Human Selenium Status Research Articles

Portable X-ray fluorescence of zinc and selenium with nail clippings-Mother and Infant Nutrition Investigation (MINI).

Zinc and selenium are essential minerals for human nutrition. Reliable biomarkers of zinc status and selenium status in humans are therefore important. This work investigates a novel portable X-ray fluorescence (XRF) method with the ability to rapidly assess zinc and selenium in nail clippings. This approach used a mono-energetic X-ray beam to excite characteristic X-rays from the clippings. Nail clippings were obtained from the Mother and Infant Nutrition Investigation (MINI), a study designed to assess nutrition in a population of women and their breastfed children in New Zealand. Twenty mother-infant pairings were selected to provide nail clippings at two time points (visit 1 at 3 months postpartum; visit 2 at 6 months postpartum). Nail clippings from each mother-infant pairing were divided into three groupings of clippings prior to analysis: those obtained from a big toe of the mother, those from the other toes of the mother, and those from the toes and fingers of the infant. Clippings were prepared and mounted prior to XRF measurement, providing four distinct fragments from each clipping grouping. These fragments were assessed by XRF using a measurement time of either 300 s (visit 1) or 180 s (visit 2). XRF results were determined through both an automated system output and an analysis of the X-ray energy spectrum. Following this assessment of zinc and selenium with the non-destructive XRF method, clippings were measured for zinc and selenium concentration using a "gold standard" technique of inductively coupled plasma mass spectrometry (ICP-MS). Mean ICP-MS concentrations ranged from 122 μg/g to 127 μg/g for zinc, and from 0.646 μg/g to 0.659 μg/g for selenium. Precision, assessed by a relative standard deviation of measurement, was superior for ICP-MS relative to XRF. For both zinc and selenium, XRF results were compared with ICP-MS concentrations. Linear equations of best fit were determined for each comparison between XRF and ICP-MS results. Coefficients of determination (r2) were stronger for zinc (from 0.74 to 0.95) than selenium (from 0.53 to 0.70). A decrease in XRF measurement time from 300 s to 180 s did not appear to adversely affect the correlation between XRF and ICP-MS results. Using the mono-energetic portable XRF method, the correlation of XRF zinc results with ICP-MS zinc concentrations was improved over previous findings, and selenium measurement was reported for the first time. The method may prove useful for future applications to trace element analysis using nail clippings as a biomarker.

Effects of Selenate Application on Growth, Nutrient Bioaccumulation, and Bioactive Compounds in Broccoli (Brassica oleracea var. italica L.)

The biofortification of edible crops with selenium (Se) is a common and effective strategy to address inadequate Se intake, which is suffered by millions of people worldwide. However, there is little information regarding the effects of this practice on crops belonging to the important Brassica family. To evaluate the efficacy of foliar Se application on broccoli, four treatments with varying Se concentrations were tested: 0%, 0.05%, 0.10%, and 0.15% (w/v), applied as sodium selenate during the early flowering stage. Although no overall effects on growth and biomass parameters were observed, the results indicate that the lowest Se dose (0.05-Se) was sufficient to notably increase Se concentration in the florets, even after boiling. Based on the increase to 14.2 mg Se kg−1 of dry matter in this broccoli fraction, it was estimated that consuming a 100-gram portion of boiled florets biofortified with 0.05% Se would provide approximately 140 µg of Se, which could be sufficient to potentially improve human selenium status, as previously documented. Moreover, the results obtained underscore how the application of this small dose was also adequate to reduce phytate concentration in the florets and to increase antioxidant and polyphenol concentrations, thereby improving the concentration and bioavailability of other essential nutrients, including Ca, Mg, Fe, and Zn, along with improving its quality as an antioxidant food.

Linkages between soil, crop, livestock, and human selenium status in Sub-Saharan Africa: a scoping review.

Selenium (Se) is essential for human health, however, data on population Se status and agriculture-nutrition-health linkages are limited in sub-Saharan Africa (SSA). The scoping review aims to identify linkages between Se in soils/crops, dietary Se intakes, and livestock and human Se status in SSA. Online databases, organisational websites and grey literature were used to identify articles. Articles were screened at title, abstract and full text levels using eligibility criteria. The search yielded 166 articles from which 112 were excluded during abstract screening and 54 full text articles were assessed for eligibility. The scoping review included 34 primary studies published between 1984 and 2021. The studies covered Se concentrations in soils (n = 7), crops (n = 9), animal tissues (n = 2), livestock (n = 3), and human Se status (n = 15). The evidence showed that soil/crop Se concentrations affected Se concentration in dietary sources, dietary Se intake and biomarkers of Se status. Soil types are a primary driver of human Se status and crop Se concentration correlates positively with biomarkers of Se dietary status. Although data sets of Se concentrations exist across the food system in SSA, there is limited evidence on linkages across the agriculture-nutrition nexus. Extensive research on Se linkages across the food chain is warranted.

Biofortification of chervil with selenium

Relevance.Production of functional food with high levels of antioxidant status and selenium is essential for human protection against viral and cardiovascular diseases as well as cancer.Methods.Evaluation of the efficiency in foliar sodium selenate biofortification (25. 50 and 75 mg Se/L) was achieved on three chervil genotypes.Results.Intervarietal differences in biofortification level was demonstrated: from 15.5 to 31.1 for 25 mg Se/L dose; from 36.9 to 64.6 for 50 mg Se/L dose; and from 72.9 to 130 for 75 mg Se/L dose. At the chosen doses, selenium supply did not affect significantly the yield, antioxidant properties and photosynthetic content of chervil. Total antioxidant activity was in the range from 30 to 42 mg GAE/g d.w., phenolics content from 9 to 13 mg GAE/g d.w, flavonoids from 5 to 12 mg-eq quercetin/g d.w., ascorbic acid from 33 to 66 mg/100 g fresh w. High levels of carotene were a typical feature of Se fortified and non-fortified chervil. A direct correlation was recorded between phenolics content and total antioxidant activity (r=+0.954, P<0.01), and between water soluble compounds and nitrates accumulation (r=+0.920, P<0.01). Biofortification with selenium did not affect significantly the mineral content of plants. Consumption of 100 g of fresh chervil leaves, fortified with selenium, provides from 50 to 75% of the adequate selenium consumption level and from 16 to 20% of potassium. Taking into account that both selenium and potassium normalize heart activity, the new functional food product may be recommended for prophylactics and treatment of cardiovascular diseases and for the human selenium status optimization.

Effect of foliar sodium selenite biofortification on cauliflower yield, nutritional value and antioxidant status

Relevance. Biofortification of agricultural crops with selenium is considered to be the most promising method for the human selenium status optimization.Methods. Effect of foliar biofortification of cauliflower, Polyarnaya Zvezda cv, with sodium selenate of different concentrations on yield, selenium content and biochemical characteristics of plants were investigated.Results. Enrichment of plants with selenium increased yield by 1.23-1.31 times, sugar content – 1.6 times, ascorbic acid concentration – 1.52-2 times. On the contrary, the treatment did not affect pholyphenol content and antioxidant activity of ethanolic extracts of plants. Selenium accumulation levels decreased according to inflorescences > leaves > roots. Sodium selenate solution at 75 mg/L concentration increased mass of cauliflower leaves 1.9 times and roots – 1.5 times. Consumption of 100 g of cauliflower fortified with 50 mg/L sodium selenate solution provided 100% of the daily adequate selenium consumption level. Utilization of higher sodium selenate concentrations ensured 127% and 418% of the daily adequate consumption level in case of 75 mg/L and 100 mg/L concentrations respectively. Taking into account insignificant differences between sugar content and antioxidants in cauliflower inflorescences fortified with different doses of selenium the most suitable concentration to be used was 50 mg/L.

Monitoring of selenium content in some food of residents of the Khabarovsk

The development of about 40 diseases, including cancer and cardiovascular diseases, is associated with a lack of selenium (Se) consumption. According to the previously obtained data, Khabarovsk Krai is characterized by low human selenium status in various age groups and low content in most foods, that is the main reason for the population Se deficit in Khabarovsk territory. To study the content of Se in some foods in Khabarovsk in the comparative aspect. Study design: prospective. The content of Se in the basic products collected in the commercial network of Khabarovsk [wheat, rye-wheat bread (48 samples), chicken eggs - 24 samples] was determined, the choice of these products was justified by their maximum availability for all segments of the population. The Se level was determined by fluorimetric method. According to previous studies, we have found low Se content in donors' blood serum and basic food products in the Khabarovsk territory, which indicated the need to for monitoring and correcting Se status. Eating exclusively local products and the influence of geochemical specificity of the area were the main reasons for the development of Se deficit, because the status of a person completely depended on the inflow of nutrient from the diet. According to the monitoring data for 10 years, Se content in wheat bread decreased more than 3 fold, in rye bread - more than twice. There was 2-fold decrease in Se content in a chicken egg. On average, residents of Khabarovsk with 1 chicken egg received only 3.7-22.6% of the adequate level of Se consumption. The selenium content in an egg enriched with this trace element was 15.85±4.3 μg (or 25.5±6.4 μg/100 g), which is twice as high as the average Se content in a standard egg. The dynamic assessment of Se content in products of daily demand of residents of the Khabarovsk territory indicates a critically low content of the element in bread and chicken eggs; the established level of Se in foods does not contribute to the accumulation of the element in the human body. The obtained data should become one of the main components of the regional program of optimization of Se status of Khabarovsk population.

Selenorhizobacteria : As biofortification tool in sustainable agriculture

Abstract Selenium biofortification in crops aims to either increase the accumulation of selenium in edible plants or to increase their bioavailability. It is one of the solutions for globally increasing hidden hunger for essential micronutrients. Plant growth promoting rhizobacteria are advantageous soil bacteria that inhabit plant roots and increase plant growth through various mechanisms in different ways. The motion of selenium across soil, crop and environment interfaces is thus of crucial importance for gain in human selenium status. This review gives an overview of microbial enhancement of selenium as beneficial element for plants, significance of selenium to human health, selenium response in soil crop system, selenium as plant protector against abiotic stresses and the possible approaches to enhancing selenium concentration through use of microorganisms (selenorhizobacteria) as biotechnological tools for increasing plant nutrition and quality.

Impact of Selenium Addition to Animal Feeds on Human Selenium Status in Serbia.

Research conducted during the 1980s demonstrated Se deficiency in humans. Increased inclusion of selenium in animal feeds started from the year 2000 onwards. The aim of this study was to estimate the effects of selenium inclusion in animal feeds on human selenium status and dietary habits of the Serbian population related to food of animal origin. Plasma selenium concentration in healthy adult volunteers, including residents of one of the regions with the lowest (Eastern Serbia, n = 60) and of one of the regions with the highest Se serum levels reported in the past (Belgrade, n = 82), was determined by hydride generation atomic absorption spectrometry. Multivariate analysis was employed to determine the correlation between Se plasma levels and dietary intake data derived from food frequency questionnaires and laboratory tests. The mean plasma Se level of the participants was 84.3 ± 15.9 μg/L (range: 47.3–132.1 μg/L), while 46% of participants had plasma Se levels lower than 80 μg/L. Frequency of meat, egg, and fish consumption was significantly correlated with plasma selenium level (r = 0.437, p = 0.000). Selenium addition to animal feed in the quantity of 0.14 mg/kg contributed to the improvement of human plasma selenium levels by approximately 30 μg/L.

Selenium in food crops

Biofortification of food crops with selenium is considered to be one of the most effective and economically beneficial way in the human selenium status optimization. At the same time as biologically activity of selenium is determined not only by a dose but also by chemical forms of the element it seems especially important to reveal peculiarities of their biosynthesis by different agricultural crops. The review presents the last data on the chemical forms of selenium in food products including food crops. Effect of agricultural crops biofortification with selenium on accumulation of special chemical forms of the element is discussed. Special attention is paid to representatives of Allium and Brassica species, capable to accumulate high concentrations of methylated derivatives of the element known to possess intensive anticarcinogenic acitivity. Selenium metabolism in hyperaccumulators and non-accumulators of selenium is discussed. Possible beneficial effects of selenium enriched cereals and vegetables on human health are presented. Success of Finland in improvement of human health via global utilization of fertilizers, fortified with selenium is indicated. The most important functional food products based on selenium fortified vegetables produced in different countries and developed in Russia are described.

Plasma selenium biomarkers in low income black and white americans from the southeastern United States.

Biomarkers of selenium are necessary for assessing selenium status in humans, since soil variation hinders estimation of selenium intake from foods. In this study, we measured the concentration of plasma selenium, selenoprotein P (SEPP1), and glutathione peroxidase (GPX3) activity and their interindividual differences in 383 low-income blacks and whites selected from a stratified random sample of adults aged 40–79 years, who were participating in a long-term cohort study in the southeastern United States (US). We assessed the utility of these biomarkers to determine differences in selenium status and their association with demographic, socio-economic, dietary, and other indicators. Dietary selenium intake was assessed using a validated food frequency questionnaire designed for the cohort, matched with region-specific food selenium content, and compared with the US Recommended Dietary Allowances (RDA) set at 55 µg/day. We found that SEPP1, a sensitive biomarker of selenium nutritional status, was significantly lower among blacks than whites (mean 4.4±1.1 vs. 4.7±1.0 mg/L, p = 0.006), with blacks less than half as likely to have highest vs. lowest quartile SEPP1 concentration (Odds Ratio (OR) 0.4, 95% Confidence Interval (CI) 0.2–0.8). The trend in a similar direction was observed for plasma selenium among blacks and whites, (mean 115±15.1 vs. 118±17.7 µg/L, p = 0.08), while GPX3 activity did not differ between blacks and whites (136±33.3 vs. 132±33.5 U/L, p = 0.320). Levels of the three biomarkers were not correlated with estimated dietary selenium intake, except for SEPP1 among 10% of participants with the lowest selenium intake (≤57 µg/day). The findings suggest that SEPP1 may be an effective biomarker of selenium status and disease risk in adults and that low selenium status may disproportionately affect black and white cohort participants.

Soil-type influences human selenium status and underlies widespread selenium deficiency risks in Malawi

Selenium (Se) is an essential human micronutrient with critical roles in immune functioning and antioxidant defence. Estimates of dietary Se intakes and status are scarce for Africa although crop surveys indicate deficiency is probably widespread in Malawi. Here we show that Se deficiency is likely endemic in Malawi based on the Se status of adults consuming food from contrasting soil types. These data are consistent with food balance sheets and composition tables revealing that >80% of the Malawi population is at risk of dietary Se inadequacy. Risk of dietary Se inadequacy is >60% in seven other countries in Southern Africa, and 22% across Africa as a whole. Given that most Malawi soils cannot supply sufficient Se to crops for adequate human nutrition, the cost and benefits of interventions to alleviate Se deficiency should be determined; for example, Se-enriched nitrogen fertilisers could be adopted as in Finland.

The influence of selenium supplementation of animal feed on human selenium intake in Serbia

The use of selenium as animal feed supplement in Serbia was approved in 1989 for some categories of pigs, sheep and poultry. From 2000 selenium in animal feed became a requirement for all categories of farm animals. The aim of this study was to determine the consumption of selenium by Serbian livestock and in poultry production between 1990-1991 and 2000-2008 and to analyze the selenium content of meat, milk and eggs sold on Serbian markets to gain insight into human selenium intake. Data indicate a low level of selenium inclusion in animal feed during 1990-1991 compared to during 2000-2008. These results coincide with Serbian regulations. From 2001 an organic form of selenium (selenized yeast) was introduced in small quantities (less than 8% of the total consumed selenium). Analysis of meat, milk and eggs from Serbian markets shows increased selenium levels compared to 1991. However, the estimated total human daily intake in Serbia is 40.9 ?g, which is under the recommended quantity. Increasing the quantity of selenium included in animal feed and the substitution of inorganic selenium with selenized yeast could be beneficial for animal health and farm productivity. As a consequence a further improvement in the human selenium status in Serbia should be possible.

Impact of dietary selenium intake on cardiac health: Experimental approaches and human studies

Selenium, a dietary trace mineral, essential for humans and animals, exerts its effects mainly through its incorporation into selenoproteins. Adequate selenium intake is needed to maximize the activity of selenoproteins, among which glutathione peroxidases have been shown to play a major role in cellular defense against oxidative stress initiated by excess reactive oxygen species. In humans, a low selenium status has been linked to increased risk of various diseases, including heart disease. The main objective of this review is to present current knowledge on the role of selenium in cardiac health. Experimental studies have shown that selenium may exert protective effects on cardiac tissue in animal models involving oxidative stress. Because of the narrow safety margin of this mineral, most interventional studies in humans have reported inconsistent findings. Major determinants of selenium status in humans are not well understood and several nondietary factors might be associated with reduced selenium status. In this review, we discuss recent studies regarding the role of selenoproteins in the cardiovascular system, the effect of dietary intake on selenium status, the impact of selenium status on cardiac health, and the cellular mechanisms that can be involved in the physiological and toxic effects of selenium.

Relevance of selenoprotein transcripts for selenium status in humans

The most commonly used methods for assessing the selenium (Se) status in humans involve analysis of Se concentration, selenoprotein activity, and concentration in the blood and its compartments. Recently, it has been suggested that the expression of selenoprotein mRNA in circulating blood leukocytes could differently reflect Se status, due to prioritization of specific selenoprotein synthesis in response to dietary Se supply. Whereas the Se levels required for optimization of selenoprotein P level and plasma glutathione peroxidise activity are well known, estimation of Se level that is required for maximal mRNA expression of selenoprotein in humans is the subject of current investigations. Studies on rats suggest that whole blood selenoprotein mRNA level can be used as the relevant molecular biomarker for assessing Se status, and suboptimal Se intake may be sufficient to achieve effective expression. Human studies, however, did not confirm this hypothesis. According to studies on rodents and humans discussed in this review, it appears that suboptimal Se intake may be sufficient to satisfy molecular requirements of Se and it is lower than current recommended dietary intake in humans. The use of selenoprotein transcripts as a molecular biomarker of Se status requires further studies on a large group of healthy individuals with different baseline Se, including data regarding genetic polymorphism of selenoproteins and data regarding potential modifiers of Se metabolism.

Detection and characterization of selenoproteins by tandem mass spectrometry assisted by laser ablation inductively coupled plasma mass spectrometry: application to human plasma selenoproteins

Accurate assessment of selenium status and selenium nutritional requirement in humans through the detection, identification and quantification of human plasma selenoprotein P (SelP) and glutathione peroxidase 3 (GPx3) has been an on-going effort and long term goal. Although several HPLC-ICP-MS analyses of human plasma/serum have reported SelP and GPx3 measurements, none of them have yet to demonstrate unambiguous mass spectrometry-based identification of these proteins. This study explored the potential of mass spectrometry techniques for the detection and identification of selenoproteins in a human plasma candidate Standard Reference Material (SRM) 1950 Metabolites in Human Plasma, with a total selenium concentration of 105.5 ± 2.3 ng g−1. Since the classical proteomic shotgun approach of depleted human plasma is not specific and sensitive enough to identify low abundant selenoproteins, a laser ablation (LA) inductively coupled plasma mass spectroscopy (ICP-MS) method was developed. The challenge was to develop a highly sensitive method to target selenoproteins at physiological concentrations by using a conventional laser device and a sensitive LA-ICP-MS method easily transposable to other equipped laboratories. Through a combination of better sample preparation, by concentrating selenoproteins onto membranes, and increased sensitivity of Se detection, by humidifying ICP with an organic solution, a LA-ICP-MS method 80 times more sensitive compared to classical LA ICP-MS methods was developed. This method was successfully applied to the detection of SelP and GPx3 selenoproteins at physiological concentrations in samples of human plasma. Once detected, these low abundant selenoproteins were unambiguously identified by tandem mass spectrometry. This study highlights the importance of an approach combining ICP-MS and tandem mass spectrometry for unequivocal selenoprotein detection and identification at physiological concentrations. This procedure can be easily performed in other laboratories to study selenoproteins or other heteroatom-tagged proteins in humans or other biological samples using widely available instrumentation.

Methods of assessment of selenium status in humans: a systematic review

Background: To understand the effect of selenium intake on health, it is important to identify sensitive and population-specific biomarkers of selenium status.Objective: The objective of this systematic review was to assess the usefulness of biomarkers of selenium status in humans.Design: The methods included a structured search strategy on Ovid MEDLINE, EMBASE (Ovid), and Cochrane databases; formal inclusion and exclusion criteria; data extraction into an Access database; validity assessment; and meta-analysis.Results: The data from 18 selenium supplementation studies (of which 9 were randomized controlled trials and 1 was considered to be at low risk of bias) indicate that plasma, erythrocyte, and whole-blood selenium, plasma selenoprotein P, and plasma, platelet, and whole-blood glutathione peroxidase activity respond to changes in selenium intake. Although there is a substantial body of data for plasma selenium, more large, high-quality, randomized controlled trials are needed for this biomarker, as well as for the other biomarkers, to explore the reasons for heterogeneity in response to selenium supplementation. There was insufficient evidence to assess the usefulness of other potential biomarkers of selenium status, including urinary selenium, plasma triiodothyroxine:thyroxine ratio, plasma thyroxine, plasma total homocysteine, hair and toenail selenium, erythrocyte, and muscle glutathione peroxidase activity.Conclusions: For all potentially useful biomarkers, more information is needed to evaluate their strengths and limitations in different population groups, including the effects of varying intakes, the duration of intervention, baseline selenium status, and possible confounding effects of genotype.

W1958 The Influence of Selenium-Enriched Milk Proteins On Selenium Status and Colorectal Cancer Risk in Humans

W1958 The Influence of Selenium-Enriched Milk Proteins On Selenium Status and Colorectal Cancer Risk in Humans

Direct determination of selenium in human serum by inductively coupled plasma-collision cell-mass spectrometry

Selenium status in humans depends on nutritional intake. To facilitate a future monitoring study with a large number of samples, an inductively coupled plasma mass spectrometry (ICP-MS) analysis method including collision cell technology was developed for the direct determination of selenium in human serum. Serum samples were diluted (1:15 v/v) with an aqueous solution containing 2-propanol, EDTA(NH(4))(2), ammonia and Triton X-100. Isotope dilution was used as the calibration method, evaluating the (78)Se/(82)Se ratio. Interference by (81)BrH(+) was corrected mathematically. Nebuliser blockage was prevented by sample centrifugation and filtration of the wash solution. Method validation was carried out using certified and spiked human sera. All values obtained for the accuracy tests were either within the certified ranges or showed recovery between 100.9% and 104.7%. Further results were relative standard deviation of 2.0% for repeatability and 3.0% for between-run precision, a limit of detection of 0.5 mug/L and a limit of quantification of 1.1 microg/L. The benefits of the new method are high accuracy combined with low sample consumption and fast sample throughput.

Increasing human intake of selenium by supplementing food animals with organic selenium

The concentration of global crop and food animal production in regions where plant selenium content is low has led to a decline in the amount of selenium in the human food supply. The central reason is that where soil pH is acidic, selenium cannot be absorbed by plants, thereby preventing transfer of selenoamino acids up the food chain through cereal grains and food animal products. Direct addition of inorganic selenium salts prevents acute deficiency symptoms, however selenium salts added to food animal diets do not provide meaningful amounts of selenium in edible animal tissues. Because human selenium status is a public health concern, researchers have examined nutritional means of increasing the selenium content of meat, milk and eggs using selenium produced by yeast, which like higher plants are able to form selenoamino acids. While part of the focus is on producing ‘designer’ foods, a more general question pertains to both existing selenium levels in food animal products and to those when commercial food animals are given selenium in naturally-occurring organic vs inorganic form. The following summarizes selenium levels in edible tissues in commercial and controlled research settings where inorganic and organic (Sel-PlexTM selenium yeast, Alltech Inc.) were compared.

The Human Selenium Status in 27 Regions of Russia

Russia is the largest nation in the world and it has vastly different climatic and geochemical conditions. The human selenium status is determined mainly by the selenium intake from foods, whose concentration is subject to geochemical, geological and temporal factors. The data on the selenium status of populations in Russia are scarce and sporadic. This review presents the most recent selenium data acquired using adequate quality assurance measures. Serum samples were obtained from 2462 healthy blood donors between 1990-1996 from 125 locations representing 27 different regions of Russia. Samples of wheat flour and dried milk were also analyzed from most regions. The mean serum selenium concentration per region varied from 0.80 mumol/l in the western regions (Pskov) to 1.84 mumol/l in the easternmost regions (Sakhalin). A low (0.76-1.00 mumol/l) serum selenium concentration was found in only 6% of the locations. In 88% of the locations the mean serum selenium concentrations were moderate (1.01-1.40 mumol/l) and the highest values, > 1.45 mumol/l were found in eight towns. Wheat flour selenium concentrations varied widely from 44 to 557 micrograms/kg depending on the origin. The low values were either domestic or European and the high values of American or Australian origin. A high correlation between serum selenium and wheat flour (r = 0.79) suggests that the selenium status in most instances is determined by high selenium in wheat. Overtly very low or high serum selenium levels were not found in the 27 regions studied in Russia.