| Selenium(Se)is one of the essential microelements for human body.The daily Se intake of residents highly depends on human health.In order to study the transportation of Se in the environment and its effect on residents' health under natural conditions,the International Society for Selenium Research initiated "Natural Selenium Biofortification Program"(NBP),which mainly focuses on the transportation of Se through the soil-crop-human chain in the natural Se rich environment,and investigates the relationship between Se and human health.This study was pre-research part of the NBP,focusing on two natural Se rich regions,Enshi Miao and Tujia Autonomous Prefecture in Hubei Province and Shitai County in Anhui Province.The distribution of Se resources in China is very uneven.There are not only saddle shaped soil Se deficient zones from northeast to southwest,but also natural Se rich areas such as Enshi in Hubei Province,Shitai in Anhui Province and Ankang in Shaanxi Province.Chian has the convenience and advantages of conducting NBP research.This study consider Dashan Village and Kushan village in Shitai,Anhui Province,Yutangba village,Liziba village and Changping village in Enshi,Hubei Province as research sites.Soil,water,main crops,human hair and plasma samples were collected from each village having 1306 samples.The dietary structure and basic population information of local residents were obtained through questionnaire survey.The contents of total Se,selenate,selenite,selenocysteine,selenomethionine and methylselenocysteine in the samples were determined by atomic fluorescence spectrometry and high performance liquid chromatography inductively coupled with plasma mass spectrometry in the laboratory.The enzyme activity level of glutathione peroxidase(GPX)and superoxide(SOD),and the Selenoprotein P level(Seppl)in the plasma samples were detected by special kits.Application of multidisciplinary research methods such as environmental soil science,nutrition,epidemiology and a variety of statistical data analysis methods were used to study the distribution of Se from soil,crop to human body in the present study.Combined with the epidemiological data,the preliminary analysis was made to find the relationship between Se intake and the prevalence of hyperlipidemia,hypertension and hair loss.The specific research results are as follows:1.Characteristics of Se contents in soil and its impact factorsDashan Village,Shitai County,Anhui Province,Yutangba village and Liziba village,Enshi Prefecture,Hubei Province were Se rich areas.The average values of total Se content in cultivated soil are 2285.9±1046.2 ?g/kg(n=14),1753.6±742.8?g/kg(n=14)and 2262.5±1388.4 ?g/kg(n=17)in Dashan,Yutangba and Liziba,respectively.The total Se content in cultivated soil in Kushan village,Shitai County,Anhui Province and Changping village,Enshi County,Hubei Province was 236.6±45.8 ?g/kg(n=16)and 259.6±37.3 ?g/kg(n=18),respectively.The results showed that the proportion of bioavailable Se was approximately 1.7± 1.1%(n=14)in Dashan,4.6±6.1%(n=16)in Kushan,2.7± 1.5%(n=14)in Yutangba,1.9± 1.0%(n=17)in Liziba and 3.4± 1.1%(n=18)in Changping.There were significant differences in bioavailable Se in the soil of the region.Besides the total Se content in the soil,it was also speculated that Se could vary with the physical and chemical properties of the soil.The results of Pearson correlation analysis showed that there was a significant positive correlation between the bioavailable Se content and the total Se content,and a significant positive correlation between the bioavailable Se content and the pH value.The total aluminum content showed a significant negative correlation,but there was no significant correlation with the organic matter content,total iron and total manganese content.The above results showed that the bioavailable Se is closely related to the physical and chemical properties of soil,especially the pH,total Se and total aluminum content of soil.2.Variations of Se contents and speciation in main cropsOrganic Se is safer and more effective than inorganic Se.In addition to the total Se content,the content differences of different Se speciation in food are also concerned.In this study,the total Se content(374.63±234.38?g/kg,n=18)of rice samples in Liziba village was significantly higher than that in any other villages.Se in rice samples mainly existed in the form of organic Se,including selenomethionine(SeMet)and selenocysteine(SeCys2),and the proportion of SeMet is as high as 80%-90%.Enrichment coefficient results of different crops in Enshi area showed that rice had the strongest Se enrichment ability(enrichment coefficient,12.2%).The results showed that although the total Se content in rice was significantly different,the proportion of organic Se(mainly Semet)was relatively high,and the rice could be the main food for people in Se deficient areas.The results of Se speciation analysis in tuber samples showed that inorganic Se and organic Se existed in potato samples at the same time.Inorganic Se accounted from 4.28%to 32.65%(mainly selenate).In addition,with the increase of total Se content,the proportion of selenate increased correspondingly.Different from the characteristics of inorganic Se content,the changes of organic Se composition in potato samples were more complex.In the low,medium and high Se samples,SeMet accounts for 40.70%,71.85%and 47.89%respectively,which shows a U-shaped curve relationship with the changes of total Se content.SeMet in the high Se samples was relatively low,which was related to the high proportion of inorganic Se in these samples.Because there was still a high proportion of inorganic Se in potato samples with high Se content,it was necessary to prevent excessive intake of inorganic Se affecting human health.The results of Se speciation analysis in vegetable radish samples showed that nearly half of Se in radish samples existed in the form of inorganic Se(mainly selenate).With the increase of total Se content in radish samples,the proportion of SeMet and SeCys2 in organic Se was significantly smaller,and unknown Se forms appeared.The proportion of unknown Se forms in middle Se and high Se radish samples was 34.80%and 46.11%,respectively.The results show that the conversion rate of Se in radish was low.When choosing radish as Se supplement food,we should pay attention to the proportion of inorganic Se.3.Variations in residents' daily Se intakeThe daily Se intakes of residents in Dashan and Kushan in Shitai County,Anhui Province were 56±79 ?g/d and 18± 10 ?g/d,respectively.Vegetables(68%)and cereals(rice,49%)account for the most Se intake of residents in Dashan and Kushan,respectively.In Yutangba,Liziba and Changping in Enshi,Hubei Province,the daily Se intakes of residents were 82±57 ?g/d,160± 106 ?g/d and 34±9 ?g/d,respectively.The food that account for the most Se intake of residents were vegetables(49%),grains(77%)and grains(65%)in Yutangba,Liziba and Changping,respectively.The results showed that the daily Se intake of residents in Kushan village and Changping village was far lower than the recommended dietary Se intake of Chinese adults(60?g/d),and residents in Kushan and Changping were faced with the risk of Se deficiency.The result also reflected that the distribution of Se rich soil in the region is spot like,and there were also Se deficient villages in some well-known Se rich regions In addition,according to the proportion of Se contribution to food,the main food types that rural residents got Se from their diet were grains and vegetables,rather than animal food with relatively high Se content.4.Variations in human Se biomarker levelsThe daily intake of Se of residents was significantly linearly related to the level of selenium in hair.The relationship could be expressed as:Se content in hair(?g/kg)=2.343 X daily intake of Se in residents(?g/d)+233.2,R2=0.757.The Se contents in hair and plasma of all residents in Dashan,Shitai,Anhui Province were significantly higher than those in Kushan.The Se contents in the hair and plasma of all residents in Yutangba,Enshi,Hubei Province were not significantly different from that in Liziba Village,but significantly higher than that in Changping.The results of Pearson correlation analysis showed that the hair Se level of all residents,male and female residents in Enshi area had a significant positive correlation with the plasma total Se level,a significant negative correlation with the plasma SOD enzyme activity,but no significant correlation with the plasma GPx enzyme activity and Sepp1 level.There was a significant positive correlation between plasma Se and Sepp1,but no significant correlation between plasma Se and GPx.The above results showed that there was not a simple linear relationship between biomarkers at different Se levels.Compared with GPx,Sepp1 needs higher Se intake to reach its maximum activity.Sepp1 level can more accurately reflect the Se level of the human body in the study area.5.Assessment of the relationship between human Se levels and healthIn order to explore the relationship between Se level and health of the population,the information of hair Se(459.9±203.3 ?g/kg,n=173)and plasma Se(85.8 ± 39.6?g/kg,n=163)of 185 volunteers in Enshi Prefecture were collected.The basic information of the population included height,weight,age,gender,income,blood lipid index,blood pressure,etc.,as the possible variables for the study.Through binary regression logic analysis,in the multivariable logistic regression model,it was found that there was a significant positive correlation between the hair Se level and the prevalence of total hyperlipidemia,high TG(Total triglyceride),high TC(total cholesterol)and low HDL(high density lipoprotein cholesterol)in Enshi.The levels of Se in hair and plasma were positively correlated with the prevalence of high SBP(systolic blood pressure).However,there was no relationship of Se levels with the prevalence of high diastolic blood pressure(DBP).The results of gender specific analysis showed that the correlation between Se level and hypertension prevalence in male volunteers was more significant than that in female volunteers.In addition,based on the results of multivariable logistic regression model,it was found that the plasma Se level of all volunteers and male volunteers had a significant negative correlation with the hair loss rate.There was no significant correlation between Se levels and the prevalence of hyperglycemia in all volunteers(p>0.05).No relationship between Se levels and insomnia was observed.The above statistical analysis results showed that the relationship between hair Se,plasma Se and human health was complex,but in general,the level of hair Se was closely related to the prevalence of hyperlipidemia and hypertension,which had a positive correlation.Considering that the cross-sectional survey,which cannot explain the causal relationship between Se and disease,it is necessary to further strengthen the relevant population intervention research in the future scope to explore the relationship between Se and human health. |
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