Dietary exposure estimates of isoflavones from the 1998 UK Total Diet Study

Food Safety Assessment of Commercial Genetically Modified Soybeans in Rats

Although the safety of commercial genetically modified (GM) soybeans has been well evaluated and GM soybeans are legally sold under government management, some consumers still have concerns about their safety. The objective of this study was to evaluate the safety of commercial GM soybeans sold in markets as a food source. In the present study, two commercial GM (GM-1 and -2) soybeans and one non-GM soybean were randomly purchased and subjected to a whole food toxicity assessment. Rats (SD), male and female, were divided into six groups (10/sex/group). Two dosages of 1 g/kg/day and 5 g/kg/day of soybeans were selected for the low- and high-dose groups. Rats were administered the soybeans via daily oral fed for 90 days. The results indicate that the body weight, organ weight, biochemistry, hematology, and urology showed no biologically adverse effects. At necropsy, no significant differences between organ weights were noted between the non-GM- and GM soybeans-treated groups. Moreover, no gross or histopathological lesions were observed in the high-dosage (5 g/kg/day) fed groups of the non-GM and GM soybean fed rats. In conclusion, this food safety assessment revealed that commercial GM soybeans are substantially equivalent to non-GM soybeans in rats.

Diet: A Source of Endocrine Disruptors

BACKGROUND

Food is indispensable for human life and determines the health and wellbeing of the consumer. As food is the source of energy for humans, it also emerges as one of the most important sources of exposure to deleterious chemicals both natural and synthetic. The food exposed chemicals cause a number of detrimental health effects in humans, with endocrine disruption being of serious concern amongst these effects. Such chemicals disrupting the health of endocrine system are known as endocrine-disrupting chemicals (EDCs). The food exposed EDCs need to be identified and classified to effectuate a cautious consumption of food by all and especially by vulnerable groups.

AIM

The aim of the present review was to discuss food as a source of exposure to common endocrine disruptors in humans. This review presents the occurrence and levels of some of the critical endocrine disruptors exposed through frequently consumed diets.

METHODS

The major source of data was PubMed, besides other relevant publications. The focus was laid on data from the last five years, however significant earlier data was also considered.

CONCLUSION

The food as a source of endocrine disruptors to humans cannot be neglected. It is highly imperative for the consumer to recognize food as a source of EDCs and make informed choices in the consumption of food items.

Use of Physiologically Based Kinetic Modeling to Predict Rat Gut Microbial Metabolism of the Isoflavone Daidzein to S-Equol and Its Consequences for ERα Activation

SCOPE

To predict gut microbial metabolism of xenobiotics and the resulting plasma concentrations of metabolites formed, an in vitro-in silico-based testing strategy is developed using the isoflavone daidzein and its gut microbial metabolite S-equol as model compounds.

METHODS AND RESULTS

Anaerobic rat fecal incubations are optimized and performed to derive the apparent maximum velocities (Vmax ) and Michaelis-Menten constants (Km ) for gut microbial conversion of daidzein to dihydrodaidzein, S-equol, and O-desmethylangolensin, which are input as parameters for a physiologically based kinetic (PBK) model. The inclusion of gut microbiota in the PBK model allows prediction of S-equol concentrations and slightly reduced predicted maximal daidzein concentrations from 2.19 to 2.16 µm. The resulting predicted concentrations of daidzein and S-equol are comparable to in vivo concentrations reported.

CONCLUSION

The optimized in vitro approach to quantify kinetics for gut microbial conversions, and the newly developed PBK model for rats that includes gut microbial metabolism, provide a unique tool to predict the in vivo consequences of daidzein microbial metabolism for systemic exposure of the host to daidzein and its metabolite S-equol. The predictions reveal a dominant role for daidzein in ERα-mediated estrogenicity despite the higher estrogenic potency of its microbial metabolite S-equol.

Knowledge, attitudes and perceptions towards menopause among highly educated Asian women in their midlife

OBJECTIVE

To determine knowledge levels, and attitudes and perceptions towards, menopause among highly educated Asian women in their midlife.

STUDY DESIGN

A cross-sectional survey.

SETTING

Five teaching institutions in Hyderabad, Pakistan.

POPULATION

In total, 200 out of 225 (89% response rate) teachers, lecturers and professors, aged 40-59 years, were surveyed in 2013 using a self-administered questionnaire.

RESULTS

The mean age of responders was 48 years. Premenopausal and perimenopausal women attributed for 58%, whereas 42% were postmenopausal. All women had a masters degree; 15% had a PhD degree. Forty-six percent of responders thought they had sufficient knowledge about the menopause and 87% had positive perceptions about it, with 76% feeling life was easier and calmer as a result of it. Reported negative perceptions included 30% of women experiencing feelings of grumpiness, irritability, altered work capability and loss of femininity. Health professionals were an information resource. of 60% of cases, only 5% of participants knew about hormone replacement therapy and none knew about available alternative therapies.

CONCLUSION

Despite the fact that the majority of women felt well informed and exhibited a positive attitude towards menopause, a strong urge for more knowledge was expressed. Public health care systems should mobilize resources and take measures to improve women's awareness and knowledge about menopause-related changes through a variety of educational tools and media, including the Internet. A recommendation would be for physicians to provide more information about menopausal symptoms and also therapies to alleviate these symptoms, regardless of the patient's socioeconomic background.

Assessment of dietary phytoestrogen intake via plant-derived foods in China

The potential influence of dietary phytoestrogen exposure on human health during different life phases including early childhood is a matter of scientific debate. In order to improve the risk-benefit assessment of exposure to dietary phytoestrogen, reliable and age-stratified exposure data are desirable. For contributing to the database on phytoestrogen exposure, in the present study plant-derived foods from the Chinese market were analysed by LC-MS/MS for their contents of phytoestrogens, including daidzein, genistein, secoisolariciresinol, glycitein and coumestrol. The analytical data showed the presence of phytoestrogens in a concentration range of less than 0.1 to about 50 μg g(-1). Dietary intake was assessed on the basis of average food intake data obtained from interviewing 1000 randomly selected people with the help of food frequency questionnaires. Based on the overall population sampled, the average total phytoestrogen intake was estimated at 232 μg kg(-1) day(-1). Genistein contributed to about 66%, secoisolariciresinol and glycitein to about 10% each, and daidzein to about 7% of the overall intake. Coumestrol was present only in trace amounts. Age-related exposure assessment indicated that pre-pubertal children (aged 0-14 years) were exposed at the highest level with an average total phytoestrogen intake of 621 μg kg(-1) day(-1). The substantially higher average exposure of children as compared with adults should trigger further research into the potential health effects of early life exposure to phytoestrogen.

Development of a food compositional database for the estimation of dietary intake of phyto-oestrogens in a group of postmenopausal women previously treated for breast cancer and validation with urinary excretion

The scientific literature contains evidence suggesting that women who have been treated for breast cancer may, as a result of their diagnosis, increase their phyto-oestrogen (PE) intake. In the present paper, we describe the creation of a dietary analysis database (based on Dietplan6) for the determination of dietary intakes of specific PE (daidzein, genistein, glycitein, formononetin, biochanin A, coumestrol, matairesinol and secoisolariciresinol), in a group of women previously diagnosed and treated for postmenopausal breast cancer. The design of the database, data evaluation criteria, literature data entry for 551 foods and primary analysis by LC–MS/MS of an additional thirty-four foods for which there were no published data are described. The dietary intake of 316 women previously treated for postmenopausal breast cancer informed the identification of potential food and beverage sources of PE and the bespoke dietary analysis database was created to, ultimately, quantify their PE intake. In order that PE exposure could be comprehensively described, fifty-four of the 316 subjects completed a 24 h urine collection, and their urinary excretion results allowed for the description of exposure to include those identified as ‘equol producers’.

Intakes and sources of isoflavones, lignans, enterolignans, coumestrol and soya-containing foods in the Norfolk arm of the European Prospective Investigation into Cancer and Nutrition (EPIC-Norfolk), from 7 d food diaries, using a newly updated database

Objective

A diet rich in phyto-oestrogens has been suggested to protect against a variety of common diseases but UK intake data on phyto-oestrogens or their food sources are sparse. The present study estimates the average intakes of isoflavones, lignans, enterolignans and coumestrol from 7 d food diaries and provides data on total isoflavone, lignan and phyto-oestrogen consumption by food group.

Design

Development of a food composition database for twelve phyto-oestrogens and analysis of soya food and phyto-oestrogen consumption in a population-based study.

Setting

Men and women, aged 40–79 years, from the general population participating in the Norfolk arm of the European Prospective Investigation into Cancer and Nutrition (EPIC-Norfolk) between 1993 and 1997, with nutrient and food data from 7 d food diaries.

Subjects

A subset of 20 437 participants.

Results

The median daily phyto-oestrogen intake for all men was 1199 μg (interquartile range 934–1537 μg; mean 1504 μg,sd1502 μg) and 888 μg for all women (interquartile range 710–1135 μg; mean 1205 μg,sd1701 μg). In soya consumers, median daily intakes were higher: 2861 μg in men (interquartile range 1304–7269 μg; mean 5051 μg,sd5031 μg) and 3142 μg in women (interquartile range 1089–7327 μg; mean 5396 μg,sd6092 μg). In both men and women, bread made the greatest contribution to phyto-oestrogen intake – 40·8 % and 35·6 %, respectively. In soya consumers, vegetable dishes and soya/goat's/sheep's milks were the main contributors – 45·7 % and 21·3 % in men and 38·4 % and 33·7 % in women, respectively.

Conclusions

The ability to estimate phyto-oestrogen intake in Western populations more accurately will aid investigations into their suggested effects on health.

High serum isoflavone concentrations are associated with the risk of precocious puberty in Korean girls

OBJECTIVE

The gradual decrease in the age of onset of puberty raises concerns about the contribution of phytoestrogen intake on sexual maturation. However, no data are available on the association between serum isoflavone (genistein, daidzein) concentration and central precocious puberty (CPP). The aim of the study was to test the association between serum isoflavone concentrations and the risk of CPP in Korean girls.

STUDY DESIGN

A case-control study was conducted at Inje University Hospital in Korea. One-hundred and eight girls with CPP (aged 8·6 ± 0·8 year) and 91 age-matched controls (aged 8·5 ± 0·8 year) were examined.

RESULTS

Serum concentrations of daidzein (P = 0·0202), genistein (P = 0·0021) and total isoflavones (P = 0·0009) were higher in children with CPP than in normal children. When the children were categorized into three groups according to total serum isoflavone as follows: <30, 30-70 and ≥70 nmol/l, serum concentrations of daidzein, genistein and total isoflavones significantly increased across three categories of serum isoflavone (P < 0·0001). The prevalence of CPP was significantly higher in children with serum isoflavone level of ≥30 nmol/l than those with serum level of <30 nmol/l (P = 0·0008). The adjusted OR for precocious puberty increased significantly across a range of total serum isoflavone (OR = 4·39; 95% CI: 1·83-10·51 vs OR = 5·22; 95% CI: 2·07-13·20; P = 0·001).

CONCLUSION

These results suggest that elevated serum isoflavones may be associated with the risk of CPP in Korean girls.

Overnight urinary excretion of isoflavones as an indicator for dietary isoflavone intake in Korean girls of pubertal age

Little is known about the bioavailability of isoflavones in children. Previous studies have shown that children excrete more isoflavone in urine compared with adults. Thus we examined the relationship between usual dietary isoflavone intake and the urinary excretion of isoflavonoids in Korean girls of pubertal age. Twelve girls each were selected from the lowest and the highest quartiles of isoflavone intake among 252 Korean girls aged 8–11 years. Age, BMI and sexual maturation stage were matched between the two groups. Dietary intakes for 3 d by diet record and overnight urine samples were collected at baseline and at 6 and 12 months. Total and individual isoflavone (daidzein, genistein and glycitein) intakes were calculated from diet records. The parent isoflavone compounds (daidzein, genistein and glycitein) and their metabolites (equol,O-desmethylangolensin (O-DMA), dihydrodaidzein and dihydrogenistein) present in the urine samples were analysed using liquid chromatography–MS. Intake levels of total and individual isoflavone compounds were significantly higher in the high isoflavone (HI) group than the levels in the low isoflavone (LI) group (P < 0·05). Urinary excretion of all isoflavone parent compounds was significantly higher in the HI group than in the LI group (P < 0·0001). Among isoflavone metabolites, onlyO-DMA and total metabolites were significantly different (P < 0·05). Total isoflavone intake was highly correlated with the urinary excretion of total parent compounds (r0·68;P < 0·01), parent compounds plus their metabolites (r0·66–0·69;P < 0·01) and total isoflavonoids (r0·72;P < 0·0001). In conclusion, overnight urinary excretion of total isoflavonoids is a reliable biomarker of usual isoflavone intake in Korean girls of pubertal age.

Breast, colorectal, and prostate cancer risk in the European Prospective Investigation into Cancer and Nutrition-Norfolk in relation to phytoestrogen intake derived from an improved database

BACKGROUND

The characterization of phytoestrogen intake and cancer risk has been hindered by the absence of accurate dietary phytoestrogen values.

OBJECTIVE

We examined the risk of breast, colorectal, and prostate cancers relative to phytoestrogen intake on the basis of a comprehensive database.

DESIGN

Demographic and anthropometric characteristics, a medical history, and 7-d records of diet were collected prospectively from participants (aged 40-79 y) in the European Prospective Investigation into Cancer and Nutrition-Norfolk (EPIC-Norfolk). Five hundred nine food items were analyzed by liquid chromatography-mass spectrometry/mass spectrometry, and (13)C(3)-labeled internal standards were analyzed for isoflavones (genistein, daidzein, glycitein, biochanin A, and formononetin), lignans (secoisolariciresinol and matairesinol), and enterolignans from gut microbial metabolism in animal food sources (equol and enterolactone). From the direct analysis, values for 10,708 foods were calculated. Odds ratios (ORs) for breast (244 cases, 941 controls), colorectal (221 cases, 886 controls), and prostate (204 cases, 812 controls) cancers were calculated relative to phytoestrogen intake.

RESULTS

Phytoestrogen intake was not associated with breast cancer among women or colorectal cancer among men. Among women, colorectal cancer risk was inversely associated with enterolactone (OR: 0.33; 95% CI: 0.14, 0.74) and total enterolignans (OR: 0.32; 95% CI: 0.13, 0.79), with a positive trend detected for secoisolariciresinol (OR: 1.60; 95% CI: 0.96, 2.69). A positive trend between enterolignan intake and prostate cancer risk (OR: 1.27; 95% CI: 0.97, 1.66) was attenuated after adjustment for dairy intake (OR: 1.19; 95% CI: 0.77, 1.82).

CONCLUSION

Dietary phytoestrogens may contribute to the risk of colorectal cancer among women and prostate cancer among men.

Analytical and compositional aspects of isoflavones in food and their biological effects

This paper provides an overview of analytical techniques used to determine isoflavones (IFs) in foods and biological fluids with main emphasis on sample preparation methods. Factors influencing the content of IFs in food including processing and natural variability are summarized and an insight into IF databases is given. Comparisons of dietary intake of IFs in Asian and Western populations, in special subgroups like vegetarians, vegans, and infants are made and our knowledge on their absorption, distribution, metabolism, and excretion by the human body is presented. The influences of the gut microflora, age, gender, background diet, food matrix, and the chemical nature of the IFs on the metabolism of IFs are described. Potential mechanisms by which IFs may exert their actions are reviewed, and genetic polymorphism as determinants of biological response to soy IFs is discussed. The effects of IFs on a range of health outcomes including atherosclerosis, breast, intestinal, and prostate cancers, menopausal symptoms, bone health, and cognition are reviewed on the basis of the available in vitro, in vivo animal and human data.

Determination of phytoestrogens in dietary supplements by LC-MS/MS

Labelling data quantifying the exact content of individual phytoestrogen analytes in dietary supplements are generally poor. As these products are commonly used in the management of menopause symptoms, any clinical benefits would be dependent on the exact dosage of isoflavones received. Well-established extraction procedures and updated isotope dilution mass spectrometry liquid chromatography coupled with tandem mass spectrometry detection (LC-MS/MS) have been used to accurately quantify the concentrations of ten common isoflavones in 35 dietary supplement samples on sale in the UK, Canada and Italy. Concentration-specific ionization suppression is described for biochanin A and formononetin. All supplements contained phytoestrogens. The soya isoflavones (genistein, daidzein, glycitein) were present in all products and the majority also contained the red clover isoflavones (biochanin A, formononetin) and some the Kudzu isoflavones (daidzein, puerarin). The content of total isoflavones per dose ranged from <1 to 53 mg. Trace amounts of coumestrol were found in six products. Other less common analytes, the prenylnaringenins (6-prenylnaringenin, 8-prenylnaringenin, 6,8-diprenylnaringenin) were not found in any of the products. Only 14 of 35 supplements were found to deliver more than or equal to 40 mg day(-1) of aglycone isoflavones, a consensus dose value recognized as delivering therapeutic benefit. Eleven did not match label claims. Six delivered less than 10 mg day (-1) of isoflavones. There has been little improvement in the overall quality of industry labelling in the five years since this was last investigated. Consequently, the public, retailers and healthcare professionals should consider using standardized isoflavone supplements, which are supported by analytical measurements.

Breast cancer risk in relation to urinary and serum biomarkers of phytoestrogen exposure in the European Prospective into Cancer-Norfolk cohort study

INTRODUCTION

Phytoestrogens are a group of compounds found in plants that structurally resemble the hormone oestradiol, and thus have the potential to act as oestrogen agonists or antagonists. Their potential effects may alter the risk of breast cancer, but only a limited range of phytoestrogens has been examined in prospective cohort studies.

METHODS

Serum and urine samples from 237 incident breast cancer cases and 952 control individuals (aged 45 to 75 years) in the European Prospective into Cancer-Norfolk cohort were analysed for seven phytoestrogens (daidzein, enterodiol, enterolactone, genistein, glycitein, o-desmethylangolensin, and equol) using liquid chromatography/mass spectrometry. Data on participants' diet, demographics, anthropometrics, and medical history were collected upon recruitment. All models were adjusted for weight, fat and energy intake, family history of breast cancer, social class, analytical batch, and factors related to oestrogen exposure.

RESULTS

Urinary or serum phytoestrogens were not associated with protection from breast cancer in the European Prospective into Cancer-Norfolk cohort. Breast cancer risk was marginally increased with higher levels of total urinary isoflavones (odds ratio = 1.08 (95% confidence interval = 1.00 to 1.16), P = 0.055); among those with oestrogen receptor-positive tumours, the risk of breast cancer was increased with higher levels of urinary equol (odds ratio = 1.07 (95% confidence interval = 1.01 to 1.12), P = 0.013).

CONCLUSION

There was limited evidence of an association between phytoestrogen biomarkers and breast cancer risk in the present study. There was no indication of decreased likelihood of breast cancer with higher levels of phytoestrogen biomarkers, but the observation that some phytoestrogen biomarkers may be associated with greater risk of breast cancer warrants further study with greater statistical power.

Safety and nutritional assessment of GM plants and derived food and feed: the role of animal feeding trials

In this report the various elements of the safety and nutritional assessment procedure for genetically modified (GM) plant derived food and feed are discussed, in particular the potential and limitations of animal feeding trials for the safety and nutritional testing of whole GM food and feed. The general principles for the risk assessment of GM plants and derived food and feed are followed, as described in the EFSA guidance document of the EFSA Scientific Panel on Genetically Modified Organisms. In Section 1 the mandate, scope and general principles for risk assessment of GM plant derived food and feed are discussed. Products under consideration are food and feed derived from GM plants, such as maize, soybeans, oilseed rape and cotton, modified through the introduction of one or more genes coding for agronomic input traits like herbicide tolerance and/or insect resistance. Furthermore GM plant derived food and feed, which have been obtained through extensive genetic modifications targeted at specific alterations of metabolic pathways leading to improved nutritional and/or health characteristics, such as rice containing beta-carotene, soybeans with enhanced oleic acid content, or tomato with increased concentration of flavonoids, are considered. The safety assessment of GM plants and derived food and feed follows a comparative approach, i.e. the food and feed are compared with their non-GM counterparts in order to identify intended and unintended (unexpected) differences which subsequently are assessed with respect to their potential impact on the environment, safety for humans and animals, and nutritional quality. Key elements of the assessment procedure are the molecular, compositional, phenotypic and agronomic analysis in order to identify similarities and differences between the GM plant and its near isogenic counterpart. The safety assessment is focussed on (i) the presence and characteristics of newly expressed proteins and other new constituents and possible changes in the level of natural constituents beyond normal variation, and on the characteristics of the GM food and feed, and (ii) the possible occurrence of unintended (unexpected) effects in GM plants due to genetic modification. In order to identify these effects a comparative phenotypic and molecular analysis of the GM plant and its near isogenic counterpart is carried out, in parallel with a targeted analysis of single specific compounds, which represent important metabolic pathways in the plant like macro and micro nutrients, known anti-nutrients and toxins. Significant differences may be indicative of the occurrence of unintended effects, which require further investigation. Section 2 provides an overview of studies performed for the safety and nutritional assessment of whole food and feed. Extensive experience has been built up in recent decades from the safety and nutritional testing in animals of irradiated foods, novel foods and fruit and vegetables. These approaches are also relevant for the safety and nutritional testing of whole GM food and feed. Many feeding trials have been reported in which GM foods like maize, potatoes, rice, soybeans and tomatoes have been fed to rats or mice for prolonged periods, and parameters such as body weight, feed consumption, blood chemistry, organ weights, histopathology etc have been measured. The food and feed under investigation were derived from GM plants with improved agronomic characteristics like herbicide tolerance and/or insect resistance. The majority of these experiments did not indicate clinical effects or histopathological abnormalities in organs or tissues of exposed animals. In some cases adverse effects were noted, which were difficult to interpret due to shortcomings in the studies. Many studies have also been carried out with feed derived from GM plants with agronomic input traits in target animal species to assess the nutritive value of the feed and their performance potential. Studies in sheep, pigs, broilers, lactating dairy cows, and fish, comparing the in vivo bioavailability of nutrients from a range of GM plants with their near isogenic counterpart and commercial varieties, showed that they were comparable with those for near isogenic non-GM lines and commercial varieties. In Section 3 toxicological in vivo, in silico, and in vitro test methods are discussed which may be applied for the safety and nutritional assessment of specific compounds present in food and feed or of whole food and feed derived from GM plants. Moreover the purpose, potential and limitations of the 90-day rodent feeding trial for the safety and nutritional testing of whole food and feed have been examined. Methods for single and repeated dose toxicity testing, reproductive and developmental toxicity testing and immunotoxicity testing, as described in OECD guideline tests for single well-defined chemicals are discussed and considered to be adequate for the safety testing of single substances including new products in GM food and feed. Various in silico and in vitro methods may contribute to the safety assessment of GM plant derived food and feed and components thereof, like (i) in silico searches for sequence homology and/or structural similarity of novel proteins or their degradation products to known toxic or allergenic proteins, (ii) simulated gastric and intestinal fluids in order to study the digestive stability of newly expressed proteins and in vitro systems for analysis of the stability of the novel protein under heat or other processing conditions, and (iii) in vitro genotoxicity test methods that screen for point mutations, chromosomal aberrations and DNA damage/repair. The current performance of the safety assessment of whole foods is mainly based on the protocols for low-molecular-weight chemicals such as pharmaceuticals, industrial chemicals, pesticides, food additives and contaminants. However without adaptation, these protocols have limitations for testing of whole food and feed. This primarily results from the fact that defined single substances can be dosed to laboratory animals at very large multiples of the expected human exposure, thus giving a large margin of safety. In contrast foodstuffs are bulky, lead to satiation and can only be included in the diet at much lower multiples of expected human intakes. When testing whole foods, the possible highest concentration of the GM food and feed in the laboratory animal diet may be limited because of nutritional imbalance of the diet, or by the presence of compounds with a known toxicological profile. The aim of the 90-days rodent feeding study with the whole GM food and feed is to assess potential unintended effects of toxicological and/or nutritional relevance and to establish whether the GM food and feed is as safe and nutritious as its traditional comparator rather than determining qualitative and quantitative intrinsic toxicity of defined food constituents. The design of the study should be adapted from the OECD 90-day rodent toxicity study. The precise study design has to take into account the nature of the food and feed and the characteristics of the new trait(s) and their intended role in the GM food and feed. A 90-day animal feeding trial has a large capacity (sensitivity and specificity) to detect potential toxicological effects of single well defined compounds. This can be concluded from data reported on the toxicology of a wide range of industrial chemicals, pharmaceuticals, food substances, environmental, and agricultural chemicals. It is possible to model the sensitivity of the rat subchronic feeding study for the detection of hypothetically increased amount of compounds such as anti-nutrients, toxicants or secondary metabolites. With respect to the detection of potential unintended effects in whole GM food and feed, it is unlikely that substances present in small amounts and with a low toxic potential will result in any observable (unintended) effects in a 90-day rodent feeding study, as they would be below the no-observed-effect-level and thus of unlikely impact to human health at normal intake levels. Laboratory animal feeding studies of 90-days duration appear to be sufficient to pick up adverse effects of diverse compounds that would also give adverse effects after chronic exposure. This conclusion is based on literature data from studies investigating whether toxicological effects are adequately identified in 3-month subchronic studies in rodents, by comparing findings at 3 and 24 months for a range of different chemicals. The 90-day rodent feeding study is not designed to detect effects on reproduction or development other than effects on adult reproductive organ weights and histopathology. Analyses of available data indicate that, for a wide range of substances, reproductive and developmental effects are not potentially more sensitive endpoints than those examined in subchronic toxicity tests. Should there be structural alerts for reproductive/developmental effects or other indications from data available on a GM food and feed, then these tests should be considered. By relating the estimated daily intake, or theoretical maximum daily intake per capita for a given whole food (or the sum of its individual commercial constituents) to that consumed on average per rat per day in the subchronic 90-day feeding study, it is possible to establish the margin of exposure (safety margin) for consumers. Results obtained from testing GM food and feed in rodents indicate that large (at least 100-fold) 'safety' margins exist between animal exposure levels without observed adverse effects and estimated human daily intake. Results of feeding studies with feed derived from GM plants with improved agronomic properties, carried out in a wide range of livestock species, are discussed. The studies did not show any biologically relevant differences in the parameters tested between control and test animals. (ABSTRACT TRUNCATED)

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.

Flavonoids and heart health: proceedings of the ILSI North America Flavonoids Workshop, May 31-June 1, 2005, Washington, DC

This article provides an overview of current research on flavonoids as presented during a workshop entitled, "Flavonoids and Heart Health," held by the ILSI North America Project Committee on Flavonoids in Washington, DC, May 31 and June 1, 2005. Because a thorough knowledge and understanding about the science of flavonoids and their effects on health will aid in establishing dietary recommendations for bioactive components such as flavonoids, a systematic review of the science of select flavonoid classes (i.e., flavonols, flavones, flavanones, isoflavones, flavan-3-ols, anthocyanins, and proanthocyanidins) was presented. The objectives of the workshop were to 1) present and discuss current research on flavonoid intake and the relation between flavonoids and heart health; 2) develop information that could lead to expert consensus on the state-of-the-science of dietary intake of flavonoids on heart health; and 3) summarize and prioritize the research needed to establish the relations between specific flavonoids and heart health. Presentations included the basics of the biology of flavonoids, including the types and distribution in foods, analytical methodologies used to determine the amounts in foods, the bioavailability, the consumption patterns and potential biomarkers of intake, risk assessment and safety evaluation, structure/function claims, and the proposed mechanism(s) of the relation between certain flavonoids and heart health endpoints. Data presented support the concept that certain flavonoids in the diet can be associated with significant health benefits, including heart health. Research gaps were identified to help advance the science.

Adolescent dietary phytoestrogen intake and breast cancer risk (Canada)

OBJECTIVE

It has been suggested that dietary phytoestrogen intake during adolescence may reduce the risk of developing breast cancer. This population-based case-control study evaluated the association between adolescent dietary phytoestrogen intake and adult breast cancer risk among women in Ontario, Canada.

METHODS

Pathology-confirmed, population-based breast cancer cases, aged 25-74 years, diagnosed between June 2002 and April 2003, were identified using the Ontario Cancer Registry. Population-based controls were recruited, and matched to cases within 5-year age groups. Adolescent phytoestrogen intake was obtained using a brief food frequency questionnaire (n = 3,024 cases, n = 3,420 controls). Logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

Higher phytoestrogen intake (both isoflavones and lignans) during adolescence was associated with a reduced breast cancer risk, and a monotonic trend was observed from the lowest to the highest quartile (OR [Q2] = 0.91, 95% CI 0.79-1.04, OR[Q3] = 0.86, 95% CI 0.75-0.98, and OR[Q4] = 0.71, 95% CI 0.62-0.82, p-trend < 0.001).

CONCLUSION

Adolescent dietary phytoestrogen intake may be associated with a decreased risk of adult breast cancer. If verified, this finding has important implications with regard to breast cancer prevention since diet is a potentially modifiable factor.

Validation of a phytoestrogen food frequency questionnaire with urinary concentrations of isoflavones and lignan metabolites in premenopausal women

OBJECTIVE

The purpose of this study was to examine the association between dietary intake of phytoestrogens estimated by a food frequency questionnaire (FFQ) with urinary metabolites.

METHODS

Participants were 26 premenopausal, Caucasian women aged 25 to 42 years. Dietary intake of isoflavones (genistein and daidzein) and lignans (secoisolariciresinol and matairesinol) were estimated by a 53-item interviewer-administered FFQ on two occasions, reflecting 'habitual' (previous 2 months) and 'recent' (previous 2 days) dietary intake. Isoflavone (genistein, daidzein) and lignan (enterolactone, enterodiol and secoisolariciresinol) concentrations were measured in 24-hour urine samples by gas chromatography-mass spectrometry. Correlations between FFQ (habitual and recent, separately) and urinary metabolite values were assessed using Spearman correlation coefficients.

RESULTS

Mean habitual isoflavone and lignan intakes were 13.7 mg/day and 13.8 mg/day, respectively. Mean urinary concentrations of isoflavones and lignans were 17.4 micromol/day and 20.6 micromol/day, respectively. Recent and habitual isoflavone intakes were correlated with urinary excretion of metabolites (r = 0.64, p < 0.001 and r = 0.54, p = 0.004, respectively). Urinary excretion of lignans was also modestly correlated with recent and habitual lignan intakes (r = 0.46, p = 0.02 and r = 0.40, p = 0.05, respectively).

CONCLUSIONS

Our results support the use of this FFQ as a measure of dietary isoflavone and lignan intake in epidemiological studies.

Phytoestrogen content of foods consumed in Canada, including isoflavones, lignans, and coumestan

Phytoestrogens may play a role in hormone-related diseases such as cancer, but epidemiological and clinical data are conflicting in part due to inadequate databases used in intake estimation. A database of nine phytoestrogens in foods relevant to Western diets was developed to more accurately estimate intakes. Foods (N = 121) available in Ontario, Canada were prepared as commonly consumed and analyzed for isoflavones (genistein, daidzein, glycitein, formononetin), lignans (secoisolariciresinol, matairesinol, pinoresinol, lariciresinol), and coumestan (coumestrol) using gas chromatography-mass spectrometry methods. Data were presented on an as is (wet) basis per 100 g and per serving. Food groups with decreasing levels of total phytoestrogens per 100 g are nuts and oilseeds, soy products, cereals and breads, legumes, meat products, and other processed foods that may contain soy, vegetables, fruits, alcoholic, and nonalcoholic beverages. Soy products contain the highest amounts of isoflavone, followed by legumes, meat products and other processed foods, cereals and breads, nuts and oilseeds, vegetables, alcoholic beverages, fruits, and nonalcoholic beverages. Decreasing amounts of lignans are found in nuts and oilseeds, cereals and breads, legumes, fruits, vegetables, soy products, processed foods, alcoholic, and nonalcoholic beverages. The richest sources of specific phytoestrogens, including coumestrol, were identified. The database will improve phytoestrogen intake estimation in future epidemiological and clinical studies particularly in Western populations.

Intakes and sources of soya foods and isoflavones in a UK population cohort study (EPIC-Norfolk)

BACKGROUND

It has been suggested that the consumption of a diet rich in phytoestrogens might protect against a variety of diseases common in Western societies. However, there are little available data on the food sources or distribution of intake in the UK diet.

OBJECTIVE

To estimate the average intake and range of soya foods and isoflavones in a population-based cohort and to provide data on isoflavone consumption by food group.

SUBJECTS

Men and women (11,843) from the Norfolk arm of the European Prospective Investigation into Cancer and Nutrition (EPIC).

METHODS

Dietary daidzein and genistein intakes were obtained from 7-day food diaries, completed by participants between 1993 and 1998 and calculated from an in-house food composition database. Energy and anthropometric measurements were also carried out.

RESULTS

Average daily isoflavone intakes for both men and women were less than 1 mg (interquartile range (IQR) men: 0.39-0.82 mg; women: 0.30-0.64 mg). However, in soya-consumers, average daily intakes were higher: 8.6 mg in women (IQR: 2.28-10.72 mg) and 7.5 mg in men (IQR: 2.22-9.17 mg). In both men and women, bread and bread rolls made the highest contribution to isoflavone intake - 62.5 and 53.0%, respectively. In soya-consuming men and women, vegetable dishes and milks were the main contributors - 25.0 and 38.5% in men and 38.5% and 26.0% in women, respectively.

CONCLUSIONS

Isoflavone intake is low in the UK but may be an underestimate due to soya added to commercial products. Future analyses of the isoflavone and lignan content of basic ingredient foods and commercial items commonly consumed in the UK diet will enable more accurate estimates of phytoestrogen intake to be made. The ability to estimate isoflavone intake in Western populations more accurately will enable investigations to be conducted into the suggested beneficial effects of phytoestrogens on health.

Phyto-oestrogen intake in Scottish men: use of serum to validate a self-administered food-frequency questionnaire in older men

OBJECTIVE

To study dietary intake and serum concentrations of isoflavones in order to provide relative validation of isoflavone intake estimates from the Scottish Collaborative Group - Food-Frequency Questionnaire (SCG-FFQ).

DESIGN

Validation study.

SETTING

Southern Scotland.

METHOD

Dietary intake of isoflavones was estimated using the semiquantitative SCG-FFQ and rank correlation and Kappa statistics were used for the relative validation of intakes against serum isoflavone concentrations in 203 male participants who were population controls in a case-control study of diet and prostate cancer.

RESULTS

The median intake of isoflavones (daidzein and genistein) was 1.0mg/day (l-QR 0.6-1.8). The median serum concentration of genistein was 33.79 nmol/l (I-QR 14.12-64.93), nearly twice that of daidzein (18.00 nmol/l, I-QR 8.26-29.45). Equol was detected in 49% of subjects; in these subjects the median was 0.67 nmol/l (I-QR 0.34-1.51). Isoflavone intake was significantly correlated with serum concentrations of daidzein (p = 0.24, P = 0.001), genistein (p = 0.26, P < 0.001) and total isoflavonoids (sum of daidzein, genistein and equol) ( p = 0.27, P < 0.001). Whereas values for weighted Kappa ranged from 0.16 (P = 0.002) for daidzein and equol combined to 0.22 (P < 0.001) for genistein.

CONCLUSIONS

These results demonstrate the suitability of the SCG-FFQ to rank usual isoflavone intakes in older Scottish men, a population observed to have low consumption of soy foods.

A soy diet accelerates renal damage in autoimmune MRL/Mp-lpr/lpr mice

Isoflavones, which are phytoestrogens present in large quantities in soy and soy-derived products, have estrogenic activity, inhibit protein tyrosine kinase, and exert other effects in the human body. Thus, the recent spread of soy consumption in Western populations emphasizes the need to more fully understand the potential effects in the body, especially in abnormal immune conditions. In the present study, the influence of a soy diet on lupus disease in MRL/Mp-lpr/lpr (MRL/lpr) mice was investigated. Weanling female MRL/lpr mice (4 weeks) were fed a soy diet (20% soybean protein and 5% soybean oil). The soy diet exacerbated renal damage; findings in this mouse strain included accelerated proteinuria, elevated serum creatinine concentrations, and reduced creatinine clearance. No effects were detected, however, in C3H/HeN mice, which have the same H-2(k) genetic background as MRL/lpr mice do. A tendency toward an increase in thymus weight and proliferation of T cells in spleen and B cells in lymph nodes were found at the age of 16 weeks. These findings indicate that a soy diet, in comparison with a casein diet, significantly exacerbates the clinical course of this autoimmune disease. Further research on the mechanism of this effect of soy-rich diets is needed, and isoflavone supplementation for systemic lupus erythematosus patients should be carefully reevaluated.

Polymorphisms in the CYP19 gene may affect the positive correlations between serum and urine phytoestrogen metabolites and plasma androgen concentrations in men

Phytoestrogens have been hypothesized to protect against prostate cancer via modulation of circulating androgen concentrations. We conducted a cross-sectional study of 267 men in the Norfolk arm of the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort with 2 aims: first, to investigate the association between phytoestrogen exposure (measured from diet, urine, and serum) and plasma concentrations of sex hormone-binding globulin (SHBG), androstanediol glucuronide, testosterone and Free Androgen Index (FAI); and second, whether the association may be modified by polymorphisms in CYP19 and SHBG genes. Dietary daidzein and genistein intakes were obtained from food diaries and computed using an in-house food composition database. Urinary and serum concentrations of 3 isoflavones (daidzein, genistein, glycitein), 2 daidzein metabolites O-desmethylangolensin (O-DMA) and 2 lignan metabolites (enterodiol and enterolactone) were measured using mass spectrometry. There was no association between dietary, urinary, and serum phytoestrogens and plasma SHBG concentrations. Enterolactone was positively associated with plasma androstanediol glucuronide concentrations (urinary enterolactone: r = 0.127, P = 0.043; serum enterolactone: r = 0.172, P = 0.006) and FAI (urinary enterolactone: r = 0.115, P = 0.067; serum enterolactone: r = 0.158, P = 0.011). Both urinary and serum equol were associated with plasma testosterone (urinary equol: r = 0.332, P = 0.013; serum equol: r = 0.318, P = 0.018) and FAI (urinary equol: r = 0.297, P = 0.027; serum equol: r = 0.380, P = 0.004) among men with the TT genotype but not the CC or CT genotypes (r = -0.029 to -0.134, P = 0.091-0.717) for the CYP19 3'untranslated region (UTR) T-C polymorphism. Urinary and serum enterolactone showed similar genotype-dependent associations with testosterone but not with FAI. In this first study on phytoestrogen-gene associations in men, we conclude that enterolactone and equol are positively associated with plasma androgen concentrations, and interactions with CYP19 gene may be involved.

Xenobiotic phenols in early pregnancy amniotic fluid

We found detectable levels of three phytoestrogens (enterolactone, daidzein and genistein) and bisphenol A (BPA) in 21 residual amniotic fluid specimens that were collected before 20 weeks gestation. Samples were obtained by amniocentesis from women who were referred to the Mount Sinai Medical center because of advanced maternal age. Phytoestrogens were present in higher concentrations than BPA. Enterolactone was detected at the highest concentration (median 95.9 microg/L), followed by daidzein and genistein (9.5 and 1.4 microg/L, respectively). BPA was present at very low concentrations (10%>LOD of 0.5 microg/L). The relative concentration of the chemicals measured in amniotic fluid were identical to those in urine reported by other studies, i.e. enterolactone>daidzein>genistein>>BPA. Amniotic fluid is a source of fetal exposure to polar xenobiotics that come from the mother.

Determination of unusual soya and non-soya phytoestrogen sources in beer, fish products and other foods

Fish and fish products (14 samples), Indian foods and meals (10 samples), spices (30 samples) and beers (10 samples) were analysed for their phytoestrogen content, and a number of significant non-soya sources of dietary phytoestrogens were identified. No isoflavones were detected in unprocessed, farmed or ocean fish, but some samples of processed fish products contained soya isoflavones, which are assumed to come from coatings or protein addition. Additionally, some processed fish products contained, genistein glycocongugates not derived from soya. Genistein was detected in Indian meals such that, for example, a single portion of a vindalooo curry contained 11 mg genistein. The origin was most likely from the spices used, since the analysis of curry powders, chilli powder, crushed red chillies, garam masala and tandoori powder revealed that some contained genistein at more than 100 mg kg(-1). Cumin was the most likely source material, although not all individual samples of cumin tested contained high levels of genistein. Prenylnaringenin phytoestrogens were determined in UK hop-based beers at mean concentrations of 0.21 mg(-1) 6-prenylnaringenin and 0.06mg(-1) 8-prenylnaringenin. The beers also contained traces of daidzein, genistein and biochanin A. The significance of 'hidden soya' in processed foods and these non-soya sources of phytoestrogens is that UK dietary intake of phytoestrogens must be assumed to be higher than estimated previously and that some sources of phytoestrogens remain poorly characterized.