables can reduce soluble oxalate by 30-87% and 5-53%, respectively. 32 However, students and parents should be informed to not rely only on vegetables to provide all of their daily calcium needs. ...
Article
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Objective: A three study research program was conducted to identify high calcium products available in the market (study I), identify high calcium products that were known or consumed by lower secondary school students in the last three months (study II), and identify the amount and sources of calcium that students had consumed in the prior 24 hours, their knowledge about sources of high calcium and how to interpret calcium information on nutrition labels of food packages (study III). Methods: In study I, a cross-sectional market survey was employed. In studies II and III, a school-based cross-sectional survey was employed. The survey population was students enrolled in grades 7-9 (11-14 years old) in a medium-sized lower secondary school in semi-urban Khon Kaen, Thailand. A total of 309 students were invited, with 168 and 209 students participating in studies II and III, respectively. Data were collected with self-administered questionnaires. Results: Ninety-three high calcium products were identified. Only 49 were known or consumed by students in the last three months. The median amount of calcium consumed in the previous 24 hours was 410 mg (IQR: 160, 983). Only 31.1% of students (65/209) consumed more than the Thai recommended daily intake (TRDI) of calcium (800mg) in the previous 24 hours. Their main source of calcium was milk. Other high calcium items that were consumed were malt drink, minnow, canned fish, calcium fortified soy milk and Chinese kale. The overall average knowledge score was 6.5±2.4 out of a maximum of 17. The average knowledge scores for high calcium food sources and for interpreting the calcium information on a sample nutrition label were 4.6+1.8 (out of 12), and 1.9±1.2 (out of 5), respectively. Discussion: Students should be introduced to high calcium products in their community such as hard tofu, minnow, and small freshwater shrimp. Educational programs on nutrition label interpretation are needed.
... Ingredients provide more explicit detail about each meal. Cooking methods (baked, pan-fried, deep-fried, steamed, grilled, boiled, roasted) transform ingredients and affect their final calories and nutrients [17,45,81]. Providing these different types of information allow users to reflect at different granularity and depth about their diet. ...
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Self-tracking can improve people's awareness of their unhealthy behaviors to provide insights towards behavior change. Prior work has explored how self-trackers reflect on their logged data, but it remains unclear how much they learn from the tracking feedback, and which information is more useful. Indeed, the feedback can still be overwhelming, and making it concise can improve learning by increasing focus and reducing interpretation burden. We conducted a field study of mobile food logging with two feedback modes (manual journaling and automatic annotation of food images) and identified learning differences regarding nutrition, assessment, behavioral, and contextual information. We propose a Self-Tracking Feedback Saliency Framework to define when to provide feedback, on which specific information, why those details, and how to present them (as manual inquiry or automatic feedback). We propose SalienTrack to implement these requirements. Using the data collected from the user study, we trained a machine learning model to predict whether a user would learn from each tracked event. Using explainable AI (XAI) techniques, we identified the most salient features per instance and why they lead to positive learning outcomes. We discuss implications for learnability in self-tracking, and how adding model explainability expands opportunities for improving feedback experience.
... This confirms the results of Onyeoziri et al. (2018), who detected a sandy texture in Amaranthus cruentus and Cleome gynandra leaves and suspected that it may be due to an interaction between calcium and oxalic acid present in the vegetables. The oxalic content of Amaranthus leaves can vary between genotypes and species, and can be reduced by boiling (Chai and Liebman 2005). ...
Article
Hedonic assessment and sensory characteristics of 13 Amaranthus genotypes, stewed with onions, tomatoes and potatoes, were evaluated. 50 consumers ranked their preference on a nine-point hedonic scale to determine overall acceptability of the stewed samples. In addition, 100 consumers were asked to select sensory characteristics that described the genotypes best, using the Check-all-that-apply question. Hedonic responses indicated significant differences (p < 0.001) between stewed samples. Significant differences were also found in the frequency with which consumers used 15 of the 23 terms generated to characterise the sensory profile of stewed Amaranthus leaves. Correspondence analysis illustrated differences in sensory characteristics between genotypes, describing 72.4% variance. Agglomerative hierarchical clustering indicated three consumer preference clusters, while external preference mapping showed the regions of maximum liking. There was no correlation between hedonic evaluation and sensory characteristics. In addition, no strong association between specific species, genotypes and sensory attributes was observed.
... The calcium absorption from oxalate-rich vegetables (spinach, Swiss chard) may be as low 5%; from beans, almonds, tahini, and figs 20-25%; from dairy products 32%; from soy products (tofu, fortified soy beverages), it is similar to dairy milk; and from low-oxalate vegetables (kale, Chinese cabbage, broccoli, bok choy, etc.) 50-60% [249][250][251]. Boiling can reduce oxalate content in green leafy vegetables [252]. A vegetarian diet, with its high intake of fruit and vegetables, is rich in anti-inflammatory phytonutrients, specifically carotenoids and flavonoids, and potassium and magnesium. ...
Article
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Plant-based diets, defined here as including both vegan and lacto-ovo-vegetarian diets, are growing in popularity throughout the Western world for various reasons, including concerns for human health and the health of the planet. Plant-based diets are more environmentally sustainable than meat-based diets and have a reduced environmental impact, including producing lower levels of greenhouse gas emissions. Dietary guidelines are normally formulated to enhance the health of society, reduce the risk of chronic diseases, and prevent nutritional deficiencies. We reviewed the scientific data on plant-based diets to summarize their preventative and therapeutic role in cardiovascular disease, cancer, diabetes, obesity, and osteoporosis. Consuming plant-based diets is safe and effective for all stages of the life cycle, from pregnancy and lactation, to childhood, to old age. Plant-based diets, which are high in fiber and polyphenolics, are also associated with a diverse gut microbiota, producing metabolites that have anti-inflammatory functions that may help manage disease processes. Concerns about the adequate intake of a number of nutrients, including vitamin B12, calcium, vitamin D, iron, zinc, and omega-3 fats, are discussed. The use of fortified foods and/or supplements as well as appropriate food choices are outlined for each nutrient. Finally, guidelines are suggested for health professionals working with clients consuming plant-based diets.
... In several leafy vegetables, soluble oxalate was quickly dissolved within 2-6 min (> 30% loss of oxalate) (Judprasong et al., 2006). In addition, soluble oxalate loss was detected in samples of spinach and carrot after boiling them in water during cooking (Chai and Liebman, 2005). The release rate of water soluble oxalate from spinach explants varies along with temperature and incubation time (Kusuma et al., 2016). ...
Article
Plants produce a variety of crystals with different shapes and sizes. Based on their appearance, calcium oxalate crystals, especially raphides, have been suggested to play a key role in the defense mechanism against insect attack and microbial infections. Colocasia esculenta, a tropical plant primarily grown for its edible corms contains a large number of cells (idioblasts) with needle-like crystals of calcium oxalate (i.e., raphides). The concentration of raphides in the plant varies with the ploidy level, cultivar, organ, and micro environment. The objective of this study was to evaluate the physiological, organic and inorganic biochemical changes in the differentiated leaves of elephant ear (Colocasia esculenta var. aquatilis) and examine the rate of release of these compounds in water soluble forms. Regarding photosynthetic functions, the net photosynthetic rate (Pn) was positively related to light intensity, especially in fully expanded and old leaves. However, the Pn, transpiration rate (E), and stomatal conductance (gs) in young leaves were lower than those in fully expanded and older leaves, resulting in low levels of total soluble sugar content in both the petioles and leaf blades of young leaves. In contrast, oxalic acid and calcium in both petioles and leaf blades peaked at > 2.0 mg·g⁻¹ FW and ~185 mg·g⁻¹ FW, respectively. A large number of idioblasts (~5.5 idioblasts per observed microscopic field) were observed in young leaves. Oxalic acid and calcium ions extracted from the leaf tissues were rapidly dissolved in hot water (85°C) for 10–15 min, leading to a decline in the number of idioblasts. Based on these results, petioles and leaf organs of elephant ear may be eaten safely after boiling in hot water for 15 min to dissolve CaOx.
... Colocasia leaves are the rich source of βcarotene, ascorbic acid, folic acid, riboflavin and minerals like Fe, Ca and P. The "itching" characteristic of colocasia is one of the major problems for direct consumption and it is due to the presence of crystals of calcium oxalate (Gaosong, 1996) and the concentrations of oxalate is relatively higher in young leaves as compared to the older leaves (Redak and Savage, 2008;Savage and Dubois, 2006). According to Oscarsson and Savage (2006), there are soluble and insoluble forms of oxalate present in colocasia and its concentration is reduced markedly after boiling it into water (Chai and Liebman, 2005). Thus, to preserve the stems and leaves of colocasia, lotha tribes cut these stem (Fig. 16) and leaves (Fig. 18 &19) into relatively small pieces for proper drying. ...
Article
Storage, preservations, processing plays a vital role for food security.. The losses of major agricultural commodities in India is estimated about Rs. 926,510 billion due to poor post harvest management. Since long back the farmers of Wokha district, Nagaland, has developed traditional system for safe storage. Deplorable transport facilities and remoteness are two major constraints for proper marketing service to the local people and as self-reliant society; they can't totally depend on the external food sources. For safe storage, effective processing and preservations indigenous techniques have been developed since ancient times. Therefore, the present investigation was made to study the indigenous traditional knowledge's (ITKs) on storage and preservation of food items by the indigenous Lotha-Naga tribe of Wokha district of Nagaland. The result reveals that the tribe follows traditional but sound scientific methods of storage, processing and preservation techniques of local food items. The tribe store rice in a bamboo made structure by plastering the same with mud, maize grains by simply tying and hanging the cobs in bunches, soybean by traditional fermentation process, Traditional gooseberry, chowchow, bamboo shoot, colocassia, fish and meat, etc. which are traditional but scientific methods of preservation of food.
... Spinach (Spinacia oleracea) was purchased from a local supermarket as a fresh-cut product (Florette SAS, Milagro, Navarra, Spain). The edible part was boiled for 10 minutes to remove oxalic acid, 25 the water was discarded, and then the cooked spinach was lyophilized and ground. The powdered samples were stored at 4°C until use. ...
Article
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Non-alcoholic fatty liver disease (NAFLD) is defined as the accumulation of fat in liver cells, which causes serious health consequences. Animal and human studies suggest that the gut microbiota plays a role in the pathogenesis of NAFLD. Here, we investigated whether spinach consumption could ameliorate high-fat-diet-induced disturbances of certain intestinal bacterial groups and products derived from their metabolism, such as short-chain fatty acids (SCFAs) and microbial phenolic catabolites. Attention is also paid to features of metabolic syndrome such as blood lipids and glucose. For the study, a rat model of high-fat-diet-induced NAFLD was used. There were six experimental groups; NC (normal diet), NB (normal diet+2.5% spinach), NA (normal diet+5% spinach), HC (high-fat diet), HB (high-fat diet+2.5% spinach) and HA (high-fat diet+5% spinach). The rats consumed these diets for five weeks, and after that were sacrificed and plasma, urine, intestinal content, faeces and liver samples were taken. Biochemical parameters were analyzed in plasma, phenolic catabolites were quantified in faeces, urine, plasma and liver by UPLC-ESI-MS/MS, and the analysis of the microbiota and SCFAs in the intestinal content was performed by qPCR and GLC. Consumption of a high-fat diet caused NAFLD and dislipaemia and altered the gut microbiota and the pattern of SCFAs and phenolic gut microbial catabolites. Supplementation with spinach partially ameliorated some alterations induced by the high-fat diet, in particular by increasing Lactobacillus counts, reducing the fasting glucose and total and LDL-cholesterol and preventing excess liver cholesterol accumulation, thereby improving the values of the steatosis biomarkers.
... Antinutrients such as phytic acid, oxalic acid, protease inhibitors, and tannins were reported to be reduced in legumes and vegetables when subjected to heat during cooking mostly at temperatures less than the boiling point for 15 min (Chai and Liebman, 2005;Onwuka 2006;Fernando et al., 2012;Udousoro and Akpan, 2014). Although the cooking time required is influenced by the type of antinutrient, food plant, and the cooking method, lengthier cooking time enhances greater reductions of antinutrients. ...
Chapter
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Human nutrition refers to the supply of nutrients to cells in the body through foodconsumption (Newton et al., 1979). These nutrients are used by the body tissues andprovide energy for the biological processes taking place in the body. Seven major nu-trient groups can be obtained from foods. These include:macronutrientsin the formof proteins, fats, carbohydrates, fibers, and water; andmicronutrientssuch as vita-mins and minerals. Extremely important role of a balanced diet and hence nutritionin human health has been appreciated since ancient times (Latham, 1998). A varietyof naturally occurring foods such as fruits and vegetables have been shown to possessfunctional properties that aid in stalling disease progression, inhibition of pathophysi-ological mechanisms, and suppression of infection (Hartmann and Meisel, 2007).With the advent of new technologies in the detection of human diseases and anin-depth understanding of the core causes of these ailments, a wide variety of drugshave been developed to target certain pathogenic molecules participating in the dis-ease processes (Kannan et al., 2011). Considering that drugs often treat the symp-toms rather than cure diseases, a more affordable alternative is to identify andconsume natural foods as well as active food components with proven therapeuticproperties such as anticancer, antianemic, antidiabetic, and antimicrobial (Reedyet al., 2014). Consequently, the study of human nutrition has evolved to be interdis-ciplinary involving physiology, biochemistry, molecular biology, psychology, an-thropology, public health, economics, and political science, with the ultimate goal being to promote optimal health, prevent nutritional deficiency diseases, and re-duce the risk of chronic nutritional illnesses (Wilk, 2012). The goal also encom-passes management of nutritional problems through valorization of food wastes, as
... Dietary oxalates that occur due to the presence of calcium oxalate are detrimental to health as they are associated with aggravation of kidney stones and malabsorption of calcium when foods containing high amounts of oxalate are consumed [25]. For this reason, they need to be eliminated or reduced to acceptable levels since the oxalate restriction, which is defined as the dietary oxalate limit, is no more than 40 -50 mg [26]. ...
... The oxalic acid content is suggested to increase with the ripeness of the fruit [66], and one of the suggested mechanisms for this increase is due to the conversion of ascorbic acid to oxalic acid as the fruit ripens. Cooking tomatoes, especially boiling fresh tomatoes, has been suggested to reduce their oxalic acid content [67]. The health-beneficial properties of tomatoes are studied the most in relation to their role in cancer prevention. ...
Article
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This review outlines the health benefits associated with the regular consumption of tomatoes and tomato products. The first section provides a detailed account of the horticultural techniques that can impact the quality of the fruit and its nutritional properties, including water availability, light intensity, temperature, and growing media. The next section provides information on the components of tomato that are likely to contribute to its health effects. The review then details some of the health benefits associated with tomato consumption, including anticancer properties, cardiovascular and neurodegenerative diseases and skin health. This review also discusses the impact tomatoes can have on the gut microbiome and associated health benefits, including reducing the risk of inflammatory bowel diseases. Other health benefits of eating tomatoes are also discussed in relation to effects on diabetes, the immune response, exercise recovery, and fertility. Finally, this review also addresses the negative effects that can occur as a result of overconsumption of tomato products and lycopene supplements.
... The oxalic acid and calcium oxalate in the L .minor plant material was 70-110 and 100-160 mg/100 g fresh weight, respectively. For steamed or boiled spinach it was reported to contain between 460 and 800 mg/100 g fresh weight, respectively [21]. Our study resulted in an increase in urinary oxalic acid for both intervention arms, but not significantly different between the spinach and the L. minor group. ...
Article
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The growing world population will increase the demand for new sustainable foods and ingredients. Here we studied the safety and tolerance of Lemna minor, a new sustainable vegetable crop from the duckweed family. Twenty-four healthy adults consumed either L. minor plant material or spinach as vegetable (170 g fresh weight) as part of a warm meal on 11 consecutively days in a randomized controlled parallel trial design. The intervention meals had a different recipe for each day of the week. All participants had to report daily if they experienced gastric complaints, feelings of hunger, fullness, desire to eat, thirst, general health, nausea, and stool consistency. Only hunger, flatulence and constipation were significantly different between both intervention groups. At the start and end of the intervention, blood and urine were sampled in order to analyze biomarkers for general health, e.g ., kidney function, liver function, cardiovascular health, inflammation and iron status. Both intervention groups did not show significant differences for these biomarkers. In taste attributes the L. minor -based products showed in only a few specific cases a significant difference compared to the spinach-based products. Based on the results we conclude that 11 consecutive days intake of 170 g fresh weight L. minor plants as a cooked vegetable does not result in any adverse effect in healthy adult subjects.
... Oxalate is one of the constituents of yam, and the amount absorbed in vivo depends on its complexed form, the calcium and magnesium present in the food, and the presence of oxalate-degrading bacteria in the gastrointestinal tract [30]. In the present study, no significant oxalate concentrations were detected in the fermented yam, due to the pre-cooking process, given that cooking can reduce the soluble oxalate by 30 to 87% [31]. Regarding phytate concentration, the fermentation with L. lactis CCMA 0415 showed a reduction of 82% (9.79 mg/100 g) while the other strains maintained the concentration found in the substrate (54.92 ...
Article
The use of lactic bacteria in the development of functional foods has increased in recent years. In addition to their probiotic characteristics, they can ferment a variety of substrates, such as cereals, roots, and tubers. Phytase producer lactic acid bacteria strains and their behavior during the fermentation process of yam-based food were studied. Leuconostoc lactis CCMA 0415, Lactobacillus plantarum CCMA 0744, and Lactobacillus fermentum CCMA 0745 were selected due to phytase production, pH reduction, and growth during 24 h of fermentation. Oxalate activity was not detected in all assays, suggesting its concentration was reduced due to the bleaching process. Among the selected strains, L. lactis CCMA 0415 appeared to be a promising strain in yam-based fermentations because it maintained a cell viability above 8 log CFU/mL and did not reduce diosgenin concentrations (around 8.0 μg/mL) after fermentation for 24 h, thereby, generating a potentially functional yam food. Furthermore, this strain promoted the decrease of pH value from 6.1 to 3.8 and produced 8.1 g/L lactic acid, at 6 h of fermentation. The L. lactis CCMA 0415 was reported as a starter culture in fermented products based on cereals, roots, and tubers.
... Although these are calcium-rich vegetables, they are also high in oxalic acid, and calcium bioavailability appears to be only ~5% (Heaney, Weaver, and Recker 1988;Mangels 2014). However, steaming and especially boiling (and discarding the water) can considerably reduce oxalic acid content (by ~30-80%) (Massey 2007;Chai and Liebman 2005). Thus, more human studies assessing bioavailability with different cooking methods would be helpful in this field (Heaney, Weaver, and Recker 1988). ...
Article
Since the beginning of the 21st century, interest in vegan diets has been rapidly increasing in most countries. Misconceptions about vegan diets are widespread among the general population and health professionals. Vegan diets can be health-promoting and may offer certain important advantages compared to typical Western (and other mainstream) eating patterns. However, adequate dietary sources/supplements of nutrients of focus specific to vegan diets should be identified and communicated. Without supplements/fortified foods, severe vitamin B12 deficiency may occur. Other potential nutrients of focus are calcium, vitamin D, iodine, omega-3 fatty acids, iron, zinc, selenium, vitamin A, and protein. Ensuring adequate nutrient status is particularly important during pregnancy, lactation, infancy, and childhood. Health professionals are often expected to be able to provide advice on the topic of vegan nutrition, but a precise and practical vegan nutrition guide for health professionals is lacking. Consequently, it is important and urgent to provide such a set of dietary recommendations. It is the aim of this article to provide vegan nutrition guidelines, based on current evidence, which can easily be communicated to vegan patients/clients, with the goal of ensuring adequate nutrient status in vegans.
Chapter
Vegetables are the major protective food in our diet, and besides providing essential nutrients, they are also the reservoirs of bioactive compounds. Bioactive compounds are the secondary metabolites that have an effect on living organisms and impart many health benefits. Most prominent bioactive compounds present in vegetables are terpenoids, carotenoids, phenolics, phytosterols, and glucosinolates. Many of these bioactive compounds are reported to possess antioxidant, immunomodulatory, anti-osteoporotic, antihypertensive, antimicrobial, antidiabetic, and anticancer properties, and are said to be effective as the reducers of cardiovascular complications. These bioactives can be extracted by various extraction techniques, and the extracted bioactives are evaluated using multiple in vitro and in vivo methods to ascertain their health benefits. This book chapter summarizes the literature available on bioactive compounds present in vegetables along with their health benefits, their extraction methods and effect of storage and processing on bioactive constituent retention.
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Faced with the need to (re)think the teaching of chemistry at its different levels, which reflects in the pedagogical strategies adopted by teachers and their evaluation mechanisms in content and form, this work has as main objective to evaluate the possibility and potentiality of use of the Food theme as an for the teaching of chemical concepts. To do this, we tried to produce a bibliographic material and adapted it to the digital format (hypermedia) as didactic resource without study in subjects of Chemistry, is available with simple and available resources (PowerPoint). Thus, we sought to explore some of the phenomena related to Food and to raise questions/questions, which seem simple and trivial, but require a greater chemical interpretation that approaches one of the aspects of the activity of a chemist: of thinking about matter and its modifications in terms of atoms and molecules, that is, of molecular theory. In general, the didactic material found on the market addresses food content from a conceptual order/sequence and a mandatory classification (water, vitamins, carbohydrates, lipids and proteins), an idea contrary to the proposal of this work. With this, the motivation to develop a contextualized material on Food Chemistry was maximized in the face of the lack of books and digital tools with this characteristic. The present work defends the educational potential of the subject 'Food' for the Chemistry teaching, emphasizing the conceptual richness to be explored by the chemistry teachers, either by the great appeal (contextual proximity) or by the global language that allows to promote. The developed material was applied in a scientific event of national scope and in the discipline of Instrumentation for the Teaching of Chemistry of a Chemistry course (Public University). The results of this research indicate the pedagogical potential of the resource and the need for re-signification of teaching practice at different levels of training, in order to make the teaching of Chemistry an experience, literally, pleasurable and relevant
Article
Pumpkin leaves (Cucurbita moschata) were subjected to different household cooking methods (boiling, microwaving, steaming, and stir-frying) to evaluate their effect on antinutrients, phenolic compounds, antioxidant properties (ABTS, and DPPH) and in vitro α-glucosidase activity. All cooking methods studied significantly reduced the antinutrients and antioxidant activities, whilst phenolic compounds p-coumaric and ferulic acids significantly increased. The cooking methods reduced the oxalates by more than 50%, tannins by 47% and phytates by 79.22%. Steaming and boiling resulted in highest concentrations of p-coumaric (195.40 mg kg-1) and ferulic acids (103.90 mg kg-1) compared to other methods. Overall, boiled leaves retained the highest total phenolic compounds, whilst steamed leaves retained the highest antioxidant capacity. Raw pumpkin leaf extracts showed higher in vitro α-glucosidase inhibitory effects than the cooked leaves. Thus, cooking affected the inhibitory effect of in vitro α-glucosidase activity. Supplementary information: The online version contains supplementary material available at 10.1007/s10068-021-00916-w.
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Soluble oxalate with potentially dietary injurious implications for human health were determined in amaranth (Amaranthus spp.) gamma-irradiation induced mutant lines by capillary isotachophoresis and compared to their non-irradiated reference samples 'Ficha' (Amaranthus cruentus L.) and interspecific hybrid 'K-433' (Amaranthus hypochondriacus × Amaranthus hybridus) during the cultivation period 2011–2014. The canonical discriminant analysis demonstrated significant differences among mutants and their reference counterparts during multiyear evaluation. Two-way ANOVA approach identified the mutant line D282 as variant with the significantly and long-term lowest soluble oxalate concentration in comparison to respective reference samples as well as other mutant lines. Decrease in a content of this antinutritional factor could be a possible effect of radiation-induced mutation event(s) in the D282 line genome. Therefore, this mutant line might be a good matrix in the further breeding programme of this naturally gluten-free pseudocereal.
Article
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.
Article
Cooking at home has experienced a decline in many countries since the mid-20th century. As rates of obesity have increased, there has been an emphasis on more frequent home cooking, including its incorporation into several food-based dietary guidelines around the world as a strategy to improve dietary quality. With the recent trend towards the adoption of diets richer in plant-based foods, many consumers cooking at home may now be cooking plant foods such as vegetables, potatoes and pulses more often. It is, therefore, timely to explore the impact that different home cooking methods have on the range of nutrients (e.g. vitamin C and folate) and bioactive phytochemicals (e.g. carotenoids and polyphenols) that such plant foods provide, and this paper will explore this and whether advice can be tailored to minimise such losses. The impact of cooking on nutritional quality can be both desirable and/or undesirable and can vary according to the cooking method and the nutrient or phytochemical of interest. Cooking methods that expose plant foods to high temperatures and/or water for long periods of time (e.g. boiling) may be the most detrimental to nutrient content, whereas other cooking methods such as steaming or microwaving may help to retain nutrients, particularly those that are water-soluble. Dishes that use cooking liquids may retain nutrients that would have been lost through leaching. It may be helpful to provide the public with more information about better methods to prepare and cook plant foods to minimise any nutrient losses. However, for some nutrients/phytochemicals the insufficient and inconsistent research findings make clear messages around the optimal cooking method difficult, and factors such as bioaccessibility rather than just quantity may also be important to consider.
Chapter
Epidemiological studies have shown certain diets such as Mediterranean diet, Okinawa diet, New Nordic diet and vegetarian diets to promote longevity. Omega-3 fatty acids, bioactive peptides, polyphenols and antioxidants are some of the implicated molecules derived from both plant and animal food that provide protection against cellular ageing. The role of gut microbiome and its interaction with dietary components has provided novel ways to understand the process of ageing. Beyond the inherent biochemical composition of plants and animals consumed, the methods employed for farming and agriculture (such as organic farming) as well as food preparation techniques (such as frying, grilling, steaming) have a major effect on the health benefits derived from the dietary source. In conclusion, health promoting effect of animal and plant based diets depend on obtaining recommended daily allowances of health promoting ingredients from a portion and minimizing intake of harmful components such as saturated fats, nitrites, nitrates, anti-nutrients amongst others. A well balanced personalized diet catering to an individual’s age, genetic predisposition to allergies and diseases and microbiome needs to be followed for longevity. Novel food processing technologies such as 3-D printing that incorporates both plant & animal ingredients will inch us closer to fabricating ideal functional food products aimed at promoting longevity in a sustainable way.
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In the context of climate change, especially for the temperate continental climate, new potential crop species are emerging, originating from the tropics. One of them is quinoa (Chenopodium quinoa Willd.) with multiple benefits for seed and leaf production. Quinoa is native to South America, grown mainly for seeds, with a high ecological plasticity. Little is known about the potential of using quinoa plants as a leafy vegetable for food diversification. In this study, the nutritional and antinutritional content of quinoa leaves was evaluated in three cultivars (Titicaca, Puno, Vikinga), considering different densities and times of sowing. Puno cultivar had a higher total content of carbohydrates, lipids, proteins and dietary fibers, and lower mineral contents in leaves. Low levels of antinutrient compounds were found in Vikinga leaves. Regarding the time of the crop establishment, the highest content of primary metabolic compounds (carbohydrates, lipids, proteins, dietary fibers) was achieved by April 17, the sowing date. Crop densities of 7.7, 3.2, and 1.6 mil. plants/ha did not significantly influence the content of compounds with antinutritive role, such as oxalates, saponins or trypsin inhibitors. The content of mineral elements such as: Fe, Zn, Na and K were significantly influenced by the cultivar, compared to Mg and Ca whose values were insignificant regardless of the treatment.
Article
Whole foods plant-based approaches to eating place an emphasis on the intake of fruits, vegetables, whole grains, and legumes and have many health benefits. While there are key nutrients and phytochemicals that can contribute to the purported health benefits, practitioners and patients should also be advised of key nutrients for which intake may be compromised when following this dietary pattern. With careful planning and utility of dietary supplements, individuals can achieve optimal intake of calcium, iron, vitamin D, omega 3 fatty acid—docosahexaenoic acid (DHA), and vitamin B12 and experience the health benefits of a dietary fiber and a host of phytochemicals. This article presents the health benefits of these food substances and approaches for overcoming nutrients of concern when following whole food plant-based eating patterns.
Article
The consumption of plant foods has been encouraged to cover a high proportion of the diet due to their health benefits. However, the occurrence of anti-nutrients in plant foods, especially soluble oxalate, is often neglected. High intake of soluble oxalate from the diet can increase the risk of kidney stone formation as well as mineral deficiency and restriction of dietary oxalate is the only way to reduce urinary oxalate. This review discussed the existing knowledge on effects of food processing on oxalate contents in plant foods. Leaching, fermentation and cooking with calcium sources could be considered as the most efficient methods to reduce soluble oxalate. Time, temperature and properties of the food (pH, fibre and fat contents, and preparation methods) are the major factors determining the treatment efficiency for oxalate reduction. Pulsed electric field, ultrasonication and enzymatic treatments have been proven as potential methods to diminish oxalates.
Article
Background: Carrot is a popular vegetable consumed by people of all age groups and is used in various food products because of its high nutritional content, especially vitamin A. Results: In the present study, colourful fresh carrot juices of 12 carrot varieties were investigated for in-vitro antidiabetic, antiaging, and anti-obesity activities with antioxidant potential by ABTS and FRAP assays. The studied juices were also compared for physicochemical characteristics: titratable acidity, pH, pectin content, total soluble solids, dry mass, ash, viscosity, turbidity, osmolality and colour. The study results showed that normal purple carrot juice exhibited the best activities in all biological and antioxidant tests, except for anti-α-glucosidase activity. Normal purple carrot juice also had the highest total mineral content with elevated results for titratable acidity, pH, total soluble solids, dry mass, ash, viscosity, and osmolality. Conclusion: Purple carrot juices demonstrated elevated health-promoting activities and could be used in blended beverage recipes to attract children's attention. The results of sensorial characteristics (appearance, colour and taste) of juices, however, showed that people are more familiar with orange carrot products. This article is protected by copyright. All rights reserved.
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Due to its high nutritional and functional value, sweet potato has become a popular subject of scientific research. The content of carbohydrates, proteins, lipids, carotenoids, anthocyanins, vitamins, and minerals in the tubers and leaves make it a particularly nutritious vegetable. The unique composition of those nutrients results in a number of health benefits, such as antioxidant, hepatoprotective, anti-inflammatory, anti-cancer and antidiabetic properties. Therefore, sweet potato and sweet-potato-based healthy products can be effectively used as ingredients of functional food.
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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.
Article
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.
Article
About 75% of all kidney stones are composed primarily of calcium oxalate and hyperoxaluria is a primary risk factor for this disorder. Since absorbed dietary oxalate can make a significant contribution to urinary oxalate levels, oxalate from legumes, nuts, and different types of grain-based flours was analyzed using both enzymatic and capillary electrophoresis (CE) methods. Total oxalate varied greatly among the legumes tested, ranging from 4 to 80 mg/100 g of cooked weight. The range of total oxalate of the nuts tested was 42–469 mg/100 g. Total oxalate of analyzed flours ranged from 37 to 269 mg/100 g. The overall data suggested that most legumes, nuts, and flours are rich sources of oxalate.
Article
Food oxalate analysis in foods is problematic due to the wide range of interfering substances. To prevent oxalate generation during sample preparation mild and rapid extraction methods were evaluated. Soluble oxalate was extracted with distilled water and total oxalate was extracted with 2 N hydrochloric acid. Filtrates were analysed using the HPLC enzyme reactor method. Evaluation yielded a high level of precision and recovery. Glyoxylic acid, d/l malic acid, isocitric acid, oxaloacetic acid, pyruvate, mesoxalic acid, ascorbic acid, d(+) glucose, d(−) fructose, chlorogenic acid, caffeic acid could be excluded as a source of oxalate generation during extraction with hot acids. The soluble and total oxalate content of about 150 food samples were investigated.
Article
Oca (Oxalis tuberosa Mol.) or New Zealand yam, in common with other members of this genus, contains oxalate, an antinutritive factor. Twelve South American and two New Zealand cultivars of oca were analyzed for total and soluble oxalate contents of the tubers. The range of total oxalate levels was 92-221 mg/100 g of fresh weight. Levels of soluble and total oxalate extracted from the tubers were not significantly different, suggesting that no calcium oxalate is formed in the tubers. The oxalate concentrations obtained in this study for oca suggest that previously reported values are too low and that oca is a moderately high oxalate-containing food. This is the first report of a tuber crop containing moderate to high levels of soluble oxalates in the tubers and no insoluble oxalates.
Article
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.
Article
This new reagent kit for the quantitative measurement of oxalate in urine is a modification of an earlier Sigma oxalate assay procedure (procedure no. 590), a coupled enzyme assay involving oxalate oxidase and horseradish peroxidase. The new analytical procedure includes methods for processing urine specimens to eliminate interference with oxalate color development at 590 nm by ascorbic acid, divalent cations, and other urinary constituents. The reaction is complete in less than 5 min, and results are linearly related to oxalate concentration up to at least 1 mmol/L. Assay sensitivity and within-run and between-run precision were within the limits acceptable for other urinary oxalate procedures. Analytical recovery of added oxalate was close to 100%. This specific, simple, rapid procedure is suitable for routine clinical use.
Article
An automated enzyme immunoassay for human lutropin for use with the Abbott IMx analyzer is described. The assay provides results in approximately 40 min with a sensitivity of 0.25 int. units of LH per liter for up to 23 serum or plasma samples. Cross-reactivity with follitropin (2000 int. units/L) and thyrotropin (2 int. units/L) was negligible; it was 0.016% with human choriogonadotropin (1 X 10(6) int. units/L). There was no interference by high concentrations of bilirubin (0.5 g/L), hemoglobin (7.50 g/L), or triglycerides (13.5 g/L). Intra-, inter-, and total assay CVs were less than or equal to 3.75%, less than or equal to 7.1%, and less than or equal to 7.94%, respectively. Values obtained with the IMx correlated well (r = 0.98, n = 194) with values obtained with Diagnostic Products' LH Double Antibody RIA, and Serono's LH MAIAclone assay. This assay should be useful for small to medium-size laboratories involved in the clinical diagnosis of reproductive pathology.
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Kidney International aims to inform the renal researcher and practicing nephrologists on all aspects of renal research. Clinical and basic renal research, commentaries, The Renal Consult, Nephrology sans Frontieres, minireviews, reviews, Nephrology Images, Journal Club. Published weekly online and twice a month in print.
A new quantitative gas chromatographic (GC) method has been developed for the determination of oxalic acid in foods. Solid sample is extracted with water (soluble oxalic acid) or 2N hydrochloric acid (total oxalic acid) at room temperature. An aliquot of sample extract is evaporated to dryness, and the oxalic acid in the residue is methylated with 7% hydrochloric acid-methanol. The reaction mixture is extracted with chloroform, and dimethyl oxalate is quantitated by GC. Recovery of oxalic acid added to liquid samples averaged 100.6%; recoveries from extracts of solid samples were 96.2-99.5 and 97.2-100.1% for water and hydrochloric acid extractions, respectively. Results are shown for determination of oxalic acid in spinach and beverages. The technique is simple, rapid, and accurate, and small samples may be used. The limit of determination is 20 micrograms.
Article
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.
Article
Dietary oxalate is currently believed to make only a minor contribution (< 20%) to urinary oxalate excretion. A recent prospective study of stone disease suggested that dietary oxalate may be a significant risk factor. This observation led us to re-evaluate the contribution of dietary oxalate to urinary oxalate excretion. Previous studies have been hampered by inaccurate food composition tables for oxalate and inadequate methods for studying intestinal oxalate absorption. This evidence as well as factors that modify oxalate absorption are reviewed. New approaches to measure food oxalate and intestinal oxalate absorption have been examined. Capillary electrophoresis appears to be well suited for the analysis of the oxalate content of food. Two individuals consumed an oxalate-free formula diet for 7 days. This diet decreased urinary oxalate excretion by an average of 67% (18.6 mg per 24 hours) compared to oxalate excretion on self-selected diets. The absence of detectable oxalate in feces by day 6 of the diet suggested that the intestinal absorption was minimal. However, an effect of the formula diet on endogenous oxalate synthesis cannot be excluded. Restoring oxalate to the formula diet increased urinary oxalate excretion and illustrates that this experimental protocol may be well-suited for studying oxalate absorption and factors that modify it. Our results suggest that the intestinal absorption of dietary oxalate makes a substantial contribution to urinary oxalate excretion and that this absorption can be modified by decreasing oxalate intake or increasing the intakes of calcium, magnesium, and fiber.
Article
There is currently intense research interest in secondary plant metabolites because of their potential preventative effects on the chronic diseases of Western societies, especially cardiovascular disease and cancer. To date most of the research has focused on the identification of plant-derived substances and their potential protective effects against specific chronic diseases. The important issue of determining the optimal intake of those substances, such that the beneficial effects are maximized without manifestation of adverse effects, has yet to be addressed in most cases. Furthermore, there are no specific functional markers that can be used to assess optimal intake, although it may be possible to use biomarkers such as serum cholesterol if the rest of the diet is strictly controlled. The present review discusses a wide range of substances associated with plants, including dietary fibre, resistant starch, oligosaccharides, phyto-oestrogens, phytosterols, flavonoids, terpenes and isothiocyanates, and attempts where possible to indicate optimal intakes and to suggest functional markers.
Article
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.
Article
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.
Article
Oxalate bioavailability is an important determinant of whether the consumption of a particular food is a high risk in individuals predisposed to kidney stones. We estimated and compared oxalate absorption from a high oxalate containing legume (black beans) and a high oxalate containing nut (almonds). We also compared an isotope method using extrinsically labeled oxalate and an oxalate load method to assess oxalate absorption. Six male and 5 female subjects participated in the 4 oxalate load tests, namely almonds, almonds with 20 mg C2-oxalic acid, black beans and black beans with 20 mg C2-oxalic acid. Each treatment provided a total of 120 mg oxalate, after which timed urine samples were collected for the analysis of oxalate, calcium and creatinine. Average oxalate absorption from the 2 almond treatments (5.9%) using the oxalate load method was significantly higher than that from the 2 black bean treatments (1.8%) during the 24-hour post-oxalate load collection period. In contrast, C2-oxalic acid absorption from the almond (7.9%) and black bean (8.6%) treatments did not significantly differ. The higher oxalate absorption from almonds than from black beans suggests that the relative amount of soluble and insoluble oxalate in food has an important role in the determination of oxalate absorption. Since extrinsically provided C2-oxalate and oxalate naturally occurring in the high oxalate test foods appeared to be differentially absorbed, the data do not support the use of extrinsically labeled oxalate to assess food oxalate absorption.
Revised manuscript received February 15 Accepted February 18 This study was supported by a grant from the VP Foundation
  • Chai
  • Liebman
Received for review November 9, 2004. Revised manuscript received February 15, 2005. Accepted February 18, 2005. This study was supported by a grant from the VP Foundation, Graham, NC. JF048128D 3030 J. Agric. Food Chem., Vol. 53, No. 8, 2005 Chai and Liebman
  • Albihn P. B. E.