Bioaccessible selenium in Italian agricultural soils: Comparison of the biogeochemical approach with a regression model based on geochemical and pedoclimatic variables

Spatial distribution and main drivers of soil selenium in Taihu Lake Basin, Southeast China

Selenium (Se) is an essential micronutrient that is both hazardous and beneficial to living organisms. However, few studies have examined soil Se distribution and its driving mechanisms on a large basin scale. Thus, multivariate statistics, geostatistics, boosted regression trees, and structural equation models were used to investigate the spatial distribution, driving factors, and multivariate interactions of soil Se based on 1753 topsoil samples (0-20 cm) from the Taihu Lake Basin. The results indicated that the soil Se concentration ranged from 0.12 to 57.26 mg kg-1, with a mean value of 0.90 mg kg-1. Overall, the spatial pattern of soil Se gradually decreased from south to north with approximately 1.06% of the soil contaminated with Se. Moisture index (MI), soil moisture (SM), and ≥ 0 ℃ accumulative temperature (AAT0) were the main determinants of soil Se accumulation. Additionally, the substantial effect of SM∩AAT0 on soil Se concentrations demonstrated that climate-soil interactions largely governed the spatial pattern of soil Se. The Se-enriched and Se-contaminated soils occurred mainly in regions with high precipitation, MI, SM, AAT0, and soil organic matter. This study provides a theoretical basis and practical guidance for the remediation of soil Se contamination and the sustainable development of Se-enriched agriculture.

Effect of red and blue light supplementation on the efficacy of Noccaea caerulescens in decontaminating metals and alleviating leaching risk

This study was conducted to investigate the impact of supplementing blue and red light on the biomass yield, metal uptake, contaminant purification, and the alleviation of leaching risks by Noccaea caerulescens, a well-known hyperaccumulator of Cd and Zn. As previously reported for the closely related Thlaspi arvense, N. caerulescens retarded the leaching of Cd and Zn but aggravated the leaching of Pb and Cu, because the species mobilized all metals in soil but only extracted Cd and Zn. Monochromic red light reduced the leaching of Pb and Cu by 13.8% and 1.3%, respectively, but simultaneously weakened Cd phytoremediation by reducing shoot biomass. Our results demonstrated that a small proportion of blue light (10%) could eliminate the negative effect of monochromatic red light on plant shoot growth. However, root biomass decreased by 14.3%, 26.2%, 21.4%, and 61.9% as the percentage of blue light increased from 10 to 100%. Noccaea caerulescens generated the most biomass and accumulated the highest metal concentrations, except for Pb, when the ratio of red to blue light was 1:1. In addition, leachate volume was significantly reduced under the 10% and 50% blue light treatments compared to other light treatments. Therefore, light supplementation with a suitable proportion of blue light can enhance metal purification by N. caerulescens and alleviate potential leaching risk during phytoremediation.

Selenium - An environmentally friendly micronutrient in agroecosystem in the modern era: An overview of 50-year findings

Agricultural productivity is constantly being forced to maintain yield stability to feed the enormously growing world population. However, shrinking arable and nutrient-deprived soil and abiotic and biotic stressor (s) in different magnitudes put additional challenges to achieving global food security. Though well-defined, the concept of macro, micronutrients, and beneficial elements is from a plant nutritional perspective. Among various micronutrients, selenium (Se) is essential in small amounts for the life cycle of organisms, including crops. Selenium has the potential to improve soil health, leading to the improvement of productivity and crop quality. However, Se possesses an immense encouraging phenomenon when supplied within the threshold limit, also having wide variations. The supplementation of Se has exhibited promising outcomes in lessening biotic and abiotic stress in various crops. Besides, bulk form, nano-Se, and biogenic-Se also revealed some merits and limitations. Literature suggests that the possibilities of biogenic-Se in stress alleviation and fortifying foods are encouraging. In this article, apart from adopting a combination of a conventional extensive review of the literature and bibliometric analysis, the authors have assessed the journey of Se in the "soil to spoon" perspective in a diverse agroecosystem to highlight the research gap area. There is no doubt that the time has come to seriously consider the tag of beneficial elements associated with Se, especially in the drastic global climate change era.

Is Glucose-6-Phosphate Dehydrogenase Deficiency a Risk Factor for Autoimmune Thyroid Disease? A Retrospective Case-Control Study

BACKGROUND

The risk of developing thyroid disorders (TDs) in subjects with inherited glucose-6-phosphate dehydrogenase (G6PD) deficiency is unknown. The aim of this study was to explore the association between autoimmune (AITD) and G6PD deficiency in Northern Sardinia, in a population with a high frequency of these two conditions.

METHODS

In this retrospective single-center case-control study, demographic and clinical data were collected from patients examined in a tertiary referral Gastroenterology Section of a teaching hospital.

RESULTS

In 8894 subjects examined (64.7% females), 1218 patients were diagnosed with TDs; more specifically, 767 were diagnosed with AITD and 451 were not (non-AITD). Overall, G6PD deficiency was more prevalent in TD patients compared with patients without TD (controls) (16.7% vs. 11.2%; p < 0.0001). Multivariable logistic regression analysis (after adjusting for age, sex, excess weight and smoking habits), confirmed a higher risk of AITD among G6PD deficient patients with an odds ratio (OR) of 1.36 and 95% confidence interval (CI) of 1.11-1.6, female patients (OR 1.33, 95% CI 1.07-1.65) and overweight patients (OR 1.22, 95% CI 1.03-1.44).

CONCLUSIONS

The risk of AITD is increased in carriers of G6PD deficiency. A careful assessment of thyroid function is advisable in patients with inherited G6PD defects.

Spatial distribution and environmental impact factors of soil selenium in Hainan Island, China

Selenium is an essential micronutrient for the human body, given its various health benefits. However, Se deficiency is widespread globally, and dietary adjustment is a feasible way to supplement people's Se daily intake. The Multi-purpose Regional Geochemical Survey (NMPRGS) conducted in Hainan Island found an abundance of Se-rich soil. These Se resources have been utilized to grow naturally Se-rich produce. However, insufficient research has been conducted into the spatial distribution and enrichment of soil Se in Hainan Island. This paper analysed the effect of the environmental impact factors (parent rock, precipitation, etc.) on soil Se, using data from the NMPRGS database. The results showed that, in comparison to the baseline value of Chinese soil, the enrichment degree of Se in the topsoil of Hainan Island was higher, but its distribution was uneven. The parent rock, precipitation, soil type, and soil characteristics all affect the concentration and spatial distribution of regional soil Se. Geographically weighted regression showed that Iodine, pH, SOC, and TFe₂O₃ have a non-stationarity spatial relationship with Se. There was a significant correlation between soil Se and Chemical alteration index (CIA) in granite areas, while CIA was also related to mean annual precipitation (MAP). The concentration enrichment factor values of Se show that the external input of Se in high MAP areas is significantly higher than that in low MAP areas. Based on these results, three important environmental impact factors on soil Se enrichment at the regional scale in Hainan Island were defined: 1) Se-rich rocks; 2) precipitation; 3) SOC. These results can provide guidance for the planning and layout of Se-rich agriculture.

Long-Aged Parmigiano Reggiano PDO: Trace Element Determination Targeted to Health

The concentrations of four health-related trace elements were measured using Atomic Absorption Spectroscopy in long-ripened (24- and 40-months) Parmigiano Reggiano (PR) PDO cheese, obtained from both summer and winter milk. To date, there are limited data on PR trace element concentrations, and no data about long-ripened cheese, especially when ripened for 40 months. Thus, the aim of this investigation is to determine chromium, manganese, selenium, and zinc concentrations, improving the available data on these trace elements and increasing knowledge of the biological properties of PR linked to their content in this cheese. The results show that 40-month ripened PR is a source of selenium and chromium, according to definitions under the European Regulation 1924/2006, as a 30 g cheese portion contains 11 ± 2 μg (summer milk) and 10 ± 1 μg (winter milk) of selenium and 8 ± 1 μg (summer and winter milk) of chromium, providing in excess of 8.25 and 6 μg per portion, respectively. This represents 15% of nutrient reference intake values for adults. These findings allow for the claim to be made that PR possesses the health properties ascribed to food sources of selenium and chromium according to European Regulation 432/2012.

Selenium in Wheat from Farming to Food

Selenium (Se) plays an important role in human health. Approximately 80% of the world's population does not consume enough Se recommended by the World Health Organization. Wheat is an important staple food and Se source for most people in the world. This review summarizes literature about Se from 1936 to 2020 to investigate Se in wheat farming soil, wheat, and its derived foods. Se fortification and the recommended Se level in wheat were also discussed. Results showed that Se contents in wheat farming soil, grain, and its derived foods around the world were 3.8-552 μg kg^-1 (mean of 220.99 μg kg^-1), 0-8270 μg kg^-1 (mean of 347.30 μg kg^-1), and 15-2372 μg kg^-1 (mean of 211.86 μg kg^-1), respectively. Adopting suitable agronomic measures could effectively realize Se fortification in wheat. The contents in grain, flour, and its derived foods could be improved from 93.94 to 1181.92 μg kg^-1, from 73.06 to 1007.75 μg kg^-1, and from 86.90 to 587.61 μg kg^-1 on average after leaf Se fertilizer application in the field. There was a significant positive correlation between the Se content in farming soil and grain, and it was extremely the same between the foliar Se fertilizer concentration rate and the grain Se increased rate. The recommended Se fortification level in cultivation of wheat in China, India, and Spain was 18.53-23.96, 2.65-3.37, and 3.93-9.88 g hm^-2, respectively. Milling processing and food type could greatly affect the Se content of wheat-derived food and should be considered seriously to meet people's Se requirement by wheat.

Selenium Deficiency Due to Diet, Pregnancy, Severe Illness, or COVID-19-A Preventable Trigger for Autoimmune Disease

The trace element selenium (Se) is an essential part of the human diet; moreover, increased health risks have been observed with Se deficiency. A sufficiently high Se status is a prerequisite for adequate immune response, and preventable endemic diseases are known from areas with Se deficiency. Biomarkers of Se status decline strongly in pregnancy, severe illness, or COVID-19, reaching critically low concentrations. Notably, these conditions are associated with an increased risk for autoimmune disease (AID). Positive effects on the immune system are observed with Se supplementation in pregnancy, autoimmune thyroid disease, and recovery from severe illness. However, some studies reported null results; the database is small, and randomized trials are sparse. The current need for research on the link between AID and Se deficiency is particularly obvious for rheumatoid arthritis and type 1 diabetes mellitus. Despite these gaps in knowledge, it seems timely to realize that severe Se deficiency may trigger AID in susceptible subjects. Improved dietary choices or supplemental Se are efficient ways to avoid severe Se deficiency, thereby decreasing AID risk and improving disease course. A personalized approach is needed in clinics and during therapy, while population-wide measures should be considered for areas with habitual low Se intake. Finland has been adding Se to its food chain for more than 35 years-a wise and commendable decision, according to today's knowledge. It is unfortunate that the health risks of Se deficiency are often neglected, while possible side effects of Se supplementation are exaggerated, leading to disregard for this safe and promising preventive and adjuvant treatment options. This is especially true in the follow-up situations of pregnancy, severe illness, or COVID-19, where massive Se deficiencies have developed and are associated with AID risk, long-lasting health impairments, and slow recovery.

Distribution, origin and speciation of soil selenium in the black soil region of Northeast China

Selenium (Se) is an essential trace element within human beings that hold with crucial biological functions. Investigating the complex origin of soil Se is of great importance to scientifically approach the land use of Se-rich land use, and the respective promotion of regional economic development. In this study, 160 soil samples from 10 profiles in farmland and woodland were collected in Hailun city, which is a typical black soil region in Northeast China, in order to characterize the distribution and speciation of Se in the black soil, and to identify the origin of soil Se. The total selenium content in the soil ranges from 0.045 to 0.444 μg g^-1, with an average selenium content in black soil (0.318 μg g^-1) of three times greater than that found in the yellow-brown soil (0.114 μg g^-1). The land-use type has a significant influence on the distribution of selenium in the black soil. Moreover, Se and heavy metals have a significant (positive or negative) correlation, in which TOC plays an important role. The black soil presents a consistent REE distribution pattern with underlying yellow-brown soil indicating black soil originates from yellow-brown soil. REE geostatistical analysis suggests that the soil Se partly originates from shale weathering and enriches in black soil. Moreover, elemental geochemical analysis and XRD results show that the paleoclimate change from humid and warm to dry and cold is favorable for organic matter accumulation, resulting in less leaching and enhanced adsorption of selenium into the black soil.

Applications of nutritional functional units in commodity-level life cycle assessment (LCA) of agri-food systems

PURPOSE

The nutritional quality of final products is attracting an increased level of attention within life cycle assessment (LCA) literature of agri-food systems. The majority of these studies, however, are based on comparisons at the dietary level and, therefore, are unable to offer immediate implications for farmers as to how best to produce food. This article evaluates recent literature examining the nutrition-environment nexus at the commodity level, with the aim to identify potential pathways towards sustainability analysis that can inform both consumers and producers.

METHODS

A systematic search of literature was carried out to produce a shortlist of studies, and strict exclusion criteria were applied to them afterwards to eliminate irrelevant material. The studies thus selected were classified into one of three tiers based on the level of complexity with regard to their functional units: (1) based on single nutrients, (2) based on composite indicators derived from multiple nutrients and (3) based on commodity-level analysis in a dietary context.

RESULTS AND DISCUSSION

Sixteen papers were identified for inclusion in the review. All of them accounted for climate change either directly or indirectly, whilst only five addressed different impact categories at the same time. Nine studies estimated environmental impacts under functional units associated with nutrient density scores, and the others utilised alternative approaches to account for nutritional value such as linear programming and end-point modelling combined with epidemiological data. A recently developed method to calculate the marginal contribution of a commodity to the overall nutritional value of a specific diet was considered to be a successful first step in bridging the aforementioned knowledge gap.

CONCLUSIONS

The LCA community should continue the ongoing effort to link farm management decisions to diet-level environmental impacts through an enhanced focus on human nutrition across the entire value chain. Future research comparing environmental performances of multiple food groups or multiple production systems should acknowledge differences in nutritional composition and bioavailability between the final products and, ideally, the effects of these nutrients on overall dietary quality.

Mortality, growth and metabolic responses by 1H-NMR-based metabolomics of earthworms to sodium selenite exposure in soils

The rapid development of selenium-enriched agriculture leads to the accumulation of selenium in the soil, which has an adverse impact on terrestrial ecosystems. In the present study, the mortality, growth inhibition rate and metabolism of earthworms were examined to investigate the toxicological effects of sodium selenite (Na₂SeO₃) on earthworms (Eisenia fetida) after exposuring for 14 days (d). We used ¹H-NMR-based metabolomics to identify sensitive biomarkers and explored the metabolic responses of earthworms exposed to Na₂SeO₃. The mortality and growth inhibition rate of earthworms exposed to 70 and 90 mg/kg Na₂SeO₃ were significantly higher than the rate of control group. The LC₅₀ (the median lethal concentration) of Na₂SeO₃ was 57.4 mg/kg in this artificial soil test of E. fetida exposed to Na₂SeO₃ for 14 d. However, there was no significant differences when earthworms were exposed to different concentrations of Na₂SeO₃. The selected metabolic markers were ATP, lactic acid, leucine, alanine, valine, glycine, glutamic acid, lysine, α-glucose and betaine. Na₂SeO₃ affected the metabolic level of earthworms, as the percentage of metabolic markers in the earthworm changes when exposed to different concentrations of Na₂SeO₃. The metabolic disturbances were greater with increasing concentrations of Na₂SeO₃. The differential metabolic markers were significantly changed when exposed to Na₂SeO₃ comparing to those in the control group, affecting the tricarboxylic acid cycle process and breaking the metabolic balance. This study showed that Na₂SeO₃ had toxic effect on the growth and development of earthworms. In addition, this study provided a biochemical insights for the development of selenium-enriched agriculture.

Selenium and Vitamin E Concentrations in a Healthy Donkey Population in Central Italy

Selenium and vitamin E protect the body against oxidative stress. Clinical manifestations of their deficiency in equids include neurologic and muscular symptoms. Despite the importance of donkeys as working and production animals, there is a dearth of scientific data on selenium and vitamin E normal values. Therefore, the aim of this study was to investigate the plasma concentrations of selenium and vitamin E in healthy donkeys belonging to different ages, sexes, and productive phases. Animals were divided into five groups including foals (group A: n = 7, n = 4 males and n = 3 females), weanlings and yearlings (group B: n = 7, n = 2 males and n = 5 females), nonpregnant nonlactating jennies (group C: n = 5), pregnant nonlactating jennies (group D: n = 9), and adult males (group E: n = 9). Plasma samples obtained from each animal were tested for vitamin E and selenium concentration. One-way analysis of variance showed significant differences in selenium concentrations (P = .001) between group A and group E. In this study, we found the selenium range for donkeys to be 0.02-0.14 μg/mL, which is lower than the recommended range for horses. The results suggest that donkeys may have a lower selenium requirement than horses. Plasma vitamin E levels were 3.29-12.99 μmol/L, with foals having lower concentrations than adults. Knowing specific reference ranges for vitamin E and selenium in healthy donkeys can help improve our understanding of how to prevent deficiencies that could compromise their overall health and well-being.

Fate of selenium in soil: A case study in a maize (Zea mays L.) field under two irrigation regimes and fertilized with sodium selenite

Selenium (Se) is a trace element necessary for both human and livestock nutrition. To increase Se human intake, soil Se fertilizations were performed but the fate of the added Se remains unclear. The present research aims to: (1) determine the influence of Se fertilization on the fractionation of Se in soil; (2) assess the influence of water availability on the distribution of soil Se chemical fractions; and (3) monitor the Se content in soil, leachates and plants. To reach these goals, 200 g Se ha^-1 was applied to soil as sodium selenite in maize crops under two irrigation regimes, and the Se content in plant, soil chemical fractions and leachates were analyzed. Se application increased the total Se content of the soil, specifically it increased the Se content of the soluble, exchangeable and organic fractions with more pronounced effect in the soils with higher water availability. These differences disappeared over time likely due to the Se loss through volatilization. The hypothesis of Se volatilization is confirmed by the absence of both leachates during the maize growing season and differences among the treatments of Se content in sub-soil samples. Also, although the Se treated plants showed higher Se content than the untreated ones, overall <1% of the added Se was assimilated by plants. Hence, this study demonstrated that the addition of selenite to the soil increased the Se contents of the plants, but the Se does not accumulate in the soil because it is likely lost via volatilization. Further, leaching of Se into groundwater is avoided due to its association with both the soil organic matter and positively charged binding sites of soil, and due to its loss via volatilization. Therefore, soil Se fertilization could increase the nutritional value of plants without consequences on the environment.

The Selenium Supplementation Influences Olive Tree Production and Oil Stability Against Oxidation and Can Alleviate the Water Deficiency Effects

Foliar fertilization with selenium (Se) may well be beneficial in increasing the nutritional and qualitative values of food in Se-deficient regions such as the Mediterranean Basin, and may contribute to an increase in drought resistance in plants. The present study has considered detachment force, flesh firmness, pigmentation, fresh and dry weight, and oil content of olive drupes from Se fertilized olive orchards (Olea europaea L.) under drought stress and well-watered conditions. This study has also evaluated the total Se, Se amino acid, phenol, carotenoid and chlorophyll contents of EVOO, plus its oxidative stability against oxidation. While there was no change in the ripening indexes and the production of olives generally, Se application did increase the total Se, Se methionine, phenol, and carotenoid and chlorophyll contents. The higher concentration of these (bio) chemical compounds in EVOO obtained from Se fertilized plants might well suggest enhanced antioxidant activity. Consequently, EVOO obtained from Se fertilized trees possesses a higher nutritional value and, as indicated by the greater oxidative stability against oxidation, longer shelf life. In addition, under water deficient conditions, a higher fresh olive weight corresponds to a higher level of phenol, carotenoid and chlorophyll, and the chlorophyll-to-carotenoid ratio in Se fertilized trees would appear to confirm the positive role of selenium in alleviating damage caused by drought stress conditions.

Distribution and translocation of selenium from soil to highland barley in the Tibetan Plateau Kashin-Beck disease area

Kashin-Beck disease (KBD), which is still active and severe in the Tibetan Plateau, is considered to be a kind of selenium (Se)-deficient disease. Highland barley as the most popular staple food in the Tibetan Plateau is one of the dominant Se sources for local people. To improve Se levels in crops in the Tibetan Plateau KBD area, the distribution and translocation of Se from soil to highland barley in both non-KBD and KBD endemic areas were investigated. The results showed that Se levels in highland barley were too low to meet the minimum requirements of human for daily intake of Se. The total Se concentrations of highland barley fractions in KBD areas were lower than that in non-KBD areas (grain P = 0.238; straw P = 0.087; root P = 0.008). However, no significant difference was observed in corresponding cultivated soil Se between the two areas (P = 0.993). The calculation of Se transfer factors indicated that the restricting step for Se translocation was from soil to root. Water-soluble, exchangeable and fulvic acid-bound Se fractions in the soil are key species dominating in this transfer process, according to their significant correlations with root Se. Se transfer from soil to root significantly increases as the pH value of soil increases (P = 0.007), and soil organic matter content decreases (P = 0.019). The information obtained may have considerable significance for proposing effective agricultural measures to increase grain Se in KBD endemic areas.

Selenium: an element for life

This review aims to illustrate the importance of selenium (Se) for maintenance of overall health, especially for the thyroid, immunity, and homeostasis. Furthermore, it outlines the role of Se in reproduction and in virology and discusses the effects of Se supplementation in critical illness. The multifaceted aspects of this essential nutrient have attracted worldwide clinical and research interest in the last few decades. Se exerts its activity in the form of the aminoacid selenocysteine incorporated in selenoproteins. The impact of Se administration should be considered in relation to its apparent U shaped effects, i.e., exhibiting major advantages in Se-deficient individuals but specific health risks in those with Se excess. Addition of selenium to the administration of levothyroxine may be useful in patients with low Se intake and with mild-form or early-stage Hashimoto's thyroiditis (HT). Serum Se concentration (possibly also at tissue level) decreases in inflammatory conditions and may vary with the severity and duration of the inflammatory process. In such cases, the effect of Se supplementation seems to be useful and rational. Meanwhile, Se's ability to improve the activity of T cells and the cytotoxicity of natural killer cells could render it effective in viral disease. However, the evidence, and this should be stressed, is at present conflicting as to whether Se supplementation is of benefit in patients with HT, though there are indications that it is advantageous in cases of mild/moderate Graves' Orbitopathy. The role of Se in type 2 diabetes mellitus (T2DM) is ambiguous, driven by both Se intake and serum levels. The evidence that insulin and glycaemia influence the transport and activity of Se, via regulatory activity on selenoproteins, and that high serum Se may have a diabetogenic effect suggests a 'Janus-effect' of Se in T2DM. Though the evidence is not as yet clear-cut, the organic form (selenomethionine), due to its pharmacokinetics, is likely to be more advantageous in long-term prevention, and supplementation efforts, while the inorganic form (sodium selenite) has proven effective in an acute, e.g., sepsis, clinical setting. Recent data indicate that functional selenoprotein single-nucleotide polymorphisms (SNPs) may interfere with Se utilization and effectiveness.

Fingerprinting sedimentary and soil units by their natural metal contents: a new approach to assess metal contamination

One of the major issues when assessing soil contamination by inorganic substances is reliable determination of natural metal concentrations. Through integrated sedimentological, pedological and geochemical analyses of 1414 (topsoil/subsoil) samples from 707 sampling stations in the southern Po Plain (Italy), we document that the natural distribution of five potentially toxic metals (Cr, Ni, Cu, Zn and Pb) can be spatially predicted as a function of three major factors: source-rock composition, grain size variability and degree of soil weathering. Thirteen genetic and functional soil units (GFUs), each reflecting a unique combination of these three variables, are fingerprinted by distinctive geochemical signatures. Where sediment is supplied by ultramafic (ophiolite-rich) sources, the natural contents of Cr and Ni in soils almost invariably exceed the Italian threshold limits designated for contaminated lands (150 mg/kg and 120 mg/kg, respectively), with median values around twice the maximum permissible levels (345 mg/kg for Cr and 207 mg/kg for Ni in GFU B5). The original provenance signal is commonly confounded by soil texture, with general tendency toward higher metal concentrations in the finest-grained fractions. Once reliable natural metal concentrations in soils are established, the anthropogenic contribution can be promptly assessed by calculating metal enrichments in topsoil samples. The use of combined sedimentological and pedological criteria to fingerprint GFU geochemical composition is presented here as a new approach to enhance predictability of natural metal contents, with obvious positive feedbacks for legislative purposes and environmental protection. Particularly, natural metal concentrations inferred directly from a new type of pedogeochemical map, built according to the international guideline ISO 19258, are proposed as an efficient alternative to the pre-determined threshold values for soil contamination commonly established by the national regulations.

Selenium fortification of an Italian rice cultivar via foliar fertilization with sodium selenate and its effects on human serum selenium levels and on erythrocyte glutathione peroxidase activity

Selenium food fortification could be a cost-effective strategy to counteract the inadequacy of selenium intake among the Italian population. In this study, the effect of foliar fertilization with sodium selenate of an Italian rice cultivar and the increase of serum selenium and of erythrocyte glutathione peroxidase (GPx) activity after intake of fortified rice, have been evaluated. The effect of foliar fertilization with sodium selenate (50 g Se/ha) vs. water was studied. Moreover, in a randomized, double-blind study, 10 healthy women supplemented their usual diet with a daily dose of 80 g of Se-enriched-rice and 10 matched-women with 80 g of regular rice. Before, after 5 and 20 days of supplementation, serum Se and GPx-activity were evaluated. The mean selenium content in Se-enriched-rice was 1.64 ± 0.28 μg/g, while in regular rice it was 0.36 ± 0.15 μg/g (p < 0.001). A significant increase of serum Se and GPx-activity was observed only in the intervention group and only after 20 days. The results show that selenium fortification of rice can be achieved with foliar fertilization with sodium selenate and that the 20 days intake of this Se-enriched-rice increases the serum selenium levels and GPx-activity.

Selenium content of Belgian cultivated soils and its uptake by field crops and vegetables

A series of 695 food crops were collected on 539 soils throughout Belgium. All samples were collected on commercial production fields, omitting private gardens. All crops were analyzed for their selenium (Se) concentration. The soils represent different soil types occurring in Belgium, with soil textures ranging from sand to silt loam, and including a few clay soils. They were analyzed for Se concentration, organic carbon content, cation exchange capacity and extractable sulphur (S) concentration. The Se concentrations in the soils were low (range 0.14-0.70 mg kg(-1) dw), but increasing soil Se concentrations were observed with increasing clay content. Stepwise multiple regressions were applied to determine relations between Se concentrations in crops and soil characteristics. Among field crops, wheat is the most important accumulator of selenium but the concentration remains rather low on the Belgian low Se-soils. Based on dry weight, leafy vegetables contain more Se than wheat. The soil is the most important source of Se and the element is transported with the water stream to the leaves, where it is accumulated. Vegetables rich in S, e.g. some Brassica and Allium species, have a higher capacity to accumulate Se as it can replace S in the proteins, although this accumulation is still limited at low soil Se concentrations. In loamy soils, weak correlations were found between the soil Se concentration and its concentration in wheat and potato. The uptake of Se increased with increasing pH. The Se concentrations in Belgian soils are far too low to generate a driving force on Se uptake. General climatic conditions such as temperature, air humidity and soil moisture are also important for the transfer of Se within the plant, and plant linked factors such as cultivar, growth stage and edible part are important as well, although their influence remains limited at low soil Se concentrations.

Study of selenocompounds from selenium-enriched culture of edible sprouts

Selenium is recognised as an essential micronutrient for humans and animals. One of the main sources of selenocompounds in the human diet is vegetables. Therefore, this study deals with the Se species present in different edible sprouts grown in Se-enriched media. We grew alfalfa, lentil and soy in a hydroponic system amended with soluble salts, containing the same proportion of Se, in the form of Se(VI) and Se(IV). Total Se in the sprouts was determined by acidic digestion in a microwave system and by ICP/MS. Se speciation was carried out by enzymatic extraction (Protease XIV) and measured by LC-ICP/MS. The study shows that the Se content of plants depends on the content in the growth culture, and that part of the inorganic Se was biotransformed mainly into SeMet. These results contribute to our understanding of the uptake of inorganic Se and its biotransformation by edible plants.

Selenium bioaccessibility and speciation in biofortified Pleurotus mushrooms grown on selenium-rich agricultural residues

Cultivation of saprophytic fungi on selenium-rich substrates can be an effective means to produce selenium-fortified food. Pleurotus florida, an edible species of oyster mushrooms, was grown on wheat straw from the seleniferous belt of Punjab (India) and its potential to mobilize and accumulate selenium from the growth substrate was studied. Selenium concentration in biofortified mushrooms was 800 times higher compared with control samples grown on wheat straw from non selenium-rich areas (141 vs 0.17 μg Se g(-1) dry weight). Seventy-five percent of the selenium was extracted after in vitro simulated gastrointestinal digestion and investigation of the selenium molecular fractions by size exclusion HPLC-ICP-MS revealed that proteins and any other high molecular weight selenium-containing molecule were hydrolyzed to peptides and low molecular weight selenocompounds. Analysis of the gastrointestinal hydrolysates by anion exchange HPLC-ICP-MS showed that the bioaccessible selenium was mainly present as selenomethionine, a good bioavailable source of selenium, which accounted for 73% of the sum of the detected species. This study demonstrates the feasibility of producing selenium-biofortified edible mushrooms using selenium-rich agricultural by-products as growth substrates. The proposed approach can be used to evaluate whether selenium-contaminated plant waste materials harvested from high-selenium areas may be used to produce selenium-biofortified edible mushrooms based on the concentration, bioaccessibility and speciation of selenium in the mushrooms.

Identification of selenosugars and other low-molecular weight selenium metabolites in high-selenium cereal crops

Several novel selenium containing compounds were characterized in staple crops (wheat, rice and maize) grown on soils naturally rich in selenium. A dedicated method based on the coupling of liquid chromatography with multiplexed detection (ICP-MS, ESI-Orbitrap MS(/MS)) was developed for the speciation of low-molecular weight (<5 kDa) selenium metabolites. Nine species present in different proportions as a function of the crop type were identified by cation-exchange HPLC-ESI-Orbitrap MS on the basis of the accurate molecular mass and MS/MS spectra. The natural origin of these species was then validated by varying extraction conditions and by using hydrophilic interaction LC (HILIC)-ESI-Orbitrap MS(/MS). Among the identified compounds, Se-containing monosaccharides (hexose moiety, m/z 317 and m/z 358) or Se-containing disaccharides (hexose-pentose moiety, m/z 407 and m/z 408) were the first selenosugars reported in edible plants. It is also the first report of the presence of 2,3-dihydroxypropionyl-selenolanthionine (m/z 345) in rice. Because these crops can be an important source of selenium in animal and human nutrition, the understanding of the origin and the fate of these species during metabolic processes will be of great interest.

Predicted dietary intake of selenium by the general adult population in Belgium

The total selenium content of about 800 food products purchased in Belgium was determined and combined with food records to determine the nutritional selenium status of Belgian people. The largest selenium concentrations (>1 mg kg(-1)) were found in Brazil nuts and offal, of which the consumption is limited. Usually consumed food groups with the highest selenium concentrations were fish and shellfish (0.2-0.9 mg kg(-1)), eggs, poultry meat, cheese, mushrooms and pasta (approximately 0.2 mg kg(-1)). The mean dietary selenium intake was calculated to be 60 µg day(-1), which is at the lower end but within the range recommended by the Superior Health Council in Belgium (60-70 µg day(-1)), and adequate according to the 55 µg day(-1) recommended by the Scientific Committee on Food (SCF) of the European Commission. The major sources of selenium intake are meat and meat products (31%), fish and shellfish (20%), pasta and rice (12%), and bread and breakfast cereals (11%).

Environmental selenium research: from microscopic processes to global understanding

Selenium is a natural trace element that is of fundamental importance to human health. The extreme geographical variation in selenium concentrations in soils and food crops has resulted in significant health problems related to deficient or excess levels of selenium in the environment. To deal with these kinds of problems in the future it is essential to get a better understanding of the processes that control the global distribution of selenium. The recent development of analytical techniques and methods enables accurate selenium measurements of environmental concentrations, which will lead to a better understanding of biogeochemical processes. This improved understanding may enable us to predict the distribution of selenium in areas where this is currently unknown. These predictions are essential to prevent future Se health hazards in a world that is increasingly affected by human activities.

Arsenic contamination of the environment-food chain: a survey on wheat as a test plant to investigate phytoavailable arsenic in Italian agricultural soils and as a source of inorganic arsenic in the diet

Seven hundred and twenty-six samples of wheat grains from the majority of Italian agricultural areas were pooled into 141 composite samples, homogeneous with respect to geographical origin and wheat variety. The average arsenic concentration of the pooled samples was 9 ng g(-1), with a range of 2-55 ng g(-1) (dry weight basis). The spread of arsenic concentrations (coefficient of variation of 91%) was related to spatial variability associated with geochemical and environmental factors. Temporal variability was investigated by a 3-year longitudinal study on 7 wheat cultivars grown in 22 areas of central and northern Italy. Average year-to-year variation in arsenic levels was low, and the average of the coefficients of variation was 23%. These results show that mapping of phytoavailable arsenic in agricultural soils can be done by measuring arsenic concentration in representative samples of wheat grains. Arsenic speciation in the grain showed that As(III) and As(V) were the major As compounds, highlighting the importance of wheat as a source of inorganic arsenic in the diet.

Changes in selenium speciation associated with increasing tissue concentrations of selenium in wheat grain

Wheat (Triticum aestivum) collected in the Nawanshahr-Hoshiarpur Region (Punjab, India) showed the highest selenium concentrations ever recorded in cereal grains (29-185 microg g(-1)). There was a strong positive relationship between the selenium content in shoots and that in kernels, showing that grain selenium concentration can be predicted from that in the vegetative tissues of the plant. The identity and content of the selenocompounds in the grain samples and in wheat-based reference materials were investigated by HPLC-ICP-dynamic reaction cell-MS. Reversed-phase, cation exchange, and anion exchange HPLC were used to separate the selenium species after ultrasound-assisted enzymatic extraction with an ultrasonic probe. Selenomethionine and selenate accounted for 72-85% and 2-6% of the sum of the selenium species, respectively. The proportion of organic Se species varied with increasing Se content; namely, SeMet showed a relative reduction whereas the other organoselenium compounds increased up to 18-22% of the total chromatographed selenium. Se-methyl-selenocysteine was detected as a minor compound (0.2-0.5%) in high-Se wheat by both reversed-phase and cation exchange HPLC using retention time matching with the standard substance spiked to the sample extracts. Regular consumption of locally produced wheat-based food items may lead the population of the study area to an excessive intake of selenium. On the other hand, the large predominance of selenomethionine shows that local wheat can be a promising raw material for naturally enriched products to be used to supplement human and animal diets in low selenium areas.

Selenium in higher plants: understanding mechanisms for biofortification and phytoremediation

Selenium (Se) is an essential micronutrient for many organisms, including plants, animals and humans. As plants are the main source of dietary Se, plant Se metabolism is therefore important for Se nutrition of humans and other animals. However, the concentration of Se in plant foods varies between areas, and too much Se can lead to toxicity. As we discuss here, plant Se uptake and metabolism can be exploited for the purposes of developing high-Se crop cultivars and for plant-mediated removal of excess Se from soil or water. Here, we review key developments in the current understanding of Se in higher plants. We also discuss recent advances in the genetic engineering of Se metabolism, particularly for biofortification and phytoremediation of Se-contaminated environments.

Climate change and food safety: an emerging issue with special focus on Europe

According to general consensus, the global climate is changing, which may also affect agricultural and livestock production. The potential impact of climate change on food security is a widely debated and investigated issue. Nonetheless, the specific impact on safety of food and feed for consumers has remained a less studied topic. This review therefore identifies the various food safety issues that are likely to be affected by changes in climate, particularly in Europe. Amongst the issues identified are mycotoxins formed on plant products in the field or during storage; residues of pesticides in plant products affected by changes in pest pressure; trace elements and/or heavy metals in plant products depending on changes in their abundance and availability in soils; polycyclic aromatic hydrocarbons in foods following changes in long-range atmospheric transport and deposition into the environment; marine biotoxins in seafood following production of phycotoxins by harmful algal blooms; and the presence of pathogenic bacteria in foods following more frequent extreme weather conditions, such as flooding and heat waves. Research topics that are amenable to further research are highlighted.

Food-chain selenium and human health: emphasis on intake

Following the publication of the landmark trial of Clark et al. in 1996 that appeared to show that Se could reduce the risk of cancer, awareness of the importance of Se to human health has markedly increased. As a result, there is now much more aggressive marketing of Se supplements and functional foods, even in situations where additional consumption of Se is inappropriate. The present review addresses how Se gets into the food chain, the wide variability in Se content of foods and the very different levels of intake between countries and regions. Though it is clear that there are adverse consequences for health of both deficient and excessive intake, health effects at intermediate levels of intake are less certain. Thus it is difficult to define optimal intake which depends on a large number of factors, such as which functions of Se are most relevant to a particular disease state, which species of Se is most prominent in the Se source, which health condition is being considered, the adequacy or otherwise of intake of other nutrients, the presence of additional stressors, and lastly whether the ability to make selenoproteins may be compromised. These complexities need to be understood, particularly by policy makers, in order to make informed judgments. Potential solutions for increasing Se intake, where required, include agronomic biofortification and genetic biofortification or, for individuals, increased intake of naturally Se-rich foods, functional foods or supplements. The difficulties of balancing the risks and benefits in relation to Se intake are highlighted.