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Nitritos e nitratos nos alimentos e possíveis riscos para a saúde
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Resumo(s)
No nosso quotidiano estamos continuamente expostos, natural ou artificialmente, a diversos compostos químico. Enquanto uns podem ser benéficos outros podem acarretar riscos para a saúde, constituindo os nitratos e os nitritos inorgânicos presentes nos alimentos um exemplo.
Podem ser encontrados na Natureza desempenhando funções cruciais para a sobrevivência de todos os seres vivos não só, através da sua participação no ciclo do azoto, como também por serem um fator fulcral para o crescimento e desenvolvimento viável de produtos hortícolas, nomeadamente vegetais verdes, através da fertilização. Contudo, a utilização desmesurada pelo Homem de fertilizantes, contribui para o desequilíbrio dos ecossistemas bem como para a sua própria saúde através da contaminação de águas e solos.
Estes dois iões, particularmente o nitrito, podem adicionalmente desempenhar funções de aditivo e conservante, nomeadamente na carne curada, conferindo-lhe cor vermelha e sabor, para além de proteger contra o crescimento do microrganismo Clostridium botulinum, responsável pela intoxicação alimentar chamada botulismo.
No ser humano, os nitratos e nitritos consumidos através dos alimentos são em grande parte excretados como nitratos rapidamente. Porém cerca de 25% do nitrato é recirculado através das glândulas salivares e 5% é convertido por bactérias da boca em nitrito. Para além disso, pode-se obter nitrato endogenamente através da conversão enzimática de arginina em monóxido de azoto.
O nitrito em excesso, pode ter efeitos nefastos, como a oxidação da hemoglobina em metahemoglobina, reduzindo a capacidade de os eritrócitos transportarem oxigénio aos tecidos. O nitrito, quer esteja já presente nos alimentos, quer seja endogenamente formado, pode também ter a capacidade de mediar a formação de compostos N-nitrosos, como nitrosaminas e nitrosamidas, alguns com ação carcinogénica.
Outros efeitos potencialmente provocados por ação dos nitratos e seus metabolitos compreendem alterações a nível da tiroide, bem como stress nitrosativo.
De forma a proteger os consumidores dos potenciais riscos relacionados com os nitratos e nitritos na alimentação existe vasta legislação, que define os teores máximos admitidos, a par do estabelecimento de valores de ingestão diária aceitável para estes dois iões.
In our daily lives we have the possibility to contact, naturally or artificially, with various chemicals. While some may be beneficial others may be malicious, constituting inorganic nitrates and nitrites in food an example. They can be found in Nature performing crucial functions for the survival of all living beings not only by participating in the nitrogen cycle, but also being a key factor in the growth and viable development of vegetable products through fertilization. However, the man-made misuse of fertilizers contributes to the imbalance of ecosystems as well as to their own personal health through contamination of water and soil. These two ions, particularly nitrite, can perform additive functions as in cured meat, giving red color and flavor, as well as protecting against the growth of Clostridium botulinum, a microorganism responsible for the intoxication called botulism. In humans, nitrates and nitrites consumed through foods are largely excreted as nitrates quickly. However about 25% of nitrate is recirculated through the salivary glands and 5% is converted by oral bacteria into nitrite. In addition to this, nitrate can be obtained endogenously by enzymatic conversion of arginine into nitrogen monoxide. Nitrite, in excess, can have harmful effects, namely, can oxidize hemoglobin in methemoglobin, reducing erythrocyte’s ability to transport oxygen to tissues. Nitrite, whether present in food or endogenously formed, can mediate the formation of N-nitroso compounds such as nitrosamines and nitrosamides, some of them with carcinogenic action. Other effects potentially caused by the action of nitrates and their metabolites include changes in thyroid as well as nitrosative stress. In order to protect consumers from the potential risks concerning nitrates and nitrites in food, there is vast legislation defining the maximum allowed levels, together with the setting of acceptable daily intake values for these two ions.
In our daily lives we have the possibility to contact, naturally or artificially, with various chemicals. While some may be beneficial others may be malicious, constituting inorganic nitrates and nitrites in food an example. They can be found in Nature performing crucial functions for the survival of all living beings not only by participating in the nitrogen cycle, but also being a key factor in the growth and viable development of vegetable products through fertilization. However, the man-made misuse of fertilizers contributes to the imbalance of ecosystems as well as to their own personal health through contamination of water and soil. These two ions, particularly nitrite, can perform additive functions as in cured meat, giving red color and flavor, as well as protecting against the growth of Clostridium botulinum, a microorganism responsible for the intoxication called botulism. In humans, nitrates and nitrites consumed through foods are largely excreted as nitrates quickly. However about 25% of nitrate is recirculated through the salivary glands and 5% is converted by oral bacteria into nitrite. In addition to this, nitrate can be obtained endogenously by enzymatic conversion of arginine into nitrogen monoxide. Nitrite, in excess, can have harmful effects, namely, can oxidize hemoglobin in methemoglobin, reducing erythrocyte’s ability to transport oxygen to tissues. Nitrite, whether present in food or endogenously formed, can mediate the formation of N-nitroso compounds such as nitrosamines and nitrosamides, some of them with carcinogenic action. Other effects potentially caused by the action of nitrates and their metabolites include changes in thyroid as well as nitrosative stress. In order to protect consumers from the potential risks concerning nitrates and nitrites in food, there is vast legislation defining the maximum allowed levels, together with the setting of acceptable daily intake values for these two ions.
Descrição
Trabalho Final de Mestrado Integrado, Ciências Farmacêuticas, 2022, Universidade de Lisboa, Faculdade de Farmácia.
Palavras-chave
Nitratos Nitritos Vegetais Carne Compostos N-nitrosos Mestrado integrado - 2022