Isoflavone content of infant foods and formulas

Formononetin, a Beer Polyphenol with Catabolic Effects on Chondrocytes

Beer consumption has been identified as a risk factor for osteoarthritis (OA), a rheumatic disease characterised by cartilage degradation, joint inflammation, and eventual joint failure. One of the main isoflavonoids in beer is formononetin (FNT), an estrogenic compound also found in multiple plants and herbs. In this study, we aimed to investigate the effect of FNT on chondrocyte viability, inflammation, and metabolism. Cells were treated with FNT with or without IL-1β for 48 h and during 7 days of differentiation. Cell viability was determined via MTT assay. Nitrite accumulation was determined by Griess reaction. The expression of genes involved in inflammation and metabolism was determined by RT-PCR. The results revealed that a low concentration of FNT had no deleterious effect on cell viability and decreased the expression of inflammation-related genes. However, our results suggest that FNT overexposure negatively impacts on chondrocytes by promoting catabolic responses. Finally, these effects were not mediated by estrogen receptors (ERs) or aryl hydrocarbon receptor (AhR). In conclusion, factors that favour FNT accumulation, such as long exposure times or metabolic disorders, can promote chondrocyte catabolism. These data may partially explain why beer consumption increases the risk of OA.

Soy protein supplement intake for 12 months has no effect on sexual maturation and may improve nutritional status in pre-pubertal children

AIM

To evaluate the intake of a soy protein-based supplement (SPS) and its effects on the sexual maturation and nutritional status of prepubertal children who consumed it for a year.

METHODS

Healthy children (n = 51) were recruited and randomly assigned to consume the lunch fruit juice with (n = 29) or without (n = 22) addition of 45 g of a commercial soy protein-based supplement (SPS) over 12 months. Nutritional assessment including anthropometry (bodyweight, height, triceps skinfold thickness, mid-upper arm circumference), body mass index (BMI), upper arm muscle area, arm muscle circumference, upper arm area, upper arm fat area data were derived from measures using usual procedures; age and gender-specific percentiles were used as reference. Sexual maturation was measured by Tanner stage. Isoflavones were quantified using liquid chromatography and tandem mass spectrometry.

RESULTS

Height, BMI/age, weight/age and height/age were significantly different (P < 0.05) at 12 months between girls in the control and intervention groups. Statistically significant differences between groups by gender (P < 0.05) were found in boys in the control group for the triceps skinfold thickness and fat area. Nutritional status was adequate according to the World Health Organization parameters. On average, 0.130 mg/kg body weight/day of isoflavones were consumed by children, which did not show significant differences in their sexual maturation.

CONCLUSION

Consumption of SPS for 12 months did not affect sexual maturation or the onset of puberty in prepubertal boys and girls; however, it may have induced an increase in height, BMI/age, height/age and weight/age of the girls, associated with variations in fat-free mass.

Mothers' Consumption of Soy Drink But Not Black Tea Increases the Flavonoid Content of Term Breast Milk: A Pilot Randomized, Controlled Intervention Study

OBJECTIVE

We performed a pilot RCT to prove the hypothesis that a controlled ingestion of polyphenol-rich beverages (soy drink, decaffeinated black tea) in nutritive dosages by nursing women has an effect on the composition (flavonoid concentration, total antioxidant capacity) of breast milk.

METHODS

Healthy nursing women were supplemented with either 250 mL of a soy drink (12 mg isoflavones; n = 18), 300 mL decaffeinated black tea (67 mg catechins; n = 18), or 300 mL water (n = 8, control) for 6 days. Milk samples were collected before, during, and after intervention. Flavonoid content (isoflavones/catechins, HPLC) and total antioxidant capacity of milk and test drinks in milk specimens were assessed.

RESULTS

Isoflavone content (genistein and daidzein) in breast milk increased up to 12 nmol/L after soy drink consumption; the major flavonoids constituents of black tea (catechin, epicatechin, and respective conjugates) could not be detected in milk samples. With both interventions, the total antioxidant capacity of breast milk was not affected.

CONCLUSIONS

Mothers' daily consumption of a soy drink considerably increases isoflavone content of breast milk resulting in an estimated daily exposure of 9.6 nmol isoflavones in a 4-month-old suckling infant. Luminal flavanol uptake from black tea consumed by the nursing mother may be too low to affect flavanol concentrations in breast milk.

Effects of Genistein or Soy Milk During Late Gestation and Lactation on Adult Uterine Organization in the Rat

In utero and lactational exposure to estrogenic agents has been shown to influence morphological and functional development of reproductive tissues. Thus, consumption of dietary phytoestrogens, such as isoflavones, during pregnancy and lactation could influence important periods of development, when the fetus and neonate are more sensitive to estrogen exposure. In this study, reproductive outcomes after developmental exposure to isoflavones were examined in Long-Evans rats maternally exposed to isoflavones via a commercial soy beverage or as the isolated isoflavone, genistein. Most reproductive end-points examined at birth, weaning, and 2 months of age were not significantly modified in pups of either sex after lactational exposure to soy milk (provided to the dams in place of drinking water) from birth until weaning. However, soy milk exposure induced a significant increase in progesterone receptor (PR) in the uterine glandular epithelium of the 2-month-old pups. In pregnant dams treated with genistein (GEN; 15 mg/kg body weight) by gavage, from Gestational Day 14 through weaning, PR expression in the uterine glandular epithelium from 2-month-old GEN-treated females (postexposure) was also significantly increased. Diethylstilbesterol (DES) also stimulated uterine PR expression only in the glandular but not luminal epithelial cells. However, unlike DES, in utero/lactational exposure to GEN did not increase expression of the proliferation marker, proliferating cell nuclear antigen (PCNA), in the luminal epithelial cells of the 2-month-old rat uteri. These experiments demonstrate that developmental exposure to dietary isoflavones, at levels comparable to the ranges of human exposure, modify expression of the estrogen-regulated PR in the uterus of sexually mature rats weeks after exposure ended. Since the PR is essential for regulating key female reproductive processes, such as uterine proliferation, implantation, and maintenance of pregnancy, its increased expression suggests that soy phytoestrogen exposure during reproductive development may have long-term reproductive health consequences.

Isoflavones and soyasaponins in soy infant formulas in Brazil: profile and estimated consumption

In the present study we determine the contents of isoflavones and soyasaponins in seven soy-based infant formulas available in the Brazilian market to estimate the intake of these bioactive compounds by infants. The mean contents of isoflavones and soyasaponins were 65.9mg/kg and 55.0mg/100g, respectively. β-Glycosylated isoflavones and soyasaponin B-I were the most abundant components in the analysed samples. The mean estimated intake of isoflavones by infants fed soy-based formulas was 0.8mg/day/kg of body weight, which is twice that of Japanese adults. For soyasaponins, the mean estimated intake was 9.2mg/day/kg of body weight, which is up to 6 times higher than the daily intake of saponins from beans by vegetarians. Considering the estimated intake of these bioactive compounds from soy-based formulas and the paucity of data regarding their bioavailability, the potential biological effects of isoflavones and soyasaponins in infants should not be overlooked and merits further investigation.

Impact of dietary soy isoflavones in pregnancy on fetal programming of endothelial function in offspring

Epidemiological evidence suggests that soy-based diets containing phytoestrogens (isoflavones) afford protection against cardiovascular diseases (CVDs); however, supplementation trials have largely reported only marginal health benefits. The molecular mechanisms by which the isoflavones genistein, daidzein, and equol afford protection against oxidative stress remain to be investigated in large scale clinical trials. Isoflavones are transferred across the placenta in both rodents and humans, yet there is limited information on their actions in pregnancy and the developmental origins of disease. Our studies established that feeding a soy isoflavone-rich diet during pregnancy, weaning, and postweaning affords cardiovascular protection in aged male rats. Notably, rats exposed to a soy isoflavone-deficient diet throughout pregnancy and adult life exhibited increased oxidative stress, diminished antioxidant enzyme and eNOS levels, endothelial dysfunction, and elevated blood pressure in vivo. The beneficial effects of refeeding isoflavones to isoflavone-deficient rats include an increased production of nitric oxide and EDHF, an upregulation of antioxidant defense enzymes and lowering of blood pressure in vivo. This review focuses on the role that isoflavones in the fetal circulation may play during fetal development in affording protection against CVD in the offspring via their ability to activate eNOS, EDHF, and redox-sensitive gene expression.

Effects of lactational exposure to soy isoflavones on reproductive system in neonatal female rats

To examine effects of lactational exposure to soy isoflavones on female reproductive system, soy isoflavones, 0 (control), 10, 50, 100, 150 or 200 mg/kg body weight, were administered to maternal rats by gavage daily during postnatal days 5-10. Ten female litters were killed on day 11. Uterine and ovary weights, serum oestradiol and progesterone concentrations, proliferating cell nuclear antigen, mRNA expressions of oestrogen receptor, androgen receptor and progesterone receptor in uterus or ovary were measured. When compared to the control group, litters in the 150 and 200 mg/kg body weight groups had significantly higher ovary and uterine weights (P < 0.05). Endometrial thickness was also significantly increased. Isoflavone-treated groups had increased proliferating cell nuclear antigen staining in comparison to the control group. Litters in the 50, 150 and 200 mg/kg body weight groups had significantly higher oestradiol concentration while lower progesterone concentrations than those in the control group (P < 0.05 or P < 0.01). All soy isoflavone-treated groups had androgen receptor mRNA expressions in ovary and uterus comparable to the control group. Progesterone receptor mRNA expression in the 150 and 200 mg/kg body weight groups was significantly lower than that in control group (P < 0.01). However, ovaries in the 150 and 200 mg/kg body weight groups had significantly higher oestrogen receptor mRNA expression while the uterus in these two treatment groups had significantly lower expressions, when compared to the control group (P < 0.05 or P < 0.01). In conclusion, lactational exposure to isoflavones could result in oestrogen-like actions on the reproductive system of neonate female rats, which mechanisms may be, at least, involved with modifications of hormone production and steroid receptor transcription in the reproductive system.

Breast development in the first 2 years of life: an association with soy-based infant formulas

OBJECTIVE

To evaluate the estrogenic effect of soy-based formulas in female infants. These formulas contain significant amounts of phytoestrogens, compounds with structural similarity to estradiol.

PATIENTS AND METHODS

A cross-sectional study consisting of 694 female infants ages 3 to 24 months that consecutively attended 10 general pediatric clinics, none of them having been referred for breast development. The presence of breast buds served as a marker for the endocrine effect of soy-derived phytoestrogens.

RESULTS

Of the participants, 92 had consumed soy formulas for more than 3 months. Breast tissue was more prevalent in the second year of life in infants fed soy-based formula vs those that were breast-fed and those fed dairy-based formula (22.0% vs 10.3%; P = 0.02) with an odds ratio of 2.45 (95% confidence interval 1.11-5.39). No differences in breast bud prevalence were observed during the first year of life. Unlike infants on dairy-based formulas and breast-feeding, infants fed a soy-based formula did not demonstrate a decline in the prevalence of breast during the second year of life.

CONCLUSIONS

We suggest that phytoestrogens impose a preserving effect on breast tissue that is evolved in early infancy, leading eventually to a slower waning of infantile breast tissue.

Exposure to phytoestrogens in the perinatal period affects androgen secretion by testicular Leydig cells in the adult rat

The use of soy-based products in the diet of infants has raised concerns regarding the reproductive toxicity of genistein and daidzein, the predominant isoflavones in soybeans with estrogenic activity. Time-bred Long-Evans dams were fed diets containing 0, 5, 50, 500, or 1000 ppm of soy isoflavones from gestational d 12 until weaning at d 21 postpartum. Male rats in all groups were fed soy-free diets from postnatal d 21 until 90 d of age. The mean +/- SD concentration of unconjugated (i.e. biologically active) genistein and daidzein in serum from the group of dams maintained on the diet containing the highest amount of isoflavones (1000 ppm) were 17 +/- 27 and 56 +/- 30 nM, respectively, at d 21 postpartum. The concentrations were considerably greater in male offspring (genistein: 73 +/- 46 nM; daidzein: 106 +/- 53 nM). Although steroidogenesis was decreased in individual Leydig cells, male rats from the highest exposure group (1000 ppm diet) exhibited elevated serum levels of the sex steroid hormones androsterone at 21 d (control: 15 +/- 1.5 vs.28 +/- 3.5 ng/ml; P < 0.05) and testosterone at 90 d of age (control: 7.5 +/- 1 vs.17 +/- 2 ng/ml; P < 0.05). Testosterone secretion by immature Leydig cells, isolated from 35-d-old male rats, decreased on exposure to 0.1 nm genistein in vitro (control: 175 +/- 5 vs. 117 +/- 3 ng/10(6) cells per 24 h; P < 0.05), indicative of direct phytoestrogen action. Thus, phytoestrogens have the ability to regulate Leydig cells, and additional studies to assess potential adverse effects of dietary soy-based products on reproductive tract development in neonates are warranted.

A newly constructed and validated isoflavone database for the assessment of total genistein and daidzein intake

The principal phyto-oestrogens (PO) in food are isoflavones, lignans, coumestans and prenylated flavonoids, with isoflavones and lignans being the most commonly found in UK diets. Until recently obtaining accurate data on the PO content of foods was hampered by lack of suitable analytical methods and validation techniques. Furthermore, although PO data exist for some foods, these foods may not be available in the UK. The aim of the present study was to construct a new, comprehensive isoflavone (total genistein + daidzein) database. Using data, mainly from recent GC–MS analysis, for approximately 300 foods available in the UK, and extensive recipe calculations, a new database was constructed containing approximately 6000 foods allocated an isoflavone value. By analysing 7d weighed food diaries, the database was subsequently used to estimate isoflavone intake in two groups of healthy volunteers, omnivores (n9) and vegetarians (n10). Mean isoflavone intake in the vegetarian and omnivorous group was 7·4 (sem 3·05) and 1·2 (sem 0·43) mg/d, respectively. Mean intake for the total group was 4·5 (sem 1·89) mg/d. Main food sources of isoflavones for the vegetarian group were soya milk (plain), meat-substitute foods containing textured vegetable protein and soya protein isolate, soya mince, wholemeal bread and rolls, white bread and rolls, croissants and pitta breads, beans, raisins and soya sauce. Main food sources of isoflavones for the omnivorous group were soya yogurts, wholemeal bread and rolls, white bread and rolls, garlic bread, nan bread and brown bread, sultanas and scones.

Infant feeding with soy formula milk: effects on puberty progression, reproductive function and testicular cell numbers in marmoset monkeys in adulthood

BACKGROUND

This marmoset study addresses concerns about feeding human male infants with soy formula milk (SFM).

METHODS

From age 4 to 5 days, seven male co-twin sets were fed standard formula milk (SMA) or SFM for 5-6 weeks; blood samples were subsequently collected at 10-week intervals. Testes from co-twins killed at 120-138 weeks were fixed for cell counts.

RESULTS

SFM- and SMA-fed twins showed normal weight gain; puberty started and progressed normally, based on blood testosterone measurements. Body weight, organ weights (prostate, seminal vesicles, pituitary, thymus and spleen) and penis length were comparable in co-twins. All SMA- and 6/7 SFM-fed males were fertile. Unexpectedly, testis weight (P = 0.041), Sertoli (P = 0.025) and Leydig cell (P = 0.026) numbers per testis were consistently increased in SFM-fed co-twins; the increase in Leydig cell numbers was most marked in males with consistently low-normal testosterone levels. Seminiferous epithelium volume per tubule showed a less consistent, non-significant increase in SFM-fed males; raised germ cell numbers per testis, probably due to increased Sertoli cells, conceivably resulted in larger testes. Average lumen size, although greater in SFM-fed group, was inconsistent between co-twins and the difference was not significant.

CONCLUSIONS

Infant feeding with SFM has no gross adverse reproductive effects in male marmosets, though it alters testis size and cell composition, and there is consistent, if indirect, evidence for possible 'compensated Leydig cell failure'. Similar and perhaps larger changes likely occur in adult men who were fed SFM as infants.

Soy-based formulas and phyto-oestrogens: a safety profile

Phyto-oestrogens are non-steroidal plant-derived compounds that possess oestrogenic activity and act as selective oestrogen receptor modulators (SERMs). Among the dietary oestrogens, the isoflavone class enjoy a wide-spread distribution in most of the members of the Leguminosae family, including such prominent high-content representatives as soybean. Phyto-oestrogen research has grown rapidly in recent years owing to epidemiological studies suggesting that diets rich in soy may be associated with potential health benefits. There is a paucity of data on endocrine effects of soy phytochemicals during infancy, the most sensitive period of life for the induction of toxicity. The safety of isoflavones in infant formulas has been questioned recently owing to reports of possible hormonal effects. Infants fed soy formula receive high levels of phyto-oestrogens in the form of isoflavones (genistein, daidzein and their glycosides). To date, no adverse effects of short- or long-term use of soy proteins have been observed in humans and exposure to soy-based infant formulas does not appear to lead to different reproductive outcomes than exposure to cow milk formulas. Soy formula seems to be a safe feeding option for most infants. Nevertheless, much closer studies in experimental animals and human populations exposed to phyto-oestrogen-containing products, and particularly soy-based infant formulas, are necessary.

Soy infant formula and phytoestrogens

Soy infant formula contains high levels of the isoflavones, genistein and daidzein, which are commonly referred to as phytoestrogens. These are non-steroidal chemicals with structural similarities to estrogen. Infants consuming soy formula have high levels of circulating isoflavones. These are an order of magnitude greater than the levels of isoflavones which have been shown to produce physiological effects in adult women consuming a high soy diet. There is conflicting evidence about the risks and benefits of soy phytoestrogens, with research presenting a contradictory picture. Some reviewers suggest that early exposure to soy may prevent cancer and heart disease. However, there is very little research on the effects of consumption of soy phytoestrogens by human neonates. Against this generally positive view there is an increasing number of recent reports that suggest that in experimental animals, phytoestrogens have adverse effects with respect to carcinogenesis, reproductive function, immune function, and thyroid disease. Despite the absence of adequate scientific research that quantifies the level of risk to infants, most would argue for a precautionary approach to be taken in situations where there are potential developmental effects from the consumption of pharmacologically active compounds in infancy and childhood.

Soy-based formulae and infant growth and development: a review

Soy-based infant formulae, initially developed for infants who were lactose intolerant or allergic to cow's milk-based formulae, now account for >25% of the infant formulae sold in the United States. Formulations have changed over the years to improve digestibility, the stability and availability of minerals, and protein quality. Recent concerns have been raised regarding the phytoestrogenic isoflavone content of soy-based formulae. A systematic review of the literature was conducted to evaluate various measures of infant health and development in clinical studies comparing modern soy-based formulae with other diets and to document areas in which further research seems warranted. Results suggest that modern soy-based formulae support normal growth and nutritional status in healthy term infants in y 1 of life. However, there are very limited data on sexual and reproductive development or outcomes such as immune function, visual acuity/cognitive development and thyroid function. Available data do not provide evidence of meaningful differences in timing of maturation, sexual development or fertility in adolescents or adults. Nonetheless, given evidence suggesting that early exposure to soy and/or isoflavones might have long-term effects, further research following infants fed soy-based formulae into adulthood is warranted.

Infant feeding with soy formula milk: effects on the testis and on blood testosterone levels in marmoset monkeys during the period of neonatal testicular activity

BACKGROUND

This study has addressed concerns about possible effects of feeding human infants soy formula milk (SFM).

METHODS

This is a feeding study in marmosets, using a mainly co-twin design. From 4-5 until 35-45 days of age, co-twin males were fed by hand with either standard (cow) formula milk (SMA = controls) or with SFM for approximately 8 h each day (2 h at weekends) and intake related to bodyweight. Blood samples were collected at 18-20 and at 35-45 days of age in 13 sets of co-twins plus two non-twin males per group and, at the later age, seven sets of co-twins were killed and the testes and pituitary gland fixed for cell counts.

RESULTS

Weight gain and formula intake were similar in both feeding groups. SMA-fed males had mean testosterone levels of 2.8-3.1 ng/ml, typical of the "neonatal testosterone rise", whereas SFM-fed males exhibited consistently lower mean levels (1.2-2.6 ng/ml); paired comparison in SMA-and SFM-fed co-twins at day 35-45 revealed 53-70% lower levels in 11 of 13 co-twins fed with SFM (P = 0.004). Further evidence for suppression of testosterone levels in SFM-fed males came from comparison of the frequency of low testosterone levels (<0.5 ng/ml). In historical controls aged 35-45 days, two out of 22 values were <0.5 ng/ml, a similar frequency as found in control SMA-fed males (one out of 15 values <0.5 ng/ml). In contrast, 12 out of 15 values for SFM-fed males were <0.5 ng/ml (P < 0.001). There was no consistent relationship between SFM intake/g and testosterone levels. Paradoxically, the mean number of Leydig cells per testis was increased by 74% (P < 0.001) in co-twins fed SFM, when compared with their SMA-fed brothers, whereas no significant changes were found in numbers of Sertoli and germ cells. Because of the lack of gonadotrophin assays, the number of immunopositive LHbeta and FSHbeta cells in the pituitary gland, and their ratio, were determined but no consistent difference was found between SMA- and SFM-fed twins.

CONCLUSIONS

Based on the average isoflavone content of the SFM brand used, intake of isoflavones was estimated at 1.6-3.5 mg/kg/day in the SFM-fed marmosets which is 40-87% of that reported in 4 month human infants fed on a 100% SFM diet. It is therefore considered likely that similar, or larger, effects to those shown here in marmosets may occur in human male infants fed with SFM. Whether the changes described result in longer-term effects is under investigation.

Estrogen depletion induces NaCl-sensitive hypertension in female spontaneously hypertensive rats

In women, arterial pressure generally increases after menopause, but several studies suggest that women who eat large amounts of plant estrogens (phytoestrogens) experience a slower rise in the incidence of postmenopausal hypertension. This suggests that both ovarian hormones (principally estrogen) and phytoestrogens may protect at least some women from hypertension. The present study tests the hypothesis that phytoestrogens blunt hypertension in estrogen-depleted female spontaneously hypertensive rats (SHR). Three-week-old ovariectomized SHR were fed one of four diets that contained basal (0.6%) or high (8%) NaCl with or without dietary phytoestrogens for 9 wk. In SHR on the basal NaCl diet, arterial pressure was unaffected by the removal of dietary phytoestrogens. In contrast, in SHR on the high-NaCl diet, arterial pressure was significantly higher in rats on the phytoestrogen-free (204 +/- 4 mmHg) compared with the phytoestrogen-replete (153 +/- 4 mmHg) diet. Ganglionic blockade resulted in reductions in arterial pressure that were directly related to the dietary NaCl-induced increases in arterial pressure. Together, these data indicate that dietary phytoestrogens protect ovariectomized female SHR from dietary NaCl-sensitive hypertension and that the sympathetic nervous system plays an important role in this effect. Furthermore, these results demonstrate that dietary phytoestrogens can have a major impact on the interpretation of studies into the physiological role of estrogen in females.