| Selenium is an essential trace element for humans and animals,which can effectively scavenge free radicals in living organisms,enhance the body’s antioxidant capacity and immune function,and reduce the risk of cancer.Both deficiencies and excesses of selenium in the human body can lead to certain diseases.Humans mainly supplement selenium through diet,selenium is absorbed by crops in the soil into the food chain,and is transferred and accumulated in plants and animals,so the different levels of selenium in the environment and the different ability of crops and animals to gather selenium will significantly affect human selenium levels.Guangxi Zhuang Autonomous Region has a large area of selenium-rich soil,but the distribution of selenium still has unevenness.This thesis mainly studies the human selenium level of residents in areas with different soil selenium content in Guangxi,and evaluates the selenium level of residents in the research area by investigating the dietary structure and the types of food consumed in the research area,testing the selenium content of agricultural products in the research area,collecting hair of residents in the research area and testing their selenium content,and making reference to the recommended intake of selenium,comparing the selenium level with that of people in other areas,and evaluating the selenium level of residents in the research area.The residents in the study area will be given reasonable dietary recommendations to guide them to take selenium supplements scientifically.In this study,based on the preliminary investigation of soil selenium content in Yulin,Guangxi,based on the relevant literature on soil selenium classification and the selenium content of soil samples that had been tested,a total of four villages,Yongning Village,Sanlong Village and Qin Village in Fumian District,Yulin,Guangxi,and Chen Village in Daping Mountain Town,Xingye County,Yulin,were selected to carry out inductively coupled plasma mass spectrometry to determine the soil selenium content,common foods and the hair selenium content of residents,residents dietary structure statistics,and the calculation of daily dietary selenium intake of residents in areas with different soil selenium contents in Guangxi,etc.The main findings are as follows.1.In this study,soil samples were collected from four villages and tested for selenium content,and there were significant differences in soil selenium content among the four villages.The village with the highest mean soil selenium content was Chen Village(1.968±0.152 mg/kg)with a median value of2.000 mg/kg.The village with the lowest mean soil selenium content was Qin Village(0.185±0.032mg/kg)with a median value of 0.184 mg/kg.2.The selenium content of vegetables,fruits,meat and cereals consumed daily by residents in the four areas of Guangxi with different soil selenium contents in this study was measured,and the results showed that among the various types of agricultural products tested,meat and eggs had the highest selenium content,with fish(0.342±0.062 mg/kg)being significantly higher than pork,chicken and duck,while the selenium content of animal offal(pig kidney 2.209±0.158 mg/kg)was higher than that of other edible parts.The mean selenium content of rice in each study area was 0.103 mg/kg,with significant differences among the sampling sites,with the highest mean selenium content in Chen Village(0.264±0.175 mg/kg)and Sanlong Village(0.048±0.027 mg/kg).The mean selenium content of rice was the lowest in Sanlong Village(0.048±0.027 mg/kg),and there was a strong correlation between the mean selenium content of rice and the mean selenium content of soil;the mean selenium content of bean products was low(0.046±0.058 mg/kg),while the mean selenium content of vegetables(0.014±0.021 mg/kg)and fruits(0.001±0.001 mg/kg)was the lowest.The highest mean selenium content was found in small onions(0.055±0.023 mg/kg),followed by leafy vegetables(0.015±0.022 mg/kg)among the various vegetables tested.3.In this study,the selenium intake of residents in areas with different soil selenium content in Guangxi ranged from 11.9～461.9μg/d,and the average daily selenium intake of residents was 77.7μg/d,with a median value of 68.0μg/d.Referring to the regression equation of dietary selenium intake and the logarithm of hair selenium content proposed by Yang Guangqi et al.in the 1980s,the reference daily dietary selenium intake of the population was calculated,with the mean value of 32.8μg/d and the median value of 32.2μg/d,ranging from 1.6 to 76.1μg/d.The contribution of meat from livestock and poultry was the largest,accounting for 60.5%;the contribution of cereals and potatoes,which are the staple food of residents,to selenium intake was 15.9%;the contribution of aquatic products to contribution to selenium intake was 12.5%,eggs 5.7%,vegetables 4.0%,beans and bean products 0.9%,milk and milk products 0.4%and fruits 0.1%.4.Analysis of the selenium content of hair of residents in areas with different soil selenium levels in Guangxi in this study revealed that the mean selenium content of hair of residents in Sanlong Village was the highest at(0.478±0.089)mg/kg,while the mean selenium content of hair of residents in Qin Village was the lowest at(0.327±0.100)mg/kg,and there were significant differences in the selenium content of hair of residents in each study area.When analysed in conjunction with the soil selenium content of each study site,the hair selenium content was positively correlated with the soil selenium content in all three study sites,except for Sanlong Village,which had the highest hair selenium content,indicating that environmental selenium levels have an influence on human selenium levels.Compared to different age groups,residents under the age of 30 had the highest selenium levels,followed by residents between the ages of 50 and 70,followed by residents between the ages of 30 and 50,and residents over 70 had the lowest.However,overall,there was no significant effect of age on selenium levels.In addition,selenium levels were slightly higher in women than in men in this study,but the difference was not significant.5.In this study,a scatter plot of the daily dietary selenium intake and selenium fraction of four villages in Guangxi with different soil selenium content was plotted and linearly regressed to obtain the relationship:daily dietary selenium intake(μg/d)=0.0322×selenium fraction(μg/kg)+73.164(R~2=0.0073,n=287). |
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