This review covers current knowledge of selenium in the dietary intake, its bioavailability, metabolism, functions, biomarkers, supplementation and toxicity, as well as its relationship with diseases and gut microbiota specifically on the symbiotic relationship between gut microflora and selenium status. Selenium is essential for the maintenance of the immune system, conversion of thyroid hormones, protection against the harmful action of heavy metals and xenobiotics as well as for the reduction of the risk of chronic diseases. Selenium is able to balance the microbial flora avoiding health damage associated with dysbiosis. Experimental studies have shown that inorganic and organic selenocompounds are metabolized to selenomethionine and incorporated by bacteria from the gut microflora, therefore highlighting their role in improving the bioavailability of selenocompounds. Dietary selenium can affect the gut microbial colonization, which in turn influences the host's selenium status and expression of selenoproteoma. Selenium deficiency may result in a phenotype of gut microbiota that is more susceptible to cancer, thyroid dysfunctions, inflammatory bowel disease, and cardiovascular disorders. Although the host and gut microbiota benefit each other from their symbiotic relationship, they may become competitors if the supply of micronutrients is limited. Intestinal bacteria can remove selenium from the host resulting in two to three times lower levels of host's selenoproteins under selenium-limiting conditions. There are still gaps in whether these consequences are unfavorable to humans and animals or whether the daily intake of selenium is also adapted to meet the needs of the bacteria.

Metabolic syndrome (MS) involves pathophysiological alterations that might compromise zinc status. The aim of this study was to evaluate zinc status biomarkers and their associations with cardiometabolic factors in patients with MS. Our case control study included 88 patients with MS and 37 controls. We performed clinical and anthropometric assessments and obtained lipid, glycemic, and inflammatory profiles. We also evaluated zinc intake, plasma zinc, erythrocyte zinc, and 24-h urinary zinc excretion. The average zinc intake was significantly lower in the MS group (p < 0.001). Regression models indicated no significant differences in plasma zinc concentration (all p > 0.05) between the two groups. We found significantly higher erythrocyte zinc concentration in the MS group (p < 0.001) independent from co-variable adjustments. Twenty-four hour urinary zinc excretion was significantly higher in the MS group (p = 0.008), and adjustments for age and sex explained 21% of the difference (R² = 0.21, p < 0.001). There were significant associations between zincuria and fasting blood glucose concentration (r = 0.479), waist circumference (r = 0.253), triglyceride concentration (r = 0.360), glycated hemoglobin concentration (r = 0.250), homeostatic model assessment—insulin resistance (r = 0.223), and high-sensitivity C-reactive protein concentration (r = 0.427) (all p < 0.05) in the MS group. Patients with MS had alterations in zinc metabolism mainly characterized by an increase in erythrocyte zinc and higher zincuria.

Adolescents with overweight and obesity report various motivations for weight loss other than the desire for better health. However, there is little evidence regarding the main motivations for weight loss in adolescents. The present systematic review aimed to identify the motivations for weight loss in adolescents with overweight and obesity. A systematic search for original articles published up to December 2016 was carried out in the PubMed, Scopus, LILACS, and ADOLEC databases. The terms used in the search were: motivation, motive, reason, “weight loss,” “lose weight,” and adolescent. Six studies (all cross-sectional) met the selection criteria and were included in the review. The instruments used to assess the participants’ motivations for weight loss were interviews and questionnaires with open questions. Seventeen motivations for weight loss were identified, the main ones being better health, esthetic/cosmetic reasons, improvements in self-esteem, and avoidance of provocation/bullying. The results of the present review show the need for validated instruments to assess the motivations for weight loss in adolescents with overweight and obesity. Moreover, the high frequency of motivations for weight loss related to appearance and social acceptance evidences the need for multidisciplinary weight loss interventions that consider not only the biological factors, but also the psychological and social aspects.