Onyesom I, Okoh P N
Department of Biochemistry, PO Box 144, Delta State University, Abraka, Nigeria.
Br J Nutr. 2006 Nov;96(5):902-5. doi: 10.1017/bjn20061915.
Plasma thiocyanate has been reported to be high among cassava-eating populations such as that in Nigeria because of the cyanide content of cassava. Thiocyanate, which is secreted into the stomach contents of animals, has been demonstrated to catalyse the formation of nitrosamines (potent carcinogens) in the stomach from secondary amines and nitrite. The main source of the nitrite precursor in this environment is vegetables, primarily eaten as the chief supplier of proteins. The present study attempts to analyse the levels of nitrate and nitrite in vegetables commonly grown and consumed in Delta State, Nigeria. The nitrate and nitrite contents in green vegetable (Amaranthus spp.), bitter leaf (Vernonia amygdalina), pumpkin (Telfaria occidentalis) and water leaf (Talinum triangulare) grown in different localities of the state were determined by standard analytical procedures. The results show that those vegetables grown in the industrialised urban centres of the state had higher nitrate (223 (SD 71) mg/kg dry weight; P<0.05) and nitrite (12.6 (SD 1.7) mg/kg dry weight; P>0.05) levels when compared with the same species (188 (SD 77) mg nitrate/kg dry weight and 10.9 (SD 1.1) mg nitrite/kg dry weight) cultivated in less industrialised suburbs. We conclude that frequent consumption of such vegetables whose nitrate and nitrite contents are high by cassava-eating individuals might put them at risk of developing stomach cancer and other possible results of nitrate and/or nitrite toxicity. In order to avoid an outbreak in our communities, appropriate agencies should monitor and regulate the release of chemicals into the environment. In the meantime, the cultivation and consumption of vegetables grown in industrialised areas of the state should be discouraged.
据报道，由于木薯含有氰化物，在尼日利亚等食用木薯的人群中，血浆硫氰酸盐含量较高。已证明分泌到动物胃内容物中的硫氰酸盐能催化胃中仲胺和亚硝酸盐形成亚硝胺（强致癌物）。在这种环境下，亚硝酸盐前体的主要来源是蔬菜，蔬菜主要作为蛋白质的主要供应来源被食用。本研究试图分析尼日利亚三角州州常见种植和食用的蔬菜中的硝酸盐和亚硝酸盐含量。通过标准分析程序测定了该州不同地区种植的绿色蔬菜（苋菜属）、苦叶（扁桃斑鸠菊）、南瓜（西方铁苋菜）和水叶（三角叶土人参）中的硝酸盐和亚硝酸盐含量。结果表明，与在工业化程度较低的郊区种植的同一物种（硝酸盐含量为188（标准差77）毫克/千克干重，亚硝酸盐含量为10.9（标准差1.1）毫克/千克干重）相比，在该州工业化城市中心种植的这些蔬菜的硝酸盐（223（标准差71）毫克/千克干重；P<0.05）和亚硝酸盐（12.6（标准差1.7）毫克/千克干重；P>0.05）含量更高。我们得出结论，食用木薯的人经常食用硝酸盐和亚硝酸盐含量高的此类蔬菜，可能会使他们面临患胃癌以及硝酸盐和/或亚硝酸盐中毒其他可能后果的风险。为避免在我们的社区爆发问题，相关机构应监测和监管化学物质向环境中的排放。与此同时，应不鼓励种植和食用该州工业化地区种植的蔬菜。
