Whole blood mercury and selenium concentrations in a selected Austrian population: does gender matter?

Emerging evidence on selenoneine and its public health relevance in coastal populations: a review and case study of dietary Se among Inuit populations in the Canadian Arctic

Selenium is an essential mineral yet both deficiency and excess are associated with adverse health effects. Dietary intake of Se in humans varies greatly between populations due to food availability, dietary preferences, and local geological and ecosystem processes impacting Se accumulation into agricultural products and animal populations. We argue there is a need to evaluate and reconsider the relevance of public health recommendations on Se given recent evidence, including the metabolic pathways and health implications of Se. This argument is particularly pertinent for Inuit populations in Northern Canada, who often exceed dietary tolerable upper intake levels and exhibit very high whole blood Se concentrations due to their dependence on local country foods high in the newly discovered Se compound, selenoneine. Since selenoneine appears to have lower toxicity compared to other Se species and does not contribute to the circulating pools of Se for selenoprotein synthesis, we argue that total dietary Se or total Se in plasma or whole blood are poor indicators of Se adequacy for human health in these populations. Overall, this review provides an overview of the current evidence of Se speciation, deficiency, adequacy, and excess and implications for human health and dietary recommendations, with particular reference to Inuit populations in the Canadian Arctic and other coastal populations consuming marine foods.

The association between serum selenium levels and pathological features of papillary thyroid cancer in 284 patients

Objective

The relationship between serum selenium levels and papillary thyroid cancer (PTC), especially the pathological features, still remains controversial. We conducted this study to investigate the relationship between serum selenium levels and PTC in a Chinese population.

Methods

Cross-sectional data of 284 patients with PTC were collected from the First Affiliated Hospital of Shandong First Medical University. The general clinical characteristics, serum selenium levels, and tumor pathological features were described in PTC. The association between serum selenium levels and pathological features in PTC was analyzed using SPSS 26.0 statistical software.

Results

Our results showed that the median serum selenium level was 79.15 μg/L (IQR: 71.00 - 86.98 μg/L) in PTC patients. Serum selenium levels were lower in females than males (p = 0.035). Serum selenium levels were negatively correlated with the number of lymph node metastases (p = 0.048). High serum selenium (OR = 0.397, 95%CI: 0.217 - 0.725) and diastolic blood pressure (OR = 1.028, 95%CI: 1.005 - 1.051) were related factors for the incidence of bilateral tumors. High serum selenium (OR = 0.320, 95%CI: 0.166 - 0.617) and diastolic blood pressure (OR = 1.066, 95%CI: 1.031 - 1.103) were related factors for tumor multifocal incidence.

Conclusions

The serum selenium levels of PTC patients in females were lower than males. High serum selenium levels might be a protective factor in PTC patients. Further research is necessary to better understand the influence of selenium on PTC progression.

Biomonitoring of Mercury, Cadmium and Selenium in Fish and the Population of Puerto Nariño, at the Southern Corner of the Colombian Amazon

Heavy metals threaten communities near biodiversity hotspots, as their protein sources come from the environment. This study assessed Hg, Cd, and Se concentrations in fish, as well as the magnitude of exposure and hematological conditions of adult citizens from Puerto Nariño (Colombian Amazon). Among fish samples, greater Hg concentrations were found in higher trophic level species, including Rhaphiodon vulpinus (880 ± 130 ng/g) and Pseudoplatystoma tigrinum (920 ± 87 ng/g). These species presented the highest hazard quotients and lowest Se:Hg molar ratios among those studied, showing their consumption represents a health risk to consumers. Moreover, some samples of Mylossoma duriventre and Prochilodus magdalenae had Cd levels greater than the regulated limit (100 ng/g). The average total Hg (T-Hg) concentrations in human hair and blood were 5.31 µg/g and 13.7 µg/L, respectively. All hair samples exceeded the 1.0 μg/g threshold set by the USEPA, whereas 93% of the volunteers had T-Hg blood levels greater than 5 μg/L, suggesting elevated exposure. The mean Cd level was 3.1 µg/L, with 21% of samples surpassing 5 µg/L, value at which mitigating actions should be taken. Eighty-four percent of participants presented Se deficiencies (<100 μg/L). There was a significant association between fish consumption and T-Hg in hair (ρ = 0.323; p = 0.032) and blood (ρ = 0.381; p = 0.011). In this last matrix, Se correlated with Cd content, whereas lymphocytes were inversely linked to Hg concentrations. The results of this study show that there is  extensive exposure to Hg in fish, the consumption of which may promote detrimental impacts on hematology parameters within the community.

Seafood, wine, rice, vegetables, and other food items associated with mercury biomarkers among seafood and non-seafood consumers: NHANES 2011-2012

Fish/seafood consumption is a source of mercury; other dietary sources are not well described. This cross-sectional study used National Health and Nutrition Examination Survey (NHANES) 2011-2012 data. Participants self-reported consuming fish/seafood (N = 5427) or not (N = 1770) within the past 30 days. Whole blood total mercury (THg), methylmercury (MeHg), and urinary mercury (UHg) were determined. Diet was assessed using 24 h recall. Adjusted regression models predicted mercury biomarker concentrations with recent food consumption, while controlling for age, sex, education, and race/ethnicity. Geometric mean THg was 0.89 µg/L (95% confidence interval (CI): 0.78, 1.02) (seafood consumers) and 0.31 µg/L (95% CI: 0.28, 0.34) (non-seafood consumers); MeHg and UHg concentrations follow similar patterns. In adjusted regressions among seafood consumers, significant associations were observed between mercury biomarkers with multiple foods, including fish/seafood, wine, rice, vegetables/vegetable oil, liquor, and beans/nuts/soy. Among non-seafood consumers, higher THg was significantly associated with mixed rice dishes, vegetables/vegetable oil, liquor, and approached statistical significance with wine (p < 0.10); higher MeHg was significantly associated with wine and higher UHg was significantly associated with mixed rice dishes. Fish/seafood consumption is the strongest dietary predictor of mercury biomarker concentrations; however, consumption of wine, rice, vegetables/vegetable oil, or liquor may also contribute, especially among non-seafood consumers.

Biomonitoring of maternal and fetal exposure to mercury in Sabzevar and its affecting risk factors

Fetuses and young children are sensitive to even low levels of exposure to Hg, which can damage their brain and adversely affect their central nervous system and cognitive development. This study was conducted to determine the maternal and fetal mercury burden levels in mothers presenting to Shahidan Mobini Hospital for delivery. Eighty-nine mothers were included in this study and 360 samples were taken from their placental tissue and blood (maternal blood) as well as their umbilical cord tissue blood (infant blood). Findings revealed a significant strong correlation (r = 0.890, p < 0.001) in blood mercury between mothers and their infants. According to multiple linear regression analysis, there was a significant positive association between living in rural areas and the level of mercury in the placental tissue (β = 11.09, p < 0.001). This positive association was also found in other samples. In addition, there was a significant association between maternal age and mercury level in the placental tissue (β = 5.56, p = 0.049), placental blood (β = 11.67, p = 0.003), umbilical cord tissue (β = 8.33, p = 0.004) and umbilical cord blood (β = 9.51, p < 0.001).

Prenatal selenium status, neonatal cerebellum measures and child neurodevelopment at the age of 18 months

OBJECTIVES

The aim of this study was to evaluate the association of maternal blood selenium (Se) levels and cord blood Se levels with neonatal cerebellum measures and child neurodevelopment at the age of 18 months. Moreover, to investigate whether the neonatal cerebellum measures could be used as a potential biomarker for selenium homeostasis during pregnancy.

STUDY GROUP AND METHODS

The study population consisted of 205 mother-child pairs from Croatian Mother and Child Cohort. Maternal blood and cord blood were obtained at delivery and selenium level was analyzed by Inductively Coupled Plasma Mass Spectrometry. Cranial ultrasonography examination was performed on 49 newborns - cerebellum length and width have been measured. Neurodevelopmental assessment of cognitive, language and motor skills were conducted on 154 children, using The Bayley Scales of Infant and Toddler Development, Third Edition (BSID-III), at the age of 18 months.

RESULTS

The mean levels of selenium in maternal blood and cord blood were 92.6 ng/g and 97.0 ng/g, respectively. Maternal blood selenium levels were moderately and negatively correlated (r = -0.372; p = 0.008) with cerebellum length, while cord blood selenium levels were positively correlated with cerebellum width (r = 0.613; p = 0.007) among female children group. Maternal blood selenium levels were weakly and positively correlated (r = 0.176; p = 0.029) with child's cognitive abilities.

CONCLUSION

To the best of our knowledge, our study is the first one investigating the association between neonatal brain measures and selenium levels in mother-child pairs. Our results indicate that prenatal selenium intake correlated with cerebellum length and width measured by cranial ultrasonography. Hence, cerebellum may be used as a potential biomarker and a target "organ" for early detection of possible adverse effects of prenatal status to various micronutrients.

Selenium for preventing cancer

BACKGROUND

This review is the third update of the Cochrane review "Selenium for preventing cancer". Selenium is a naturally occurring element with both nutritional and toxicological properties. Higher selenium exposure and selenium supplements have been suggested to protect against several types of cancer.

OBJECTIVES

To gather and present evidence needed to address two research questions:1. What is the aetiological relationship between selenium exposure and cancer risk in humans?2. Describe the efficacy of selenium supplementation for cancer prevention in humans.

SEARCH METHODS

We updated electronic searches of the Cochrane Central Register of Controlled Trials (CENTRAL; 2017, Issue 2), MEDLINE (Ovid, 2013 to January 2017, week 4), and Embase (2013 to 2017, week 6), as well as searches of clinical trial registries.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and longitudinal observational studies that enrolled adult participants.

DATA COLLECTION AND ANALYSIS

We performed random-effects (RE) meta-analyses when two or more RCTs were available for a specific outcome. We conducted RE meta-analyses when five or more observational studies were available for a specific outcome. We assessed risk of bias in RCTs and in observational studies using Cochrane's risk assessment tool and the Newcastle-Ottawa Scale, respectively. We considered in the primary analysis data pooled from RCTs with low risk of bias. We assessed the certainty of evidence by using the GRADE approach.

MAIN RESULTS

We included 83 studies in this updated review: two additional RCTs (10 in total) and a few additional trial reports for previously included studies. RCTs involved 27,232 participants allocated to either selenium supplements or placebo. For analyses of RCTs with low risk of bias, the summary risk ratio (RR) for any cancer incidence was 1.01 (95% confidence interval (CI) 0.93 to 1.10; 3 studies, 19,475 participants; high-certainty evidence). The RR for estimated cancer mortality was 1.02 (95% CI 0.80 to 1.30; 1 study, 17,444 participants). For the most frequently investigated site-specific cancers, investigators provided little evidence of any effect of selenium supplementation. Two RCTs with 19,009 participants indicated that colorectal cancer was unaffected by selenium administration (RR 0.99, 95% CI 0.69 to 1.43), as were non-melanoma skin cancer (RR 1.16, 95% CI 0.30 to 4.42; 2 studies, 2027 participants), lung cancer (RR 1.16, 95% CI 0.89 to 1.50; 2 studies, 19,009 participants), breast cancer (RR 2.04, 95% CI 0.44 to 9.55; 1 study, 802 participants), bladder cancer (RR 1.07, 95% CI 0.76 to 1.52; 2 studies, 19,009 participants), and prostate cancer (RR 1.01, 95% CI 0.90 to 1.14; 4 studies, 18,942 participants). Certainty of the evidence was high for all of these cancer sites, except for breast cancer, which was of moderate certainty owing to imprecision, and non-melanoma skin cancer, which we judged as moderate certainty owing to high heterogeneity. RCTs with low risk of bias suggested increased melanoma risk.Results for most outcomes were similar when we included all RCTs in the meta-analysis, regardless of risk of bias. Selenium supplementation did not reduce overall cancer incidence (RR 0.99, 95% CI 0.86 to 1.14; 5 studies, 21,860 participants) nor mortality (RR 0.81, 95% CI 0.49 to 1.32; 2 studies, 18,698 participants). Summary RRs for site-specific cancers showed limited changes compared with estimates from high-quality studies alone, except for liver cancer, for which results were reversed.In the largest trial, the Selenium and Vitamin E Cancer Trial, selenium supplementation increased risks of alopecia and dermatitis, and for participants with highest background selenium status, supplementation also increased risk of high-grade prostate cancer. RCTs showed a slightly increased risk of type 2 diabetes associated with supplementation. A hypothesis generated by the Nutritional Prevention of Cancer Trial - that individuals with low blood selenium levels could reduce their risk of cancer (particularly prostate cancer) by increasing selenium intake - has not been confirmed. As RCT participants have been overwhelmingly male (88%), we could not assess the potential influence of sex or gender.We included 15 additional observational cohort studies (70 in total; over 2,360,000 participants). We found that lower cancer incidence (summary odds ratio (OR) 0.72, 95% CI 0.55 to 0.93; 7 studies, 76,239 participants) and lower cancer mortality (OR 0.76, 95% CI 0.59 to 0.97; 7 studies, 183,863 participants) were associated with the highest category of selenium exposure compared with the lowest. Cancer incidence was lower in men (OR 0.72, 95% CI 0.46 to 1.14, 4 studies, 29,365 men) than in women (OR 0.90, 95% CI 0.45 to 1.77, 2 studies, 18,244 women). Data show a decrease in risk of site-specific cancers for stomach, colorectal, lung, breast, bladder, and prostate cancers. However, these studies have major weaknesses due to study design, exposure misclassification, and potential unmeasured confounding due to lifestyle or nutritional factors covarying with selenium exposure beyond those taken into account in multi-variable analyses. In addition, no evidence of a dose-response relation between selenium status and cancer risk emerged. Certainty of evidence was very low for each outcome. Some studies suggested that genetic factors might modify the relation between selenium and cancer risk - an issue that merits further investigation.

AUTHORS' CONCLUSIONS

Well-designed and well-conducted RCTs have shown no beneficial effect of selenium supplements in reducing cancer risk (high certainty of evidence). Some RCTs have raised concerns by reporting a higher incidence of high-grade prostate cancer and type 2 diabetes in participants with selenium supplementation. No clear evidence of an influence of baseline participant selenium status on outcomes has emerged in these studies.Observational longitudinal studies have shown an inverse association between selenium exposure and risk of some cancer types, but null and direct relations have also been reported, and no systematic pattern suggesting dose-response relations has emerged. These studies suffer from limitations inherent to the observational design, including exposure misclassification and unmeasured confounding.Overall, there is no evidence to suggest that increasing selenium intake through diet or supplementation prevents cancer in humans. However, more research is needed to assess whether selenium may modify the risk of cancer in individuals with a specific genetic background or nutritional status, and to investigate possible differential effects of various forms of selenium.

Macro- and microelements in the rat liver, kidneys, and brain tissues; sex differences and effect of blood removal by perfusion in vivo

Concentrations of macro- and microelements in animal organs indicate the animal health status and represent reference data for animal experiments. Their levels in blood and tissues could be different between sexes, and could be different with and without blood in tissues. To test these hypotheses, in adult female and male rats the concentrations of various elements were measured in whole blood, blood plasma, and tissues from blood-containing (nonperfused) and blood-free liver, kidneys, and brain (perfused in vivo with an elements-free buffer). In these samples, 6 macroelements (Na, Mg, P, S, K, Ca) and 14 microelements (Fe, Mn, Co, Cu, Zn, Se, I, As, Cd, Hg, Pb, Li, B, Sr) were determined by inductively coupled plasma mass spectrometry following nitric acid digestion. In blood and plasma, female- or male-dominant sex differences were observed for 6 and 5 elements, respectively. In nonperfused organs, sex differences were observed for 3 (liver, brain) or 9 (kidneys) elements, whereas in perfused organs, similar differences were detected for 9 elements in the liver, 5 in the kidneys, and none in the brain. In females, perfused organs had significantly lower concentrations of 4, 5, and 2, and higher concentrations of 10, 4, and 7 elements, respectively, in the liver, kidneys, and brain. In males, perfusion caused lower concentrations of 4, 7, and 2, and higher concentrations of 1, 1, and 7 elements, respectively, in the liver, kidneys, and brain. Therefore, the residual blood in organs can significantly influence tissue concentrations of various elements and their sex-dependency.

Mercury exposure and a shift toward oxidative stress in avid seafood consumers

Mechanisms of mercury (Hg) toxicity at low doses from seafood consumption, the most common exposure route, are not well understood. We tested the hypothesis that seafood Hg exposure is related to a shift in redox status, indicated by a decrease in the ratio of reduced to oxidized glutathione (GSH:GSSG) in blood, or increase in redox potential (Eh). We also examined whether key seafood nutrients (selenium (Se), omega-3 fatty acids) confound or modify this shift. We measured blood concentrations of total Hg, Se, GSH, GSSG, and the Omega-3 Index (% omega-3s of total fatty acids in red blood cell membranes) in seafood consumers in Long Island, NY. We examined relationships between Hg, GSH:GSSG ratio and Eh. Elevated blood Hg (>5.8µgL(-1)) was associated with lower GSH:GSSG (β=-116.73, p=0.01), with no evidence of confounding by Se or Omega-3 Index. However, in models stratified by Omega-3 Index levels, Hg-GSH:GSSG associations were weakened among those with high Omega-3 Index levels (>6% of fatty acids, β=-63.46, p=0.28), and heightened among those with low Omega-3 Index (β=-182.53, p<0.01). We observed comparable patterns for Eh in relation to Hg. These results support the hypothesis that Hg exposure from seafood is linked to a shift in redox status toward oxidative stress, modified by omega-3 fatty acids in this population. Further work should examine the role of different seafood nutrients and Hg-induced shifts in redox status in the diverse health effects associated with elevated Hg exposure.

Biological monitoring of exposure and effects in workers employed in a selenium-processing plant

PURPOSE

The aim of the study was to assess external and internal selenium exposure and potential biological effects in employees working in a selenium-processing plant.

METHODS

Twenty male employees of a selenium-processing plant (exposed) and 20 age-matched male individuals without occupational selenium exposure (controls) participated in the study. Exposure to selenium at the workplace was determined by personal air sampling. Internal exposure was assessed by measuring total selenium concentration in plasma after a workshift and after holidays as well as by measuring the selenium concentration in urine before and after shift and after holidays. The activity of glutathione peroxidase (GPx) in blood and the prothrombin time were determined as biological effect parameters.

RESULTS

The exposure to selenium in the workplace air ranged from 8 to 950 µg/m(3) and exceeded in a large part current occupational exposure limits. The selenium levels in plasma samples of the exposed ranged from 49 to 182 µg/L during exposure and were significantly higher than the plasma levels observed after holidays as well as in the control group. The selenium concentration in pre- and post-shift urine samples did not differ significantly, and the average urinary selenium levels of the employees (18-1,104 µg/g creatinine) were significantly higher than those measured after holidays or determined in controls. Both the concentration of selenium in plasma and in urine did not correlate with the current external exposure of the employees at the workplace. However, we found a strong and significant association between the two biomonitoring parameters. In spite of the considerable high external exposure to elemental selenium, we did not find any effect on the GPx activity in blood as well as on the prothrombin time.

CONCLUSIONS

Both the selenium levels in plasma and urine may be used as biological monitoring parameters for the assessment of chronic occupational exposure to selenium. Nevertheless, the toxicokinetics of the urinary excretion of selenium remain still unclear and require further investigations. Moreover, our findings emphasise the necessity of a re-evaluation of occupational exposure limits for elemental selenium and inorganic selenium compounds.

Blood levels of lead, cadmium, and mercury in the elderly living in institutionalized care in the Czech Republic

BACKGROUND

There is limited research examining the chemical load of toxic metals in the elderly. The aim of the present study was two-fold: to determine the body burden of lead, cadmium and mercury in association with age, gender, locality, lifestyle factors and potential health impacts among this population and to compare the values with blood values from the general Czech population aged 18-64 years.

METHODS

Lead, cadmium and mercury were examined in the blood of institutionalized senior citizens (46 males, 151 females aged 61-100 years) from two localities in the Czech Republic (Prague and Teplice) from 2009 through 2011. Measurements were made using inductively coupled plasma mass spectrometry (Pb, Cd) and a single purpose spectrometer AMA 254 (Hg).

RESULTS

Geometric means (GM) of whole blood lead (B-Pb), cadmium (B-Cd) and mercury (B-Hg) levels were 25.3μg/l, 0.55μg/l and 0.21μg/l, respectively. No age-related differences were found for B-Pb and B-Cd levels but a negative correlation with age was observed for B-Hg levels (p=0.04). B-Pb levels in men were significantly higher than in women (GM 29.9μg/l vs. 24.1μg/l). B-Cd was significantly higher in women (GM 0.57μg/l) than in men (0.50μg/l) (p=0.007) and in smokers (GM 1.29μg/l) than in nonsmokers (GM 0.53μg/l) (p=<0.001) and in seniors from Prague (GM 0.60μg/l) compared to those from Teplice (GM 0.43μg/l) (p=<0.001). Seniors with a history of chronic kidney disease, stroke and those using psycho-pharmaceuticals had higher B-Pb levels (p=0.008, 0.04 and 0.05, resp.), seniors diagnosed with atherosclerosis had higher B-Cd levels (p=0.002) and seniors using psycho-pharmaceuticals had higher B-Hg levels (p=0.07). B-Hg levels were also positively correlated with blood albumin levels (p=0.015).

CONCLUSIONS

This study provides data on levels of heavy metals in a group of elderly people. Such information is very scarce. Associations with diseases should be the subject of further investigation.

Blood and urine levels of heavy metal pollutants in female and male patients with coronary artery disease

BACKGROUND

Heavy metal pollutants such as cadmium (Cd), lead (Pb), and mercury (Hg) are rarely the subjects of cardiovascular research although they have been suspected for decades to negatively impact the circulatory system.

METHODS

Apart from detailed anamnestic data, urinary levels of Cd and full blood levels of Pb and Hg were measured in 53 female (mean age: 68.04±7.03 years) and 111 male (mean age: 60.68±11.43 years) nonsmoking or never-smoking patients with angiographically verified and precisely quantified coronary artery disease (CAD).

RESULTS

Although Cd was quantifiable in 68.3% of subjects, only 34.1% of these patients exceeded the critical 1 μg/L Human Biomonitoring (HBM)-I level. Median Pb (20 μg/L) and Hg (0.55 μg/L) levels were lower than the HBM-I, as well as reference levels of Pb. Wine consumption was the main source for Pb, fish and wine consumption for Hg, and previous nicotine abuse for Cd. There was no correlation between Cd, Pb, or Hg and severity of CAD although severity correlated positively with atherosclerosis parameters (uric acid, creatinine, triglycerides, blood urea nitrogen, C-reactive protein) and negatively with high density lipoprotein cholesterol.

CONCLUSION

Cd levels detected in CAD patients were high compared to German and European reference levels but it could not be proven that urine levels of Cd and blood levels of Hg or Pb played a major role in the genesis of CAD, particularly when compared to well-known biomarkers such as blood pressure, glucose, and lipids.

Global methylmercury exposure from seafood consumption and risk of developmental neurotoxicity: a systematic review

OBJECTIVE

To examine biomarkers of methylmercury (MeHg) intake in women and infants from seafood-consuming populations globally and characterize the comparative risk of fetal developmental neurotoxicity.

METHODS

A search was conducted of the published literature reporting total mercury (Hg) in hair and blood in women and infants. These biomarkers are validated proxy measures of MeHg, a neurotoxin found primarily in seafood. Average and high-end biomarkers were extracted, stratified by seafood consumption context, and pooled by category. Medians for average and high-end pooled distributions were compared with the reference level established by a joint expert committee of the Food and Agriculture Organization (FAO) and the World Health Organization (WHO).

FINDINGS

Selection criteria were met by 164 studies of women and infants from 43 countries. Pooled average biomarkers suggest an intake of MeHg several times over the FAO/WHO reference in fish-consuming riparians living near small-scale gold mining and well over the reference in consumers of marine mammals in Arctic regions. In coastal regions of south-eastern Asia, the western Pacific and the Mediterranean, average biomarkers approach the reference. Although the two former groups have a higher risk of neurotoxicity than the latter, coastal regions are home to the largest number at risk. High-end biomarkers across all categories indicate MeHg intake is in excess of the reference value.

CONCLUSION

There is a need for policies to reduce Hg exposure among women and infants and for surveillance in high-risk populations, the majority of which live in low-and middle-income countries.

Selenium for preventing cancer

BACKGROUND

This review is an update of the first Cochrane publication on selenium for preventing cancer (Dennert 2011).Selenium is a metalloid with both nutritional and toxicological properties. Higher selenium exposure and selenium supplements have been suggested to protect against several types of cancers.

OBJECTIVES

Two research questions were addressed in this review: What is the evidence for:1. an aetiological relation between selenium exposure and cancer risk in humans? and2. the efficacy of selenium supplementation for cancer prevention in humans?

SEARCH METHODS

We conducted electronic searches of the Cochrane Central Register of Controlled Trials (CENTRAL, 2013, Issue 1), MEDLINE (Ovid, 1966 to February 2013 week 1), EMBASE (1980 to 2013 week 6), CancerLit (February 2004) and CCMed (February 2011). As MEDLINE now includes the journals indexed in CancerLit, no further searches were conducted in this database after 2004.

SELECTION CRITERIA

We included prospective observational studies (cohort studies including sub-cohort controlled studies and nested case-control studies) and randomised controlled trials (RCTs) with healthy adult participants (18 years of age and older).

DATA COLLECTION AND ANALYSIS

For observational studies, we conducted random effects meta-analyses when five or more studies were retrieved for a specific outcome. For RCTs, we performed random effects meta-analyses when two or more studies were available. The risk of bias in observational studies was assessed using forms adapted from the Newcastle-Ottawa Quality Assessment Scale for cohort and case-control studies; the criteria specified in the Cochrane Handbook for Systematic Reviews of Interventions were used to evaluate the risk of bias in RCTs.

MAIN RESULTS

We included 55 prospective observational studies (including more than 1,100,000 participants) and eight RCTs (with a total of 44,743 participants). For the observational studies, we found lower cancer incidence (summary odds ratio (OR) 0.69, 95% confidence interval (CI) 0.53 to 0.91, N = 8) and cancer mortality (OR 0.60, 95% CI 0.39 to 0.93, N = 6) associated with higher selenium exposure. Gender-specific subgroup analysis provided no clear evidence of different effects in men and women (P value 0.47), although cancer incidence was lower in men (OR 0.66, 95% CI 0.42 to 1.05, N = 6) than in women (OR 0.90, 95% CI 0.45 to 1.77, N = 2). The most pronounced decreases in risk of site-specific cancers were seen for stomach, bladder and prostate cancers. However, these findings have limitations due to study design, quality and heterogeneity that complicate interpretation of the summary statistics. Some studies suggested that genetic factors may modify the relation between selenium and cancer risk-a hypothesis that deserves further investigation.In RCTs, we found no clear evidence that selenium supplementation reduced the risk of any cancer (risk ratio (RR) 0.90, 95% CI 0.70 to 1.17, two studies, N = 4765) or cancer-related mortality (RR 0.81, 95% CI 0.49 to 1.32, two studies, N = 18,698), and this finding was confirmed when the analysis was restricted to studies with low risk of bias. The effect on prostate cancer was imprecise (RR 0.90, 95% CI 0.71 to 1.14, four studies, N = 19,110), and when the analysis was limited to trials with low risk of bias, the interventions showed no effect (RR 1.02, 95% CI 0.90 to 1.14, three studies, N = 18,183). The risk of non-melanoma skin cancer was increased (RR 1.44, 95% CI 0.95 to 1.17, three studies, N = 1900). Results of two trials-the Nutritional Prevention of Cancer Trial (NPCT) and the Selenium and Vitamin E Cancer Trial (SELECT)-also raised concerns about possible increased risk of type 2 diabetes, alopecia and dermatitis due to selenium supplements. An early hypothesis generated by NPCT that individuals with the lowest blood selenium levels at baseline could reduce their risk of cancer, particularly of prostate cancer, by increasing selenium intake has not been confirmed by subsequent trials. As the RCT participants were overwhelmingly male (94%), gender differences could not be systematically assessed.

AUTHORS' CONCLUSIONS

Although an inverse association between selenium exposure and the risk of some types of cancer was found in some observational studies, this cannot be taken as evidence of a causal relation, and these results should be interpreted with caution. These studies have many limitations, including issues with assessment of exposure to selenium and to its various chemical forms, heterogeneity, confounding and other biases. Conflicting results including inverse, null and direct associations have been reported for some cancer types.RCTs assessing the effects of selenium supplementation on cancer risk have yielded inconsistent results, although the most recent studies, characterised by a low risk of bias, found no beneficial effect on cancer risk, more specifically on risk of prostate cancer, as well as little evidence of any influence of baseline selenium status. Rather, some trials suggest harmful effects of selenium exposure. To date, no convincing evidence suggests that selenium supplements can prevent cancer in humans.

Potentially-toxic and essential elements profile of AH1N1 patients in Mexico City

During spring of 2009, a new influenza virus AH1N1 spread in the world causing acute respiratory illness and death, resulting in the first influenza pandemic since 1968. Blood levels of potentially-toxic and essential elements of 40 pneumonia and confirmed AH1N1 were evaluated against two different groups of controls, both not infected with the pandemic strain. Significant concentrations of potentially-toxic elements (lead, mercury, cadmium, chromium, arsenic) along with deficiency of selenium or increased Zn/Cu ratios characterized AH1N1 cases under study when evaluated versus controlled cases. Deficiency of selenium is progressively observed from controls I (influenza like illness) through controls II (pneumonia) and finally pneumonia -AH1N1 infected patients. Cases with blood Se levels greater than the recommended for an optimal cut-off to activate glutathione peroxidase (12.5 μg/dL) recovered from illness and survived. Evaluation of this essential element in critical pneumonia patients at the National Institutes is under evaluation as a clinical trial.

Blood total mercury concentrations in the Canadian population: Canadian Health Measures Survey cycle 1, 2007-2009

OBJECTIVES

We present total mercury (THg) in blood of Canadians 6-79 years of age from the first to-date nationally-representative survey, the Canadian Health Measures Survey (CHMS). This analysis is particularly relevant in the context of recent changes to Health Canada's blood Hg guidance values.

METHODS

We used data from cycle 1 (2007-2009) of the CHMS, in particular focussing on 5,319 respondents aged 6-79 years for whom blood THg data were available. We calculated descriptive statistics of blood Hg levels and analyzed the associations between blood THg levels and relevant variables. We also compared blood THg levels to existing Health Canada blood Hg guidance values.

RESULTS

The geometric mean blood THg level of the Canadian population was 0.69 µg/L (95% CI 0.56-0.86 µg/L). The majority (97.8%) of Canadian women aged 16-49 years, including pregnant women, had blood Hg values below the provisional HC blood guidance value of 8 µg/L. Mean blood THg levels were significantly higher in the "other or mixed" (1.14 µg/L, p=0.0003) and Asian (1.41 µg/L, p=0.0476) groups compared to those who self-identified as solely Caucasian (0.62 µg/L). There was however no significant difference between participants self-identified as Aboriginal Canadians versus Caucasians (0.56 µg/L vs 0.62 µg/L, p=0.2902).Fish and shellfish consumption significantly influenced blood Hg levels, as did alcohol consumption and the presence of dental amalgams.

CONCLUSION

This paper presents the first description of blood THg levels in the general Canadian population. These findings will serve as a national baseline for monitoring future changes should they arise.

Mercury, arsenic and selenium exposure levels in relation to fish consumption in the Mediterranean area

In order to assess mercury (Hg), selenium (Se) and arsenic (As) exposure in the Mediterranean area, total mercury (THg), monomethylmercury (MeHg), Se and As levels were measured in umbilical cord blood and breast milk from Italian (n=900), Slovenian (n=584), Croatian (n=234) and Greek (n=484) women. THg, MeHg, As, and Se levels were also determined in blood samples of the same mothers from Italy and Croatia. In addition, THg and MeHg were determined in the same women's hair from all the countries involved in this study and As and Se levels were determined in the mother's urine samples from Italy, Croatia and Greece. Besides recording the consumption of other food items, the frequencies of fish consumption were assessed by detailed food frequency questionnaires, since fish represents an important source of Hg, Se and As in humans. The highest levels of THg and As were found in cord blood (Med((THg))=5.8 ng/g; Med((As))=3.3 ng/g) and breast milk (Med((THg))=0.6 ng/g; Med((As))=0.8 ng/g) from Greek women, while the highest Se levels were found in cord blood (Med=113 ng/g) from Italy. Significant linear correlations were found between Hg, Se and As in blood, cord blood and breast milk. In addition, significant relations were found between the frequencies of total fish consumption and biomarkers of As, MeHg and Se exposure, with the strongest Spearman rank coefficients between frequencies of total fish consumption and THg levels in cord blood (r(s)=0.442, p<0.001) or THg levels in hair (r(s)=0.421, p<0.001), and between frequencies of total fish consumption and As levels in cord blood (r(s)=0.350, p<0.001). The differences in Hg and As exposure between countries were probably due to different amounts of fish consumption and the consumption of different species of fish of different origin, while the highest Se levels in women from Italy were probably the consequence of the more frequent consumption of different non specific food items. Moreover, fish consumption, the possible common source of As, Hg and Se intake, could explain the correlations between the elements determined in cord blood, mother's blood or breast milk.

Dietary mercury exposure in a population with a wide range of fish consumption--self-capture of fish and regional differences are important determinants of mercury in blood

Human, low level, chronic exposure to mercury (Hg) from fish is of concern because of potential neurodevelopmental and cardiovascular toxicity. The purpose of the study was to 1) measure total mercury (THg) in blood and estimate dietary exposure in a population group with a wide range of seafood consumption, 2) assess the intake and blood concentration in relation to tolerable intake values, 3) characterise dietary sources, and 4) to investigate the relationship between dietary THg with THg in blood (BTHg), including factors that can explain the variance in BTHg concentrations. The participants (n=184) filled in an extensive food frequency questionnaire which was combined with a database on THg concentrations in Norwegian food, and donated blood and urine. Median consumption of seafood was 65 g/day (range 4 to 341 g/day). The calculated mean dietary THg exposure was 0.35 (median 0.30) μg/kg body weight/week. Seafood contributed on average 95% to the exposure. The JECFA Provisional Tolerable Weekly Intake (PTWI) of 1.6 μg MeHg/kg bw/week was not exceeded by any of the participants. BTHg ranged from 0.6 to 30 μg/L, with a mean of 5.3 (median 4.0 μg/L). There was a strong relationship between total seafood consumption and BTHg concentrations (r=0.58 95%CI: 0.48, 0.67) and between estimated THg dietary exposure and BTHg (r=0.46 95%CI: 0.35, 0.57). Fish consumption, sex, catching >50% of their seafood themselves, and living in coastal municipalities were significant factors in linear regression models with lnBTHg. Including urinary Hg in the regression model increased the explained variance from 54% to 65%. In a toxicokinetic model, the calculated dietary intake appeared to moderately underestimate the measured BTHg among the participants with the highest BTHg. Only two of the participants had BTHg slightly above a value equivalent to the JECFA PTWI, but none of them were women in fertile age.

Blood selenium concentration in a selected population of children inhabiting industrial regions in Upper Silesia (Poland)

PURPOSE

Present study aimed at determining blood selenium concentration (Se-B) in a selected population of children inhabiting industrial regions.

METHODS

The studies were conducted on a group of 267 children inhabiting industrial regions in Upper Silesia (Poland). Determination of Se-B was performed using hydride generation atomic absorption technique.

RESULTS

In the studied group of children mean Se-B amounted to 76.75±12.52μg/L. Only in 38.20% of studied children the estimated Se-B could be regarded as an optimal. Children with underweight (BMI<15th centile) manifested a significantly lower Se-B than children with BMI within the normal range (BMI 15-85th centile). In the entire study group of children a significant positive linear correlation was disclosed between BMI and Se-B (r=0.16, p<0.05). Regression analysis demonstrated that in the studied subgroup of children (with normal height, body mass and BMI) a higher BMI represented an independent factor of Se-B increase and a more pronounced age an independent factor of Se-B decrease. Moreover, maternal education represented an independent factor of Se-B increase in the studied group of children (with normal height, body mass and BMI).

CONCLUSIONS

Se-B in the studied group children from industrial area in Upper Silesia corresponded with the lower range of blood selenium concentrations noted in recent years in other populations. A negative relationship was documented between age and Se-B and a positive relationship between BMI of a child and maternal education on one hand and Se-B of a child on the other.

Daily intake of selenium and concentrations in blood of residents of Riyadh City, Saudi Arabia

Concentrations of selenium (Se) in food from local markets of Riyadh, Kingdom of Saudi Arabia (KSA) were measured and daily intake calculated based on information from a questionnaire of foods eaten by healthy Saudis. The daily intake of Se was then compared to concentrations of Se in blood serum. Primary sources of Se in the diet of Saudis were as follows: meat and meat products (31%), egg (20.4%), cereals and cereal products (16%), legumes (8.7%), fruits (6.8%), milk and dairy products (2.0%), beverages (2%), sweets (1.8%), pickles (0.2%), and oil (0.02%). Daily intake of Se, estimated to be 93 μg Se/person/day, was slightly greater than that calculated from the Food and Agriculture Organization (FAO) food balance sheet for KSA, which was approximately 90 μg Se/person/day. The daily intake of Se by Saudis in Riyadh was greater than that of Australians or Dutch but less that of Canadians and Americans. There was a statistically significant correlation (R = +0.38, P < 0.05) between daily intake of Se and concentrations of Se in blood serum of Saudis in Riyadh. The mean concentration of Se in serum was 1.0 × 10(2) ± 30.5 μg Se/l. Taken together, the results suggest that the average Se intake and Se serum concentrations are within the known limits and recommendations, making it unlikely that Saudis are on average at risk of deficiency or toxicity.

Reference values for lead, cadmium and mercury in the blood of adults from the metropolitan area of Sao Paulo, Brazil

Human biomonitoring is an important tool for the evaluation of environmental exposure to contaminants. The data that are obtained from these studies might be compared to appropriate reference values (RVs) in a specific population. The RVs were derived from the rounded values of the upper limit of the 95th confidence interval of the 95th percentile for lead (Pb), cadmium (Cd) and mercury (Hg) in blood from adults in the metropolitan area of Sao Paulo (MASP), Brazil to investigate the association between blood metals and sociodemographic and lifestyle factors. Blood samples from 653 nonsmoking blood donors without occupational exposure to the studied metals were collected in 2006. Our evaluations distinguished a younger group (18-39 years) and an older group (40-65 years). RVs in the younger group were 60 μgPb/L and 4 μgHg/L for men and 47 μgPb/L and 4 μgHg/L for women. RVs in the older group were 80 μgPb/L and 5 μgHg/L for men and 63 μgPb/L and 6 μgHg/L for women. The RV for Cd was 0.6 μg/L for adults aged 18-65 years. Pb and Cd levels demonstrated a significant association with sex and age. Male blood contained 50% more Pb, and the older group exhibited 23% more Pb. Fish consumption and amalgam fillings were primarily related to Hg levels. RVs for lead were similar to the Czech Republic and Germany but higher than the US population. The RV for Cd in Brazil was well below the RVs of these countries. The RVs for Hg in Brazil were similar to the US but higher than Germany and the Czech Republic.

Whole blood selenium levels in healthy adults from the west of Algeria

The purpose of this study was to assess whole blood selenium levels of 300 healthy adults living in four selected areas of the west of Algeria. Selenium was measured using differential pulse cathodic stripping voltammetry with a detection limit of 29.20 μg/L. The mean of whole blood selenium concentrations was 85.65 ± 21.60 μg/L ranging between 30.90 and 144.04 μg/L. This concentration did not vary significantly (P > 0.05) in relation to the gender of the subject, with concentrations of 87.75 ± 21.30 μg/L in men and 83.95 ± 21.60 μg/L in women group. Individuals older than 60 years had a whole blood selenium concentration significantly lower than the rest of the population. However, the measured selenium concentrations in the residential areas were not statistically different (P > 0.05). A total of 32 (10.70%) individuals exhibited whole blood selenium level below 60 μg/L. These results are similar to those of some European countries but are much lower than data observed in USA or seleniferous regions.

Gender differences for associations between circulating levels of metals and coronary risk in the elderly

Several studies have pointed out associations between various metals and cardiovascular disease. Since cardiovascular disease prevalence is different between males and females, we investigated whether circulating levels of metals related differently to coronary risk in men and women. In the Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS) study, coronary risk was assessed by the Framingham Risk Score together with circulating blood levels of 11 different trace and heavy metals in 1016 subjects aged 70 years. Circulating levels of cadmium, copper and manganese were significantly higher in women than in men, while mercury, zinc and lead were significantly lower following adjustment for kidney function (measured by glomerular filtration rate, GFR). No significant differences between women and men were seen regarding levels of aluminium, molybdenum, cobalt, chromium and nickel. When all 11 metals were entered as independent variables together with GFR in multiple models in the Framingham Risk Score as the dependent variable, cadmium was the major determinant of the Framingham Risk Score in women (p<0.0001, followed by zinc p=0.03), while copper was the major determinant of the Framingham Risk Score in men (p<0.0001, followed by inverse relations vs. aluminium p=0.01 and nickel p=0.01). There are gender differences in levels of metals and also regarding the association between metals and coronary risk, with cadmium levels being most important for women and copper levels for men in this elderly population.

Internal exposure to trace elements in non-smoking residents living in a northern Taiwan industrial city

A total of 94 (54 males, 40 females) healthy adult residents living in an industrial city in northern Taiwan were recruited to study their exposure to industrial metals by measuring their blood levels of V, Cr, Mn, Ni, Co, As, Se, Mo, Cd, Pb, and W. All participants were non-smokers without obvious direct occupational exposure to these elements, although by working in administrative sectors in industrial facilities their indirect or potential exposure was increased. The average concentrations of V, Cr, Mn, Ni, Co, As, Se, Mo, Cd, Pb, and W in blood were 0.30, 1.49, 15.1, 3.84, 2.73, 21.1, 204, 3.2, 0.76, 51.1, and 0.40 ng/mL, respectively. These values were significantly higher than reference values reported for the general population, in some cases exceeding those of occupationally exposed workers. The principal component and correlation analyses among blood element levels suggested that the predominant sources of exposure were glass manufacturing and traffic-related sources. Despite of some limitations, the study demonstrates that the residents in this industrial area may suffer adverse chronic health effects attributable to exposures to these elements.

Selenium for preventing cancer

BACKGROUND

Selenium is a trace element essential to humans. Higher selenium exposure and selenium supplements have been suggested to protect against several types of cancers.

OBJECTIVES

Two research questions were addressed in this review: What is the evidence for1. an aetiological relationship between selenium exposure and cancer risk in women and men?2. the efficacy of selenium supplementation for cancer prevention in women and men?

SEARCH STRATEGY

We searched electronic databases and bibliographies of reviews and included publications.

SELECTION CRITERIA

We included prospective observational studies to answer research question (a) and randomised controlled trials (RCTs) to answer research question (b).

DATA COLLECTION AND ANALYSIS

We conducted random effects meta-analyses of epidemiological data when five or more studies were retrieved for a specific outcome. We made a narrative summary of data from RCTs.

MAIN RESULTS

We included 49 prospective observational studies and six RCTs. In epidemiologic data, we found a reduced cancer incidence (summary odds ratio (OR) 0.69 (95% confidence interval (CI) 0.53 to 0.91) and mortality (OR 0.55, 95% CI 0.36 to 0.83) with higher selenium exposure. Cancer risk was more pronouncedly reduced in men (incidence: OR 0.66, 95% CI 0.42 to 1.05) than in women (incidence: OR 0.90, 95% CI 0.45 to 1.77). These findings have potential limitations due to study design, quality and heterogeneity of the data, which complicated the interpretation of the summary statistics.The RCTs found no protective efficacy of selenium yeast supplementation against non-melanoma skin cancer or L-selenomethionine supplementation against prostate cancer. Study results for the prevention of liver cancer with selenium supplements were inconsistent and studies had an unclear risk of bias. The results of the Nutritional Prevention of Cancer Trial (NPCT) and SELECT raised concerns about possible harmful effects of selenium supplements.

AUTHORS' CONCLUSIONS

No reliable conclusions can be drawn regarding a causal relationship between low selenium exposure and an increased risk of cancer. Despite evidence for an inverse association between selenium exposure and the risk of some types of cancer, these results should be interpreted with care due to the potential limiting factors of heterogeneity and influences of unknown biases, confounding and effect modification.The effect of selenium supplementation from RCTs yielded inconsistent results. To date, there is no convincing evidence that selenium supplements can prevent cancer in men, women or children.

Association of blood mercury concentrations with atopic dermatitis in adults: a population-based study in Korea

Atopic dermatitis is one of the most common inflammatory skin diseases among children and adults. Although the risk factors for atopic dermatitis have not yet been fully identified, exposure to mercury may be an important environmental risk factor. The objective of this study was to evaluate the association between mercury body burden and prevalence of atopic dermatitis in an adult population. We recruited participants (n=1990) aged 20 years or older, using stratified random sampling of Korean census blocks. Demographic characteristics and medical history of atopic dermatitis were collected from participants by questionnaire, and mercury levels were determined by an analysis of blood samples. We found that demographic factors such as sex, age, alcohol drinking status, income, and fish or shellfish consumption were important covariates determining blood mercury concentration. Sex and cigarette smoking status were important demographic variables affecting the prevalence of atopic dermatitis. After adjusting for demographic factors, blood mercury concentrations were positively associated with lifetime prevalence of atopic dermatitis [odds ratio (OR), highest vs. lowest tertile=1.50; 95% confidence interval (CI), 1.02-2.21; p for trend=0.057]. This association became stronger for 1-year prevalence of atopic dermatitis (OR, highest vs. lowest tertile=1.82; 95% CI, 1.17-2.83; p for trend=0.026). Mercury body burden and atopic dermatitis prevalence vary across demographic characteristics, and increased blood level of mercury was related to an incidence of atopic dermatitis in this adult population.

Assessment of reference ranges for blood Cu, Mn, Se and Zn in a selected Italian population

The reference ranges for blood Cu, Mn, Se and Zn of 215 adult subjects non-occupationally exposed and living in the Nuoro province (Sardinia, insular Italy) were assessed. Metals were determined by sector field inductively coupled plasma mass spectrometry after microwave-assisted acid digestion of blood. The blood reference ranges estimated as P5-P95 percentiles (geometric mean, GM) were 776-1495μg/L (1036μg/L) for Cu; 4.73-17.0μg/L (8.91μg/L) for Mn; 106-185μg/L (140μg/L) for Se and 4686-8585μg/L (6418μg/L) for Zn. These results were then stratified for sex, age, alcohol consumption, smoking habit and living area. The GM value of Cu was significantly higher in females (1127μg/L) than in males (957μg/L). Age, alcohol intake, smoking habit and residential area did not influence blood Cu. The GM of Mn was significantly higher in females (9.98μg/L) respect to males (8.01μg/L) and in drinkers (9.67μg/L) compared to non-drinkers (8.38μg/L). The other variables did not change the Mn data. Selenium concentrations did not differ significantly as a function of individuals factors. With reference to Zn, males had GM of 6804μg/L and females of 6031μg/L, and more blood Zn was found in subjects consuming alcohol (6618μg/L) respect to abstainers (6155μg/L). In addition, blood Zn was not affected by age, smoking habit and place of living.

The mercury burden of the Czech population: An integrated approach

In this paper an integrated approach in assessment of the population exposure from various sources of total mercury (THg) oral intake in the Czech Republic is presented. The information on total mercury levels in diet, drinking water, surface urban soil and body fluids and tissues stem from the Czech national Environmental Health Monitoring System (EHMS) operated since 1994. The THg concentration was determined by the special atomic absorption spectrophotometer AMA 254. The data on THg content in food from the sales network were collected in 12 cities. The estimated average dietary intake representing more than 95% of weight of usual diet composition ranged 1-2% of the JECFA/FAO WHO provisional tolerable weekly intake (PTWI) value for total mercury (5 microg/kg b.w./week). Data on drinking water quality stem from the nationwide monitoring database. The content of THg in drinking water is generally low; only 0.2% of the Czech population supplied with drinking water from the distribution networks (total of 92% of the population) has a mercury intake from drinking water higher than 1% PTWI and not exceeding 5% PTWI. The estimation of potential mercury intake by unintentional consumption of soil in small children was based on THg content in surface soil of a total of 324 nursery schools in 24 cities and towns. Median value was 0.16 mg/kg. Human biomonitoring was performed in 9 Czech cities. In 2007, the mercury median values in blood of adults (N=412) were 0.85 and 0.89 microg/l in males and in females, respectively; urine median value in adults was 1.10 microg/g creatinine. In 2008, the blood median value in children (N=324) amounted to 0.35 microg/l; urine median value is 0.16 microg/g creatinine. In children's hair the median THg value was 0.18 microg/g. The correlation between fish consumption and blood THg levels was observed in both adults and children. Also the biomonitoring outputs did not reveal a substantial burden of the population.

Dietary habits of Greek adults and serum total selenium concentration: the ATTICA study

PURPOSE

The trace element selenium is an essential micronutrient for human health, and its low levels in serum are implicated in the pathogenesis of several chronic diseases. The determination of total serum selenium levels may contribute to the assessment of the health status of all populations. Since the serum selenium levels are highly affected by diet, we assessed its association with the dietary habits of Greek adults.

METHODS

Serum selenium levels were determined with inductively coupled plasma mass spectrometry in a cohort of 506 participants (men: 296, women: 210) aged 18-75 from the ATTICA study. Food consumption was evaluated with a validated food-frequency questionnaire.

RESULTS

Evaluation of the relationship between serum total selenium with major food groups and beverages by multi-adjusted analysis revealed that serum selenium was positively correlated with the consumption of red meat (2.37 ± 0.91, p = 0.01) while the consumption of other selenium-containing foods (i.e., fish, cereals, dairy products, vegetables) did not demonstrate such a relationship. Moreover, principal component analysis revealed that the adoption of a vegetarian type of diet is inversely correlated with total selenium (-3.94 ± 2.28, p = 0.08).

CONCLUSIONS

Among the dietary habits that were examined, red meat seems to be the major determinant of serum selenium in Greek adults.

Sex-dependent alterations in erythrocyte trace element levels and antioxidant status after a month of moderate daily red wine consumption

OBJECTIVE

We tested the hypothesis whether trace elements and antioxidant status change in a sex-dependent manner may contribute to sex-dependent hepatic effects of moderate daily wine consumption.

PATIENT AND METHODS

Twenty-one healthy young men and women were enrolled to this study who consumed red wine 0.3 and 0.2 l per day, respectively, for a month. Blood was taken at baseline (BV) and at end of the study (EV). Red cell trace element levels, red cell and plasma antioxidant status and serum routine blood chemistry were assessed at baseline and at the end of the study.

RESULTS

No sign of hepatotoxicity was detected. BV level of some trace elements (i.e. Zn, Pb) and Zn/Cu ratios were higher in women than in men. Ca, Mg, Pb, Sr and Zn levels and the Zn/Cu ratio had lower EV than BV in women. In men, Al, Ca, Li, Pb and Sr levels had lower EV than BV. The tested antioxidant parameters improved in both the sexes.

CONCLUSION

Although no hepatotoxicity was observed, changes in trace element content were detected after 1 month of moderate red wine consumption. The most remarkable sex-specific alteration was the decrease of Zn levels and of the Zn/Cu ratio in women. Given the protective effect of Zn against liver damage, this finding suggests a possible contribution of decreased Zn levels to sex-dependent effects of red wine.

Genetic background of lead and mercury metabolism in a group of medical students in Austria

BACKGROUND

Information on the impact of genetic predisposition on metal toxicokinetics in the human body is limited. There is increasing evidence that certain genetic polymorphisms modify lead and mercury toxicokinetics. This called for analysis of further candidate genes.

OBJECTIVES

Medical students (N=324) were examined in order to detect potential associations between lead exposure and polymorphisms in HFE, VDR, ALAD, and MT genes, as well as between mercury exposure and GSTT1, GSTM1, GSTA1, GSTP1, GCLC, and MT polymorphisms.

METHODS

The levels of lead and mercury exposure of students were determined by blood, urine, and hair analyses (ICP-MS, CV-AAS). Genotyping of common polymorphisms was examined by MALDI-TOF MS and the TaqMan methodology. Associations between lead and mercury exposures and genetic background were examined by bivariate analysis, and by categorical regression analysis (CATREG) controlled by metal- and matrix-specific variables.

RESULTS

Lead and mercury levels in urine, blood, and hair indicated low exposures. VDR polymorphism and joint presence of VDR/ALAD polymorphisms were significantly and independently associated with urine lead concentrations (CATREG P<0.05). Polymorphisms in GSTP1-114 and MT4 genes as well as dual gene combinations including GSTP1, GCLC, GSTT1, and GSTM1 polymorphisms were independent variables related to mercury body burdens (CATREG P<0.05). GSTP1-114/GSTT1 and GSTP1-105/GCLC combinations showed synergistic effects on hair mercury levels compared to single-gene variants.

CONCLUSIONS

We found evidence that certain genetic backgrounds were associated with lead and mercury metabolism, suggesting gene-environment and gene-gene-environment interactions. The modes of interaction remain to be evaluated.

Serum selenium and selenoprotein P status in adult Danes - 8-year followup

Selenium is an essential micronutrient important to human health. The main objective of this study is to describe serum selenium and selenoprotein P status in two samples of the Danish population. In addition, the influence of various factors potentially associated with selenium status was investigated. Blood samples from a total of 817 randomly selected subjects from two cities in Denmark were analyzed. Half of the samples were collected in 1997-1998 and the other half in 2004-2005. Samples from women aged 18-22, 40-45 and 60-65 years, and men aged 60-65 years were selected for this study. All subjects had filled in a food frequency questionnaire (FFQ) and a questionnaire with information about smoking habits, alcohol consumption and exercise habits. Mean serum selenium level was 98.7+/-19.8microg/L and median selenoprotein P level was 2.72 (2.18-3.49)mg/L. Serum selenium and selenoprotein P increased with age, and selenoprotein P was higher in men than in women. Serum selenium levels decreased by 5% on average from 1997-98 to 2004-05 (P<0.001), whereas selenoprotein P level increased (P<0.001). The intake of fish correlated weakly with serum selenium level (r=0.14, P<0.001) but not with selenoprotein P level. Smoking status, alcohol intake, exercise habits, BMI and medicine use did not influence selenium status. It is concluded that selenium status in this Danish population is at an acceptable level. No major groups with regard to age, sex or lifestyle factors could be identified as being in risk for selenium deficiency.

Biomarkers of mercury exposure at a mercury recycling facility in Ukraine

This study evaluates biomarkers of occupational mercury exposure among workers at a mercury recycling operation in Gorlovka, Ukraine. The 29 study participants were divided into three occupational categories for analysis: (1) those who worked in the mercury recycling operation (Group A, n = 8), (2) those who worked at the facility but not in the yard where the recycling was done (Group B, n = 14), and (3) those who did not work at the facility (Group C, n = 7). Urine, blood, hair, and nail samples were collected from the participants, and a questionnaire was administered to obtain data on age, gender, occupational history, smoking, alcohol consumption, fish consumption, tattoos, dental amalgams, home heating system, education, source of drinking water, and family employment in the former mercury mine/smelter located on the site of the recycling facility. Each factor was tested in a univariate regression with total mercury in urine, blood, hair, and nails. Median biomarker concentrations were 4.04 microg/g-Cr (urine), 2.58 microg/L (blood), 3.95 microg/g (hair), and 1.16 microg/g (nails). Occupational category was significantly correlated (p < 0.001) with both blood and urinary mercury concentrations but not with hair or nail mercury. Four individuals had urinary mercury concentrations in a range previously found to be associated with subtle neurological and subjective symptoms (e.g., fatigue, loss of appetite, irritability), and one worker had a urinary mercury concentration in a range associated with a high probability of neurological effects and proteinuria. Comparison of results by occupational category found that workers directly involved with the recycling operation had the highest blood and urinary mercury levels. Those who worked at the facility but were not directly involved with the recycling operation had higher levels than those who did not work at the facility.

Selenium in food and the human body: a review

Selenium levels in soil generally reflect its presence in food and the Se levels in human populations. Se food content is influenced by geographical location, seasonal changes, protein content and food processing. Periodic monitoring of Se levels in soil and food is necessary. Diet is the major Se source and approximately 80% of dietary Se is absorbed depending on the type of food consumed. Se bioavailability varies according to the Se source and nutritional status of the subject, being significantly higher for organic forms of Se. Se supplements can be beneficial for subjects living in regions with very low environmental levels of Se. Several strategies have been followed: (1) employment of Se-enriched fertilizers; (2) supplementation of farm animals with Se; (3) consumption of multimicronutrient supplements with Se. Nevertheless, detailed investigations of possible interactions between Se supplements and other food components and their influence on Se bioavailability are needed. Suppliers also need to provide more information on the specific type of Se used in supplements. In addition, research is lacking on the mechanisms through which Se is involved in hepatocyte damage during hepatopathies. Although Se potential as an antioxidant for the prevention of cardiovascular diseases (CVD) is promising, additional long-term intervention trials are necessary. As a result, indiscriminate Se supplements cannot be reliably recommended for the prevention of CVD in human beings. Some interesting findings reported an association of Se intake with a reduced prevalence and risk for prostate and colon cancer. However, random trials for other cancer types are inconclusive. As a final conclusion, the general population should be warned against the employment of Se supplements for prevention of hepatopathies, cardiovascular or cancer diseases, because benefits of Se supplementation are still uncertain, and their indiscriminate use could generate an increased risk of Se toxicity.