Isoflavones in breastfed infants after mothers consume soy

Which is the optimal choice for neonates' formula or breast milk?

The incidence of prematurity has been increasing since the twenty-first century. Premature neonates are extremely vulnerable and require a rich supply of nutrients, including carbohydrates, proteins, docosahexaenoic acid (DHA), arachidonic acid (ARA) and others. Typical breast milk serves as the primary source for infants under six months old to provide these nutrients. However, depending on the individual needs of preterm infants, a more diverse and intricate range of nutrients may be necessary. This paper provides a comprehensive review of the current research progress on the physical and chemical properties, biological activity, function, and structure of breast milk, as well as explores the relationship between the main components of milk globular membrane and infant growth. Additionally, compare the nutritional composition of milk from different mammals and newborn milk powder, providing a comprehensive understanding of the differences in milk composition and detailed reference for meeting daily nutritional needs during lactation.

Developmental exposure to phytoestrogens found in soy: New findings and clinical implications

Exposure to naturally derived estrogen receptor activators, such as the phytoestrogen genistein, can occur at physiologically relevant concentrations in the human diet. Soy-based infant formulas are of particular concern because infants consuming these products have serum genistein levels almost 20 times greater than those seen in vegetarian adults. Comparable exposures in animal studies have adverse physiologic effects. The timing of exposure is particularly concerning because infants undergo a steroid hormone-sensitive period termed "minipuberty" during which estrogenic chemical exposure may alter normal reproductive tissue patterning and function. The delay between genistein exposure and reproductive outcomes poses a unique challenge to collecting epidemiological data. In 2010, the U.S. National Toxicology Program monograph on the safety of the use of soy formula stated that the use of soy-based infant formula posed minimal concern and emphasized a lack of data from human subjects. Since then, several new human and animal studies have advanced our epidemiological and mechanistic understanding of the risks and benefits of phytoestrogen exposure. Here we aim to identify clinically relevant findings regarding phytoestrogen exposure and female reproductive outcomes from the past 10 years, with a focus on the phytoestrogen genistein, and explore the implications of these findings for soy infant formula recommendations. Research presented in this review will inform clinical practice and dietary recommendations for infants based on evidence from both clinical epidemiology and basic research advances in endocrinology and developmental biology from mechanistic in vitro and animal studies.

Human Milk Antioxidative Modifications in Mastitis: Further Beneficial Effects of Cranberry Supplementation

Mastitis is the inflammation of one or several mammal lobes which can be accompanied by a mammary gland infection, and is the leading cause of undesired early weaning in humans. However, little information exists regarding the changes that this disease may induce in the biochemical composition of human milk, especially in terms of oxidative status. Given that newborns are subject to a significant increase in total ROS burden in their transition to neonatal life and that their antioxidant defense system is not completely developed, the aim of this study was to evaluate antioxidant defense (glutathione peroxidase (GPx), reduced glutathione (GSH), total polyphenol content (TPP), and total antioxidant capacity (TAC)) in milk samples from mothers suffering from mastitis and controls. We also measured the oxidative damage to lipids (malondyaldehyde (MDA)) and proteins (carbonyl group content (CGC)) in these samples. Finally, we tested whether dietary supplementation with cranberries (a product rich in antioxidants) in these breastfeeding mothers during 21 days could improve the oxidative status of milk. GPx activity, TPP, and TAC were increased in milk samples from mastitis-affected women, providing a protective mechanism to the newborn drinking mastitis milk. MDA concentrations were diminished in the mastitis group, confirming this proposal. Some oxidative damage might occur in the mammary gland since the CGC was increased in mastitis milk. Cranberries supplementation seems to strengthen the antioxidant system, further improving the antioxidative state of milk.

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.

Skeletal Effects of Early-Life Exposure to Soy Isoflavones-A Review of Evidence From Rodent Models

Isoflavones are dietary phytoestrogens commonly found in soy-based products. The widespread presence of isoflavones in soy infant formula and breast milk may have long-lasting effects on the development of sex hormone-sensitive organs like the skeleton. Animal early-life programming models are suitable for testing the skeletal effects of pre- and neonatal exposure of soy isoflavones. This review aims to collate the impacts of early-life exposure of soy isoflavones as evidenced in animal models. The isoflavones previously studied include daidzein, genistein, or a combination of both. They were administered to rodent pups during the first few days postnatal, but prolonged exposure had also been studied. The skeletal effects were observed when the animals reached sexual maturity or after castration to induce bone loss. In general, neonatal exposure to soy isoflavones exerted beneficial effects on the skeletal system of female rodents, but the effects on male rodents seem to depend on the time of exposure and require further examinations. It might also protect the animals against bone loss due to ovariectomy at adulthood but not upon orchidectomy. The potential benefits of isoflavones on the skeletal system should be interpreted together with its non-skeletal effects in the assessment of its safety and impacts.

Hydrogen sulfide intervention in cystathionine-β-synthase mutant mouse helps restore ocular homeostasis

AIM

To investigate the applications of hydrogen sulfide (H₂S) in eye-specific ailments in mice.

METHODS

Heterozygous cystathionine-β-synthase (CBS^+/-) and wild-type C57BL/6J (WT) mice fed with or without high methionine diet (HMD) were administered either phosphate buffered saline (PBS) or the slow-release H₂S donor: GYY4137. Several analyses were performed to study GYY4137 effects by examining retinal lysates for key protein expressions along with plasma glutamate and glutathione estimations. Intraocular pressure (IOP) was monitored during GYY4137 treatment; barium sulfate and bovine serum albumin conjugated fluorescein isothiocyanate (BSA-FITC) angiographies were performed for examining vasculature and its permeability post-treatment. Vision-guided behavior was also tested employing novel object recognition test (NORT) and light-dark box test (LDBT) recordings.

RESULTS

CBS deficiency (CBS^+/-) coupled with HMD led disruption of methionine/homocysteine (Hcy) metabolism leading to hyperhomocysteinemia (HHcy) in CBS^+/- mice as reflected by increased Hcy, and s-adenosylhomocysteine hydrolase (SAHH) levels. Unlike CBS, cystathionine-γ lyase (CSE), methylenetetrahydrofolate reductase (MTHFR) levels which were reduced but compensated by GYY4137 intervention. Heightened oxidative and endoplasmic reticulum (ER) stress responses were mitigated by GYY4137 effects along with enhanced glutathione (GSH) levels. Increased glutamate levels in CBS^+/- strain were prominent than WT mice and these mice also exhibited higher IOP that was lowered by GYY4137 treatment. CBS deficiency also resulted in vision-guided behavioral impairment as revealed by NORT and LDBT findings. Interestingly, GYY4137 was able to improve CBS^+/- mice behavior together with lowering their glutamate levels. Blood-retinal barrier (BRB) appeared compromised in CBS^+/- with vessels' leakage that was mitigated in GYY4137 treated group. This corroborated the results for occludin (an integral plasma membrane protein of the cellular tight junctions) stabilization.

CONCLUSION

Findings reveal that HHcy-induced glutamate excitotoxicity, oxidative damage, ER-stress and vascular permeability alone or together can compromise ocular health and that GYY4137 could serve as a potential therapeutic agent for treating HHcy induced ocular disorders.

An exploratory study of red raspberry (Rubus idaeus L.) (poly)phenols/metabolites in human biological samples

Red raspberry (Rubus idaeus L.) contains a variety of polyphenols including anthocyanins and ellagitannins. Red raspberry polyphenols absorbed in different forms (parent compounds, degradants or microbial metabolites) are subject to xenobiotic metabolism in the intestine, liver, and/or kidney, forming methylate, glucuronide, and sulfate conjugated metabolites. Upon acute exposure, (poly)phenol/metabolite presence in the blood depends mainly on intestinal absorption, enterohepatic circulation, and metabolism by resident microbiota. However, chronic exposure to red raspberry polyphenols may alter metabolite patterns depending on adaptions in the xenobiotic machinery and/or microbiota composition. Understanding the metabolic fate of these compounds and their composition in different biological specimens relative to the exposure time/dose will aid in designing future health benefit studies, including the mechanism of action studies. The present exploratory study applied ultra-high performance liquid chromatography (UHPLC) coupled with quadrupole time-of-flight (QTOF) and triple quadrupole (QQQ) mass spectrometries to characterize red raspberry polyphenols in fruit and then their appearance, including metabolites in human biological samples (plasma, urine and breast milk) after the chronic intake of red raspberries. The results suggested that the most abundant polyphenols in red raspberries included cyanidin 3-O-sophoroside, cyanidin 3-O-glucoside, sanguiin H6 and lambertianin C. Sixty-two (poly)phenolic compounds were tentatively identified in the plasma, urine and breast milk samples after the intake of red raspberries. In general, urine contained the highest content of phenolic metabolites; phase II metabolites, particularly sulfated conjugates, were mainly present in urine and breast milk, and breast milk contained fewer parent anthocyanins compared to urine and plasma.

Phytochemicals in Human Milk and Their Potential Antioxidative Protection

Diets contain secondary plant metabolites commonly referred to as phytochemicals. Many of them are believed to impact human health through various mechanisms, including protection against oxidative stress and inflammation, and decreased risks of developing chronic diseases. For mothers and other people, phytochemical intake occurs through the consumption of foods such as fruits, vegetables, and grains. Research has shown that some these phytochemicals are present in the mother’s milk and can contribute to its oxidative stability. For infants, human milk (HM) represents the primary and preferred source of nutrition because it is a complete food. Studies have reported that the benefit provided by HM goes beyond basic nutrition. It can, for example, reduce oxidative stress in infants, thereby reducing the risk of lung and intestinal diseases in infants. This paper summarizes the phytochemicals present in HM and their potential contribution to infant health.

Soy isoflavone intake is associated with risk of Kawasaki disease

Kawasaki disease (KD) is an acute vasculitis affecting children. Incidence of KD varies according to ethnicity and is highest in Asian populations. Although genetic differences may explain this variation, dietary or environmental factors could also be responsible. The objectives of this study were to determine dietary soy and isoflavone consumption in a cohort of KD children just before disease onset and their mothers' intake during pregnancy and nursing. We tested the hypothesis that soy isoflavone consumption is associated with risk of KD in US children, potentially explaining some of the ethnic-cultural variation in incidence. We evaluated soy food intake and isoflavone consumption in nearly 200 US KD cases and 200 age-matched controls using a food frequency questionnaire for children and in their mothers. We used a logistic regression model to test the association of isoflavones and KD. Maternal surveys on soy intake during pregnancy and nursing showed no significant differences in isoflavone consumption between groups. However, we identified significantly increased KD risk in children for total isoflavone (odds ratio [OR], 2.33; 95% confidence interval [CI], 1.37-3.96) and genistein (OR, 2.46; 95% CI, 1.46-4.16) intakes, when comparing high soy consumers vs nonconsumers. In addition, significantly increased KD risk occurred in Asian-American children with the highest consumption (total isoflavones: OR, 7.29; 95% CI, 1.73-30.75; genistein: OR, 8.33; 95% CI, 1.92-36.24) compared to whites. These findings indicate that childhood dietary isoflavone consumption, but not maternal isoflavone intake during pregnancy and nursing, relates to KD risk in an ethnically diverse US population.

Absorption, distribution, metabolism, and excretion of isoflavonoids after soy intake

Soy is the major source of dietary exposure to isoflavonoids (IFLs). Accumulating evidence supports a role for soy and IFLs in the protection against many chronic diseases including cancer. After soy intake we found a biphasic IFL appearance pattern in plasma as well as in urine that we suggest to be due to IFL absorption in the small intestine (ca. 10%) during the first 2h after intake and IFL absorption in the large intestine (ca. 90%) 4-6 h after intake. While each IFL disappears from the circulation at different times excellent correlations between urinary and circulating IFL values were discovered and algorithms to convert urinary excretion values into circulating levels were established. We suggest the term 'apparent bioavailability' when using urinary data to describe IFL exposure. The IFL bioavailability was found to be influenced by gut bacteria, oral antibiotic treatment (OABX), and an individual's age and health status. While daidzein (DE) and genistein start to be absorbed minutes after intake, equol (EQ) appears in plasma only after a minimum of 8h following soy intake owing to the required transit time of DE to the colon where the conversion of DE to EQ takes place by intestinal microbiota. We have also shown that the apparent IFL bioavailability is higher in children than adults, higher in healthy versus non-healthy individuals, and decreased in children but increased in adults during OABX. Finally, we propose to use a urinary EQ/DE ratio of 0.018 with a DE threshold to identify EQ producers. With this cutoff definition we observed that EQ production is inconsistent over time in 5-30% of both premenopausal and postmenopausal women.

S-(-)equol production is developmentally regulated and related to early diet composition

S-(-)7-hydroxy-3-(4'-hydroxyphenyl)-chroman, or S-(-)equol, a biologically active intestinally derived bacterial metabolite of the soy isoflavones daidzin/daidzein, is not produced in neonatal life. Because its synthesis is dependent on equol-producing bacteria, we hypothesized that early nutrition may influence equol production. This prospective 2.5-year study determined the frequency of S-(-)equol production in healthy infants (n = 90) fed breast milk, soy infant formula, or cow's milk formula in their first year. Urinary S-(-)equol and daidzein were quantified by mass spectrometry after a standardized 3.5-day soy isoflavone challenge. Infants were tested at 6, 9, 12, 18, 24, and 36 months of age, and 3-day diet records were obtained at each visit to explore the effect of early and postweaning (>12 months) macronutrient and micronutrient dietary composition and S-(-)equol production. Use of antibiotics was also recorded. At age 6 months, none of the breast-fed infants produced S-(-)equol, whereas 3.8% and 6.0%, respectively, of soy and cow's milk formula-fed infants were equol producers. By age 3 years, 50% of the formula-fed infants were equol producers, compared with 25% of breast-fed infants. Use of antibiotics was prevalent among infants and may have impacted the stability of S-(-)equol production. No significant differences among the groups were observed in postweaning dietary intakes of total energy, carbohydrate, fiber, protein, fat, saturated fatty acids, or polyunsaturated fatty acids and the propensity to make S-(-)equol. In conclusion, S-(-)equol production is developmentally regulated and initially related to diet composition with the proportion of equol producers increasing over the first 3 years of life, with a trend for formula feeding favoring S-(-)equol production.

Environmental epigenetics and phytoestrogen/phytochemical exposures

One of the most important environmental factors to promote epigenetic alterations in an individual is nutrition and exposure to plant compounds. Phytoestrogens and other phytochemicals have dramatic effects on cellular signaling events, so have the capacity to dramatically alter developmental and physiological events. Epigenetics provides one of the more critical molecular mechanisms for environmental factors such as phytoestrogens/phytochemicals to influence biology. In the event these epigenetic mechanisms become heritable through epigenetic transgenerational mechanisms the impacts on the health of future generations and areas such as evolutionary biology need to be considered. The current review focuses on available information on the environmental epigenetics of phytoestrogen/phytochemical exposures, with impacts on health, disease and evolutionary biology considered. This article is part of a Special Issue entitled 'Phytoestrogens'.

Urinary estrogen metabolites during a randomized soy trial

One of the hypothesized protective mechanisms of soy against breast cancer involves changes in estrogen metabolism to 2-hydroxy (OH) and 16α-OH estrogens. The current analysis examined the effect of soy foods on the 2:16α-OH E(1) ratio among premenopausal women during a randomized, crossover intervention study; women were stratified by equol producer status, a characteristic thought to enhance the protective effects of soy isoflavones. The study consisted of a high-soy diet with 2 soy food servings/day and a low-soy diet with <3 servings of soy/wk for 6 mo each; estrogen metabolites were measured in 3 overnight urines (baseline and at the end of the low- and high-soy diet) using gas chromatography mass spectrometry for the 82 women who completed the study. Urinary isoflavonoids were assessed by liquid chromatography mass spectrometry. When applying mixed models, the 2:16α-OH E(1) ratio increased (P = 0.05) because of a nonsignificant decrease in 16α-OH E(1) (P = 0.21) at the end of the high-soy diet. Similar nonsignificant increases in the 2:16α-OH E(1) ratio were observed in equol producers (P = 0.13) and nonproducers (P = 0.23). These findings suggest a beneficial influence of soy foods on estrogen metabolism regardless of equol producer status.

The volume of nipple aspirate fluid is not affected by 6 months of treatment with soy foods in premenopausal women

Based on the hypothesis that soy food consumption may influence breast tissue activity, we examined its effect on the production of nipple aspirate fluid (NAF), a possible indicator of breast cancer risk. Of 310 premenopausal women screened, 112 (36%) produced at least 10 μL of NAF, the minimum for study participation. In a crossover design, we randomized 96 women to 2 groups who, in reverse order, consumed a high-soy diet with 2 soy servings/d (1 serving = 177 mL soy milk, 126 g tofu, or 23 g soy nuts) and a low-soy diet with <3 servings/wk of soy for 6 mo each separated by a 1-mo washout period. During each diet period, 3 NAF samples were obtained (baseline and 3 and 6 mo) using a FirstCyte Aspirator and 4 urine samples (baseline and 1, 3, and 6 mo) were analyzed for isoflavonoids by liquid chromatography tandem MS. Adherence to the study protocol according to 24-h dietary recalls and urinary isoflavonoid excretion was high. The drop-out rate was 15% (n = 14); 82 women completed the intervention. The 2 groups produced similar mean NAF volumes at baseline (P = 0.95) but differed in age and previous soy intake and in their response to the intervention (P = 0.03). In both groups, NAF volume decreased during the first 3 mo of the high-soy diet period and returned to baseline at 6 mo, but there was no effect of the high-soy diet on NAF volume (P = 0.50 for diet; P-interaction = 0.21 for diet with time). Contrary to an earlier report, soy foods in amounts consumed by Asians did not increase breast tissue activity as assessed by NAF volume.

Urine accurately reflects circulating isoflavonoids and ascertains compliance during soy intervention

BACKGROUND

Isoflavonoids (IFL) may protect against chronic diseases, including cancer. IFL exposure is traditionally measured from plasma (PL), but the reliability of urine is uncertain. We assessed whether IFL excretion in overnight urine (OU) or spot urine (SU) reliably reflects IFLs in PL and the usefulness of the three matrices to determine soy intake compliance.

METHODS

In a randomized, double-blind, placebo-controlled soy intervention trial with 350 postmenopausal women, IFLs (daidzein, genistein, glycitein, equol, O-desmethylangolensin, dihydrodaidzein, dihydrogenistein) were analyzed by liquid chromatography/mass spectrometry in OU, SU, and PL collected at baseline and every 6 months over 2.5 years.

RESULTS

High between-subject intraclass correlations between all three matrices (median, 0.94) and high between-subject Pearson correlations (median r(OU-PL) = 0.80; median r(SU-PL) = 0.80; median r(OU-SU) = 0.92) allowed the development of equations to predict IFL values from any of the three matrices. Equations developed from a randomly selected 87% of all available data were valid because high correlations were found on the residual 13% of data between equation-generated and measured IFL values (median r(OU-PL) = 0.86; median r(SU-PL) = 0.78; median r(OU-SU) = 0.84); median absolute IFL differences for OU-PL, SU-PL, and OU-SU were 8.8 nmol/L, 10.3 nmol/L, and 0.28 nmol/mg, respectively. All three matrices showed highly significant IFL differences between the placebo and soy intervention group at study end (P < 0.0001) and highly significant correlations between IFL values and counted soy doses in the intervention group.

CONCLUSIONS

OU and SU IFL excretion reflect circulating PL IFL levels in healthy postmenopausal women accurately.

IMPACT

Noninvasively-collected urine can be used to reliably determine systemic IFL exposure and soy intake compliance.

Circulating levels of genistein in the neonate, apart from dose and route, predict future adverse female reproductive outcomes

Developmental exposure to estrogenic compounds can disrupt sexual differentiation and adult reproductive function in many animals including humans. Phytoestrogens (plant estrogens) in the diet comprise a significant source of estrogenic exposure to humans, particularly in infants who are fed soy-based infant formula. Animal models have been developed to test the effects of phytoestrogen exposure on the developing fetus and neonate. Here we review studies quantifying the amount of phytoestrogen exposure in human adults and infants and discuss the few available epidemiological studies that have addressed long-term consequences of developmental phytoestrogen exposure. We then describe in detail rodent models of developmental exposure to the most prevalent phytoestrogen in soy products, genistein, and the effects of this exposure on female reproductive function. These models have used various dosing strategies to mimic the phytoestrogen levels in human populations. Serum circulating levels of genistein following each of the models and their correlation to reproductive outcomes are also discussed. Taken together, the studies clearly demonstrate that environmentally relevant doses of genistein have significant negative impacts on ovarian differentiation, estrous cyclicity, and fertility in the rodent model. Additional studies of reproductive function in human populations exposed to high levels of phytoestrogens during development are warranted.

The pros and cons of phytoestrogens

Phytoestrogens are plant derived compounds found in a wide variety of foods, most notably soy. A litany of health benefits including a lowered risk of osteoporosis, heart disease, breast cancer, and menopausal symptoms, are frequently attributed to phytoestrogens but many are also considered endocrine disruptors, indicating that they have the potential to cause adverse health effects as well. Consequently, the question of whether or not phytoestrogens are beneficial or harmful to human health remains unresolved. The answer is likely complex and may depend on age, health status, and even the presence or absence of specific gut microflora. Clarity on this issue is needed because global consumption is rapidly increasing. Phytoestrogens are present in numerous dietary supplements and widely marketed as a natural alternative to estrogen replacement therapy. Soy infant formula now constitutes up to a third of the US market, and soy protein is now added to many processed foods. As weak estrogen agonists/antagonists with molecular and cellular properties similar to synthetic endocrine disruptors such as Bisphenol A (BPA), the phytoestrogens provide a useful model to comprehensively investigate the biological impact of endocrine disruptors in general. This review weighs the evidence for and against the purported health benefits and adverse effects of phytoestrogens.

Genistein effects on Ca2+ handling in human umbilical artery: inhibition of sarcoplasmic reticulum Ca2+ release and of voltage-operated Ca2+ channels

Isoflavones are a group of natural phytoestrogens including the compound genistein. Health beneficial effects have been attributed to the consumption of this compound, but the fact that it has estrogen-like activity has raised doubts regarding its potential risk in infants, newborns, or in the fetus and placenta during pregnancy. This work is aimed at studying genistein effects on Ca2+ handling by smooth muscle cells of the human umbilical artery (HUA). Using fluorometric techniques, we found that in these cells genistein reduces the intracellular Ca2+ peak produced by serotonin. The same result could be demonstrated in absence of extracellular Ca2+, suggesting that the isoflavone reduces Ca2+ release from the sarcoplasmic reticulum. Force measurement experiments strengthen these results, since genistein reduced the peak force attained by intact HUA rings stimulated by serotonin in a Ca2+-free solution. Moreover, genistein induced the relaxation of HUA rings precontracted either with serotonin or a depolarizing high-extracellular K+ solution, hinting at a reduction of extracellular Ca2+ entry to the cell. This was confirmed by whole-cell patch-clamp experiments where it was shown that the isoflavone inhibits ionic currents through voltage-operated Ca2+ channels. In summary, we show that genistein inhibits two mechanisms that could increase intracellular Ca2+ in human umbilical smooth muscle cells, behaving in this way as a potential vasorelaxing substance of fetal vessels. Taking into account that genistein is able to cross the placental barrier, these data show that isoflavones may have important implications in the regulation of feto-maternal blood flow in pregnant women who consume soy-derived products as part of their meals.

Apparent bioavailability of isoflavones after intake of liquid and solid soya foods

Isoflavone (IFL) intake may provide numerous health benefits, but IFL bioavailability differences among soya foods remains uncertain. Urinary IFL excretion (UIE) was shown to provide a reliable surrogate for systemic IFL exposure and therefore can be used as a measure of 'apparent bioavailability' (AB). We investigated the AB of IFL in fourteen healthy adults, consuming two liquid and two solid soya foods in a crossover designed study. Volunteers consumed the foods with a self-selected breakfast, which was kept identical for all four soya items (soya nuts, soya milk, soya protein bar and soya protein powder drink in water; average 23.7 mg IFL, 88-96 % glycosides, by HPLC analysis) and collected all urine up to 26 h. Liquid foods showed initially higher UIE values than solid foods, but this difference was considerably reduced or disappeared entirely after 24-26 h. Conclusive AB results were obtained only after 24-26 h; earlier collections were not reliable. At 26 h, adjusted UIE values for daidzein (DE) were 20 micromol in the milk and bar and 17 micromol for the nut and powder; urinary genistein excretion was the highest in the milk group (10 micromol) followed by the nut, bar (both 6 micromol) and powder groups (5 micromol); the UIE for glycitein was the highest for bars (4 micromol), followed by powder and nuts (3 micromol), and milk (2 micromol). DE makes the largest contribution to urinary total IFL. The AB of IFL was found to be variable depending on the analyte and soya food consumed.

Phytoestrogenic isoflavonoids in epidemiologic and clinical research

Isoflavones (IFLs) are natural products to which humans have been traditionally exposed predominantly through soy foods; more recently humans are also exposed to them through soy protein addition to processed foods or through supplements. They are structurally similar to steroidal estrogens and can exert estrogenic or antiestrogenic effects depending on their concentrations and on the tissue considered. These properties qualify IFLs to be classified as phytoestrogens and are believed to account for many of the biological effects observed for soy and/or IFL exposure including benefits for bone and heart health or prevention of menopausal symptoms and certain types of cancer. In order to evaluate the function of IFLs, alone or when exposure happens through soy intake, pharmacokinetics and bioavailability are critical issues to be considered in epidemiologic and clinical research. For this purpose precise, accurate, robust, fast, and affordable techniques for IFL analyses are required.

Epigenetic and phenotypic changes result from a continuous pre and post natal dietary exposure to phytoestrogens in an experimental population of mice

BACKGROUND

Developmental effects of exposure to endocrine disruptors can influence adult characters in mammals, but could also have evolutionary consequences. The aim of this study was to simulate an environmental exposure of an experimental population of mice to high amounts of nutritional phytoestrogens and to evaluate parameters of relevance for evolutionary change in the offspring. The effect of a continuous pre- and post-natal exposure to high levels of dietary isoflavones was evaluated on sexual maturity, morphometric parameters and DNA methylation status in mice. Adult mice male/female couples were fed ad libitum either with control diet (standard laboratory chow) or ISF diet (control diet plus a soy isoflavone extract at 2% (w/w) that contained the phytoestrogens genistein and daidzein). In the offspring we measured: i) the onset of vaginal opening (sexual maturation) in females, ii) weight and size in all pups at 7, 14, 21 and 42 days post-natal (dpn) and iii) DNA methylation patterns in skeletal alpha-actin (Acta1), estrogen receptor-alpha and c-fos in adults (42 dpn).

RESULTS

Vaginal opening was advanced in female pups in the ISF group, from 31.6 +/- 0.75 dpn to 25.7 +/- 0.48. No differences in size or weight at ages 7, 14 or 21 dpn were detected between experimental groups. Nevertheless, at age 42 dpn reduced size and weight were observed in ISF pups, in addition to suppression of normal gender differences in weight seen in the control group (males heavier that females). Also, natural differences seen in DNA methylation at Acta1 promoter in the offspring originated in the control group were suppressed in the ISF group. Acta1 is known to be developmentally regulated and related to morphomotric features.

CONCLUSION

This study demonstrates in mammals that individuals from a population subjected to a high consumption of isoflavones can show alterations in characters that may be of importance from an evolutionary perspective, such as epigenetic and morphometric characters or sexual maturation, a life history character.

Urinary isoflavonoid excretion is similar after consuming soya milk and miso soup in Japanese-American women

Based on the hypothesis that isoflavones are absorbed more efficiently from fermented than from non-fermented soya foods, we compared the urinary isoflavonoid excretion (UIE) after intake of miso soup or soya milk. We recruited twenty-one women with Japanese ancestry who consumed standardized soya portions containing 48 mg isoflavones. On day 1, half the women consumed soya milk, the other half started with miso soup. On day 3, the subjects ate the other soya food and on day 5, they repeated the first food. Each participant collected a spot urine sample before and an overnight urine sample after soya food intake. All urine samples were analysed for daidzein, genistein and equol using LC-MS and were expressed as nmol/mg creatinine. We applied mixed models to evaluate the difference in UIE by food while including the baseline values and covariates. Relative to baseline, both groups experienced significantly higher UIE after consuming any of the soya foods. We observed no significant difference in UIE when soya milk was compared to miso soup (P = 0.87) among all women or in the seven equol producers (P = 0.88). Repeated intake of the same food on different days showed high reproducibility within subjects. These preliminary results indicate similar UIE after consuming a fermented soya food (miso) as compared to a non-fermented soya food (soya milk). Therefore, recommendations favouring fermented soya foods are not justified as long as the intestinal microflora is capable of hydrolysing the isoflavone glucosides from non-fermented soya foods.