Espinafre e o cozimento para redução de oxalato de cálcio

Fatores antinutricionais dos alimentos são aqueles que prejudicam a assimilação de nutrientes ou provocam outras reações negativas no organismo. Muitos dos alimentos utilizados na alimentação e principalmente os denominados plantas alimentícias não convencionais, possuem esses fatores com o objetivo principal de defesa contra os mais diferentes tipos de estresses que o vegetal sofre.

No entanto, no ato do preparo do alimento é possível reduzir ou até mesmo eliminar por completo o fator antinutricional.

Com relação ao espinafre, ou espinafres, pois há pelo menos duas espécies com esse nome, pesquisas indicam que possuem altos teores de ácido oxálico. Dentre eles, o que possui maior teor é o espinafre, de origem asiática, denominado cientificamente por Spinacia oleracea (foto). É uma planta com 0,4 a 0,6 cm de altura e não muito comum no Brasil. Outra espécie é a Tetragonia tetragonoides, cujas folhas são maiores e espessas.

http://www.fiel.pt/pt/catalogo/folhas-baby-para-saladas/folha-baby-espinafre/

O Spinacia oleracea é muito conhecido por suas características nutricionais. É um alimento rico em nutrientes, como, por exemplo, cálcio, ferro, fósforo, magnésio, potássio e sódio. Além de possuir vitaminas A, C, K e do complexo B, pesquisas mostram grande eficácia no tratamento e na prevenção de doenças tais como: anemia, câncer e cardiovasculares.

O cozimento da hortaliça é uma forma de reduzir a sua concentração do ácido oxálico. Essa substância interfere na absorção de ferro. Na digestão, oxalato e ferro reagem e formam o “oxalato Ferroso”, tornando o ferro indisponível para o organismo e excretado na urina. O oxalato na urina, devido a reação cálcio, pode se cristalizar e causar pedras no rim. 

Em experimento com folhas de brócolis, couve-flor e couve, Santos (2006) demonstrou que o cozimento reduz os teores de ácido oxálico nessas hortaliças 

Referências:

SANTOS, M. A. T. Efeito do Cozimento sobre alguns fatores antinutricionais em folhas de brócoli, couve-flor e couve. Ciênc. Agrotec., v. 30, n. 2, p. 294-301, 2006. Disponível em: http://www.scielo.br/pdf/cagro/v30n2/v30n2a15.pdf. Acesso em: 27 set 2017.

https://drjulianopimentel.com.br/alimentacao/fatores-antinutricionais-oxalato-e-as-pedras-nos-rins/

http://www.mundoboaforma.com.br/oxalato-o-que-e-alimentos-ricos-dieta-e-dicas/7

http://www.portalsaofrancisco.com.br/alimentos/espinafre

Texto:

Amanda Cristine Custódio Pinto - acadêmica de nutrição - UNITAU

Marcos Roberto Furlan - Engenheiro agrônomo - Professor UNITAU/FIC

Espinafres

Fatores antinutricionais - 3. Espinafres. Spinacia não é fácil de ser encontrado, mas é confundido com o Tetragonia (espinafre-da-nova-zelândia). O espinafre do gênero Spinacia é um dos campeões nos teores de oxalato. #nutrição #verduras #fatoresantinutricionais #oxalato

Uma foto publicada por Marcos Roberto Furlan (@quintaisimortais) em Out 28, 2016 às 3:57 PDT

Fatores antinutricionais - oxalato

Poesia e plantas medicinais -1. Neruda se refere ao boldo-do-chile. O aroma adocicado (para alguns enjoativo) é muito semelhante ao da erva-de-santa-maria (Chenopodium ambrosioides), pois ambas as espécies possuem em seu óleo essencial, o ascaridol. #literatura #plantasmedicinais #plantasmedicinales #medicinalplants

Uma foto publicada por Marcos Roberto Furlan (@quintaisimortais) em Out 20, 2016 às 10:31 PDT

Phthalate Metabolites, Consumer Habits and Health Effects

Phthalates are multifunctional chemicals used in a wide variety of consumer products. The aim of this study was to investigate whether levels of urinary phthalate metabolites in urine samples of Austrian mothers and their children were associated with consumer habits and health indicators. Within an Austrian biomonitoring survey, urine samples from 50 mother-child pairs of five communities (two-stage random stratified sampling) were analysed. The concentrations of 14 phthalate metabolites were determined, and a questionnaire was administered. Monoethyl phthalate (MEP), mono-n-butyl phthalate (MnBP), mono-isobutyl phthalate (MiBP), monobenzyl phthalate (MBzP), mono-(2-ethylhexyl) phthalate (MEHP), mono-(2-ethyl-5-hydroxyhexyl) phthalate (5OH-MEHP), mono-(2-ethyl-5-oxohexyl) phthalate (5oxo-MEHP), mono-(5-carboxy-2-ethylpentyl) phthalate (5cx-MEPP), and 3-carboxy-mono-propyl phthalate (3cx-MPP) could be quantified in the majority of samples. Significant correlations were found between the use of hair mousse, hair dye, makeup, chewing gum, polyethylene terephthalate (PET) bottles and the diethyl phthalate (DEP) metabolite MEP. With regard to health effects, significant associations of MEP in urine with headache, repeated coughing, diarrhoea, and hormonal problems were observed. MBzP was associated with repeated coughing and MEHP was associated with itching.

Wallner, P.; Kundi, M.; Hohenblum, P.; Scharf, S.; Hutter, H.-P. Phthalate Metabolites, Consumer Habits and Health Effects. Int. J. Environ. Res. Public Health 2016, 13, 717.

Link:

http://www.mdpi.com/1660-4601/13/7/717

Exposure to phthalates could be linked to pregnancy loss

Date: September 2, 2015

Source: American Chemical Society (ACS)

Summary:

A new study of more than 300 women suggests that exposure to certain phthalates -- substances commonly used in food packaging, personal-care and other everyday products -- could be associated with miscarriage, mostly between 5 and 13 weeks of pregnancy.

See more at:

http://www.sciencedaily.com/releases/2015/09/150902102649.htm

Add Some Vapor Flavor to Your Next Dish!

Antinutrientes: inhibidores enzimáticos

Do site:

http://www.conasi.eu/

Entre los antinutrientes, un grupo muy importante son losinhibidores enzimáticos. Nuestra digestión ocurre gracias a la acción de enzimas, que descomponen los nutrientes en la digestión para que los podamos absorber. Pero hay ciertas sustancias en algunos alimentos que impiden la correcta acción de esas enzimas:

Inhibidores de las enzimas protéicas

Impiden la proteólisis digestiva (o sea, la descomposición de las proteínas en aminoácidos). Las proteínas deben llegar descompuestas enaminoácidos a nuestro intestino. Si no lo están, estos fragmentos pueden pasar por un intestino demasiado permeable y causar problemas a nuestro sistema inmune o a nuestro riñón. Incluso pueden originar problemas de crecimiento, debido a la baja absorción de proteínas y también porque estos inhibidores hipertrofian el páncreas y estimulan su (esto se puede reconocer por el aumento del nitrógeno fecal).

Normalmente, al cocinar el calor desnaturaliza estos factores y con ello casi todo su efecto inhibidor, aunque suele quedar un valor residual inhibidor del 5-20%. El significado tóxicológico de este efecto residual se desconoce en la actualidad.

Estos inhibidores son:

• Antitripsinas o inhibidores de proteasas: son sustancias que impiden el uso o metabolismo enzimático de las proteínas. Se encuentran en productos tanto de origen vegetal –leguminosas, patata, batata, cacahuete- como animal –leche, calostro, huevo (ovomucoide y ovoinhibidor)-. El más conocido y destacado es el inhibidor de tripsina, que se encuentra en la soja, judías…

• Inhibidores de la tripsina y quimotripsina bovina: en la soja se han hallado inhibidores del tipo factor Bowman-Birk y factor de Kunitz. También se han aislado inhibidores similares en judías, cacahuetes, guisantes, lentejas, aunque la actividad de cada uno es diferente.

Anticarbohidrasas

Estas sustancias impiden el uso completo de los hidratos de carbono, porque afectan a las enzimas que hidrolizan (descomponen) los hidratos de carbono.

Estos inhibidores son:

• Antiamilasas: evitan que asimilemos el almidón. Se encuentran en leguminosas, trigo integral.

• Antiinvertasas: en patatas y maíz.

Recomendaciones prácticas ante los inhibidores enzimáticos

No tomar las legumbres crudas: no usar molidas o en forma de harina, sin cocinar.

Las legumbres deben cocinarse o germinarse: una vez germinadas se recomienda calentar en un salteado ligero (los brotes de soja, de garbanzos) para eliminar los inhibidores que hayan podido quedar.

Evitar el consumo de plátanos y mango verde, que contienen antiamilasas.

¡Ojo con los comprimidos de vainas de judías para el tratamiento de la obesidad y la diabetes! 

También contienen antiamilasas.

Antinutrientes

Antinutrientes: antivitaminas

Antinutrientes: Inhibidores de la asimilación de minerales

Link:

http://www.conasi.eu/blog/productos/deshidratadores/deshidratacion-la-forma-mas-antigua-y-sana-de-conservar-los-alimentos/

Antinutrientes: sustancias antitiroideas

Do site:

http://www.conasi.eu/

Glándula del tiroides

Tioglucósidos

Algunos vegetales comestibles poseen unos compuestos tóxicos llamados tioglucósidos (tiocianato, isotiocianato, tioxazolidina y antocianos) que actúan como sustancias bociógenas -impiden la formación de hormonas tiroideas-. El colinabo, nabo, col, mostaza, coliflor, coles de bruselas, escarola, lombarda, berza, brócoli, zanahoria y espinacas se encuentran en este grupo.

Aunque el calor destruye estos principios activos inhibidores (al inactivar la enzima mirosinasa), las bacterias intestinales también los metabolizan, por lo cual no se debe abusar de su consumo.

Glucósidos cianógenos

Son sustancias que segregan algunas plantas como mecanismo de defensa frente a depredadores. Estos glucósidos liberan ácido cianhídrico al ser dañadas o comidas. Se encuentran por ejemplo, en la raíz de la mandioca, en las almendras amargas, en las semillas del melocotón y el albaricoque, pera, fresa y poseen también acción bociógena.

Polifenoles

Existen miles de polifenoles y son más conocidos por su beneficioso efecto antioxidante, pero algunos, como los polifenoles contenidos en la cascarilla del cacahuete, en la nuez de acajú y en la capuchina y los alquilsulfuros que se encuentran en el ajo y la cebolla, poseen este mismo efecto inhibidor sobre la glándula tiroides.

Link:

http://www.conasi.eu/blog/productos/deshidratadores/deshidratacion-la-forma-mas-antigua-y-sana-de-conservar-los-alimentos/

Artigo: Are medicinal plants polluted with phthalates?

Soodabeh Saeidnia1† and Mohammad Abdollahi2*†

*Corresponding author: Mohammad Abdollahi Mohammad@TUMS.Ac.Ir

† Equal contributors

Author Affiliations

1Medicinal Plants Research Center, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran 1417614411, Iran

2Department of Toxicology and Pharmacology, Faculty of Pharmacy and Pharmaceutical Sciences Research Center, Tehran University of Medical Sciences, Tehran 1417614411, Iran

DARU Journal of Pharmaceutical Sciences 2013, 21:43 doi:10.1186/2008-2231-21-43

The electronic version of this article is the complete one and can be found online at:http://www.darujps.com/content/21/1/43

Received: 24 March 2013

Accepted: 16 April 2013

Published: 29 May 2013

© 2013 Saeidnia and Abdollahi; licensee BioMed Central Ltd. 

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Phthalic acid esters (PAEs) have been employed in polymer materials as a plasticizer to form them more flexible, adhesive, and soluble. These compounds are mainly used in paints, varnishes, personal cares, cosmetics, paper coatings, and adhesives even in bottled waters, shampoo, body deodorant, hairspray, and gels. Phthalates are able to possess remarkable toxic variations depending on their structures. So far, Di-(2-EthylHexyl) Phthalate DEHP and Di-n- Butyl Phthalate DBP have been found to cause reproductive and developmental toxicities. The U.S. Environmental Protection Agency (EPA) classified DEHP as probable human carcinogen. To the best of our knowledge, phthalates showed diverse toxicity profiles according to their structures in the liver, kidneys, thyroid, and testes, which are involved in general toxicity. Furthermore, they are introduced as hormonally-active agents, because they can interfere with the endocrine system in human. Incidence of developmental abnormalities (like skeletal malformations and cleft palate, and undescended testes, lowering testes weight and anogenital distance) seems increasing via high exposure to phthalate metabolites. Although, increasing the capacity for phthalate free plasticizer productions is the first step to restrict the distribution of these toxic manmade compounds, finding the new ways for phthalate absorption from the soil in agricultural fields may have benefits. Also, evaluation and examination of diverse sources of medicinal and food plants to determine the level of phthalate accumulation in their organs are extremely recommended to avoid creating toxicity particularly in reproductive systems.

Editorial

Phthalic acid esters (PAEs) have been employed in polymer materials as a plasticizer to form them more flexible, adhesive, and soluble. These compounds are mainly used in paints, varnishes, personal cares, cosmetics, paper coating, and adhesives even in bottled waters, shampoo, body deodorant, hairspray and gels [1]. Di-n-Butyl Phthalate (DBP) and Di-(2-EthylHexyl) Phthalate (DEHP) are two remarkable and mostly applied ones, which can be released into the environment during production and processing through wastewater. It is reported that the EU produced about 10,000 tons of DBP and 341,000 tons of DEHP during 2007. They can contaminate the agricultural soils through the air as well as oil leakages from farm machinery or organic fertilizers. In soils and sediments, DEHP persists and shows high potential for bioaccumulation [2].

Phthalates are able to possess remarkable toxic variations depending on their structures. So far, DEHP and DBP have been found to cause reproductive and developmental toxicities. The U.S. Environmental Protection Agency (EPA) classified DEHP as probable human carcinogen. To the best of our knowledge, phthalates showed diverse toxicity profiles according to their structures in the liver, kidneys, thyroid, and testes, which are involved in general toxicity. Furthermore, they are introduced as hormonally-active agents, because they can interfere with the endocrine system in human [3].

Incidence of developmental abnormalities (like skeletal malformations and cleft palate, and undescended testes, lowering testes weight and anogenital distance) seems increasing via high exposure to phthalate metabolites [3]. The important concern around phthalates, anti-androgenic effect is associated with human reproductive system, such as affecting sperm counts and histopathological alterations in the testes leading to male infertility. In addition, literature review reveals that there is a correlation between phthalate metabolite concentrations in maternal breast milk and sex hormone concentration in male offspring. Furthermore, fetal exposure to phthalate shows a relation with behavior and mental ability (Figure 1). For instance, in a study on pregnant women (highly exposed to phthalate in third trimester of pregnancy) in the U.S., the neurorogical problems in their children had been prolonged even enhanced until 4–9 years old [4]. Another group in risk, is children exposed to phthalates via mouthing items as well as breast milk, infant formulas, plastic food container and toys, cups and bowls, and even indoor air. Epidemiological evidence revealed that boys, whose mothers exposed to phthalates during pregnancy, showed an augmented incidence of inborn genital malformations and spermatogenic dysfunction [5]. Regarding to the broad range of phthalate toxicity in human, animals and marines, their distribution in various parts of plants including agricultural and medicinal herbs could be a serious concern.

Figure 1.

A diagram of the natural circulation, deposition and bioaccumulation of phthalates in relation to human exposure and health effects.

Interestingly, plants receive both nutrients and toxic substances through the roots as well as above-ground green parts. High accumulation of phthalates in stems of some types of crops has been reported [6]. For instance, three important food plants such as agricultural crops (Triticum aestivum, Brassica napus, Zea mays) have been specifically mentioned [2]. Actually in one study on seedlings of radish (Raphanus sativas) and wheat (T. aestivum) exposed to the vapor of DBP, the accumulation of phthalate (106 times per 3 days) was observed significantly in the cuticular and wax layers [7].

Surprisingly, some species of the genus Phyllanthus, the famous medicinal plants, have been reported to produce phthalates (bis (2-ethyloctyl) phthalate and bis (2-ethylicosyl) phthalate), which most often exhibited antimicrobial activities [8]. Moreover, phytochemical investigation on flowers of Calotropis gigantea led to separation of DEHP. The minimum inhibitory concentration (MIC) of this compound was measured between 13 and 128 μg/mL against Staphylococcus aureus, Bacillus subtilis, B. megaterium, Sarcina lutea, Escherichia coli, Shigella sonnei, S. shiga, S. dysenteriae, Aspergillus niger, A. flavus, A. fumigatus and Fusarium sp. This compound showed toxicity against Artemia salina larvae (IC50 = 9.2 μg/mL) too [9]. In addition, the leaves of Pongamia pinnata, an Indian medicinal plant, have been reported to consist of bis (2-methylheptyl) phthalate and the mentioned compound exhibited inhibitory activity against White Spot Syndrome Virus (WSSV) [10]. There is an increase in employment of commercial herbal extracts, particularly liquid preparations, which are packaged in plastic containers. Although there are some phyto-analytical techniques for detection and quantification of DEHP in herbal remedies, the quality of these products, regarding to their safety, remains under question [11].

Nevertheless, the presence of phthalates in plant and algae sources might be associated with environmental exposure, production or formation of new brands of phthalates in plants is still in doubt and case of discussion between scientists. Additionally, it is proved that brown algae (likeSargassum) can synthesize phthalate esters, but their production process and physiological role have not been clear so far [12]. Dimethyl terephthalate has been also identified as pollutants in various red algae such as Phyllophora neruosa, Acanthophora delilei and Hypnea musciformis, while DBP is isolated from brown and green algae (Undaria pinnatifida, Laminaria japonica, and Ulva sp.) raised a concern that DBP might be generated naturally [13]. The challenge will be raised when many of these plants and marine algae are consumed as food or medicinal resources.

Based on our unpublished data, accumulation of phthalates can occur in some medicinal plants e.g.Lythrum, that are usually grown in water flow in rivers and canals. In such cases, wastewater might be the origin of pollution and phthalate exposure to these plants. Sometimes, high exposure to phthalates resulted in about half part of essential oil extraction, which can cause worries to consume such medicinal plants, crops or vegetables. Although, increasing the capacity for phthalate free plasticizer productions is the first step to restrict the distribution of these toxic manmade compounds, finding the new ways for phthalate absorption from the soil in agricultural fields may have benefits. Also, evaluation and examination of diverse sources of medicinal and food plants to determine the level of phthalate accumulation in their organs are extremely recommended to avoid creating toxicity particularly in reproductive systems.

Competing interest

The authors declared that there is no conflict of interest.

Authors’ contributions

Both authors contributed equally to the paper. Both authors read and approved the final manuscript.

References

1. Al-Saleh I, Shinwari N, Alsabbaheen A: Phthalates residues in plastic bottled waters. J Toxicol Sci 2011, 36:469-478. PubMed Abstract | Publisher Full Text
2. Zorníkova G, Jarosova A, Hrivna L: Distribution of phthalic acid esters in agricultural plants and soil. Acta Univ Agr Silvic Men Brun 2011, 31:233-238.
3. Herr C, Nieden A, Koch HM, Schuppe HC, Fieber C, Angerer J, Eikmann T, Stilianakis NI:Urinary di (2-ethylhexyl) phthalate (DEHP) metabolites and male human markers of reproductive function. Int J Hyg Env Health 2009, 212:648-653. Publisher Full Text
4. Walter J, Crinnion ND: Toxic effects of the easily avoidable phthalates and parabens. Alt Med Rev 2012, 15:190-196.
5. Carbone S, Szwarcfarb B, Ponzo O, Reynoso R, Cardoso N, Deguiz L, Moguilevsky JA, Scacchi P: Impact of gestational and lactational phthalate exposure on hypothalamic content of amino acid neurotransmitters and FSH secretion in peripubertal male rats. Neurotoxicology 2010, 31:747-751. PubMed Abstract | Publisher Full Text
6. Yin R, Lin XG, Wang SG, Zhang HY: Effect of DBP/DEHP in vegetable planted soil on the quality of capsicum fruit. Chemosphere 2003, 50:801-805. PubMed Abstract | Publisher Full Text
7. Virgin HI: Accumulation of di-n-butylphthalate in plants and its effect on pigment and protein content. Physiol Plantarum 1988, 72:190-196. Publisher Full Text
8. Saleem M, Nazir M, Akhtar N, Onocha PA, Riaz N, Jabbar A, Shaiq Ali M, Sultana N: New phthalates from Phyllanthus muellerianus (Euphorbiaceae). J Asian Nat Prod Res 2009, 11:974-977. PubMed Abstract | Publisher Full Text
9. Rowshanul Habib M, Rezaul Karim M: Antimicrobial and cytotoxic activity of di-(2-ethylhexyl) Phthalate and anhydrosophoradiol-3-acetate isolated from Calotropis gigantea (Linn.) Flower. Mycobiology 2009, 37:31-36. Publisher Full Text
10. Rameshthangam P, Ramasamy P: Antiviral activity of bis(2-methylheptyl)phthalate isolated from Pongamia pinnata leaves against White Spot Syndrome Virus of Penaeus monodon Fabricius. Virus Res 2007, 126:38-44. PubMed Abstract | Publisher Full Text
11. Ndhlala AR, Ncube B, Van Staden J: Ensuring quality in herbal medicines: Toxic phthalates in plastic-packaged commercial herbal products. South Afr J Bot 2012, 82:60-66.
12. Chen CY: Biosynthesis of di-(2-ethylhexyl) phthalate (DEHP) and di-n-butyl phthalate (DBP) from red alga Bangia atropurpurea. Water Res 2004, 38:1014-1018. PubMed Abstract | Publisher Full Text
13. Kuang QJ, Zhao WY, Cheng SP: Toxicity of dibutyl phthalate to algae. Bull Env Contam Toxicol 2003, 71:602-608. Publisher Full Text

Industrial Chemicals Found in Food Samples

Mar. 6, 2013 — Researchers at The University of Texas Health Science Center at Houston (UTHealth) have discovered phthalates, industrial chemicals, in common foods purchased in the United States. Phthalates can be found in a variety of products and food packaging material, child-care articles and medical devices.

"Although it's not completely understood how phthalates get into our food, packaging may be a contributor to the levels of the toxin in food," said lead investigator Arnold Schecter, M.D., M.P.H., professor of environmental health at The University of Texas School of Public Health Dallas Regional campus, part of UTHealth.

The study is published in the online edition of Environmental Health Perspectives. Schecter believes this is the first study to compile an analysis of phthalates in foods found in the United States. National Institutes of Health researcher Linda Birnbaum, Ph.D., is the senior author on the study publication.

"It's unfortunate that we have these toxic chemicals in our bodies," said Schecter. "However, this is not a cause for alarm because the amount of phthalates found in the food falls below what the Environmental Protection Agency considers safe. But it is cause for concern because these toxins and others previous reported by this group do not belong in our food or our bodies."

Phthalates are synthetic compounds that are used as a plasticizers and in personal care products such a shampoo, soap, perfumes and other common household products. According to Schecter, exposure to phthalates has been reported to be associated with harmful effects including reproductive changes such as damage in sperm, premature breast development in girls and premature birth.

A sample of 72 commonly consumed foods including pizza, meats and beverages from supermarkets in Albany, N.Y., were purchased and tested for the presence of phthalates. Researchers detected some level of phthalate in every food product they sampled, Schecter said.

Schecter believes further research is necessary to fully characterize phthalates in U.S. foods.

The study was funded by the Gustavus and Louise Pfeiffer Research Foundation.

In other studies, Schecter and his colleagues have found bisphenol A (BPA), a chemical produced in large quantities for use primarily in the production of polycarbonate plastics and epoxy resins, and hexabromocyclododecane (HBCD), a widely-used flame retardant, in foods. Polybrominated diphenyl ether (PBDE), another kind of flame retardant, was found in butter and its paper wrapping, which led to butter contamination.

Journal Reference:

Schecter A, Lorber M, Guo Y, Wu Q, Yun SH, Kannan K, Hommel M, Imran N, Hynan LS, Cheng D, Colacino JA, Birnbaum LS. Phthalate Concentrations and Dietary Exposure from Food Purchased in New York State.Environmental Health Perspectives, 2013 DOI:10.1289/ehp.1206367

Link:

http://www.sciencedaily.com/releases/2013/03/130307124701.htm

Fatores antinutricionais - II

Apesar de muitas espécies espontâneas possuírem potencial para utilização na alimentação, é importante, antes de estimular o consumo dessas plantas, verificar a presença de fatores antinutricionais, os quais são definidos no artigo no link: http://quintaisimortais.blogspot.com.br/2012/05/fatores-antinutricionais-i.html.

Como primeiro composto nesta série de artigos sobre fatores antinutricionais, escolhemos o oxalato de cálcio, pois também é encontrado em olerícolas como, por exemplo, espinafre, acelga, beterraba e tomate.  Esta substância, quando absorvida, não será  metabolizada, sendo liberada pela urina. No entanto, quando em excesso, poderá se transformar em cálculos renais, além de irritações na mucosa intestinal.

Tanto o oxalato de cálcio quanto o fosfato de cálcio, são os principais responsáveis, por exemplo, pela formação dos cálculos urinários, sendo as plantas as principais fornecedoras dos cristais de oxalato de cálcio.

Nos vegetais, os cristais de oxalato de cálcio, denominados de ráfides, são encontrados nas células, tanto das nas partes subterrâneas quanto aéreas. No jardim, encontramos algumas plantas consideradas tóxicas também porque possuem ao alto teor de oxalato de cálcio, como, por exemplo, comigo-ninguém-pode (Dieffenbachia picta Schott.), copo-de-leite (Zantedeschia aethiopica Spreng.) e tinhorão (Caladium bicolor Schott.). Estas espécies podem, se ingeridas, causar graves intoxicações porque além de ferir a mucosa, liberam outras substâncias, o que não é comum nas plantas comestíveis ricas em oxalato de cálcio, que provocam, entre outros sintomas, vômitos, diarreia, salivação abundante, edemas de lábios, boca e língua, e este inchaço poderá provocar asfixia.

Texto: Marcos Roberto Furlan e Isabella Ribeiro, acadêmica de Nutrição da Universidade de Taubaté

Fatores antinutricionais - I

Neste ano, realizaremos na Universidade de Taubaté pesquisas sobre os fatores antinutricionais em plantas espontâneas comestíveis, pois, após verificarmos que a maioria possui consideráveis teores de nutrientes para o ser humano, é imprescindível verificar se há substâncias que prejudicam a absorção desses nutrientes ou que são tóxicas para o consumidor.

O termo “fator antinutricional” pode ser definido como as substâncias ou os grupos de substâncias presentes em um grande número de alimentos de origem vegetal, os quais, quando em teores elevados, podem provocar reações tóxicas, interferir na biodisponibilidade ou na digestibilidade de alguns nutrientes, ou até provocar todas essas reações. Os fatores antinutricionais podem ser de ocorrência natural, nos ingredientes (endógenos), ou quando o produto sofre ação de contaminantes químicos ou biológicos (exógenos).

Nos alimentos, os fatores antinutricionais são de natureza variada e ainda são pouco conhecidos em relação à sua estrutura físico-química e sobre os seus mecanismos de ação fisiológica. Como exemplos de compostos ou de classe de compostos já estudados, temos o oxalato de cálcio, o nitrato, o cianeto, o inibidor de tripsina, a hemaglutinina e os polifenóis. 

São exemplos de fatores antinutricionais e suas respectivas ações: o consumo elevado de nitratos e a sua redução a nitritos desencadeia reações que liberam substâncias tóxicas; os inibidores de tripsina, particularmente os da soja, causam diminuição da digestibilidade protéica de leguminosas que foram insuficientemente cozidas; e as hemaglutininas interagem com a mucosa intestinal, causando inflamação e interferindo na absorção de nutrientes por lesão da mucosa.

Texto: Marcos Roberto Furlan e Isabella Ribeiro, Acadêmica de Nutrição da UNITAU