Selenium exposure and depressive symptoms: the Coronary Artery Risk Development in Young Adults Trace Element Study

Reliability of low mass toenail samples as biomarkers of chronic metal exposure

BACKGROUND

Toenails are a promising matrix for chronic metal exposure assessment, but there are currently no standard methods for collection and analysis. Questions remain about sample mass requirements and the extent to which metals measured in this matrix are representative of chronic body burden.

OBJECTIVE

This study proposes a method to maximize sample conservation for toenail metals analysis using inductively coupled plasma mass spectrometry (ICP-MS). We demonstrate the reliability of an ~25 mg toenail sample (typically 1-2 clippings) for metals analysis and evaluate the intra-individual variability of multiple metals in this matrix over time in men from the Gulf Long-term Follow-up (GuLF) Study.

METHODS

Toenail samples from 123 GuLF Study participants were collected at two visits 3 years apart and analyzed for 18 elements using ICP-MS. Participants with samples exceeding 200 mg at the first visit (n = 29) were selected for triplicate sub-sample analysis. Kendall's coefficient of concordance (W) was used to assess sub-sample reliability and Spearman's correlation coefficients (ρ) were used to evaluate fluctuations in elemental concentrations over time.

RESULTS

Results were not reported for Cd, Co, Mo, Sb, and V (detected in <60% of the samples). There was strong agreement among triplicate samples (Kendall's W: 0.72 (Cu)-0.90 (Cu)) across all elements evaluated, moderate correlations of elemental concentrations (Spearman's ρ: 0.21-0.42) over 3 years for As, Ca, Cr, Fe, Pb, Mn, and Zn, and strong correlations (>0.50) for Se, Cu, and Hg.

IMPACT STATEMENT

This toenail reliability study found that a low-mass (~25 mg) toenail sample (1-2 clippings) is suitable for the determination of most elements using ICP-MS and helps to increase the analytical capacity of limited toenail biospecimens collected in cohort studies. The results highlight differences in the suitability of toenails for chronic metal exposure assessment by element and underscore the need to consider intra-person variability, especially when comparing results across studies. We also provide recommendations for analytical standardization and the partitioning of the total collected toenail sample into multiple analytic sub-samples for future studies using toenail biospecimen for multiple assays.

Association between selenium intake and migraine: a nationwide cross-sectional study

Background

Dietary interventions for migraine are receiving increasing attention. However, it remains unclear whether there is any relationship between migraine and selenium intake. The aim of this study was to investigate the association between selenium intake and migraine.

Methods

We used multivariate logistic regression equations to explore the association between selenium intake and migraine. Restricted cubic splines were used to examine the presence of non-linear relationships. Upon finding a non-linear relationship, a recursive algorithm was used to calculate the inflection point. Population differences were also explored through stratified analysis.

Results

In the model adjusted for all covariates, the ORs (95% CI) for the association between selenium intake and migraine were 0.96 (0.88, 1.04), which was no statistical significance. However, the result of the linear trend test with quadrilles of selenium intake indicated the association between selenium intake and migraine may be non-linear. The restricted cubic splines confirmed this non-linear relationship, finding an inflection point (93.1 mcg/day), where the odds of migraine decreased with increasing selenium intake before the inflection point, and no statistically significant relationship was found after the inflection point. The association between selenium intake and migraine was non-linear in all strata except the obese.

Conclusion

We found a non-linear association between selenium intake and migraine in the general American population.

Appropriate Macronutrients or Mineral Elements Are Beneficial to Improve Depression and Reduce the Risk of Depression

Depression is a common mental disorder that seriously affects the quality of life and leads to an increasing global suicide rate. Macro, micro, and trace elements are the main components that maintain normal physiological functions of the brain. Depression is manifested in abnormal brain functions, which are considered to be tightly related to the imbalance of elements. Elements associated with depression include glucose, fatty acids, amino acids, and mineral elements such as lithium, zinc, magnesium, copper, iron, and selenium. To explore the relationship between these elements and depression, the main literature in the last decade was mainly searched and summarized on PubMed, Google Scholar, Scopus, Web of Science, and other electronic databases with the keywords "depression, sugar, fat, protein, lithium, zinc, magnesium, copper, iron, and selenium". These elements aggravate or alleviate depression by regulating a series of physiological processes, including the transmission of neural signals, inflammation, oxidative stress, neurogenesis, and synaptic plasticity, which thus affect the expression or activity of physiological components such as neurotransmitters, neurotrophic factors, receptors, cytokines, and ion-binding proteins in the body. For example, excessive fat intake can lead to depression, with possible mechanisms including inflammation, increased oxidative stress, reduced synaptic plasticity, and decreased expression of 5-Hydroxytryptamine (5-HT), Brain Derived Neurotrophic Factor (BDNF), Postsynaptic density protein 95(PSD-95), etc. Supplementing mineral elements, such as selenium, zinc, magnesium, or lithium as a psychotropic medication is mostly used as an auxiliary method to improve depression with other antidepressants. In general, appropriate nutritional elements are essential to treat depression and prevent the risk of depression.

The Relationship Between Serum Selenium Level, Cognitive Functions, and Depression in Patients With Chronic Kidney Disease

Introduction Impairment of cognitive functions can commonly develop in patients with chronic kidney disease (CKD) and increase morbidity and mortality. The antioxidant activity of selenium reduces cognitive decline by protecting neurons from free radical damage. We aimed to explore the associations between serum selenium levels, cognitive impairment, and depression in CKD patients in this research. Methods In this prospective cross-sectional research, 100 participants between the ages of 20 and 65 were included, and four groups of 25 patients each were formed (control group, stage 3-4 CKD, peritoneal dialysis [PD], hemodialysis [HD]). The Standardized Mini Mental Test (sMMT) was used to measure cognitive skills, and the Beck Depression Inventory (BDI) was utilized to diagnose depression. Simultaneously, measurements of serum selenium levels were done from collected blood samples. Results Cognitive impairment was detected in 4% of the control group, 16% of CKD patients (n=75), and 30% of the dialysis patients (n=50). Depression was found in 16% of the control group, 40% of the stage 3-4 CKD group, 50% of the PD group, and 44% of the HD group. In the control group, sMMT scores were higher than the other groups (p<0.001 for all), while the BDI score was statistically significantly lower (p=0.003). Serum selenium levels were found to be higher than HD and PD groups in patients with non-dialysis CKD and control groups in the post hoc analyses (p=0.001, p<0.001, p<0.001, p<0.001, respectively). Conclusion Depression and cognitive impairment are particularly prevalent in CKD and dialysis patients. Our results indicate serum selenium insufficiency may be related to depression and cognitive impairment in this patient group. Nonetheless, these findings need to be confirmed by larger-scale studies.

Role of selenium in type 2 diabetes, insulin resistance and insulin secretion

Selenium is a trace mineral essential for life that acts physiologically through selenoproteins. Among other actions, the endogenous antioxidant selenoprotein glutathione peroxidase and the selenium transporter in blood, selenoprotein P, seem to play an important role in type 2 diabetes mellitus and insulin resistance by weakening the insulin signaling cascade through different mechanisms. Recent findings also suggest that selenoproteins also affect insulin biosynthesis and insulin secretion. This review discussed the role of selenium in type 2 diabetes and the complex interplay between selenoproteins and insulin pathways.

Mendelian randomization investigation highlights different roles of selenium status in mental disorders

Observational studies have suggested a relationship between selenium status and mental disorders (MDs). However, it remains unclear whether selenium status was causally associated with MDs. Thus, we performed a two-sample Mendelian randomization analysis using genome-wide association studies (GWAS) summary statistics to investigate the causal effects of selenium levels on seven MDs, including schizophrenia, major depressive disorder (MDD), autism spectrum disorder (ASD), bipolar disorder (BD), anorexia nervosa (AN), attention-deficit/hyperactivity disorder (ADHD), and panic disorder (PD). Strong genetic instruments of blood selenium (n = 9) and blood-toenail selenium (n = 12) were applied to the above seven MDs GWAS datasets from Psychiatric Genomics Consortium, which were further replicated in the FinnGen Biobank. The inverse-variance weighted method was employed to calculate the causal effects. The results showed that genetically predicted blood selenium levels were associated with a decreased risk of schizophrenia (odds ratio [OR] = 0.90, 95% CI: 0.87-0.95) and AN (OR = 0.87, 95% CI: 0.77-0.97). However, both blood and blood-toenail selenium levels were linked to an increased risk of MDD (blood: OR = 1.08, 95% CI: 1.05-1.12; blood-toenail: OR = 1.08, 95% CI: 1.04-1.13) and ASD (blood: OR = 1.11, 95% CI: 1.05-1.17; blood-toenail: OR = 1.13, 95% CI: 1.05-1.21), respectively. No obvious associations were found between selenium levels and BD as well as ADHD. Our findings highlighted a protective role of selenium in SZ and AN, while a risk effect in MDD and ASD. Further studies are required to verify the underlying mechanism mediating the unequal effects of Se on different MDs, which will pave a new path for the intervention of MDs.

Dietary factors, risk of developing depression, and severity of its symptoms in older adults-A narrative review of current knowledge

Depression is one of the most common diseases in the older population. Difficulties in recognizing its etiology and recurrence make depression a major challenge for health care professionals. The risk of developing depression is influenced by many factors, including lifestyle and diet. Research studies have shown a relationship between the consumption of specific macro- and microelements and depression. However, so far, no nutritional recommendations on how to reduce the risk of the disease and its relapses in older adults have been developed. This review outlines research results of conducted studies and focuses on both basic and potentially promising elements of diet, such as proteins, carbohydrates, fats, dietary fiber, vitamins (D, E, C, and B), and microelements such as magnesium, zinc, selenium, or iron.

Early pregnancy essential and non-essential metal mixtures and maternal antepartum and postpartum depressive symptoms

BACKGROUND

Mood disorders are common during and after pregnancy, and environmental metals may contribute to increased risk. Antepartum metal exposures have not been well characterized in relation to maternal depression. We evaluated the extent to which early pregnancy erythrocyte concentrations of essential and non-essential metals were prospectively associated with antepartum and postpartum depressive symptoms.

METHODS

Participants were 1226 women in Project Viva, a longitudinal cohort recruited during pregnancy (1999-2002). We measured concentrations of 11 metals in maternal first trimester erythrocytes (arsenic, barium, cadmium, cesium, copper, mercury, magnesium, manganese, lead, selenium, zinc). Using the Edinburgh Postnatal Depression Scale (EPDS), we assessed elevated depressive symptoms (≥13; 0-30 scale) at mid-pregnancy and at 6 and 12 months postpartum. We applied latent class mixed modeling to identify symptom trajectories. Adjusting for maternal sociodemographics and co-exposures, we examined associations between the metal mixture and depressive symptoms using logistic (for EPDS≥13)/multinomial (for symptom trajectories) regression and quantile g-computation.

RESULTS

In this cohort of moderately high socioeconomic status participants (e.g., 72 % college graduate), low-level metal concentrations were weakly to moderately correlated (Spearman: -0.24 to 0.59); the prevalence of depressive symptoms ranged from 9 % (mid-pregnancy) to 6 % (12 months postpartum); and three trajectories (stable low; elevated mid-pregnancy, then decreasing; moderate mid-pregnancy, then increasing) best fit the EPDS data. The early pregnancy erythrocyte metal mixture was not associated with maternal depressive symptoms in logistic, multinomial, or mixture models. For individual metals, most confidence intervals (CI) included the null. There was weak evidence that arsenic, lead, and selenium were moderately associated with elevated odds of depressive symptoms and/or trajectories. However, the odds ratios (95 % CI) per doubling of these three metals were imprecise [e.g., arsenic: 1.13 (0.94, 1.40) for EPDS≥13 at six months postpartum; lead: 1.19 (0.80, 1.77) for EPDS≥13 at mid-pregnancy; selenium: 2.35 (0.84, 6.57) for elevated mid-pregnancy, then decreasing versus stable low trajectory].

DISCUSSION

We did not observe strong, consistent evidence of associations between early pregnancy erythrocyte metal concentrations and subsequent maternal antepartum and postpartum depressive symptoms.

Lack of sufficient evidence to support a positive role of selenium status in depression: a systematic review

CONTEXT

Globally, depression affects more than 322 million people. Studies exploring the relationship between diet and depression have revealed the benefits of certain dietary patterns and micronutrients in attenuating the symptoms of this disorder. Among these micronutrients, selenium stands out because of its multifaceted role in the brain.

OBJECTIVE

To assess the impact of selenium intake and status on symptoms of depression.

DATA SOURCES

A systematic search was performed in databases, including PubMed, Web of Science, EMBASE, PsycINFO, Scopus, and gray literature (on April 6, 2021, updated on January 28, 2022), without restrictions of date, language, or study type.

DATA EXTRACTION

Studies of adults (18-60 y of age) with depression or depressive symptoms were included. Data on selenium biomarkers and/or intake were included. The risk of bias was assessed using the Joanna Briggs Institute checklists.

DATA ANALYSIS

Of the 10 studies included, 2 were cohorts (n = 13 983 and 3735), 3 were cross-sectional (n = 736, 7725, and 200), 1 was case-control (n = 495), and 4 were randomized controlled trials (n = 30, 11, 38, and 63). Several studies have indicated that low selenium intake or concentration may be associated with symptoms of depression. However, this association was inconsistent across the studies included in this systematic review; due to the high heterogeneity, it was not possible to perform meta-analyses. The main contributing factors to the high heterogeneity include the different methodological designs, methods for diagnosing depression, selenium assessment, and clinical conditions.

CONCLUSION

Overall, there is insufficient evidence to support a positive role of selenium status in depression. Studies with more accurate methods and adequate assessment of selenium status are needed to better understand the role of this nutrient in depression.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD42021220683.

Lower serum selenium concentration associated with anxiety in children

PURPOSE

Few studies have examined the role of selenium in anxiety. This study aimed to evaluate the association between serum selenium concentrations and anxiety disorders and symptoms in children.

DESIGN AND METHODS

This study utilized data from 831 children participating in the China Jintan Child Cohort Study (mean age = 12.67 years; 46.1% female). Serum selenium samples were collected and anxiety was assessed using the Chinese version of the Screen for Child Anxiety Related Disorders. Six types of anxiety scores were calculated, including total anxiety, panic/somatic, generalized anxiety, separation anxiety, social anxiety, and school phobia.

RESULTS

Controlling for covariates, children with lower serum selenium concentrations were more likely to meet clinical cutoffs for total anxiety (OR = 0.992, p < 0.01), panic/somatic disorder (OR = 0.993, p < 0.05), generalized anxiety disorder (OR = 0.990, p < 0.05), social anxiety disorder (OR = 0.991, p < 0.01), and school phobia (OR = 0.989, p < 0.01), but not separation anxiety (OR = 1.000, p > 0.05). Controlling for covariates, lower serum selenium concentrations were also associated with higher continuous total anxiety, generalized anxiety, and school phobia scores (p < 0.05).

CONCLUSIONS

Lower serum selenium concentrations were associated with higher anxiety. To our knowledge, this was the first study to examine the relationship between serum selenium and anxiety disorders in a sample of children. Results indicate an association between children's micronutrient levels and anxiety disorders.

PRACTICE IMPLICATIONS

Improving child nutrition may be a promising strategy to help reduce childhood anxiety.

Chronic Stress and Oxidative Stress as Common Factors of the Pathogenesis of Depression and Alzheimer's Disease: The Role of Antioxidants in Prevention and Treatment

There is a growing body of scientific research showing the link between depression and dementia in Alzheimer’s disease (AD). The chronic stress contributes to the formation of oxidative stress in the parts of the brain involved in the development of depression and AD. The scientific literature reports the significant role of antioxidants, which are highly effective in treating these diseases. In this review, we have summarized the relationship between chronic stress, oxidative stress, and the changes in the brain they cause occurring in the brain. Among all the compounds showing antioxidant properties, the most promising results in AD treatment were observed for Vitamin E, coenzyme Q10 (CoQ10), melatonin, polyphenols, curcumin, and selenium. In case of depression treatment, the greatest potential was observed in curcumin, zinc, selenium, vitamin E, and saffron.

Antioxidant stress and anticancer activity of peptide‑chelated selenium in vitro

The association between selenium and peptide in gastric cancer is an important research topic. The present study reported the facile synthesis of anticancer bioactive peptide (ACBP)-functionalized selenium (ACBP-S-Se) particles with enhanced anticancer activities and a detailed mechanistic evaluation of their ability to regulate oxidative stress in vitro. Structural and chemical characterizations were revealed by ultraviolet absorption, Fourier transform infrared, X-ray photoelectron, nuclear magnetic resonance carbon and hydrogen, energy dispersive X-ray spectroscopy and inductively coupled plasma mass spectrometry, as well as scanning electron microscopy. Sulfhydrylation modifications of ACBP were achieved with Sacetylmercaptosuccinic anhydride via chemical absorption. After the polypeptide was modified by sulfhydrylation, the ACBP chain was linked to sulfhydryl groups by amide bonds to form the ACBP-chelated selenium complex. Two gastric cancer cell lines (MKN-45 and MKN-74 cells) demonstrated high susceptibility to ACBP-S-Se particles and displayed significantly decreased proliferation ability following treatment. The results suggested that the bioactive peptide-chelated selenium particles effectively inhibited the proliferation of MKN-45 and MKN-74 cells in vitro. The genes encoding CDK inhibitor 1A (CDKN1A), cyclin B1, thioredoxin (TXN) and mitogen-activated protein kinase kinase kinase 5 are associated with regulation of oxidative stress, while CDKN1A and TXN protect cells by decreasing oxidative stress and promoting cell growth arrest. Therefore, ACBP-S-Se may be an ideal chemotherapeutic candidate for human cancer, especially gastric cancer.

Association of Selenium Intake and Development of Depression in Brazilian Farmers

Introduction: Depression and deficiency in the consumption of micronutrients are a public health problem, especially in the rural population. The deficiency in selenium consumption affects mental health, contributing to the development of major depressive disorders. Thus, this study aimed to evaluate selenium intake and its association with depressive symptoms in farmers in southeastern Brazil.

Material and Methods: Epidemiological, cross-sectional, and analytical study with 736 farmers aged between 18 and 59. A semistructured questionnaire was used to collect sociodemographic, lifestyle and clinical condition data. For evaluation of food intake, three 24-h recalls were applied, and for identification of depressive episodes, the Mini-International Neuropsychiatric Interview was conducted.

Results: A total of 16.1% (n = 119) of the farmers presented symptoms of major depressive episodes, 5.8% (n = 43) presented symptoms of current depressive episodes, and 10.3% (n = 76) presented symptoms of recurrent major depressive episodes. Sociodemographic factors associated with depression were gender (p < 0.001), marital status (p = 0.004), and socioeconomic class (p = 0.015). The consumption of high doses of selenium was associated with a reduction of ~54% in the chances of occurrence of depression (OR = 0.461; 95% CI = 0.236–0.901).

Conclusion: High selenium intake is associated with a lower prevalence of depression even after adjusting for sociodemographic variables, lifestyle, and pesticide intoxication. The findings of this study contributed to highlighting the high prevalence of depression in rural areas and its relationship with selenium intake.

Toenails as biomarker of exposure to essential trace metals: A review

Health problems associated with essential trace metals can result from both inadequate (i.e., low intake) and excessive exposures (i.e., from environmental and/or occupational source). Thus, measuring the exposure level is a real challenge for epidemiologists. Among non-invasive biomarkers that intend to measure long-term exposure to essential trace metals, the toenail is probably the biological matrix with the greatest potential. This systematic review collects the current evidence regarding the validity of toenail clippings as exposure biomarker for trace metals such as boron, cobalt, copper, iron, manganese, molybdenum, selenium, silicon, vanadium and zinc. Special attention was paid to the time-window of exposure reflected by the toenail, the intraindividual variability in exposure levels over time in this matrix, and the relationship of toenail with other biomarkers, personal characteristics and environmental sources. Our search identified 139 papers, with selenium and zinc being the most studied elements. The variability among studies suggests that toenail levels may reflect different degrees of exposure and probably correspond to exposures occurred 3-12 months before sampling (i.e., for manganese/selenium). Few studies assessed the reproducibility of results over time and, for samples obtained 1-6 years apart, the correlation coefficient were between 0.26 and 0.66. Trace metal levels in toenails did not correlate well with those in the blood and urine and showed low-moderate correlation with those in the hair and fingernails. Available data suggests that for some elements (Se, Mn, Zn) toenail concentrations reflect long-term external exposures in fairly reproducible levels, while for other metals, this association has not yet been assessed. Among dietary factors, only toenail selenium showed clear associations with the intake of supplements or specific foods. The toenail levels could also represent occupational exposure, for instance, Mn exposure in welders. The scarcity of information on other essential trace elements, together with the great heterogeneity among studies makes the validation of the usage of toenails as biomarkers of exposure to these elements difficult. Standardization of sample collection, quality control, analytical techniques and reporting procedures might facilitate further research focused on the clear understanding of the significance of essential levels in this promising matrix and would enhance its utility in epidemiological research.

Is selenium intake associated with the presence of depressive symptoms among US adults? Findings from National Health and Nutrition Examination Survey (NHANES) 2011-2014

OBJECTIVES

This study aimed to examine the cross-sectional association between dietary and serum selenium measures and depressive symptoms among a nationally representative sample of US adults.

METHODS

Dietary selenium intake and serum selenium concentration were evaluated on 7725 adult participants from National Health and Nutrition Examination Survey (NHANES) 2011-2014. Participants' selenium intake, assessed by 24-h recall, was classified based on the recommended dietary allowance (dietary selenium intake ≥ 55 μg/d) and estimated average requirement (dietary selenium intake ≥ 45 μg/d) criteria. Serum selenium and depressive symptoms were assessed using inductively coupled plasma mass spectrometry and a patient health questionnaire or use of an antidepressant, respectively. Univariate and multivariate logistic regression, accounting for the complex survey design of NHANES, were employed to estimate the cross-sectional association between measures of selenium and the presence of depressive symptoms.

RESULTS

The median selenium concentration was 193.9 µg/L (interquartile range = 179.3-209.3). Approximately 8% of the participants met the case definition for depressive symptoms. Based on the recommended dietary allowance of selenium, participants not meeting the recommended dietary intake, compared with those meeting the requirement, had higher odds of depressive symptoms (odds ratio [OR] = 1.57, 95% confidence interval [CI]: 1.03-2.38). When analyzing by quintile of dietary selenium intakes, compared with the first quintile, participants in higher quintiles had significantly lower odds of depressive symptoms. However, based on quintiles of serum selenium and using the first quintile as referent category, except for quintile 3, results indicated a higher but not significant association (quintile 2 [OR = 1.08, 95% CI: 0.73-1.61], quintile 4 [OR = 1.17, 95% CI: 0.89-1.55], and quintile 5 [OR = 1.14, 95% CI: 0.83-1.58]). Power analysis indicated sufficient power. Notably, study participants had a very high serum selenium concentration. The findings, although not significant, between serum selenium concentrations and depressive symptoms had a U-shaped association, supported by the current literature.

CONCLUSIONS

Our study supports an inverse association between participants recommended dietary intake of selenium and depressive symptoms. Although results were not statistically significant for the association by quartile of serum selenium concentrations and depressive symptoms, a U-shaped association was identified.

Zinc, Magnesium, Selenium and Depression: A Review of the Evidence, Potential Mechanisms and Implications

Micronutrient deficiency and depression are major global health problems. Here, we first review recent empirical evidence of the association between several micronutrients—zinc, magnesium, selenium—and depression. We then present potential mechanisms of action and discuss the clinical implications for each micronutrient. Collectively, empirical evidence most strongly supports a positive association between zinc deficiency and the risk of depression and an inverse association between zinc supplementation and depressive symptoms. Less evidence is available regarding the relationship between magnesium and selenium deficiency and depression, and studies have been inconclusive. Potential mechanisms of action involve the HPA axis, glutamate homeostasis and inflammatory pathways. Findings support the importance of adequate consumption of micronutrients in the promotion of mental health, and the most common dietary sources for zinc and other micronutrients are provided. Future research is needed to prospectively investigate the association between micronutrient levels and depression as well as the safety and efficacy of micronutrient supplementation as an adjunct treatment for depression.

Are Dietary Patterns Associated with Depression in U.S. Adults?

Nutrition is one of the most important modifiable determinants for and consequences of both mental and physical heath. Depression has become an increasingly important public health issue. We tested whether dietary patterns derived from food group intake are associated with depression in U.S. adults in a cross-sectional study with national population. This study included 4180 men and 4196 women aged 20-79 years in the 2007-2010 National Health and Nutrition Examination Surveys (NHANES), with complete data of one 24-h dietary recall, sociodemographics, lifestyles, and Patient Health Questionnaires (PHQ-9) for screening depression. Two major dietary patterns identified by factor analysis were investigated for their associations with presence of depression (PHQ-9 score ≥10) by using linear and multivariate logistic regressions. One of two major patterns, labeled "Western" dietary pattern was characterized by high intakes of nonwhole grain, white potatoes, cheese, meat, discretionary oil and fat, and added sugar; the second dietary pattern that was labeled "Healthy" dietary pattern was characterized by high intakes of whole grains, vegetables, fruits, fish, nuts and seeds. The "Western" dietary pattern was not significantly associated with depression in both men and women. The "Healthy" dietary pattern scores were inversely associated with the PHQ-9 depression scores and odd ratios (ORs) of depression after adjustment for covariates in women but not in men. The OR of depression in women with the highest quintile of "Healthy" dietary pattern scores was 0.60 (95% confidence interval [CI]: 0.42-0.85, P < .001) compared to the lowest quintile as a reference. These findings warrant future interventions or clinical trials in elucidating causal and effect relations of depression and dietary patterns, an important public health concern.

Toenail selenium and risk of type 2 diabetes: the ORDET cohort study

Epidemiologic studies, particularly randomized controlled trials, have shown a direct relation between dietary and environmental exposure to the metalloid selenium and risk of type 2 diabetes. We investigated the association between baseline toenail selenium levels and diabetes occurrence in a case-control study nested in ORDET, a population-based female cohort in Northern Italy. After a median follow-up of 16 years, we identified 226 cases of type 2 diabetes cases and 395 age-matched control women with available toenail samples at baseline. The multivariate odds ratios of diabetes in increasing a priori defined categories of toenail selenium exposure were 1.09 (95% confidence interval 0.61, 1.96), 0.71 (0.38, 1.34) and 1.14 (0.46, 2.80) compared with the lowest category. The results were not substantially altered when quartile distribution of toenail selenium in controls was used to define exposure categories. Spline regression analysis did not show homogeneous risk trends. Overall, we did not find an association between toenail selenium and subsequent development of diabetes. Since the diabetogenic activity of selenium is strongly supported by experimental studies and some observational investigations, our null results might be explained by the limitations of overall selenium toenail content to assess environmental exposure to selenium species of etiologic relevance in the study population.

Selenium speciation in human serum and its implications for epidemiologic research: a cross-sectional study

Observational studies addressing the relation between selenium and human health, particularly cancer risk, yielded inconsistent results, while most recent randomized trials showed a fairly consistent pattern suggesting null or adverse effects of the metalloid. One of the most plausible explanations for such inconsistencies is inadequate exposure assessment in observational studies, commonly carried out by measuring total Se content without taking into account the specific exposure to the individual chemical forms of the metalloid, whose toxic and nutritional properties may vary greatly. Data on the distribution of these species in human blood and their correlation with overall selenium levels are very limited. The concentrations of organic and inorganic selenium species were analyzed in serum of fifty subjects sampled from the general population of the municipality of Modena, northern Italy, aged from 35 to 70 years. Samples were collected during a 30-month period, and determinations of selenium species were carried out using high pressure liquid chromatography coupled with inductively coupled plasma dynamic reaction cell mass spectrometry. The majority of selenium was found to be present as organic species, but the inorganic forms showed higher levels than expected. These species showed limited correlations with age, sex and body mass index, while the organic forms increased in subjects consuming selenium-containing dietary supplements and decreased in smokers. The length of the sample storage period strongly influenced the distribution of selenium compounds, with a clear tendency towards higher inorganic and lower organic selenium levels over time. In multivariate analysis adjusting for potential confounders, total serum selenium correlated with human serum albumin-bound selenium and, in males, with two organic species of the metalloid (selenocysteine and glutathione peroxidase-bound selenium), while little association existed with the other organic forms and the inorganic ones. These findings highlight the potential for exposure misclassification of observational epidemiologic investigations based on overall selenium content in blood and possibly other tissues, and the critical role of the storage conditions for speciation analysis.

Optimal serum selenium concentrations are associated with lower depressive symptoms and negative mood among young adults

BACKGROUND

There is evidence that low, and possibly high, selenium status is associated with depressed mood. More evidence is needed to determine whether this pattern occurs in young adults with a wide range of serum concentrations of selenium.

OBJECTIVE

The aim of this study was to determine if serum selenium concentration is associated with depressive symptoms and daily mood states in young adults.

METHODS

A total of 978 young adults (aged 17-25 y) completed the Center for Epidemiological Studies-Depression scale and reported their negative and positive mood daily for 13 d using an Internet diary. Serum selenium concentration was determined by inductively coupled plasma mass spectrometry. ANCOVA and regression models tested the linear and curvilinear associations between decile of serum selenium concentration and mood outcomes, controlling for age, gender, ethnicity, BMI, and weekly alcohol intake. Smoking and childhood socioeconomic status were further controlled in a subset of participants.

RESULTS

The mean ± SD serum selenium concentration was 82 ± 18 μg/L and ranged from 49 to 450 μg/L. Participants with the lowest serum selenium concentration (62 ± 4 μg/L; decile 1) and, to a lesser extent, those with the highest serum selenium concentration (110 ± 38 μg/L; decile 10) had significantly greater adjusted depressive symptoms than did participants with midrange serum selenium concentrations (82 ± 1 to 85 ± 1 μg/L; deciles 6 and 7). Depressive symptomatology was lowest at a selenium concentration of ∼85 μg/L. Patterns for negative mood were similar but more U-shaped. Positive mood showed an inverse U-shaped association with selenium, but this pattern was less consistent than depressive symptoms or negative mood.

CONCLUSIONS

In young adults, an optimal range of serum selenium between ∼82 and 85 μg/L was associated with reduced risk of depressive symptomatology. This range approximates the values at which glutathione peroxidase is maximal, suggesting that future research should investigate antioxidant pathways linking selenium to mood. This trial was registered with the Australian New Zealand Clinical Trials Registry as ACTRN12613000773730.

Selenium and Human Health: Witnessing a Copernican Revolution?

In humans, selenium was hypothesized to lower the risk of several chronic diseases, mainly due to the antioxidant activity of selenium-containing proteins. Recent epidemiologic and laboratory studies, however, are changing our perception of the biological effects of this nutritionally essential trace element. We reviewed the most recent epidemiologic and biochemical literature on selenium, synthesizing the findings from these studies into a unifying view. Randomized trials have shown that selenium did not protect against cancer and other chronic diseases, but even increased the risk of specific neoplasms such as advanced prostate cancer and skin cancer, in addition to type 2 diabetes. Biochemical studies indicate that selenium may exert a broad pattern of toxic effects at unexpectedly low concentrations. Furthermore, its upregulation of antioxidant proteins (selenium-dependent and selenium-independent) may be a manifestation of self-induced oxidative stress. In conclusion, toxic effects of selenium species occur at lower concentrations than previously believed. Those effects may include a large range of proteomic changes and adverse health effects in humans. Since the effects of environmental exposure to this element on human health still remain partially unknown, but are potentially serious, the toxicity of selenium exposure should be further investigated and considered as a public health priority.

Solidified floating organic drop microextraction for speciation of selenium and its distribution in selenium-rich tea leaves and tea infusion by electrothermal vapourisation inductively coupled plasma mass spectrometry

Solidified floating organic drop microextraction was combined with electrothermal vapourisation inductively coupled plasma mass spectrometry for Se species in Se-rich tea leaves and tea infusion, including total, suspended, soluble, organic and inorganic Se as well as Se(IV) and Se(VI). Ammonium pyrrolidinedithiocarbamate was used as both chelating reagent and chemical modifier in this study. Se(IV) and Se(VI) were separated at pH range of 2.0-5.0. An enrichment factor of 500 was obtained for Se(IV) from this method. Under the optimum conditions, the detection limits for Se(IV) and Se(VI) were 0.19 and 0.26pgmL(-1), respectively. The relative standard deviations were less than 5.5% (c=0.1ngmL(-1), n=9). This method was applied for Se species, its content and distribution in Se-rich tea leaves and tea infusion with satisfactory results. The recoveries of spike experiments are in the range of 92.2-106%. A certified reference material of tea leaves was analyzed by this method, and the results were in agreement with certified values.