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The authors of this Comment are longstanding selenium investigators with a total of 200 or more published articles on selenium; the corresponding author (Margaret P [...].

Selenium (Se) and zinc (Zn) are essential micronutrients that are often lacking in the diet of humans and animals. Application of mineral Se and Zn fertilizers into soils may lead to a waste of Se and Zn due to the fast leaching and low utilization by plants. Slow-release Se and Zn biofertilizer may therefore be beneficial. This study aims to assess the potential of SeZn-enriched duckweed and sludge produced from wastewater as slow-release Se and Zn biofertilizers. Pot experiments with green beans (Phaseolus vulgaris) and sampling of Rhizon soil pore water were conducted to evaluate the bioavailability of Se and Zn in sandy and loamy soils mixed with SeZn-enriched duckweed and sludge. Both the Se and Zn concentrations in the soil pore water increased upon amending the two biomaterials. The concentration of Se released from SeZn-enriched duckweed rapidly decreased in the first 21 days and slowly declined afterwards, while it remained stable during the entire experiment upon application of SeZn-enriched sludge. The Zn content in the soil pore water gradually increased over time. The application of SeZn-enriched duckweed and sludge significantly increased the Se concentrations in plant tissues, in particular in the form of organic Se-methionine in seeds, without a negative impact on plant growth when an appropriate dose was applied (1 mg Se/kg soil). While, it did not increase Zn concentrations in plant seeds. The results indicate that the SeZn-enriched duckweed and sludge could be only used as organic Se biofertilizers for Se-deficient soils. Particularly, the SeZn-enriched sludge dominated with elemental nano-Se was an effective Se source and slow-release Se biofertilizer. These results could offer a theoretical reference to choose an alternative to chemical Se fertilizers for biofortification, avoiding the problem of Se losses by leaching from mineral Se fertilizers while recovering resources from wastewater. This could contribute to the driver for a future circular economy., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Introduction: Certain trace elements are essential for life and affect immune system function, and their intake varies by region and population. Alterations in serum Se, Zn and Cu have been associated with COVID-19 mortality risk. We tested the hypothesis that a disease-specific decline occurs and correlates with mortality risk in different countries in Europe., Methods: Serum samples from 551 COVID-19 patients (including 87 non-survivors) who had participated in observational studies in Europe (Belgium, France, Germany, Ireland, Italy, and Poland) were analyzed for trace elements by total reflection X-ray fluorescence. A subset (n=2069) of the European EPIC study served as reference. Analyses were performed blinded to clinical data in one analytical laboratory., Results: Median levels of Se and Zn were lower than in EPIC, except for Zn in Italy. Non-survivors consistently had lower Se and Zn concentrations than survivors and displayed an elevated Cu/Zn ratio. Restricted cubic spline regression models revealed an inverse nonlinear association between Se or Zn and death, and a positive association between Cu/Zn ratio and death. With respect to patient age and sex, Se showed the highest predictive value for death (AUC=0.816), compared with Zn (0.782) or Cu (0.769)., Discussion: The data support the potential relevance of a decrease in serum Se and Zn for survival in COVID-19 across Europe. The observational study design cannot account for residual confounding and reverse causation, but supports the need for intervention trials in COVID-19 patients with severe Se and Zn deficiency to test the potential benefit of correcting their deficits for survival and convalescence., Competing Interests: LS holds shares of selenOmed GmbH, a company involved in selenium status assessment. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Demircan, Chillon, Bracken, Bulgarelli, Campi, Du Laing, Fafi-Kremer, Fugazzola, Garcia, Heller, Hughes, Ide, Klingenberg, Komarnicki, Krasinski, Lescure, Mallon, Moghaddam, Persani, Petrovic, Ruchala, Solis, Vandekerckhove and Schomburg.)

Selenium (Se) is an essential trace element for humans and animals with a narrow window between deficiency and toxicity levels. Application of conventional chemical Se fertilizers to increase the Se content of crops in Se deficient areas could result in environmental contamination due to the fast leaching of inorganic Se. Slow-release Se-enriched biofertilizers produced from wastewater treatment may therefore be beneficial. In this study, the potential of Se-enriched biomaterials (sludge and duckweed) as slow-release Se biofertilizers was evaluated through pot experiments with and without planted green beans (Phaseolus vulgaris). The Se concentration in the bean tissues was 1.1-3.1 times higher when soils were amended with Se-enriched sludge as compared to Se-enriched duckweed. The results proved that the Se released from Se-enriched biomaterials was efficiently transformed to health-beneficial selenoamino acids (e.g., Se-methionine, 76-89%) after being taken up by beans. The Se-enriched sludge, containing mainly elemental Se, is considered as the preferred slow-release Se biofertilizer and an effective Se source to produce Se-enriched crops for Se-deficient populations, as shown by the higher Se bioavailability and lower organic carbon content. This study could offer a theoretical reference to choose an environmental-friendly and sustainable alternative to conventional mineral Se fertilizers for biofortification, avoiding the problem of Se losses by leaching from chemical Se fertilizers while recovering resources from wastewater. This could contribute to the driver for a future circular economy., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Selenium (Se) and zinc (Zn) are essential trace elements needed for appropriate immune system responses, cell signalling and anti-viral defence. A cross-sectional observational study was conducted at two hospitals in Ghent, Belgium, to investigate whether Se and/or Zn deficiency upon hospital admission correlates to disease severity and mortality risk in COVID-19 patients with or without co-morbidities. Trace element concentrations along with additional biomarkers were determined in serum or plasma and associated to disease severity and outcome. An insufficient Se and/or Zn status upon hospital admission was associated with a higher mortality rate and a more severe disease course in the entire study group, especially in the senior population. In comparison to healthy European adults, the patients displayed strongly depressed total Se (mean ± SD: 59.2 ± 20.6 vs. 84.4 ± 23.4 µg L -1 ) and SELENOP (mean ± SD: 2.2 ± 1.9 vs. 4.3 ± 1.0 mg L -1 ) concentrations at hospital admission. Particularly strong associations were observed for death risk of cancer, diabetes and chronic cardiac disease patients with low Se status, and of diabetes and obese patients with Zn deficiency. A composite biomarker based on serum or plasma Se, SELENOP and Zn at hospital admission proved to be a reliable tool to predict severe COVID-19 course and death, or mild disease course. We conclude that trace element assessment at hospital admission may contribute to a better stratification of patients with COVID-19 and other similar infectious diseases, support clinical care, therapeutic interventions and adjuvant supplementation needs, and may prove of particular relevance for patients with relevant comorbidities.

This study assessed the selenium (Se) removal efficiency of two pilot-scale high-rate algae ponds (HRAPs) treating domestic wastewater and investigated the production of Se-enriched microalgae as potential feed supplement. The HRAP-Se had an average Se, NH 4 -N, total phosphorus and COD removal efficiency of, respectively, 43%, 93%, 77%, and 70%. Inorganic Se taken up by the microalgae was mainly (91%) transformed to selenoamino acids, and 49-63% of Se in the Se-enriched microalgae was bioaccessible for animals. The crude protein content (48%) of the microalgae was higher than that of soybeans, whereas the essential amino acid content was comparable. Selenium may induce the production of the polyunsaturated fatty acids omega-3 and omega-6 in microalgae. Overall, the production of Se-enriched microalgae in HRAPs may offer a promising alternative for upgrading low-value resources into high-value feed supplements, supporting the drive to a circular economy.+ -N, total phosphorus and COD removal efficiency of, respectively, 43%, 93%, 77%, and 70%. Inorganic Se taken up by the microalgae was mainly (91%) transformed to selenoamino acids, and 49-63% of Se in the Se-enriched microalgae was bioaccessible for animals. The crude protein content (48%) of the microalgae was higher than that of soybeans, whereas the essential amino acid content was comparable. Selenium may induce the production of the polyunsaturated fatty acids omega-3 and omega-6 in microalgae. Overall, the production of Se-enriched microalgae in HRAPs may offer a promising alternative for upgrading low-value resources into high-value feed supplements, supporting the drive to a circular economy., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Selenium (Se) deficiency is associated with increased risk of clinical disorders. Yet, it has not been considered as an important public health issue in Africa. The health burden of this 'hidden hunger' remains largely unknown. Using a case study of central Kenya highlands, a cross-sectional survey assesses Se status of agricultural soils, foods, hair, and actual average dietary Se intake of the local population and investigates the soil-food Se concentration and Se intake-individual Se status relationships. The survey examines eight locations characterized by different agricultural soil types and assesses average dietary Se intake among 159 children and 111 women based on 24-h dietary recall data. Soil Se concentration does not explain Se concentration in foods, which instead is associated with soil's pH, organic matter, and P and Fe content. Cereal grains, beans and potato/green banana form a large portion of the local diet while intake of animal-based foods is limited. This results in Se intake of 15 and 33 µg p -1  d -1 for children and women, respectively. On average, 87% of children and 97% of women have inadequate average daily dietary Se intake, and the hair Se concentration of 92% children and 94% women is below the reference values. Soil's characteristics contribute to variation in Se concentration in foods and consequently the dietary Se intake. A low diversified diet is a key contributing factor to inadequate dietary Se intake in the region. These findings call for the need to investigate potential intervention measure and the health burden of Se deficiency.

Selenium (Se) and zinc (Zn) are essential micronutrients that are often lacking in the diet of humans and animals, leading to deficiency diseases. Lemna and Azolla are two aquatic plants with a substantial protein content, which offer the possibility of utilizing them to remove Se and Zn from (waste)water while producing micronutrient-enriched dietary proteins and fertilizers. In this study, we explored interaction effects occurring between Se and Zn when these micronutrients are taken up by Azolla and Lemna. The two aquatic plants were grown on hydroponic cultures containing 0-5.0 mg/L of Se (Se(IV) or Se(VI)) and Zn. The Se and Zn content of the plants, growth indicators, bioconcentration factor (BCF) and Se/Zn removal efficiency from the water phase were evaluated. The results demonstrated that Se(IV) is more toxic than Se(VI) for both plant species, as evidenced by the remarkable decrease of biomass content and root length when exposed to Se(IV). Both aquatic plants took up around 10 times more Se(IV) than Se(VI) from the medium. Moreover, the Se accumulation and removal efficiency increased by 66-99% for Se(IV) and by 34-59% for Se(VI) in Lemna when increasing Zn dosage from 0 to 5.0 mg/L in the medium, whereas it declined by 13-26% for Se(IV) and 21-35% for Se(VI) in Azolla, suggesting a synergetic effect in Lemna, but an antagonistic effect in Azolla. The maximum BCF of Se in Lemna and Azolla were 507 and 667, respectively. The protein content in freeze-dried Lemna and Azolla was approximately 17%. The high tolerance and accumulation of Se and Zn in Lemna and Azolla, combined with their rapid growth, high protein content and transformation of inorganic to organic Se species upon Se(IV) exposure make Lemna and Azolla potential candidates for the production of Se(IV)- and Zn-enriched biomass that can be used as crop fertilizers or protein-rich food/feed supplements or ingredients. Accordingly, by growing the Azolla and Lemna on wastewater, a high-value product can be produced from wastewater while recovering resources., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Enrichment of food crops with iodine is an option to alleviate dietary deficiencies. Therefore, foliar iodine fertilizer was applied on wheat and rice, in the presence and absence of the other micronutrients zinc and selenium. This treatment increased the concentration of iodine, as well as zinc and selenium, in the staple grains. Subsequently, potential iodine losses during preparation of foodstuffs with the enriched grains were studied. Oven-heating did not affect the iodine content in bread. Extraction of bran from flour lowered the iodine in white bread compared to wholegrain bread, but it was still markedly higher compared to the control. During subsequent in vitro gastrointestinal digestion, a higher percentage of iodine was released from foods based on extracted flour (82-92%) compared to wholegrain foods (50-76%). The foliar fertilization of wheat was found to be adequate to alleviate iodine deficiency in a population with a moderate to high intake of bread.

Deficiency in calcium, zinc, selenium, and iodine remains a major health issue in Africa. A selenium (Se) status survey conducted in central Kenya highlands revealed a high risk of dietary Se deficiency. This study investigates the effect of soil and foliar Se fertilizer application on Se concentration in maize and bean grains. It further tests the combination of Se fertilizer with phosphorus and nitrogen fertilizers, and with zinc and iodine fertilizers. Selenium fertilization results in a significant increase in Se concentration in grains. For the soil application, Se concentration increases on average by 3 µg kg -1 in maize and by 10 µg kg -1 in beans, for each gram of Se applied as sodium selenate. Foliar Se fertilization is more effective and increases Se concentration in grains on average by 18 µg kg -1 in maize, and by 67 µg kg -1 in beans. Total soil phosphorus/availability appears as an important factor influencing soil Se availability. Addition of phosphorus fertilizers positively affects the impact of Se fertilization in locations with low soil P, Fe, and Al. A Se + Zn + I fertilizer combination does not affect the impact on Se concentration in grains. Fertilizing beans alone is found to be more efficient compared to fertilizing only maize. In locations at high risk of dietary Se deficiency, foliar application at 10 g Se ha -1 on beans or 31 g Se ha -1 on maize is sufficient to achieve adequate daily dietary Se intake. The study points towards a multi-mineral agronomic biofortification, based on a site-specific biofortification strategy.

Background: As an essential but also potentially toxic element, both overexposure and underexposure to selenium (Se) can significantly affect public health. Rice is a common source of Se, especially in Asia. Not all Se may be released from the rice and become available for absorption into the bloodstream upon digestion in the gastrointestinal tract. Therefore, the bioaccessibility of Se in cooked white (polished) rice was assessed in vitro using the static gastrointestinal simulator SHIME (Simulator of the Human Intestinal Microbial Ecosystem)., Results: The common cooking procedure in China prior to consumption [i.e. boiling at low rice:water ratios (1:3) until all of the water is absorbed into the rice] did not change total Se levels in the rice. Gastrointestinal digestion of the cooked rice matrix revealed a Se bioaccessibility of 67-76% of total Se. Subsequent microbial activity in the colon reduced the accessibility of Se in the cooked rice to 51-62%., Conclusion: Not all Se present in cooked white rice should be considered as being bioavailable in the small intestine. A minor part is transferred with the remaining food matrix to the colon, where it is available for the microbial metabolism. © 2017 Society of Chemical Industry., (© 2017 Society of Chemical Industry.)

There is a growing concern for the long-term health effects of selenium (Se) over- or underfeeding. The efficiency of utilization of dietary Se is subject to many factors. Our study in dogs evaluated the effect of diet type (canned versus kibble) and dietary protein concentration on Se digestibility and bioactivity. Canned and kibble diets are commonly used formats of dog food, widely ranging in protein concentration. Twenty-four Labrador retrievers were used and four canned and four kibble diets were selected with crude protein concentrations ranging from 10.1 to 27.5 g/MJ. Crude protein concentration had no influence on the digestibility of Se in either canned or kibble diets, but a lower Se digestibility was observed in canned compared to kibble diets. However, the biological activity of Se, as measured by whole blood glutathione peroxidase, was higher in dogs fed the canned diets than in dogs fed the kibble diets and decreased with increasing crude protein intake. These results indicate that selenium recommendations in dog foods need to take diet type into account.

Background: Inadequate dietary selenium (Se) intake in humans and animals can lead to long term health problems, such as cancer. In view of the owner's desire for healthy longevity of companion animals, the impact of dietary Se provision on long term health effects warrants investigation. Little is currently known regards biomarkers, and rate of change of such biomarkers in relation to dietary selenium intake in dogs. In this study, selected biomarkers were assessed for their suitability to detect changes in dietary Se in adult dogs within eight weeks., Results: Twenty-four dogs were fed a semi-purified diet with an adequate amount of Se (46.1 μg/MJ) over an 8 week period. They were then divided into two groups. The first group remained on the adequate Se diet, the second were offered a semi-purified diet with a low Se concentration (6.5 μg/MJ; 31% of the FEDIAF minimum) for 8 weeks. Weekly urine and blood was collected and hair growth measurements were performed. The urinary Se to creatinine ratio and serum Se concentration were significantly lower in dogs consuming the low Se diet from week 1 onwards, by 84% (adequate 25.3, low 4.1) and 7% (adequate 257 μg/L, low 238 μg/L) respectively. Serum and whole blood glutathione peroxidase were also significantly lower in dogs consuming the low Se diet from weeks 6 and 8 respectively. None of the other biomarkers (mRNA expression and serum copper, creatine kinase, triiodothyronine:thyroxine ratio and hair growth) responded significantly to the low Se diet over the 8 week period., Conclusions: This study demonstrated that urinary Se to creatinine ratio, serum Se and serum and whole blood glutathione peroxidase can be used as biomarkers of selenium status in dogs. Urinary Se to creatinine ratio and serum Se concentrations responded faster to decreased dietary Se than the other parameters. This makes these biomarkers candidates for early screening of long term effects of dietary Se provision on canine health.

Se bioavailability in commercial pet foods has been shown to be highly variable. The aim of the present study was to identify dietary factors associated with in vitro accessibility of Se (Se Aiv) in pet foods. Se Aiv is defined as the percentage of Se from the diet that is potentially available for absorption after in vitro digestion. Sixty-two diets (dog, n 52; cat, n 10) were in vitro enzymatically digested: fifty-four of them were commercially available (kibble, n 20; pellet, n 8; canned, n 17; raw meat, n 6; steamed meat, n 3) and eight were unprocessed (kibble, n 4; canned, n 4) from the same batch as the corresponding processed diets. The present investigation examined if Se Aiv was affected by diet type, dietary protein, methionine, cysteine, lysine and Se content, DM, organic matter and crude protein (CP) digestibility. Se Aiv differed significantly among diet types (P< 0·001). Canned and steamed meat diets had a lower Se Aiv than pelleted and raw meat diets. Se Aiv correlated positively with CP digestibility in extruded diets (kibbles, n 19; r 0·540, P =0·017) and negatively in canned diets (n 16; r - 0·611, P =0·012). Moreover, the canning process (n 4) decreased Se Aiv (P =0·001), whereas extrusion (n 4) revealed no effect on Se Aiv (P =0·297). These differences in Se Aiv between diet types warrant quantification of diet type effects on in vivo Se bioavailability.

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., (© 2013.)

Leek was fertilized with sodium selenite (Na(2)SeO(3)) and sodium selenate (Na(2)SeO(4)) in a green house to assess the impact of selenium (Se) fertilization on Se uptake by the crop and its speciation in the crop. The bioaccessibility of Se in the Se-enriched leek was assessed using an in vitro extraction protocol mimicking the human gastrointestinal tract (stomach, small intestine, and colon). The lowest Se uptake was observed when Na(2)SeO(3) was used as a fertilizer, which results in a higher risk for Se accumulation in the soil on a longer term. When soil was amended with Na(2)SeO(4), 55 ± 5% of total Se in the leek occurred in an inorganic form, while only 21 ± 8% was inorganic when Na(2)SeO(3) was applied. Se-methylselenocysteine and selenomethione were the major organic species in both treatments. However, concentrations of Se-methylselenocysteine and γ-glutamyl-Se-methyl-selenocysteine, which were previously reported to induce positive health effects, were lower as compared to other Allium species. The majority of the Se in the leek was found to be bioaccessible in the stomach (around 60%) and small intestine (around 80%). However, a significant fraction also has good chances to reach the colon, where it seems to be taken up by the microbial community and may also induce positive health effects.

Aims: This study has been carried out to determine the spatial variability of faba bean seed Fe, Zn and Se content across agro-ecological zones in central and southwestern Ethiopia, where it is an important source of protein in the diet. The study assessed whether soil properties, arbuscular mycorrhizal fungi (AMF), faba bean characteristics and genetic diversity and agro-ecological zone as random factor affect seed Fe, Zn and Se content. Methodology: Multi-location fields were sampled in three important faba bean growing agro-ecologies during the 2018–2019 cropping season. Results: Seed Fe content varied from 45.7–61.9, 41.6–102 and 31.1–77.0 mg kg−1 in Cheliya, Dedo and Dendi, respectively. Likewise, Zn content ranged from 38.3–56.3, 44.6–73.6 and 21.6–49.9 mg kg−1. Selenium content varied from 10.1–45.1, 12.1–160 and 16.2–167 μg kg−1. Significant differences were observed for Zn and Se content across agro-ecologies. Consumption of 100 g faba beans per day can provide an overall average of 64 and 28% of the recommended daily allowance (RDA) for Fe, 45 and 62% for Zn and only 8% for Se for male and female adults, respectively. Soil properties explained seed Fe, Zn and Se content variation. However, for Zn and Se content the largest share of the difference was explained by agro-ecological mediated environmental variations. As a consequence, differences in dietary intake of micro-nutrients via faba beans are determined by living area. Conclusion: Soil properties and especially agro-ecological mediated environmental conditions explained seed Zn and Se content of faba bean and hence potential dietary intake. [ABSTRACT FROM AUTHOR]

Selenium (Se) and chromium (Cr) in water might be harmful because of their high toxicity in the aquatic environment. Efficient removal of their hexavalent forms (Se(VI) and Cr(VI)) from extreme acidic wastewater is still challenging. Therefore, several new hydrochars suited for efficient removal of trace Se(VI) and Cr(VI) from acidic wastewater were fabricated from biomass through a hydrothermal method. Most functional groups were retained in the hydrochar, which gave it an excellent adsorption capacity (43.2 mg·g−1 and 132 mg·g−1 for Se(VI) and Cr(VI), respectively). After one batch treatment at exceptionally low pH and a hydrochar dose of 0.2 g·L−1, Se(VI) and Cr(VI) could be removed from 1 mg·L−1 to 6 μg·L−1 and 15 μg·L−1, respectively. The mechanism of adsorption at various pH was elucidated by Scanning Electron Microscopy, Thermogravimetry, Fourier Transform Infrared Spectrometer, X-Ray Photoelectron Spectroscopy and density functional theory (DFT) calculation. The adsorption mechanism for Se(VI) in acidic solution involved the binding of SeO 4 2− with protonated amino groups (−NH 3 +) of Mix hydrochar. In the pH range of 6.5 to 7, Cr(VI) combined with −NH 3 + functional groups primarily in the form of CrO 4 2−. When the pH fell below 6.5, Cr(VI) bound with both −NH 3 + and carbonyl groups (−C=O) in the form of HCrO 4 −. Fast kinetics were observed during the removal process of Se(VI) and Cr(VI). The hydrochar adsorbent showed good stability in acidic environments and during many adsorption cycles. These findings provide theoretical basis for design of adsorption materials for acidic wastewater treatment. • New sorbents derived from mixed biomass were fabricated through a one-pot hydrothermal process. • The abundant functional groups in hydrochar imparts high Se(VI)/Cr(VI) adsorption capacity to it at low pH. • The adsorption mechanism by various functional groups at various pH levels was revealed. [ABSTRACT FROM AUTHOR]

Selenium (Se) is an essential nutrient for humans as it plays an important role in glutathione peroxidase (GPx) activity. Moreover, it may reduce cancer risks. The objective of this work was to examine in vitro the bioaccessibility of Se in three different Se-enriched food supplements and two different Se-enriched food crops, with reference to two pure Se standards, and changes in its speciation during intestinal digestion. Selenate was found to be stable throughout the entire digestion, whereas incubation of selenomethionine resulted in the chemical and microbial production of minor metabolites. The bioaccessibility of Se in Se-enriched food supplements and food crops was found to be highest in the small intestine. Compared to SelenoPrecise and Se-ACE tablets, a yoghurt-based supplement exhibited a much lower Se bioaccessibility, possibly due to the presence of nano- or microparticles of elemental Se. Colon microbiota were found to primarily affect Se bioaccessibility in the colon environment, with the presence of inactivated microbiota resulting in a higher bioaccessibility. A higher potential of Se to reach the colon and become accessible in this phase may result in beneficial effects on the colon health. [ABSTRACT FROM AUTHOR]