Thyroid diseases are common conditions that have a negative impact on the health of all populations. The literature sheds light on the differences in the composition of the intestinal microbiota in patients suffering from thyroid diseases compared to healthy individuals. The microbiome affects the proper functioning of the thyroid gland, and the existence of the gut–thyroid axis is discussed in the context of both thyroid diseases and intestinal dysbiosis. The purpose of this review is to describe associations between the microbiome and its metabolites and thyroid dysfunction. We try to explain the role of the microbiome in the metabolism of thyroid hormones and the impact of thyroid autoimmune diseases. In addition, we raise issues related to the influence of bacterial metabolites, such as short-chain fatty acids or secondary bile acids, in the functioning of the thyroid gland. Last but not least, we explored the interactions between the gut microbiota and therapeutics and supplements typically administered to patients with thyroid diseases.

We aim to systematically review the efficacy of prebiotics in reducing anthropometric and biochemical parameters in individuals with non-alcoholic fatty liver disease (NAFLD). A systematic search using PubMed/MEDLINE, Embase, clinicaltrials.gov, Cinahl, and Web of Science of articles published up to 20 March 2020 was performed for randomized controlled trials enrolling >20 adult patients. Random-effect meta-analysis for metabolic outcomes in NAFLD patients was performed for anthropometric data in addition to liver enzyme, carbohydrate, and lipid parameters. We found six trials (comprising a total of 242 patients) with NAFLD, with subjects aged 38–52 years. The mean time of fiber administration varied between 10 and 12 weeks. The main fiber types were psyllium (seeds or powder), Ocimum basilicum (seeds), and high-performance inulin and oligofructose powder at doses of either 10 or 16 g per day. The control group received either maltodextrin (powder or capsules) or crushed wheat (powder). Patients on the diet with added fiber had improvements in body mass index (BMI) (standardized mean difference (SMD) = −0.494, 95% confidence interval (CI): −0.864 to −0.125, p = 0.009); alanine aminotransferase (ALT) (SMD = −0.667, 95% CI: −1.046 to −0.288, p = 0.001); aspartate aminotransferase (AST) (SMD = −0.466, 95% CI: −0.840 to −0.091, p = 0.015); fasting insulin (SMD = −0.705, 95% CI: −1.115 to −0.295, p = 0.001); and homeostasis model assessment for insulin resistance (HOMA-IR) (SMD = −0.619, 95% CI: −1.026 to −0.211, p = 0.003). Hence, the results show that fiber supplements result in favorable changes as reflected in the measurement of anthropometric, metabolic, and liver-related biomarkers, i.e., body mass index (BMI), homeostasis model assessment for insulin resistance (HOMA-IR), insulin, alanine aminotransferase (ALT), and aspartate aminotransferase (AST). These effects suggest the potential benefits of fiber consumption for NAFLD populations. More prospective, controlled studies should be conducted to reveal specific details regarding the fiber type, dosage, and duration for optimal intervention.

The gut microbiota have gained much scientific attention recently. Apart from unravelling the taxonomic data, we should understand how the altered microbiota structure corresponds to functions of this complex ecosystem. The metabolites of intestinal microorganisms, especially bacteria, exert pleiotropic effects on the human organism and contribute to the host systemic balance. These molecules play key roles in regulating immune and metabolic processes. A subset of them affect the gut brain axis signaling and balance the mental wellbeing. Neurotransmitters, short chain fatty acids, tryptophan catabolites, bile acids and phosphatidylcholine, choline, serotonin, and L-carnitine metabolites possess high neuroactive potential. A scoping literature search in PubMed/Embase was conducted up until 20 June 2020, using three major search terms “microbiota metabolites” AND “gut brain axis” AND “mental health”. This review aimed to enhance our knowledge regarding the gut microbiota functional capacity, and support current and future attempts to create new compounds for future clinical interventions.

Background and objective: The health supplement bovine colostrum reportedly improves immunity and regulates intestinal homeostasis. Reliable assessment methods are needed to ensure the satisfactory biological activity of all marketed colostrum products. Of the well-established effects of colostrum use, the restoration of appropriate intestinal permeability assessed with the lactulose/mannitol (L/M) differential sugar absorption test upon supplementation with colostrum has been consistently observed. Milking time after delivery is one of the factors that influences the composition of bovine colostrum, which causes a rapid decrease in bioactive components. Materials and methods: We use the L/M test to evaluate the intestinal permeability reduction upon supplementation with colostrum (2 × 500 mg) harvested at various times after delivery (2, 24, and 72 h) or a placebo (whey). In our randomized, double-blind placebo-controlled (DBPC) trial, 31 healthy athletes were divided into four groups and assessed at baseline and after the intervention. Results: The trial revealed that only colostrum collected after 2 h and 24 h caused a significant reduction of intestinal permeability. The comparison of post-intervention vs. baseline Δ values produced statistically significant results for 2 h colostrum versus the placebo and 72 h colostrum groups. Conclusions: We conclude that the change of bovine colostrum composition over the first three days of lactation is accompanied by a decrease in its biological activity as measured with the L/M test. This test may offer a biological quality measure for colostrum.

Increased triacylglycerols’ (TAG) synthesis, insulin resistance, and prolonged liver lipid storage might lead to the development of non-alcoholic fatty liver disease (NAFLD). Global prevalence of NAFLD has been estimated to be around 25%, with gradual elevation of this ratio along with the increased content of adipose tissue in a body. The initial stages of NAFLD may be reversible, but the exposition to pathological factors should be limited. As dietary factors greatly influence various disease development, scientists try to find dietary components, helping to alleviate the steatosis. These components include n-3 polyunsaturated (PUFA) fatty acids, especially eicosapentaenoic acid (EPA) and docosahexaenoic acids (DHA). This review focused on the role of resolvins, protectins and merensins in NAFLD.