ABSTRACT
Nitrate and oxalates are often regarded as anti-quality factors in food products and animal feeds. Nitrate is a key component of the global nitrogen cycle. Its uptake and assimilation in plants are of fundamental importance in the synthesis of plant proteins and other nitrogenous compounds, and therefore indirectly also of nitrogenous substances in animals. The chapter is a critical appraisal of knowledge of the occurrence and toxicity of nitrate and oxalates. In higher plants, nitrate is assimilated in the cytoplasm, but some is also channeled into vacuoles where, under conditions of excess nitrogen, large amounts can accumulate. Nitrite has a vasodilatory action on animals, causing circulatory disturbances such as a reduction in blood pressure. Oxalic acid is the strongest dicarboxylic acid commonly present in living organisms, forming highly soluble neutral and acidic salts with monovalent metals such as potassium and sodium, and poorly soluble chelates with divalent cations such as calcium.
