Actual levels of soy phytoestrogens in children correlate with thyroid laboratory parameters

Flavonoids Alleviate Peripheral Neuropathy Induced by Anticancer Drugs

Simple Summary

Chemotherapy-induced peripheral neuropathy (CIPN) is a debilitating condition that severely reduces the quality of life of a considerable proportion of cancer patients. There is no cure for CIPN to date. Here, we explore the potential of flavonoids as pharmacological agents in combating CIPN. Flavonoids alleviate CIPN by reducing oxidative stress, inflammation, and neuronal damage, among other mechanisms. Future research should evaluate the efficacy and side effects of flavonoids in human models of CIPN.

Abstract

Purpose: This study aimed to assess the potential of flavonoids in combating CIPN. Methods: PubMed and Google Scholar were used, and studies that investigated flavonoids in models of CIPN and models of neuropathic pain similar to CIPN were included. Only studies investigating peripheral mechanisms of CIPN were used. Results: Flavonoids inhibit several essential mechanisms of CIPN, such as proinflammatory cytokine release, astrocyte and microglial activation, oxidative stress, neuronal damage and apoptosis, mitochondrial damage, ectopic discharge, and ion channel activation. They decreased the severity of certain CIPN symptoms, such as thermal hyperalgesia and mechanical, tactile, and cold allodynia. Conclusions: Flavonoids hold immense promise in treating CIPN; thus, future research should investigate their effects in humans. Specifically, precise pharmacological mechanisms and side effects need to be elucidated in human models before clinical benefits can be achieved.

Neither soyfoods nor isoflavones warrant classification as endocrine disruptors: a technical review of the observational and clinical data

Soybeans are a rich source of isoflavones, which are classified as phytoestrogens. Despite numerous proposed benefits, isoflavones are often classified as endocrine disruptors, based primarily on animal studies. However, there are ample human data regarding the health effects of isoflavones. We conducted a technical review, systematically searching Medline, EMBASE, and the Cochrane Library (from inception through January 2021). We included clinical studies, observational studies, and systematic reviews and meta-analyses (SRMA) that examined the relationship between soy and/or isoflavone intake and endocrine-related endpoints. 417 reports (229 observational studies, 157 clinical studies and 32 SRMAs) met our eligibility criteria. The available evidence indicates that isoflavone intake does not adversely affect thyroid function. Adverse effects are also not seen on breast or endometrial tissue or estrogen levels in women, or testosterone or estrogen levels, or sperm or semen parameters in men. Although menstrual cycle length may be slightly increased, ovulation is not prevented. Limited insight could be gained about possible impacts of in utero isoflavone exposure, but the existing data are reassuring. Adverse effects of isoflavone intake were not identified in children, but limited research has been conducted. After extensive review, the evidence does not support classifying isoflavones as endocrine disruptors.

Is There Such a Thing as "Anti-Nutrients"? A Narrative Review of Perceived Problematic Plant Compounds

Plant-based diets are associated with reduced risk of lifestyle-induced chronic diseases. The thousands of phytochemicals they contain are implicated in cellular-based mechanisms to promote antioxidant defense and reduce inflammation. While recommendations encourage the intake of fruits and vegetables, most people fall short of their target daily intake. Despite the need to increase plant-food consumption, there have been some concerns raised about whether they are beneficial because of the various ‘anti-nutrient’ compounds they contain. Some of these anti-nutrients that have been called into question included lectins, oxalates, goitrogens, phytoestrogens, phytates, and tannins. As a result, there may be select individuals with specific health conditions who elect to decrease their plant food intake despite potential benefits. The purpose of this narrative review is to examine the science of these ‘anti-nutrients’ and weigh the evidence of whether these compounds pose an actual health threat.

Effects of Dietary Phytoestrogens on Hormones throughout a Human Lifespan: A Review

Dietary phytoestrogens are bioactive compounds with estrogenic activity. With the growing popularity of plant-based diets, the intake of phytoestrogen-rich legumes (especially soy) and legume-derived foods has increased. Evidence from preclinical studies suggests these compounds may have an effect on hormones and health, although the results of human trials are unclear. The effects of dietary phytoestrogens depend on the exposure (phytoestrogen type, matrix, concentration, and bioavailability), ethnicity, hormone levels (related to age, sex, and physiological condition), and health status of the consumer. In this review, we have summarized the results of human studies on dietary phytoestrogens with the aim of assessing the possible hormone-dependent outcomes and health effects of their consumption throughout a lifespan, focusing on pregnancy, childhood, adulthood, and the premenopausal and postmenopausal stages. In pregnant women, an improvement of insulin metabolism has been reported in only one study. Sex hormone alterations have been found in the late stages of childhood, and goitrogenic effects in children with hypothyroidism. In premenopausal and postmenopausal women, the reported impacts on hormones are inconsistent, although beneficial goitrogenic effects and improved glycemic control and cardiovascular risk markers have been described in postmenopausal individuals. In adult men, different authors report goitrogenic effects and a reduction of insulin in non-alcoholic fatty liver patients. Further carefully designed studies are warranted to better elucidate the impact of phytoestrogen consumption on the endocrine system at different life stages.

Effects of isoflavones on breast tissue and the thyroid hormone system in humans: a comprehensive safety evaluation

Isoflavones are secondary plant constituents of certain foods and feeds such as soy, linseeds, and red clover. Furthermore, isoflavone-containing preparations are marketed as food supplements and so-called dietary food for special medical purposes to alleviate health complaints of peri- and postmenopausal women. Based on the bioactivity of isoflavones, especially their hormonal properties, there is an ongoing discussion regarding their potential adverse effects on human health. This review evaluates and summarises the evidence from interventional and observational studies addressing potential unintended effects of isoflavones on the female breast in healthy women as well as in breast cancer patients and on the thyroid hormone system. In addition, evidence from animal and in vitro studies considered relevant in this context was taken into account along with their strengths and limitations. Key factors influencing the biological effects of isoflavones, e.g., bioavailability, plasma and tissue concentrations, metabolism, temporality (pre- vs. postmenopausal women), and duration of isoflavone exposure, were also addressed. Final conclusions on the safety of isoflavones are guided by the aim of precautionary consumer protection.

Endocrine Disrupters and the Safety of Food Chains

Endocrine disrupters (ED) are a heterogeneous group of chemicals including persistent contaminants, pesticides, as well as compounds present in consumer products and natural substances. For most ED, the food chain is a current major exposure route for the general population. ED can enter the food chain through the living environment (e.g., feeds, fertilizers) of food-producing organisms, be directly employed in food production (e.g., pesticides) or be released from food contact materials (such as bisphenol A or phthalates); in addition, the endocrine disruption potential of some natural compounds in edible plants, including the so-called phytoestrogens, should not be overlooked. An exposure assessment has to consider the specific liability of food commodities to contamination with specific ED (e.g., polychlorinated and polybrominated chemicals in lipid-rich foods). The paper discusses the main toxicological research issues in order to support the risk assessment of ED in food chains, including: the potential for additive, 'cocktail' effects (as from multiple pesticide residues); the long-term effects on target body systems (e.g., reproductive, nervous) elicited by exposure during prenatal as well as postnatal life stage windows, and toxicant/nutrient interactions (e.g., thyroid-targeting ED and iodine status). Food safety systems should exploit the available knowledge to improve prevention of long-term risks along the whole food chain.

Dietary Factors Associated with Plasma Thyroid Peroxidase and Thyroglobulin Antibodies

The knowledge about dietary habits and their influence in the development of autoimmune thyroid disease is insufficient. The aim of this study was to analyse the association of dietary factors and plasma thyroid peroxidase antibodies (TPO-Ab) and/or thyroglobulin antibodies (Tg-Ab). The study enrolled 1887 participants originating from the South Croatia. Participants with elevated plasma TPO-Ab and/or Tg-Ab were defined as cases (n = 462) and those with TPO-Ab and/or Tg-Ab within referent values were defined as controls (n = 1425). Dietary intake was evaluated according to a food frequency questionnaire containing 58 food items. Principal component analysis was used to group food items into dietary groups. We used logistic regression analysis to examine dietary groups associated with positive plasma TPO-Ab and/or Tg-Ab. The results indicate that the dietary group with frequent consumption of animal fats and butter is associated with positive plasma TPO-Ab and/or Tg-Ab (p = 0.01). The dietary group with frequent consumption of vegetables as well as the dietary group with high consumption of dried fruit, nuts, and muesli are associated with negative findings of TPO-Ab and/or Tg-Ab (p = 0.048 and p = 0.02, respectively). We showed that the anti-inflammatory dietary groups are associated with the negative findings of plasma TPO-Ab and/or Tg-Ab.

Serum concentrations of anti-thyroid peroxidase and anti-thyroglobulin antibodies in children and adolescents without apparent thyroid disorders

OBJECTIVE

The age-dependent prevalence and clinical relevance of anti-thyroid peroxidase (TPOAb) and anti-thyroglobulin (TGAb) antibodies in children and adolescents without thyroid diseases are unknown. The aim of this study was to measure the concentration of these thyroid autoantibodies in a large cohort of hospitalized and out-patient subjects. Additionally, we investigated the correlation of TPOAb and TGAb with thyroid parameters as well as with putative confounding parameters such as standard deviation scores (SDS) of height, BMI-SDS and CRP.

METHODS

Serum samples from 841 patients with non-thyroid related diseases between 1 day post partum and 20 years of age were used in a cross-sectional study. TPOAb, TGAb, thyroid parameters (TSH, fT3, fT4 and thyroglobulin) and CRP were measured by the Modular System (Roche, Mannheim).

RESULTS

The values of TPOAb and TGAb showed an age-dependent maximum of antibody frequency for both genders during the first year of life with concentrations of 163 IU/mL and 161 IU/mL in the 95th percentile. In girls, a second maximum was observed during puberty with concentrations of 82 IU/mL TPOAb and 582 IU/mL TGAb in the 95th percentile. Both antibodies correlated significantly (p<0.05) with each other, with fT3, fT4, BMI-SDS (only TPOAb) and CRP and TSH (only TGAb).

CONCLUSION

The prevalence of TPOAb and TGAb was shown to be age-dependent with increased values in the first year of life and during puberty. The increased "physiological" concentrations of TPOAb and TGAb have to be considered when used as diagnostic indicators of autoimmune thyroid disease in a paediatric population.

Soy extracts suppressed iodine uptake and stimulated the production of autoimmunogen in rat thyrocytes

Soy consumption is associated with thyroid disorders such as hypothyroidism, goiter, and autoimmune thyroid disease (ATD) as well as increased iodine requirement in certain cases. However, the anti-thyroid component(s) in soy are yet to be identified and the molecular mechanism(s) involved remain unclear. This study examined the effects of soy isoflavones (ISF) on iodide uptake and expression of thyroglobulin (Tg) and sodium/iodide symporter (NIS) in thyrocytes. Fischer rat thyroid cells (FRTL) were treated with Novasoy (a soy alcohol extract containing 30% ISF) or major ISF aglycones or glycosides for 24 h. Iodide uptake was measured by a colorimetric assay. The protein level of Tg and NIS was measured by Western blotting. Cytotoxicity of tested compounds was determined by the MTT cell proliferation assay. Iodide uptake in FRTL cells was dose-dependently suppressed by Novasoy added into the cell culture (10, 25, or 50 µg/mL, P < 0.05). However, neither the major ISF aglycones nor glycosides alone or in combination had similar effects. Novasoy (up to 200 µg/mL) had no cytotoxic effect. Novasoy (1, 10, and 50 µg/mL) and genistein (1 and 10 µM) markedly increased the protein content of a 40 kDa Tg fragment (P40, a known autoimmunogen) and non-glycosylated NIS in the FRTL cells (P < 0.05). Overall, this study demonstrated that the alcohol soluble component(s) other than the major ISF in soy remarkably inhibited iodide uptake in the FRTL cells. Soy ISF, particularly genistein, induced the production of P40, which might be responsible for the higher incidence of ATD reported in soy infant formula-fed children.

Micronutrient intake and status in Central and Eastern Europe compared with other European countries, results from the EURRECA network

Objective

To compare micronutrient intakes and status in Central and Eastern Europe (CEE) with those in other European countries and with reference values.

Design

Review of the micronutrient intake/status data from open access and grey literature sources from CEE.

Setting

Micronutrients studied were folate, iodine, Fe, vitamin B12 and Zn (for intake and status) and Ca, Cu, Se, vitamin C and vitamin D (for intake). Intake data were based on validated dietary assessment methods; mean intakes were compared with average nutrient requirements set by the Nordic countries or the US Institute of Medicine. Nutritional status was assessed using the status biomarkers and cut-off levels recommended primarily by the WHO.

Subjects

For all population groups in CEE, the mean intake and mean/median status levels were compared between countries and regions: CEE, Scandinavia, Western Europe and Mediterranean.

Results

Mean micronutrient intakes of adults in the CEE region were in the same range as those from other European regions, with exception of Ca (lower in CEE). CEE children and adolescents had poorer iodine status, and intakes of Ca, folate and vitamin D were below the reference values.

Conclusions

CEE countries are lacking comparable studies on micronutrient intake/status across all age ranges, especially in children. Available evidence showed no differences in micronutrient intake/status in CEE populations in comparison with other European regions, except for Ca intake in adults and iodine and Fe status in children. The identified knowledge gaps urge further research on micronutrient intake/status of CEE populations to make a basis for evidence-based nutrition policy.

Update on genistein and thyroid: an overall message of safety

Genistein aglycone, one of the soy isoflavones, has been reported to be beneficial in the treatment of menopausal vasomotor symptoms, osteoporosis, and cardiovascular diseases, as well as in a variety of cancers. However, issues of potential harm on thyroid function resulting from soy isoflavones consumption have been raised. Much of the evidence for the goitrogenic effects of isoflavones is derived from experimental in vitro and in vivo studies. Goitrogenic effects were also noted in infants fed non-iodine-fortified, soy-based formula, a problem that was easily solved with iodine fortification. Recent studies suggest that genistein shows a good profile of safety on the thyroid although definitive conclusions have not reached. The aim of this brief review is to summarize and better clarify the effects of genistein on human thyroid health.

Effects of dietary soy intake on maternal thyroid functions and serum anti-thyroperoxidase antibody level during early pregnancy

Soy and its isoflavones have been suggested to suppress thyroperoxidase (TPO), induce goiter, inhibit deiodinase, and modulate immune functions. This study initially investigated the effects of dietary soy consumption on maternal thyroid functions and anti-TPO antibody (TPOAb) production during early pregnancy. Data were collected through questionnaire from 505 women enrolled during early pregnancy by random sampling in Shenyang, China. Based on soy intake frequency, the subjects were divided into three groups (frequent [three or more times per week], conventional [more than twice per month but less than three times per week], and occasional [two or fewer times per month]). Serum thyrotropin (TSH), free thyroxine (FT(4)), and TPOAb were measured by chemiluminescence immunoassay. Additionally, the concentrations of two primary isoflavones (daidzein and genistein) and creatinine were assessed in the spot urine samples from representative subjects (about 20%) randomly selected from the three groups. The percentages of frequent, conventional, and occasional consumers were 18.6%, 62.6%, and 18.8%, respectively. No difference was found in age, medical records, family history of thyroid diseases, serum FT(4), TSH, and TPOAb levels, TPOAb-positive percentages, or prevalence of thyroid dysfunctions among the groups. Both urinary daidzein and genistein levels were significantly higher in the frequent consumers compared with the other two groups. No correlations were found between urinary isoflavone levels and serum FT(4) or TSH. Urinary isoflavone levels were not significantly different between TPOAb-positive and -negative women among the randomly selected representative subjects. On the whole, our findings suggest dietary soy consumption during early pregnancy is not associated with the development of thyroid dysfunction or autoimmunity.

Which sources of flavonoids: complex diets or dietary supplements?

There is increasing interest in the potential health benefits of dietary flavonoids. Fruits and vegetables, tea, and cocoa are rich natural sources of flavonoids. Epidemiological studies have indicated that consumption of these foods is likely to be associated with a reduced risk of cardiovascular disease, but the etiology of this benefit is not yet clearly defined. Furthermore, in some acute interventions, a positive effect of tea and cocoa on vascular function has been reported. An alternative source of flavonoids is dietary supplements, which have become increasingly popular in the recent past. In this context, it needs to be critically evaluated whether vascular health-promoting and other positive properties of flavonoid-rich diets can be replaced by purified flavonoids as dietary supplements. Plant sources of flavonoids contain a complex mixture of secondary plant metabolites and not only flavonoids per se. This complex mixture of secondary plant metabolites cannot be simply exchanged by single purified compounds as dietary supplements. If flavonoids are given as dietary supplements, toxicity issues as well as nutrient drug interactions need to be taken into account. Purified flavonoids given in high doses as dietary supplements may affect trace element, folate, and vitamin C status. Furthermore, they may exhibit antithyroid and goitrogenic activities. In this review article, the available literature on the safety issues surrounding high dose supplemental flavonoid consumption has been summarized.

Genistein effects on haematoimmune cells in a newly developed alternative toxicological model

Unexpected, sometimes opposite effects of dietary isoflavonic phytoestrogens on immunity may suggest that classical mammalian toxicological assays are not entirely suitable for preclinical safety tests of these compounds. We evaluated a new alternative model of haemocytes of Egyptian cotton worm in vivo following genistein administration. Genistein induced significant changes in nucleolar morphology of haemocytes but did not influence their counts and nucleolar indices. The results indicate that genistein does not affect proliferation and differentiation of normal cells but potentiates their immuno-competence. Egyptian cotton worm larvae seem to be the new alternative biomodel for immunological screening.

Soy protein diet alters expression of hepatic genes regulating fatty acid and thyroid hormone metabolism in the male rat

We hypothesized that consumption of soy protein isolate (SPI) or the soy isoflavone genistein (GEN) would modulate mRNA expression of genes underlying lipid and thyroid hormone metabolism in livers and small intestines of young adult male Sprague-Dawley rats. Early pregnant rat dams were placed on AIN-93G diets containing casein (CAS, control protein), SPI, or CAS+GEN. Litters were weaned to the same diet as their dam. SPI-fed (but not GEN-fed) male rats of 48 days of age had significant reductions in body weight, abdominal fat pad weight and hepatic content of lipid droplets and triglycerides. Hepatic peroxisome proliferator-activated receptor α (Ppara) transcripts were elevated with SPI but not GEN diet. Hepatic pyruvate dehydrogenase kinase-4 (Pdk4) and cytochrome P450 4A10 (Cyp4a10) mRNA abundance was reduced with SPI; the SPI effect on Cyp4a10 was recapitulated by GEN diet. SPI (but not GEN) suppressed Pdk4 and 3-hydroxy-3-methylglutaryl-CoA synthase 2 (Hmgcs2) mRNA abundance in duodenum. Liver iodothyronine deiodinase types 1 and 2 (Dio1 and Dio2) mRNA levels were increased with SPI diet; the effect on Dio2, but not Dio1 mRNAs, also was observed with GEN. SPI and GEN increased hepatic types 1 and 2 iodothyronine deiodinase (D1 and D2) activities. Effects of SPI and GEN on the above gene expression may contribute to the observed reductions in body and adipose tissue weight and liver lipid content in this model. Identification of the regulation, by genistein and soy protein, of iodothyronine deiodinase synthesis has potential applications for treatment and prevention of fatty liver disease and obesity.

The menace of endocrine disruptors on thyroid hormone physiology and their impact on intrauterine development

The delivery of the appropriate thyroid hormones quantity to target tissues in euthyroidism is the result of unopposed synthesis, transport, metabolism, and excretion of these hormones. Thyroid hormones homeostasis depends on the maintenance of the circulating 'free' thyroid hormone reserves and on the development of a dynamic balance between the 'free' hormones reserves and those of the 'bound' hormones with the transport proteins. Disturbance of this hormone system, which is in constant interaction with other hormone systems, leads to an adaptational counter-response targeting to re-establish a new homeostatic equilibrium. An excessive disturbance is likely to result, however, in hypo- or hyper- thyroid clinical states. Endocrine disruptors are chemical substances forming part of 'natural' contaminating agents found in most ecosystems. There is abundant evidence that several key components of the thyroid hormones homeostasis are susceptible to the action of endocrine disruptors. These chemicals include some chlorinated organic compounds, polycyclic aromatic hydrocarbons, herbicides, and pharmaceutical agents. Intrauterine exposure to endocrine disruptors that either mimic or antagonize thyroid hormones can produce permanent developmental disorders in the structure and functioning of the brain, leading to behavioral changes. Steroid receptors are important determinants of the consequences of endocrine disruptors. Their interaction with thyroid hormones complicates the effect of endocrine disruptors. The aim of this review is to present the effect of endocrine disruptors on thyroid hormones physiology and their potential impact on intrauterine development.