硒的人体最大安全摄入量的研究 一、居民硒的日摄入量和组织硒的含量

在恩施高硒及邻近地区选择了高、中及低硒三个试验点,各点间的距离不超过20～30公里。低、中及高硒点成年居民年平均硒摄入量分别为66.3,196.4及1338.4μg,组织中硒含量随硒摄入量的增加而增加。在摄入量处于营养水平时,血硒的变化具有一定的代表性。但当硒摄入量超过正常水平时,血硒的反应不如发及甲硒灵敏,后者硒浓度的变化与尿近似,它们似具有明显的排泄功能。文中界限摄入量即根据血硒值计算而得。本研究课题总的实验设计在文中作了纲要性的叙述。     

硒的人体最大安全摄入量的研究——一、居民硒的日摄入量和组织硒的含量

在恩施高硒及邻近地区选择了高、中及低硒三个试验点,各点间的距离不超过20～30公里。低、中及高硒点成年居民年平均硒摄入量分别为66.3,196.4及1338.4μg,组织中硒含量随硒摄入量的增加而增加。在摄入量处于营养水平时,血硒的变化具有一定的代表性。但当硒摄入量超过正常水平时,血硒的反应不如发及甲硒灵敏,后者硒浓度的变化与尿近似,它们似共有明显的排泄功能。文中界限摄入量即根据血硒值计算而得。本研究课题总的实验设计在文中作了纲要性的叙述。     

淮北市居民硒营养水平调查与评价

目的了解淮北市居民微量元素硒的营养水平状况,并为建立全国微量元素营养数据库提供有效的数据。方法于2003年9月—2004年6月,随机选取在淮北市出生或在淮北市居住10a以上健康居民513人,采用催化极谱法测定发硒含量,并划分硒丰度区;以发硒含量估算膳食硒摄入量,按照《中国居民膳食营养素参考摄入量》进行评价。结果淮北市居民发硒含量为(0.3903±0.1045)μg/g,仅有51.9%(266/513)的居民发硒含量属于适硒区水平。淮北市居民膳食硒摄入量为(31.92±9.93)μg/d;除0～6岁人群外,其他各年龄段人群膳食硒摄入量远低于中国营养学会推荐的摄入量。达到推荐摄入量(RNI)、平均需要量(EAR)标准的居民分别占19.9%(102/513)和32.9%(169/513),也远未达到满足群体中50%个体生理需要量的摄入水平。结论淮北市民从膳食中摄取的硒量严重不足,提醒市民应适当补充微量元素硒。     

淮北市健康居民与癌症患者硒营养水平比较研究

目的：调查淮北市民与癌症患者硒营养水平是否存在差异。方法：随机选取335名健康居民和214例癌症患者进行发硒含量测定，以发硒估算膳食硒摄入量，考察两者之间的差异。结果：淮北市民硒营养水平较低，且癌症患者显著低于健康居民，差异有统计学意义（P〈0．050）。结论：淮北市民癌症发病率较高与硒的低营养水平有一定的相关性。     

不同硒水平地区人群发样扫描电镜观察

我国湖北省恩施县部分地区为高硒地区,根据以往对当地居民的调查,每人每日硒摄入量曾高达3.2～6.7mg,平均5mg,并出现脱发及指甲改变等中毒症状。本文对不同硒水平地区人群发样表面形态作对比观察,结果表明,对照及低硒地区发样粗细均匀、光滑、表面鳞片状角化细胞排列整齐;恩施花被高硒地区8 例发样皆有不同程度表面形态改变,变化的严重程度与血硒水平及指甲中毒症状的出现有关,提示除肝、肾外,发亦是硒作用部位之一。     

不同硒水平地区人群发样扫描电镜观察

我国湖北省恩施县部分地区为高硒地区,根据以往对当地居民的调查,每人每日硒摄入量曾高达3.2～6.7mg,平均5mg,并出现脱发及指甲改变等中毒症状。本文对不同硒水平地区人群发样表面形态作对比观察,结果表明,对照及低硒地区发样粗细均匀、光滑、表面鳞片状角化细胞排列整齐;恩施花被高硒地区8 例发样皆有不同程度表面形态改变,变化的严重程度与血硒水平及指甲中毒症状的出现有关,提示除肝、肾外,发亦是硒作用部位之一。     

富硒食品含硒量范围标准的研究

目的:制定富硒食品含硒量范围标准,规范富硒食品的生产、加工与销售行为。方法:采集不同硒区农副产品、预包装食品和居民膳食样品,按GB5009.93食品中硒的测定方法进行检测,参考国内相关资料提出的富硒食品含硒量量值设定范围,下限设置注重补硒有效性,上限设置注重食物安全性。结果:谷物硒含量0.1~0.4 mg/kg,蔬菜0.03~0.25 mg/kg,肉食品0.2~1.0 mg/kg范围内的富硒食品,可使居民每天硒的摄入量稳定在50~250μg/d的最适宜摄入量范围之内。     

硒的人体最大安全摄入量研究 六、硒的最高界限摄入量和最大安全摄入量

体检349名成年居民结果,发现血硒水平在1.02μg/ml以下者无硒中毒病人,又5名指甲变形长期不能恢复正常者,他们中间最低血浓度为1.054μg/ml(硒日摄入量910μg)。生化检查结果发现当血硒浓度上升到1μg/ml(硒日摄入量850μg)时,凝血酶原时间延长的病例显著上升;此外,在血硒浓度接近0.9μg/ml(硒日摄入量743μg)时,血浆硒/红血球硒的比值下降至低血硒状态时的1/3至1/4。据上述结果,界限日硒摄入量应在750～850μg范围内。考虑到个体差异,建议用2.0作为安全因子,即最高安全摄入量为400μg。又考虑我国高硒区的某些具体情况如居民适应性及环境中某些拮抗元素的存在等,建议在高硒区用1.3作为安全因子,即最高安全摄入量约为每日550μg。     

淮北市15岁以上健康居民硒营养水平调查

硒是人体所必需的微量元素，研究认为，发硒与膳食硒摄入量之间有良好的相关性，是反映人体硒营养状态的指标之一。调查我市健康人群发硒含量，有助于评价居民硒的营养水平。为此，对淮北市15岁以上健康居民进行调查。     

硒的人体最大安全摄入量研究 六、硒的最高界限摄入量和最大安全摄入量

体检349名成年居民结果,发现血硒水平在1.02μg/ml以下者无硒中毒病人,又5名指甲变形长期不能恢复正常者,他们中间最低血浓度为1.054μg/ml(硒日摄入量910μg)。生化检查结果发现当血硒浓度上升到1μg/ml(硒日摄入量850μg)时,凝血酶原时间延长的病例显著上升;此外,在血硒浓度接近0.9μg/ml(硒日摄入量743μg)时,血浆硒/红血球硒的比值下降至低血硒状态时的1/3至1/4。据上述结果,界限日硒摄入量应在750～850μg范围内。考虑到个体差异,建议用2.0作为安全因子,即最高安全摄入量为400μg。又考虑我国高硒区的某些具体情况如居民适应性及环境中某些拮抗元素的存在等,建议在高硒区用1.3作为安全因子,即最高安全摄入量约为每日550μg。     

Selenium-enriched broccoli decreases intestinal tumorigenesis in multiple intestinal neoplasia mice

Multiple intestinal neoplasia (Min) mice are a good model for the investigation of the effects of dietary alterations in a genetic model for intestinal cancer. Previous studies have shown that selenium-enriched broccoli is protective against chemically induced colon cancer susceptibility. This study investigated whether selenium-enriched broccoli would be protective against intestinal cancer susceptibility in Min mice. Five-week-old heterozygotic male Min mice were fed an AIN-93-based diet containing either low-selenium broccoli or an equivalent amount of high-selenium broccoli for 10 wk. Mice fed the selenium-enriched broccoli had fewer (P < 0.02) small intestinal (46.4 +/- 3.7 vs. 65.6 +/- 6.1) and large intestinal (0.43 +/- 0.17 vs. 1.93 +/- 0.27) tumors than those fed an equivalent amount of unenriched broccoli. Min mice fed the selenium-enriched broccoli had small but significant (P < 0.0001) increases in plasma and liver selenium concentrations and red blood cell glutathione peroxidase activity. These results extend previous observations that selenium-enriched broccoli is protective against chemically induced mammary and colon cancer in rats.     

Dietary mineral and trace element intake and squamous cell carcinoma of the esophagus in a Chinese population

Few studies have been conducted in low-selenium areas of China to assess the relationships between dietary intake of selenium and zinc and the risk of squamous cell carcinoma of the esophagus (SCCE). We studied dietary mineral and trace element intake and risk of SCCE in a population- based, case-control study in Taixing, China, in 2000. A total of 218 SCCE patients and 415 population healthy controls were interviewed using a standard dietary and health questionnaire. The median and quartiles were calculated to represent the average level and distribution of selected dietary minerals and trace elements estimated by the Chinese Standard Tables of Food Composition. The adjusted odds ratios (ORs) comparing the highest with the lowest quartiles were 0.30 (95% confidence intervals, CIs = 0.13-0.67) for selenium intake and 0.28 (95% CI = 0.11-0.70) for zinc intake with obvious dose-dependent patterns (P values for trend = 0.01). The adjusted OR for the combined effect of selenium and zinc intake was 0.53 (95% CI = 0.29-0.96) after controlling for potential confounding factors, including age, gender, educational level, body mass index, and total energy intake. Our results suggested that the potential joint effect of zinc and selenium might contribute to SCCE risk. Increased dietary intake of selenium and zinc may decrease the risk of SCCE in a low-selenium area of China.     

Selenium intake, age, gender, and smoking in relation to indices of selenium status of adults residing in a seleniferous area

Duplicate meals, serum, whole blood, and toenails were collected every 3 mo for 1 y from a group of 44 free-living adults residing in high-selenium areas of South Dakota and Wyoming to assess the relation of selenium intake to indices of selenium status. The average selenium values for the group were as follows: dietary intake, 174 +/- 91 micrograms/d (mean +/- SD), 2.33 +/- 1.08 micrograms/kg body wt; serum, 2.10 +/- 0.38 mumol/L; whole blood, 3.22 +/- 0.79 mumol/L; and toenails, 15.2 +/- 3.0 nmol/g. Selenium intake (micrograms/kg body wt) was strongly correlated (all values, P less than 0.01) with selenium concentration of serum (r = 0.63), whole blood (r = 0.62), and toenails (r = 0.59). Men and women had similar mean values of serum, whole blood, and toenail selenium despite higher selenium intakes in men. Smokers had lower tissue selenium concentrations than did nonsmokers due, at least in part, to lower selenium intake. Age was not associated with tissue selenium content. Of the variables examined selenium intake was clearly the strongest predictor of tissue selenium concentration.     

An estimation of selenium requirements for New Zealanders.

BACKGROUND: Current US dietary recommendations for selenium are based on maximization of plasma glutathione peroxidase (GSHPx) activity according to data from one study of Chinese men. OBJECTIVE: The effect of various amounts of supplemental selenium on GSHPx activities in blood of New Zealand adults was investigated to calculate a selenium requirement for New Zealanders. The effect on plasma selenoprotein P and thyroid hormones was also investigated. DESIGN: Fifty-two adults with low blood selenium concentrations ingested a placebo or 10, 20, 30, or 40 microgram Se as L-selenomethionine daily for 20 wk. RESULTS: Plasma and whole-blood GSHPx activities increased in all supplemented groups but reached a plateau only in the group receiving 40 microgram Se, as determined by statistical analysis. Increases in selenoprotein P were greater than those for selenium and GSHPx at all supplement intakes. Thyroxine concentrations decreased in supplemented groups but the decrease was significantly different from that in the control group only for the 10-microgram group and for all supplemented groups combined. CONCLUSIONS: An upper estimated requirement of 90 microgram Se/d was calculated as the intake necessary for maximization of plasma GSHPx activity, as used in the derivation of the US recommended daily allowance. Our lower estimated requirement of 39 microgram Se/d was the intake necessary to reach two-thirds of maximal GSHPx activity, as was used in calculating the World Health Organization normative requirement. The lower estimate is a realistic goal for New Zealand but the upper estimate could be achieved only with regular inclusion of high-selenium foods.     

Inhibition by selenium of intrahepatic cholangiocarcinoma induction in Syrian golden hamsters by N'-nitrosobis(2-oxopropyl)amine.

The effects of selenium supplementation on induction of cholangiocarcinomas and related precancerous lesions in female Syrian Golden hamsters by N'-nitrosobis(2-oxopropyl)amine (BOP) were investigated. Four-week-old animals were divided into two groups according to the selenium level contained in the drinking water (0.1 ppm or 4.0 ppm) and fed a purified diet containing less than 0.05 ppm of the trace element. Starting at Week 4 of the experiment, hamsters were administered 10 weekly injections of BOP (10 mg/kg body wt) and then killed 18 weeks after the last carcinogen administration. Animals receiving physiological saline alone served as controls. Cholangiocellular carcinomas tended to be reduced, and putative preneoplastic lesions of cholangiofibrosis were significantly decreased in the high-as opposed to the low-selenium groups in terms of both incidence rate and number per effective animal. The respective high and low selenium values for incidence and number were 24/38% and 0.34/0.66, respectively, for cholangiocarcinomas and 50/89% and 1.21/8.44, respectively, for cholangiofibroses. Proliferation of intrahepatic bile ducts was also significantly inhibited in the high-selenium group along with cyst formation. Biochemical investigation revealed both selenium level and glutathione peroxidase activity to be significantly greater in the high-than in the low-selenium group livers. The results thus suggest that selenium may inhibit BOP-induction of bile duct lesions, possibly via glutathione peroxidase-mediated alteration of carcinogenesis.     

硒暴露水平与农村老年人认知能力关系的研究

目的了解硒(Se)暴露水平与农村老年人认知能力的关系以及影响因素。方法对200名农村老年人进行膳食问卷调查和6项认知能力调查,采集当地环境样品、食物样品以及研究对象的指甲和血样,采用2,3-二氨基萘荧光法测定样品中硒含量,结合膳食和问卷调查结果,综合考虑可能影响老年认知能力影响因素。结果不同Se暴露指标间均有很好的相关性,在综合考虑了年龄、受教育情况、APOE基因型等因素后,膳食Se摄入量和血Se含量水平的减少与老年认知能力的下降有显著性正相关关系(P0.001)。结论老年认知能力的降低可能与Se暴露水平的降低有关。     

褪黑素对低硒饮食大鼠脂质过氧化的影响

目的 :研究褪黑素对低硒粮喂养的大鼠脂质过氧化增强的影响 ,并讨论其可能机制。方法 :将SD大鼠分为 3组 ,分别用低硒饲料、低硒饲料加硒、低硒饲料加褪黑素灌胃饲养 ,12周时检测血Se、血GSH—Px及心肌组织、肝组织匀浆MDA水平。结果 :12周时低硒组大鼠血Se、GSH—Px较加硒组 (对照组 )显著降低 ,心肌组织、肝组织匀浆MDA均明显高于其它两组。加硒组与褪黑素组MDA无显著差异。结论 :褪黑素可以显著抑制低硒饮食大鼠脂质过氧化的增强 ,作用与其抗氧化机制有关     

Metabolism of selenite in men with widely varying selenium status.

OBJECTIVE: This study was undertaken to investigate the metabolism of selenite in men with life-long intakes of deficient, adequate and excess selenium. METHODS: Stable isotopes of selenium were infused for five hours into Chinese men living in deficient, adequate or excessive selenium areas, and 24-hour urine and blood samples were collected daily for the next seven days. Stable isotopic selenium excretion was determined in urine and in whole plasma and plasma fractions. RESULTS: Even though there was a positive correlation of selenium intake with the urinary excretion of this element, this relationship was not linear over the entire range (deficient, adequate, excessive) of selenium intake. When the urine excretion was normalized internally within each group, a sharp increase in the slope of this relationship was found when long-term intake increased to adequate amounts, but the slope reached a plateau when the daily intake exceeded the adequate group. The plasma selenoprotein P fraction was labeled initially, but the incorporation in the glutathione peroxidase fraction subsequently increased by a small amount. A two-month dietary restriction of selenium of the subjects from the excess area did not result in a reduction of urinary excretion of infused selenite. CONCLUSION: A complex relationship exists between long-term intake of selenium and selenium status, and subjects living in the excess area are more saturated with selenium than anticipated. More than two months of depletion are required to affect urinary excretion of selenium.