High Selenium Concentrations Research Articles

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Selenium is an essential element with a narrow margin between beneficial and toxic effects. The learning and sensory motor reflexes-changes were studied after the perinatal exposure of mice to acute toxic doses of sodium selenite. Atomic absorption as well as the behavioral observations were employed. Adult pregnant mice was assigned into three groups: the first group was remained as a control group; the second and the third groups were orally administrated sodium selenite at doses of 1 mg/Kg (1 ppm) and 4 mg/kg (4 ppm) of the diet, respectively started from the 7th day of gestation to the 15th day of birth. Results revealed that body weight gain came significantly lower in pups born to treated mothers than those of the control pups. The appearance of body hair and opening of eyes of the pups from treated mothers were delayed in a dose-dependent manner. Selenite also inhibited the sensory motor reflexes in all elements in a dose dependent manner. The active avoidance test indicated that selenite exposure was associated with learning impairment. Acetylcholine recorded a significant decrease in treated pups. Significant high concentrations of selenium in the brain, liver and kidney was detected, indicating active transfer of selenium from mothers during pregnancy and lactation periods.   Key words: Perinatal, sodium selenite, atomic absorption, acetylcholine, active avoidance test, sensory motor reflexes, mice.

Serum selenium, genetic variation in selenoenzymes, and risk of colorectal cancer: primary analysis from the Women's Health Initiative Observational Study and meta-analysis.

Selenium may prevent colorectal cancer. However, several previous studies are small and few investigated the association between selenium and colorectal cancer among women whose selenium metabolism may differ from men. Furthermore, genetic variants in selenoenzymes may be associated with colorectal cancer risk. This nested case-control study investigated whether serum selenium concentration and genetic variants in five selenoenzymes (glutathione peroxidase 1-4 and selenoprotein P) were associated with colorectal cancer risk in 804 colorectal cancer cases and 805 matched controls from the Women's Health Initiative (WHI) Observational Study. A meta-analysis was conducted to compare the WHI result with previous studies including 12 observational studies and two clinical trials on selenium. Within the WHI, selenium concentrations were relatively high (mean = 135.6 μg/L) and were not associated with colorectal cancer risk (P(trend) = 0.10); the adjusted OR comparing the fifth with first quintile was 1.26 (95% CI, 0.91-1.73). Moreover, genetic variants in selenoenzymes were not significantly associated with colorectal cancer risk. Consistent with the finding in WHI, our meta-analysis showed no association between selenium and colorectal tumor risk in women (OR = 0.97; 95% CI, 0.79-1.18) comparing the highest quantile with the lowest); however, in men, there was a significant inverse association (OR = 0.68; 95% CI, 0.57-0.82) (P = 0.01). Consistent with previous studies, we observed no protective effect of selenium on colorectal cancer among women. Our analyses suggest that a population with relatively high selenium concentrations, especially women, would not benefit from increasing selenium intake.

Selenium exposure in subjects living in areas with high selenium concentrated drinking water: Results of a French integrated exposure assessment survey

BackgroundSelenium is an essential element which can be toxic if ingested in excessive quantities. The main human exposure is food. In addition, intake may be boosted by consumption drinking water containing unusual high selenium concentration. ObjectiveWe measured the individual selenium level of people exposed to selenium concentration in drinking water greater than the maximum recommended limit which is 10μg/L. MethodsWe carried out a prospective cohort study on 80 adults (40 exposed subjects i.e. living in the involved area and 40 non-exposed ones i.e. living elsewhere) in western France. We used three different approaches: (1) direct measurement of ingested selenium by the duplicate portion method, (2) dietary reconstitution with a food frequency questionnaire (FFQ) and (3) evaluation of the individual selenium status by measuring the selenium content in toenail clippings. Analyses were performed by inductively coupled plasma-mass spectrometry. The association between toenail selenium concentration and area of residence was analyzed using linear regression with repeated measurements. ResultsWe estimated selenium intake from FFQ at 64±14μg/day for exposed subjects as opposed to 52±14μg/day for the non-exposed ones. On the basis of 305 duplicate diet samples, average intake was estimated at 64±26μg/day for exposed subjects. Area of residence (p=0.0030) and smoking (p=0.0054) were independently associated with toenail selenium concentration. ConclusionWhatever method used for estimating selenium intake, the selenium level in this studied area with high selenium concentrated drinking water is much lower than in seleniferous areas.

Assessment of Selenium Concentration in Selected Organs of Farmed Raccoon Dogs (Nyctereutes Procyonoides)

Assessment of Selenium Concentration in Selected Organs of Farmed Raccoon Dogs (Nyctereutes Procyonoides)The aim of the study was to determine selenium concentrations in the liver, kidneys, lungs, heart and muscles of farmed raccoon dogs (Nyctereutes procyonoides) and to evaluate their impact on hair coat quality. Selenium concentration was determined using the modified Watkinson's spectrofluorometric method. Subjects were 20 farmed raccoon dogs (Nyctereutes procyonoides) at the age of 8-9 months, which were kept on a farm in south-eastern Poland. The results show that liver selenium content averaged 0.23±0.10 μg/g w.w. (wet weight). The concentrations ranged from 0.04 to 0.49 μg/g w.w. Kidney selenium concentration (0.49±0.17 μg/g w.w. on average) was over twice that of liver concentration. Animals with higher scores for hair coat quality had lower selenium concentrations in the kidneys and liver, and higher selenium concentrations in muscles, but the differences were not significant. When relating Se concentrations determined in the liver of raccoon dogs to the biochemical criteria, it is concluded that 80% of the analysed raccoon dogs were deficient in this element and 20% had marginal levels. The results obtained in our study suggest that the food used on the farm did not fully meet the Se requirement of the raccoon dogs.

Content of phenolic antioxidants and selenium in grain of einkorn (Triticum monococcum), emmer (Triticum dicoccum) and spring wheat (Triticum aestivum) varieties

Wheat is worldwide consumed and contributes significantly to the intake of antioxidants with beneficial healthy effects. In the precise two-year field experiments in 2008 and 2009 two varieties of wheat einkorn, two varieties of emmer wheat and three varieties of spring wheat and in 2009 in addition two other spring wheat varieties, three einkorn varieties and three emmer wheat varieties were evaluated for selenium content and antioxidants – total polyphenols (TP). Selenium content was determined by atomic absorption spectrometry with hydride generation technique (HGAAS) and total polyphenols with Folin-Ciocalteau assay. Higher selenium content in grain is related to emmer (58.9–68.4 mg/kg DM) and einkorn (50.0–54.8 mg/kg DM) varieties; in spring varieties selenium content ranged from 29.8 to 39.9 mg/kg DM. Among the varieties with high TP (expressed in gallic acid equivalents) emmer varieties prevail (584–692 mg/kg DM), less represented are einkorn (507–612 mg/kg DM) and spring wheat (502–601 mg/kg DM) varieties. Among varieties significant differences were determined. TP were significantly higher in emmer wheat varieties and one einkorn and one spring wheat variety. Between TP and Se significant linear correlation was determined (r = 0.709).  

Selenium and 17 other largely essential and toxic metals in muscle and organ meats of Red Deer (Cervus elaphus) — Consequences to human health

Concentrations, composition and interrelationships of selenium and metallic elements (Ag, Ba, Cd, Co, Cr, Cs, Cu, Ga, Mn, Mo, Pb, Rb, Sb, Sr, Tl, V and Zn) have been examined in muscle and organ meats of Red Deer hunted in Poland. The analytical data obtained were also discussed in terms of Se supplementation and deficit to Deer as well as the benefits and risk to humans associated with the essential and toxic metals intake resulting from consumption of Deer meat and products. These elements were determined in 20 adult animals of both sexes that were obtained in the 2000/2001 hunting season from Warmia and Mazury in the north-eastern part of Poland. The whole kidneys contained Ba, Cd, Cr, Ga, Pb, Se, Sr and Tl at statistically greater concentrations than liver or muscle tissue from the same animal. Liver showed statistically greater concentrations of Ag, Co, Cu, Mn and Mo than kidneys or muscle tissue, and muscle tissue was richer in Zn, when compared to the kidneys or liver. Cs and Rb were similarly distributed between all three tissue types, while V was less abundant in liver than kidneys or muscle tissue. There were significant associations between some metallic elements retained in Red Deer demonstrated by Principal Component Analysis (PCA) of the data set. In organ and muscle meats (kidneys, liver and muscle tissue considered together) the first principal component (PC1) was strongly influenced by positively correlated variables describing Se, Ba and Cd and negatively correlated variables describing Ag, Co, Cs, Mn, Pb, Tl and V; PC2, respectively, by Cu, Mn and Mo (+) and Zn (−); PC3 by Ga (+) and PC4 by Sb (+). Selenium occurred in muscle tissue, liver and kidneys at median concentrations of 0.13, 0.19 and 4.0mg/g dry weight, respectively. These values can be defined as marginally deficient (<0.6mg Se/kg liver dw) or satisfactory (≤3.0mg Se/kg kidneys dw) for the amount required to maintain the Deer's body condition and health, depending on the criterion for supplementation used. In terms of human nutritional needs, a relatively high selenium content of kidneys can be beneficial. The muscle meat, liver and kidneys of Red Deer can be considered as a very good source of essential Co, Cr, Cu, Mo, Mn, Se and Zn in the human diet. Lead is generally considered as toxic, and the concentrations found in Red Deer (via the food chain intake) were well below the European Union tolerance limit. Pb from the lead bullets can always create food hygienic problem, if not well recognized during sanitary inspection, and this was noted for one muscle meat sample in this study (5% surveyed). There is no tolerance limit of Cd in game animal meats. The median values of Cd noted in fresh muscle tissue, liver and whole kidneys were 0.07, 0.18, and 3.3mg/kg wet weight, respectively. Cd exists as a chemical element present at trace levels in plants and mushrooms in Deer's food chain in background (uncontaminated) areas. When these are consumed by the Deer, the amount of Cd sequestered with metallothioneins and retained in the organ and muscle meat in this study is low enough to be considered safe for human consumption.

Selenium Dynamics in Boreal Streams: The Role of Wetlands and Changing Groundwater Tables

The concentrations of selenium in 10 catchments of a stream network in northern Sweden were monitored over two years, yielding almost 350 observations of selenium concentrations in streamwater. The export of selenium was found to be systematically greater from forests than from mires. Accounting for atmospheric deposition, which was monitored over four years, there was a net accumulation of selenium in mires, while the export from forest soils was approximately equal to the atmospheric deposition. In forest dominated catchments the concentrations of selenium oscillated rapidly back and forth from high to low levels during spring floods. High selenium concentrations coincided with rising groundwater tables in the riparian forest soils, while low selenium concentrations were associated with receding groundwater. Thermodynamic modeling indicated that precipitation of elemental selenium would occur under reducing conditions in the riparian soils. Since changes in the redox conditions are likely to occur near the transition from the unsaturated to the saturated zone, it is hypothesized that the transport of selenium from forest soils to streams is controlled by redox reactions in riparian soils.

Neurobehavioral changes in mice offspring induced by prenatal exposure to acute toxicity of sodium selenite

Selenium is an essential element with a narrow margin between beneficial and toxic effects. This study was aimed to determine the neurobehavioral changes resulted from the prenatal exposure of mice to high doses of sodium selenite during fetal and early postnatal development. Atomic absorption for monitoring the placental transfer of selenium to offspring was employed. The developmental observations as well as the behavioral tests, such as sensory motor reflexes, and learning and memory test in automatic reflex conditioner (shuttle box) (active avoidance responses) were applied. Adult mice was assigned into three groups: the first group was remained as a control group given phosphate buffered saline; the second and the third groups were orally administrated sodium selenite at doses of 1 mg/kg and 4 mg/kg of the diet, respectively started from the 7th day to the end of the gestation period. Appearance of body hair and opening of eyes of the pups from treated mothers were delayed in a dose-dependent manner. The body weight gain came significantly lower than those of the control especially at the higher dose. Selenite also inhibited the sensory motor reflexes in all elements of acts and postures in a dose dependent manner. The active avoidance training-test indicated that selenite exposure was associated with learning impairment. Acetylcholine recorded a significant decrease in almost all the period of this study. By using atomic absorption, we found a significant high concentration of selenium in the brain, liver and kidney until the 40th postnatal day, indicating active transfer of selenium from mothers to embryos.

Comparisons of Macrophyte Breakdown, Associated Plant Chemistry, and Macroinvertebrates in a Wastewater Dominated Stream

AbstractReplacement of native macrophyte species with exotic or invasive ones affects the quality of detritus entering streams and can alter nutrient cycles and community structure in aquatic ecosystems. Decomposition of air‐dried native hardstem bulrush (Schoenoplectus acutus), invasive southern cattail (Typha domingensis), and exotic common reed (Phragmites australis) were studied in an urban stream (Las Vegas, Nevada, USA) using litter bags. Samples were analyzed for dry mass, lignin, nutrients, trace elements, and macroinvertebrates. Litter type and sediment deposited on plant material influenced material loss. Trace elements arsenic and selenium increased in plant material to concentrations considered marginal for ecosystem contamination by exposure day 76. Mercury increases were inconsistent across plant species and did not exceed limits. Bulrush decomposed faster, and tended to have higher selenium concentrations, than did invasive southern cattail and exotic common reed. Macroinvertebrate communities colonizing litter bags were similar across plant litter types, but differed from mesh‐only bags and samples collected with a kick‐net. Macroinvertebrate exclusion resulted in significantly lower loss rates, but functional feeding groups such as shredders were not associated with decomposition differences. The caddisfly, Smicridea, physically modified stem material and aided in processing, but microbes appeared most important in biological material breakdown. (© 2011 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Producing milk with uniform high selenium concentrations on commercial dairy farms

Six herds on five commercial dairy farms were involved in the production of high selenium (Se) milk. The farms had a range of herd sizes, herd structures, feeding systems and milk production per cow. On all farms, pelleted concentrate supplements containing Se yeast were fed twice daily in the dairy for 16 days. The objectives were to: (1) produce milk with Se concentrations exceeding 225 μg/kg on the five farms for pilot-scale production of a high protein milk powder; (2) validate a predictive relationship between Se intake and milk Se concentration developed in research; and (3) examine the time taken from the introduction of Se yeast to steady-state concentrations of Se in milk under a range of commercial farming conditions. We hypothesised that the relationship between Se intake and its concentration in milk found in research would apply on commercial farms. Daily Se intake, which was primarily from Se yeast in the pelleted concentrates, varied from 35 to 51 mg Se/cow. Grazed pasture and conserved forage contributed less than 1 mg Se/cow on all farms. The time taken from the introduction of pellets containing Se yeast to steady-state milk Se concentrations was 4–7 days. The steady-state Se concentrations in milk varied from 166 to 247 µg/kg, but these concentrations were only 55–72% of predicted values. All the milk produced from the five farms on the last 2 days of feeding of Se-enriched pellets was used to produce a milk protein concentrate with a Se concentration of 5.4 mg/kg. Factors that might have affected Se incorporation into milk and the implications of these results for commercial production of high Se milk or milk products are discussed.

The effect of dietary selenium sources and levels on performance, selenium content in muscle and glutathione peroxidase activity in broiler chickens

The study examined the effect of dietary supplements of sodium selenite (SS), selenium-enriched yeast (Sel-Plex&amp;reg;, SP) and selenium-enriched alga Chlorella (SCH) on growth traits, carcass analysis, selenium content in breast meat, glutathione peroxidase (GSH-Px) activity in breast and thigh meat and liver of chickens. The experiment was realized with seven hundred thirty-five cockerels Ross 308 randomly divided into 7 dietary treatments with 3 replications in each treatment. Chickens were fed a diet supplemented with 0 (control), 0.15 or 0.30 mg of selenium/kg in the form of sodium selenite (SS), Sel-Plex&amp;reg; (SP) and selenium-enriched alga Chlorella (SCH). Selenium addition influenced body weight at 21 (P &amp;le; 0.001) and 35 (P &amp;le; 0.05) days of age. Significantly higher body weight at 35 days of age was determined in chickens receiving 0.15 mg of selenium from SP (2 122 g) and 0.3 mg of selenium from SCH (2 116 g) contrary to dietary treatment with a lower level of selenium from SCH (2 010 g) per kg of feed. The selenium content in breast muscle was increased (P &amp;le; 0.001) by both the lower and higher selenium concentration in the form of SP (0.6 and 0.85 mg/kg dry matter) and SCH (0.6 and 0.82 mg/kg dry matter) in comparison with the control (0.31 mg/kg dry matter). A significant increase (P &amp;le; 0.001) was ascertained even in SS treatments, but no significant differences were found between both levels. The selenium source and level, including SS, significantly (P &amp;le; 0.001) influenced the GSH-Px activity in breast and thigh meat. &amp;nbsp;

Health Evaluation of Leatherback Turtles (Dermochelys coriacea) in the Northwestern Atlantic During Direct Capture and Fisheries Gear Disentanglement

Health evaluations were conducted in the northwestern Atlantic for 19 leatherback turtles, which included 12 turtles directly captured as part of a satellite telemetry study and 7 turtles entangled in fishing gear. Assessment included physical examination; determination of heart rate and respiratory rate; and hematologic, plasma biochemical, nutritional, toxicologic, parasitologic, and microbiological investigations. Significant differences were found between directly captured and entangled turtles for curved carapace length, curved carapace width, blood urea nitrogen, chloride, sodium, triglycerides, relative heterophil count, relative monocyte count, relative and absolute eosinophil count, pH, bicarbonate, lead, and beta-hydroxybutyrate. Directly captured turtles showed evidence of mild respiratory acidosis. Significant differences were found between sexes for curved carapace length, curved carapace width, total protein, globulin, sodium, relative monocyte count, gamma-globulin, and anion gap. Relatively high blood concentrations of selenium and cadmium were found in all turtles.

Selenium contents of Portuguese commercial and wild edible mushrooms

The selenium contents of 66 mushroom samples, wild growing or commercially available in Portugal, fresh, canned or dried, were determined. The samples consisted of 18 mushroom species, mainly selected in accordance with their availability and consumer preference. The selenium contents varied considerably between different mushroom species. The highest selenium contents were found in the wild species Boletus aestivalis (48.5mg/kg dry weight, DW), Boletus pinophilus (19.9mg/kg DW), Boletus edulis (14.9mg/kg DW), Boletus aereus (12.3mg/kg DW), Boletus fragans and Boletus spretus (∼2mg/kg DW). Other mushrooms having considerable selenium contents included Marasmius oreades (1.5mg/kg DW), Agaricus bisporus “Portobello” (1.25mg/kg DW), A. bisporus (1.0mg/kg DW) and Russula cyanoxantha (0.72mg/kg DW). The selenium contents of these mushrooms are sufficient to provide nutritionally significant amounts in relation to the total daily intake of selenium. Other edible mushrooms, such as Lentinula edodes, Pleurotus ostreatus, Cantharellus cibarius,Craterellus cornucopioides and Lepista nuda, contained only small amounts of selenium. The importance of these mushrooms as a source of selenium is therefore marginal.

Selenium removal from drinking water by adsorption to chitosan–clay composites and oxides: Batch and columns tests

Polymer–clay composites were designed to adsorb selenium from water. The highest adsorption efficiency was obtained for chitosan–montmorillonite composites. These composites were characterized by XRD, zeta potential, and FTIR measurements. Adsorption isotherms of selenate on the composite, on Al-oxide and on Fe-oxide were in good agreement with the Langmuir model, yielding a somewhat higher capacity for the composite, 18.4, 17.2 and 8.2 mg/g, respectively. In addition, adsorption by the composite was not pH dependent while its adsorption by the oxides decreased at high pH. Selenium removal from well water (closed due to high selenium concentrations, 0.1 mg/L) by the composite, brought levels to below the WHO limit (0.01 mg/L) and was selective for selenium even in the presence of sulfur (13 mg/L). Selenium adsorption by the composite was higher than by the Al-oxide due to high adsorption of sulfur by the later. Unlike employment in batch Al-oxide is more suitable for employment in filtration columns due to its high hydraulic conductivity. A semi-pilot columns experiment demonstrated selenium removal from the well water below the recommended limit (first 400 pore volumes) by Al-oxide columns. Regeneration of Al-oxide and of the composite was studied and readsorption of selenium was demonstrated.

The scuttle fly

The scuttle fly

Tissue Distribution of Selenium and Effect of Season and Age on Selenium Content in Roe Deer from Northwestern Poland

The aim of the study was to compare selenium concentrations in different organs of roe deer from northwestern Poland. Samples of liver, kidneys, heart and lungs, collected from 74 roe deer shot during the hunting seasons of 2008-2009 in northwestern Poland, were studied. Selenium concentration in the organs was determined spectrofluorimetrically. Mean selenium concentration was 0.06 µg/g w.w. in the liver, 0.41 µg/g w.w. in the kidneys and 0.05 µg/g w.w. in the heart and lungs. Season had a significant effect on selenium concentration in the liver, kidneys, lungs and heart. In all the organs, the highest selenium concentration was found in spring and the lowest in autumn and winter. All animals studied were deficient in selenium. The low selenium concentration in the liver or heart can disturb their function, and in the future, it may be a factor contributing to the population decline of roe deer in the northwestern part of Poland.

Abstract 4825: Serum selenium concentration and risk of colorectal cancer in postmenopausal women: The Women's Health Initiative Observational Study

Abstract In vitro and animal experimental studies have reported beneficial effects of selenium on colorectal cancer (CRC), yet results from epidemiological studies are inconsistent. Few of these studies have examined CRC risk among women, and none have been sufficiently large to examine risk in subgroups. This study investigated whether baseline serum selenium concentration was associated with subsequent CRC risk among postmenopausal women in a case-control study nested within the Women's Health Initiative Observational Study. We included 804 CRC cases diagnosed between October 1993 and September 2005 and 804 controls matched to cases on age, enrollment date, clinical center, race/ethnicity, hysterectomy status, and prevalent condition at baseline. Baseline serum selenium concentration was measured by atomic absorption spectrometry. Multivariate logistic regression was used to estimate the odds ratios (OR) and 95% confidence intervals (95% CI) associated with increasing serum selenium concentrations. The corresponding median selenium concentrations in the 1st to 5th quintiles were 110.5, 123.2, 133.5, 144.8, and 162.2 µg/l (range: 81.03 - 398.70 µg/l). The selenium concentration was weakly and positively associated with the risk of CRC (ptrend = 0.08); the adjusted ORs (95% CIs) for the risk of CRC comparing the 2nd, 3rd, 4th, and 5th quintile of serum selenium concentrations with the 1st quintile were 1.14 (0.83-1.58), 1.16 (0.84-1.60), 1.36 (0.99-1.87) and 1.27 (0.92-1.76). The trend was somewhat stronger for past and current smokers [OR (95% CI) for the 5th vs. 1st quintile = 1.38 (0.89-2.13), ptrend = 0.13] than never smokers [OR (95% CI) for the 5th vs. 1st quintile = 1.16 (0.72-1.87), ptrend = 0.48]. However, the difference was not statistically significant (pinteraction = 0.53). Findings from this large study with relatively high serum selenium concentrations suggest no beneficial effect of selenium on colorectal cancer among women, which is consistent with results of previous smaller observational studies. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4825.

Defects in Bi2Te3−x Se x single crystals

Single crystals of a ternary system based on Bi2Te3−x Se x (nominally x=0.0–0.2) were prepared using the Bridgman technique. Samples with varying content of Se were characterized by the measurement of lattice parameters, electrical conductivity σ⊥c and Hall coefficient R H(B‖ c). The actual concentration of selenium c Se in the samples was determined using atomic emission spectroscopy. While a small selenium concentration enhances the free hole concentration P after passing a maximum, the hole concentration decreases at higher selenium concentrations. The extreme-like dependence P=f(c Se) is explained in terms of a change of the native defect concentration due to the substitution of selenium atoms by tellurium ones.

CuInSe2 Films Prepared by a Plasma-Assisted Selenization Process in Different Working Pressures

The effects of working pressure on the composition, structure and surface morphology properties of CuInSe2 (CIS) films selenized with a plasma-assisted selenization process is investigated. Higher selenium content, better crystalline quality and much more regular surface particles compared to the others are found in the CIS film with 40 Pa working pressure. A Cu(In,Ga)Se2 device fabricated with the optimized plasma-assisted selenization process is demonstrated to be better than our previous result. After discussion, the reason for these phenomena is attributed to the compromise of electron temperature and plasma density.

Serum selenium and serum lipids in US adults: National Health and Nutrition Examination Survey (NHANES) 2003–2004

ObjectiveHigh selenium has been recently associated with several cardiovascular and metabolic risk factors including diabetes, blood pressure and lipid levels. We evaluated the association of serum selenium with fasting serum lipid levels in the National Health and Nutrition Examination Survey (NHANES) 2003–2004, the most recently available representative sample of the US population that measured selenium levels. MethodsCross-sectional analysis of 1159 adults ≥40 years old from NHANES 2003–2004. Serum selenium was measured by inductively coupled plasma-dynamic reaction cell-mass spectrometry. Fasting serum total cholesterol, triglycerides, and HDL cholesterol were measured enzymatically and LDL cholesterol was calculated. ResultsMean serum selenium was 136.7μg/L. The multivariable adjusted average differences (95% confidence interval) comparing the highest (≥147μg/L) to the lowest (<124μg/L) selenium quartiles were 18.9 (9.9, 28.0)mg/dL for total cholesterol, 12.7 (3.3, 22.2)mg/dL for LDL cholesterol, 3.9 (0.4, 7.5)mg/dL for HDL cholesterol, and 11.5 (−7.6, 30.7)mg/dL for triglycerides. In spline regression models, total and LDL cholesterol levels increased progressively with increasing selenium concentrations. HDL cholesterol increased with selenium but reached a plateau above 120μg/L of serum selenium (20th percentile). The triglyceride–selenium relationship was U-shaped. ConclusionIn US adults, high serum selenium concentrations were associated with increased serum concentrations of total and LDL cholesterol. Selenium was associated with increasing HDL cholesterol only at low selenium levels. Given increasing trends in dietary selenium intake and supplementation, the causal mechanisms underlying these associations need to be fully characterized.