Serum selenium concentration of a healthy northwest Spanish population

Relationship between serum selenium, sociodemographic variables, other trace elements and lipid profile in an adult Spanish population

INTRODUCTION

Several studies have shown an inverse relationship between selenium status and cardiovascular health, although epidemiologic evidence yielded by the randomized trials did not find a beneficial effect of selenium administration. The aim of this study was to analyze the association between serum selenium levels and lipid profile adjusted by age, sex and other associated factors among a general adult population in Spain.

MATERIALS AND METHODS

We recruited 372 hospital employee volunteers (60 men and 312 women) with a mean age of 47 (SD: 10.9), whom were given a standardized questionnaire. Serum selenium concentration was measured by electrothermal atomization atomic absorption spectrometry. Serum copper and zinc concentrations were measured using flame atomic absorption spectrometry.

RESULTS

The mean of serum selenium was 79.5μg/L (SD: 11.7) with no sex-dependent differences. In the multivariate linear regression analysis, the associated factors with the mean levels of selenium were: age (β=0.223; CI 95%: 0.101-0.345), p<0.001; widowhood (β=-9.668; CI 95%: -17.234 to -2.102), p=0.012; calcium supplements (β=3.949; CI 95%: 0.059-7.838), p=0.047; zinc (β=0.126; CI 95%: 0.013-0.238), p=0.028 and glucose (β=0.172; CI 95%: 0.062- 0.281), p=0.002; Participants with serum selenium≥79.5μg/L were 1.98 (OR=1.98; CI 95% 1.17-3.35; p=0.011) and 2.04 times (OR=2.04; CI 95% 1.06-3.97; p=0.034) more likely to have cholesterol ≥200mg/dL and LDL-c ≥100mg/dL respectively than those with serum selenium <79.5μg/L.

CONCLUSIONS

Higher selenium was positively associated with increased total and LDL cholesterol but not with HDL-c and triglycerides. More studies are needed in order to confirm the lower serum selenium findings in widows.

Serum levels of antioxidants (Zn, Cu, Se) in healthy volunteers living in Tehran

Zinc (Zn), copper (Cu), and selenium (Se) are well-known as essential trace elements. These elements attract a great interest, not only in the scientific world, but also in the public option. The aim of this study was to evaluate the serum Zn, Cu, and Se levels in healthy volunteers (60 females and 55 males) living in Tehran. The age (6-62 years) and sex of the subjects, as well as drug and tobacco consumption, were registered. The concentrations of these elements were determined by atomic absorption spectrometry. The serum levels of Zn, Cu, and Se in the normal population of Tehran was 0.89 +/- 0.16 mg/L, 0.95 +/- 0.20 mg/L, and 99.10 +/- 21.78 microg/L, respectively. There was no significant gender-related difference in serum Zn concentration (p < 0.15). However, a significant difference (p < 0.05) in both Cu and Se levels was observed between males and females.

Serum selenium levels in healthy women in Tabriz, Iran

BACKGROUND

Selenium is of fundamental importance to human health, and selenium deficiency is associated with disease conditions.

OBJECTIVE

The objective of this study was to investigate the serum level of selenium in women of childbearing age and postmenopausal women living in Tabriz, Iran.

METHODS

In this cross-sectional study, 60 healthy women of childbearing age and 60 healthy postmenopausal women were studied with the use of biochemical methods (measurement of serum selenium by graphite furnace atomic absorption spectrometry), anthropometric measurements (weight and height), and interviews.

RESULTS

The average serum selenium was 76.67 +/- 17.98 microg/L (range, 42.00 to 166.61 microg/L). This level was lower than those reported in other provinces of Iran and some other countries. Sixty-nine women (57.5%) had serum selenium concentrations under 80 microg/L. There was no significant difference in selenium level between the two groups of women. Serum selenium level did not vary with age and body mass index.

CONCLUSIONS

Some Iranian women are of borderline selenium status and as a consequence are more susceptible to selenium-deficiency diseases. There is a need for community-based programs to encourage people to increase consumption of selenium-rich sources, such as marine foods.

Serum selenium and glutathione peroxidase concentrations in type 2 diabetes mellitus patients

AIMS

Antioxidant selenium (Se) properties and, its protective role against oxidative damage play an important role in diabetic complications. Our objective was to gain further insight on a link between selenium status and diabetic nephropathy.

METHODS

We assessed glutathione peroxidase (GPx) and Se in type 2 diabetes mellitus patients with microalbuminuria (MA) (group 1), without microalbuminuria (group 2), and in control subjects (group 3). Glucose, urea, creatinine and glycated hemoglobin tests were tested in sera. A complete clinical record was elaborated.

RESULTS

For diabetic patients both, the time from diagnosis and plasma glucose concentration were higher in group 1 as compared to group 2. Control group showed higher serum Se concentrations as compared to the diabetic groups. The two groups of diabetic patients showed similar serum Se levels. Serum concentration of GPx was significantly lower in group 1 as compared to groups 2 and 3. Microalbuminuria (MA) test showed a positive correlation with glucose, and a negative relationship with serum Se and GPx. Multiple regression revealed an inverse relationship between selenium or GPx in serum and the results of the MA test.

CONCLUSIONS

Our results suggest that lower Se and GPx levels in diabetic patients may be implicated in the diabetic nephropathy.

Selenium level in the environment and the population of Zhoukoudian area, Beijing, China

The objective of this study was to detect the selenium level in the environment and the population of Zhoukoudian area, Beijing, and to discuss the influence of various factors on serum selenium level. The soil, drinking water, and foodstuff samples and venous blood samples of 401 individuals were obtained to determine the selenium level by gas chromatograph equipped with a (63)Ni electron capture detector (ECD). The selenium level was 0.210+/-0.013 microg/g in soil, 0.017 microg/L+/-0.002 in drinking water, 0.034+/-0.002 microg/g in rice, and 0.034+/-0.012 microg/g in wheat flour. This index showed that the Zhoukoudian area of Beijing was a moderate or marginal level selenium ecological landscape. The mean serum selenium level of the population was 75.01+/-28.35 microg/L, ranging between 35.2 and 160.4 microg/L. A total of 279 (69.6%) individuals exhibited serum selenium level below 80 microg/L, which is the lowest threshold for the activity of glutathione peroxidases (GPx) in vivo. A total of 35 (8.5%) individuals exhibited serum selenium level below 45 microg/L. It is widely recommended that below this value (45 microg/L) there is an increased risk of cardiovascular disease and cancer. Multiple linear regression analysis showed that serum selenium level was positively associated with body mass index (beta=0.137; P=0.011), serum total cholesterol TC (beta=0.785; P=0.000), however, negatively associated with systolic blood pressure (beta=-0.172; P=0.023), serum triglyceride (beta=-0.170; P=0.007), high density lipoprotein-cholesterol (beta=-0.121; P=0.027), and low high density lipoprotein-cholesterol (beta=-0.568; P=0.027).

Selenium in global food systems

Food systems need to produce enough of the essential trace element Se to provide regular adult intakes of at least 40 μg/d to support the maximal expression of the Se enzymes, and perhaps as much as 300 μg/d to reduce risks of cancer. Deprivation of Se is associated with impairments in antioxidant protection, redox regulation and energy production as consequences of suboptimal expression of one or more of the Se-containing enzymes. These impairments may not cause deficiency signs in the classical sense, but instead contribute to health problems caused by physiological and environmental oxidative stresses and infections. At the same time, supranutritional intakes of Se, i.e. intakes greater than those required for selenocysteine enzyme expression, appear to reduce cancer risk. The lower, nutritional, level is greater than the typical intakes of many people in several parts of the world, and few populations have intakes approaching the latter, supranutritional, level. Accordingly, low Se status is likely to contribute to morbidity and mortality due to infectious as well as chronic diseases, and increasing Se intakes in all parts of the world can be expected to reduce cancer rates.

The effects of a mixture of brown and black rice on lipid profiles and antioxidant status in rats

BACKGROUND

The present study was designed to investigate the influence of natural brown and black rice consumption on serum lipid parameters and hepatic enzyme activities in rats fed different combinations of grains.

METHODS

50 male rats were divided into 4 groups and raised for 8 weeks on diets containing white rice (WH), white rice and brown rice (WHBR), white rice and black rice (WHBL), brown rice and black rice (BRBL). Blood samples were collected for lipid measurements, and the oxidant and antioxidant status of liver was evaluated.

RESULTS

Plasma triglyceride, total cholesterol and low-density lipoprotein cholesterol in rats fed the WH diet were higher than in other groups. High-density lipoprotein cholesterol was significantly higher in rats fed diets including black rice such as WHBL and BRBL compared with WH and WHBR. The level of thiobarbituric acid reactive substances in liver is shown to be higher in rats in the order of those fed WH, WHBR, WHBL and BRBL. While superoxide dismutase and chloramphenicol acetyltransferase did not differ among the 4 groups, glutathione and glutathione peroxidase in WH were significantly lower than in other groups.

CONCLUSION

This study demonstrates that brown and black rice have cardioprotective effects.

Food Intake and Serum Selenium Concentration in Elderly People

BACKGROUND/AIMS

It is becoming apparent that the essential trace element selenium plays a critical role in the maintenance of optimal health status. The objective of this study was to identify the food groups that most contributed to selenium intake and its serum levels in elderly people.

METHODS

Dietary intake was assessed in 205 institutionalized elderly by means of a 1-year food frequency questionnaire (FFQ). Intake of macronutrients and minerals of the diet were estimated. Selenium was determined in serum and analyzed by graphite-furnace atomic absorption spectrometry.

RESULTS

Selenium intake and serum concentration were both within the normal range. The major contributors to selenium intake were cereals and bakery, fish and shellfish, meat and meat products and dairy products. All of them except cereals were also associated to serum selenium. Intake of animal protein, but not the vegetable one, contributed to serum selenium.

CONCLUSION

An adequate intake of fish and meat would be of importance to improve selenium status and health principally in elderly people who are at high risk of mineral deficiency.

Comparison of the serum selenium content of healthy adults living in the Antwerp region (Belgium) with recent literature data

Graphite furnace atomic absorption spectrometry, after improved matrix modification and using Zeeman background correction, was used to measure the serum selenium content of healthy adults living in the Antwerp region (Belgium). The mean serum concentration of 13 men and 13 women, sampled once a month during 1 year, was 84.3 +/- 9.4ng/ml with a broad range of 51.4-121.7 ng/ml. The intra-individual variation was remarkably high. Recent literature on selenium concentrations is reviewed and values are tabulated, with limitation to healthy adults and European countries. The mean serum selenium concentration measured corresponded well to older literature data for Belgium. The obtained values were found to be in the medium range compared with the literature data for other European countries.

Biological monitoring of environmental exposure to manganese in blood samples from residents of the city of Barcelona, Spain

Serum manganese levels were determined in 250 healthy subjects (122 men and 128 women) living in Barcelona in northeastern Spain. The study was designed to assess the reference levels for serum manganese and to investigate its relationship to age and sex. The age distribution ranged from 15 to 90 years. The assays were performed by means of a graphite furnace atomic absorption spectrometry. The geometric mean of serum manganese concentration was 1.1 microg/l, ranging from 0.3 microg/l to 2.5 microg/l. In almost every case, the 95th upper percentiles of this element were < 1.8 microg/l. No correlation between the concentration of manganese and sex could be established, but in the younger population the manganese levels were nearly three times higher than the results obtained in the older population.

Selenium status of Irish adults: evidence of insufficiency

BACKGROUND

Sub-optimal selenium status may have a role in the aetiology of various pathologies. Selenium status depends on adequate selenium in the diet. A relatively high proportion of Irish adults (17% men; 46% women) have an inadequate dietary intake.

AIM

A study was designed to examine the selenium status of healthy Irish adults.

METHODS

Ninety-one healthy Irish adults, aged 18-67 years, were recruited from the Cork City area. A fasting blood sample was collected from each subject and each was assayed for serum selenium an index of serum selenium.

RESULTS

Mean (+/- SD) serum selenium concentration in healthy Irish adults was 76 (+/- 21)microg/l. There was no significant difference in values between males and females or between postmenopausal and premenopausal women or between the three main age categories.

CONCLUSION

Current serum selenium values of Irish adults would not appear to be sufficient to achieve optimal activity of glutathione peroxidase, which occurs at serum selenium concentration around 95microg/l. Sub-optimal selenium status may increase susceptibility to various chronic disorders.

Reference values of selenium in plasma in population from Barcelona. Comparison with several pathologies

Plasma selenium reference values from healthy donors in the metropolitan area of Barcelona are determined. A random sample from 156 healthy adults (control group) is analysed by using electrothermal atomic absorption spectrometry with Zeeman effect background correction. The relationship between several pathologies and Se content is also evaluated. Se content from 64 samples from subjects with chronic renal failure and 54 from subjects suffering from several malignancies are determined and the results are compared to the reference values. Moreover, Se contents are determined and compared in two groups of children, healthy (19 samples) and children of mothers infected with HIV-1 (16 samples). In the control group, Se plasma concentration ranges between 50 and 145 microg x L(-1) (82.2 +/- 17.5 microg x L(-1)). Significantly lower values are found in the two pathologies studied (malignancy and chronic renal failure), compared to the control group. However, no significant differences in Se content are found between the two groups studied regarding malignancy and chronic renal failure. In children of mothers infected with HIV-1, Se status is significantly lower than that of healthy children.

Red and black rice decrease atherosclerotic plaque formation and increase antioxidant status in rabbits

The influence of white, red and black rice consumption on atherosclerotic plaque formation induced by hypercholesterolemia was investigated in rabbits. Male rabbits (n = 36) were divided into five groups. They were fed a normal laboratory purified diet (normal group, n = 6), a high cholesterol (0.5 g/100 g) diet (HC group, n = 6), a high cholesterol diet with 30 g/100 g white rice (WR group, n = 8), 30 g/100 g red rice (RR group, n = 8), or 30 g/100 g black rice (BR group, n = 8) for 10 wk. Blood samples were collected for lipid measurements and aorta were removed for assessment of atherosclerotic plaques at the end of the protocol. The oxidant and antioxidant status of blood, erythrocytes, liver and aorta was evaluated. The area of atherosclerotic plaque was 50% lower in rabbits fed the red or black rice diets than in those fed the white rice diet. Compared with the HC and WR groups, serum HDL cholesterol and apolipoprotein (apo) A-I concentration were greater (P < 0.05) in the RR and BR groups. Liver reactive oxygen species (ROS) and aortic malondialdehyde (MDA) were significantly lower, and the liver total antioxidative capacity (TAC) and erythrocyte superoxide dismutase (SOD) activity were significantly higher in the RR and BR groups compared with the HC and WR groups. Red or black rice consumption reduced or retarded the progression of atherosclerotic plaque development induced by dietary cholesterol. The enhanced serum HDL cholesterol and apo A-I concentrations, and the increased antioxidant and decreased oxidative status may be mechanisms of the antiatherogenic effect of red or black rice.

Serum selenium concentration in a representative sample of the Canarian population

The concentration of serum selenium in 395 individuals (187 males + 218 females) living in the Canary Islands, Spain was determined by hydride generation atomic absorption spectrometry. The mean selenium concentration was 74.7 +/- 25.2 microg/l ranging between 7.86 and 182.3 microg/l. Twenty-two adults (7.2% of the total) had serum selenium concentrations under 45 microg/l. It is widely accepted that below this selenium serum concentration (45 microg/l) there is an increased risk of cardiovascular disease and cancer. Our results fall within data recently published in other Spanish and European regions and are much lower than data observed in USA or seleniferous regions. The estimated Se intakes of our population were lower than the Recommended Dietary Allowances for American people. Individuals from Lanzarote had a mean Se concentration significantly higher than individuals from the other islands. This could be attributed to differences in Se content of soil and/or differences in dietary habits of the populations. Serum selenium concentration did not vary with the sex of the subjects. Individuals younger than 14 years old had a serum selenium concentration significantly lower than the rest of the individuals. No relationship with socio-economic status, educational level, smoking habits, physical exercise or beer consumption was found. However, individuals who consume wine more than three times a week showed higher selenium concentrations than individuals with lower consumption. Also, individuals with consumption above seven units of spirit drinks a week had the highest mean selenium concentration.

Selenium status in Saudi Arabia

Selenium (Se) is a naturally occurring trace element that is essential for animal and human nutrition, but the range between dietary requirements and toxic levels is relatively narrow. In this review, we are interested in the beneficial effects of selenium and we report on a number of studies of the selenium status of different populations in Saudi Arabia. The Status reflects the geographical area inhabited by the populations. Apart from the few available studies reviewed here, no data on the human status of Se in Saudi Arabia has been obtained. A further objective of this paper is throw some the light on the direction of future studies.

Trace element reference values in serum determined by inductively coupled plasma atomic emission spectrometry

Serum reference values for Ba, B, Cd, Cu, Fe, Mn, Li, Se, Sr, and Zn in 141 healthy Norwegians were determined. The trace element concentrations were determined by the inductively coupled plasma atomic emission spectrometry technique that we have recently validated. The reference intervals were established according to the recommendations of the International Federation of Clinical Chemistry and Laboratory Medicine. Also coverage intervals with coverage uncertainties were calculated according to the International Union of Pure and Applied Chemistry. The population studied consisted of 69 men and 72 women of the ages 21-87 years. The effects of gender, age, smoking, and oral contraceptives on serum levels of trace elements were investigated. Median concentrations of the different trace elements in (micromol/l) were as follows: Ba (0.44), B (1.50), Cd (0.004), Cu (17.1), Fe (21.4), Li (0.06), Mn (0.003), Se (1.26), Sr (0.17), and Zn (13.3). An increase in serum Ba and Sr was detected with age. These metals and Se were also significantly higher in women over 50 years of age in comparison to younger women. Women had higher serum Cu than men and those on oral contraceptives had higher serum Cu and Fe. Serum B tended to increase with age, while it was significantly reduced with smoking.

Selenium

The 4 natural oxidation states of selenium are elemental selenium (0), selenide (-2), selenite (+4), and selenate (+6). Inorganic selenate and selenite predominate in water whereas organic selenium compounds (selenomethionine, selenocysteine) are the major selenium species in cereal and in vegetables. The principal applications of selenium include the manufacture of ceramics, glass, photoelectric cells, pigments, rectifiers, semiconductors, and steel as well as use in photography, pharmaceutical production, and rubber vulcanizing. High concentrations of selenium in surface and in ground water usually occur in farm areas where irrigation water drains from soils with high selenium content (Kesterson Reservoir, California) or in lakes receiving condenser cooling water from coal-fired electric power plants (Belews Lake, North Carolina). For the general population, the primary pathway of exposure to selenium is food, followed by water and air. Both selenite and selenate possess substantial bioavailability. However, plants preferentially absorb selenates and convert them to organic compounds. Aquatic organisms (e.g., bivalves) can accumulate and magnify selenium in the food chain. Selenium is an essential component of glutathione peroxidase, which is an important enzyme for processes that protect lipids in polyunsaturated membranes from oxidative degradation. Inadequate concentrations of selenium in the Chinese diet account, at least in part, for the illness called Keshan disease. Selenium deficiency occurs in the geographic areas where Balkan nephropathy appears, but there is no direct evidence that selenium deficiency contributes to the development of this chronic, progressive kidney disease. Several lines of scientific inquiry suggest that an increased risk of cancer occurs as a result of low concentrations of selenium in the diet; however, insufficient evidence exists at the present time to recommend the use of selenium supplements for the prevention of cancer. The toxicity of most forms of selenium is low and the toxicity depends on the chemical form of selenium. The acute ingestion of selenious acid is almost invariably fatal, preceded by stupor, hypotension, and respiratory depression. Chronic selenium poisoning has been reported in China where changes in the hair and nails resulted from excessive environmental exposures to selenium. Garlic odor on the breath is an indication of excessive selenium exposure as a result of the expiration of dimethyl selenide. The US National Toxicology Program lists selenium sulfide as an animal carcinogen, but there is no evidence that other selenium compounds are carcinogens.