Containsof Nutrients And Pollutants In Cultured Fish As Well As Its"Benefit-risk" Effects On Human Health

In contemporary world, fish contain not only nutrients, but also environmental pollutants, such as, such as the heavy metals or organic pollutants, thus fish has been a package of beneficial and adverse elements for human health. In order to understand the content of nutrients and contaminants in the common fish in Shanghai markets and provide scientific advice offish consumption for local residents, we firstly measured the content of nutrients and heavy metal pollutants of five common fishes in different tissues from Shanghai market, and then carried on the comprehensive evaluation for thebenefit and risk ofcommon fish intake to resident of Shanghai. After that, we use tilapia as the model to study the distribution of the organic pollutants PCB1254 in the body of fish fed diets containing different lipid levels. The studies contained in this thesis provide not only a scientific advice of fish consumptionfor residents of Shanghai, but also some basic data and important reference for the further research of the biological metabolism of organic pollutants.1、The comparative analysis of the fatty acid composition for fish brain and eyes of five kinds of economic fish in winter and summerPotential health benefits of eating fish can be attributed to n-3 highly unsaturated fatty acids (HUFAs) contained in fish, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).hese two kinds of important fatty acids cannot be synthesized by the human body, and also can’t get from the livestock meat, so eating fish became the only sources of these nutrients.In the traditional diet, fish filetis the main edible part, But fish brains and eyes are commonly consumed in China, however, their nutritional importance has not been evaluated. We investigated the fatty acid (FA) profiles in brains and eyes of five economically important fish species with different food habits (carnivorous, omnivorous, and herbivorous). The fatty acid profiles were also compared between winter and summer. The FA compositions of brains and eyes of carnivorous and marine fishes were similar, and differed from those of omnivorous and herbivorous freshwater fishes. In winter, there were higher proportions of n-3 polyunsaturated fatty acids in brains and eyes of carnivorous and marine fishes than in those of omnivorous and herbivorous freshwater fishes; the magnitude of this difference was smaller in summer. The FA compositions of brains and eyes of these five fishes were comparable to those reported for their fillets in previous studies. Therefore, fish brains and eyes are not more nutritious than fillets of the same species.2. The risk and benefit evaluation of five kinds of economic fish consumptionof Shanghai on human healthFish contain not only important nutrients which is essential to human health, but also quantities of pollutants, such as heavy metals. The consumption of fish food has become the most important way of heavy metal pollutants entering our body, leading to a potential health risk to human health. With the improvement of living standard, the proportion of fish consumption in daily life become higher and higher, but the actual conflict of the coexistence of nutrients and pollutants has brought a lot of confusion to ordinary consumers and government advisory apartments. Therefore, precise measurement of nutrients and contaminants to assess the values and risks offish edible part is urgently required.According to different regions, a comprehensive assessment of the health risks and benefits of fish consumption ("risk-benefit" evaluation) is required to conduct. In the present experiment, five fish species were investigated:large yellow croaker (Pseudosciaena crocea), silvery pomfret (Pampus argenteus), river eel (Anguilla japonica), tilapia (Oreochromis mossambicus) and grass carp (Ctenopharyngodon idellus). Fish were purchased from three normal supermarkets at Minhang, Putuo and Huangpu Districts in Shanghai. In Shanghai, these fish are generally consumed for many years by the local residents, thus the survey results can represent the co-intake of nutrients and pollutants of Shanghai residents through consumption of these fishes. When collected fish samples, together the same species, and taken five tissues of every samples,including dorsal muscles,abdominal muscles, tail muscle, liver and abdominal adipose tissue (large yellow croaker and silver pomfret had no abdominal adipose tissue) after peel and anatomy. The results show that the content of Cu, Cd, Pb and Hg detected in the three kinds of fish muscles did not exceed the national standard, and the content in fish which can provide human with the minimum daily demand of EPA+DHA and also under the national standard of TDI. Only few individual fish liver had exceeded the national standard of mercury content. These indicate that the daily dietary fish is unlikely to bring risks caused by these kinds of pollutants. However, the present study also shows that the potential risk of Hg in aquatic products should be paid higher attentionthan other heavy metal pollutant.3. Study on the accumulation and distribution of PCBs in fishPCB is a persistent organic pollutant. When it gets into the environment, PCBs will eventually accumulate in the human body through the food chain. However, there are some questions remaining According to the theory of similarity and compatibility, the accumulation of PCBs is likely related with fat. In order to investigate the correlation between PCB accumulation and body fat deposition, we conducted an experiment on the accumulation and distribution of PCB1254 in fish.Used the safety concentration of PCB1254 for tilapia,4 mg/L, and dissolved PCB1254 in the organic solvent DMSO. The same concentration of DMSO without PCBs to the experiment was used as the control. Under the same concentration of PCB1254, three kinds of diets containing different fat concentrations (1%,7%,13%) were fed to tilapia for 10 weeks. After the experiment, muscle, liver and adipose tissue which had different content of lipid were collected. Then, second stage of the experiment was carried out using the remaining fish. Before the second stage of the experiment, prior water was instead by clean water, and the remaining fish were divided evenly into two groups. One group (after referred to as the starvation group) wasfasted for 4 weeks, while, another group (after referred to as the recovery group) were still fed by the prior diets which used for stage one but without PCBs for 4 weeks. After the experiment, collected samples as the same as first stage of the experiment. Through the determination and analysis of PCBs and fat content, we found that PCB accumulation is actually correlated with body fat, PCBs is positively correlated with fat content, in muscle, liver or the adipose tissue. But when the fat was exhausted by starvation, PCBs was not eliminated with the decreased fat. So our study indicated that the accumulation of PCBs is tightly correlated to adipose tissue distribution, and could be concentrated when fat is decreasing.