Sources of phytoestrogen exposure among non-Asian women in California, USA

Exploring the Complex Mechanisms of Isoflavones: From Cell Bioavailability, to Cell Dynamics and Breast Cancer

In Western countries, the increase in the consumption of soy-derived products raises the population's exposure to isoflavones. These molecules, present in many foods, have numerous effects on the body's cells, including regulation of the transcription and epigenetics, cell signaling, cell cycle, cell growth, apoptosis, and oxidative stress. However, despite the multitude of studies conducted, on these compounds, it remains difficult to draw definitive conclusions regarding their safety or dangerousness in the diet. Indeed, some epidemiological studies highlight health benefits in consuming isoflavone-rich foods, notably by reducing the risk of certain cancers. However, several studies conducted on cell models show that these molecules can have negative effects on cell fate, particularly with regard to proliferation and survival of mammary tumor cells. Isoflavones are mainly genistein, daidzein, formononetin, and biochanin A. These molecules belong to the family of phytoestrogens, which are capable of interacting with both nuclear estrogen receptor, ERα and ERβ, to trigger agonistic and antagonistic effects. Due to their estrogenic properties, isoflavones are suspected to promote hormone-dependent cancers such as breast cancer. This suspicion is based primarily on their ability to bind to ERα in breast cells, thereby altering the signaling pathways that control cell growth. However, study results are sometimes contradictory. Some studies suggest that isoflavones may protect against breast cancer by acting as selective estrogen receptor modulators, while others highlight their potential role in stimulating tumor growth. This review explores the literature on the effects of isoflavones, focusing on their influence on ERα-dependent signaling in breast tumor cells.

Validation of ELISAs for Isoflavones and Enterolactone for Phytoestrogen Intake Assessment in the French Population

Phytoestrogens are dietary compounds with low estrogenic activity. The two main categories in the French diet are isoflavones from pulses and enterolignans metabolized by the gut flora from various lignans found in fruits, vegetables, grains, and beverages. Isoflavones and lignans have different effects on human physiology and can antagonize each other. Comprehensive lists of phytoestrogen sources were constructed based on measurements and literature data. The 24 h and 48 h dietary recalls were proposed to the volunteers of the ISOLED cohort (NCT03421184). Urine and plasma samples from these volunteers were assayed for genistein, daidzein, equol, and enterolactone. A dietary score was constructed considering the pharmacokinetic characteristics of these compounds. Correlation analyses were applied to fluid concentrations associated with dietary scores. Pearson correlations reached 0.921 (p < 0.001) for urine_IF, 0.900 (p < 0.001) for plasma_IF, 0.764 (p < 0.001) for urine_ENL, and 0.723 (p < 0.001) for plasma_ENL. ELISAs associated with careful intake assessments proved to be good tools for phytoestrogens' exposure estimation.

Soy consumption and serum uric acid levels: A systematic review and meta-analysis

Background

Soy consumption has health benefits, but the relationship between soy and uric acid remains uncertain. This meta-analysis and systematic review evaluated the effects of soy intake on plasma uric acid.

Methods

PubMed, Embase, CNKI, and the Cochrane Library were searched for studies evaluating the effects of soy, soy products, soy protein, and soy isoflavones on uric acid levels. The primary outcome was serum or plasma uric acid concentration. Study quality was evaluated by the Cochrane Collaboration and SYRCLE risk-of-bias tools.

Results

A total of 17 studies were included. Qualitative analysis of three human clinical studies of acute effects revealed that soy consumption increased serum uric acid concentration; however, soy-derived products, including tofu, bean curd cake, and dried bean curd sticks, had no significant effect on serum uric acid. A meta-analysis of five long-term human studies (10 data sets) revealed that soy protein and soy isoflavones had no significant effects on uric acid levels [weighted mean difference (WMD) = -2.11; 95% confidence interval (CI): -8.78, 4.55; p = 0.53]. However, most epidemiological data revealed that soy intake is inversely associated with uric acid levels. Meta-analysis of nine animal trials (29 data sets) revealed that soy protein and soy isoflavones significantly reduced serum uric acid concentrations (vs. controls; MD = -38.02; 95% CI: -50.60, -25.44; p < 0.001).

Conclusion

Soy and its products have different effects on serum uric acid. Soy products like tofu, bean curd cake, and dried bean curd sticks could be high-quality protein sources for individuals with hyperuricemia or gout. It can be beneficial to nutritionists and healthcare decision-makers reconsider their conceptions about the relationship between soy and uric acid levels according to the latest and further scientific study results.

Systematic review registration

[www.crd.york.ac.uk/PROSPERO], identifier [CRD42022331855].

Enterolignan Production in a Flaxseed Intervention Study in Postmenopausal US Women of African Ancestry and European Ancestry

Lignans are phytochemicals studied extensively as dietary factors in chronic disease etiology. Our goal was to examine associations between the gut microbiota and lignan metabolism and whether these associations differ by ethnicity. We conducted a flaxseed (FS) dietary intervention in 252 healthy, postmenopausal women of African ancestry (AA) and European ancestry (EA). Participants consumed ~10 g/d ground flaxseed for 6 weeks and provided overnight urine collections and fecal samples before and after intervention. The gut microbiota was characterized using 16S rRNA gene sequencing and differences in microbial community composition compared by ethnicity and intervention status. We observed a significant difference in the composition of the microbiota measured as beta diversity (p < 0.05) between AA and EA at baseline that was attenuated with FS consumption. Genera that were significantly associated with ENL production (e.g., Klebsiella, Lactobacillus, Slackia, Senegalimassilia) were unique to each group. Bacteria (e.g., Fusobacteria, Pyramidobacter and Odoribacter) previously associated with colorectal cancer and cardiovascular disease, both diet-related chronic diseases, were unique to either AA or EA and were significantly reduced in the FS intervention. This study suggests that ethnic variation in ENL metabolism may be linked to gut microbiota composition, and its impact on disease risk deserves future investigation.

Dietary Assessment Methods to Estimate (Poly)phenol Intake in Epidemiological Studies: A Systematic Review

Nutritional epidemiological studies have frequently reported associations between higher (poly)phenol intake and a decrease in the risk or incidence of noncommunicable diseases. However, the assessment methods that have been used to quantify the intakes of these compounds in large-population samples are highly variable. This systematic review aims to characterize the methods used to assess dietary (poly)phenol intake in observational studies, report the validation status of the methods, and give recommendations on method selection and data reporting. Three databases were searched for publications that have used dietary assessment methods to measure (poly)phenol intake and 549 eligible full texts were identified. Food-frequency questionnaires were found to be the most commonly used tool to assess dietary (poly)phenol intake (73%). Published data from peer-reviewed journals were the major source of (poly)phenol content data (25%). An increasing number of studies used open-access databases such as Phenol-Explorer and USDA databases on flavonoid content since their inception, which accounted for 11% and 23% of the data sources, respectively. Only 16% of the studies reported a method that had been validated for measuring the target (poly)phenols. For future research we recommend: 1) selecting a validated dietary assessment tool according to the target compounds and target period of measurement; 2) applying and combining comprehensive (poly)phenol content databases such as USDA and Phenol-Explorer; 3) detailing the methods used to assess (poly)phenol intake, including dietary assessment method, (poly)phenol content data source; 4) follow the Strengthening the Reporting of Observational Studies in Epidemiology-Nutritional Epidemiology (STROBE-nut) framework; and 5) complementing dietary intake assessment based on questionnaires with measurement of (poly)phenols in biofluids using appropriate and validated analytical methods.

Soy, Soy Foods and Their Role in Vegetarian Diets

Soy is a basic food ingredient of traditional Asian cuisine used for thousands of years. In Western countries, soybeans have been introduced about a hundred years ago and recently they are mainly used for surrogate foods production. Soy and soy foods are common nutritional solutions for vegetarians, due to their high protein content and versatility in the production of meat analogues and milk substitutes. However, there are some doubts about the potential effects on health, such as the effectiveness on cardiovascular risk reduction or, conversely, on the possible disruption of thyroid function and sexual hormones. The soy components that have stimulated the most research interest are isoflavones, which are polyphenols with estrogenic properties highly contained in soybeans. In this review, we discuss the characteristics of soy and soy foods, focusing on their nutrient content, including phytoestrogens and other bioactive substances that are noteworthy for vegetarians, the largest soy consumers in the Western countries. The safety of use will also be discussed, given the growing trend in adoption of vegetarian styles and the new soy-based foods availability.

Soy Intake Modifies the Relation Between Urinary Bisphenol A Concentrations and Pregnancy Outcomes Among Women Undergoing Assisted Reproduction

CONTEXT

Experimental data in rodents suggest that the adverse reproductive health effects of bisphenol A (BPA) can be modified by intake of soy phytoestrogens. Whether the same is true in humans is not known.

OBJECTIVE

The purpose of this study was to evaluate whether soy consumption modifies the relation between urinary BPA levels and infertility treatment outcomes among women undergoing assisted reproduction.

SETTING

The study was conducted in a fertility center in a teaching hospital.

DESIGN

We evaluated 239 women enrolled between 2007 and 2012 in the Environment and Reproductive Health (EARTH) Study, a prospective cohort study, who underwent 347 in vitro fertilization (IVF) cycles. Participants completed a baseline questionnaire and provided up to 2 urine samples in each treatment cycle before oocyte retrieval. IVF outcomes were abstracted from electronic medical records. We used generalized linear mixed models with interaction terms to evaluate whether the association between urinary BPA concentrations and IVF outcomes was modified by soy intake.

MAIN OUTCOME MEASURE

Live birth rates per initiated treatment cycle were measured.

RESULTS

Soy food consumption modified the association of urinary BPA concentration with live birth rates (P for interaction = .01). Among women who did not consume soy foods, the adjusted live birth rates per initiated cycle in increasing quartiles of cycle-specific urinary BPA concentrations were 54%, 35%, 31%, and 17% (P for trend = .03). The corresponding live birth rates among women reporting pretreatment consumption of soy foods were 38%, 42%, 47%, and 49% (P for trend = 0.35). A similar pattern was found for implantation (P for interaction = .02) and clinical pregnancy rates (P for interaction = .03) per initiated cycle, where urinary BPA was inversely related to these outcomes among women not consuming soy foods but unrelated to them among soy consumers.

CONCLUSION

Soy food intake may protect against the adverse reproductive effects of BPA. As these findings represent the first report suggesting a potential interaction between soy and BPA in humans, they should be further evaluated in other populations.

Phytoestrogens dietary intake and health status of retiree from middle-north Slovakia region

Phytoestrogens found in foods of plant origin presents chemical substances that possess a wide range of biochemical benefits. It has been found that they contribute in different health related problems. A wide range of commonly consumed foods contain appreciable amounts of phytoestrogens. Consumption of diet rich to phytoestrogen acts as a protective factor against many diseases such as cardiovascular diseases, post-menopausal symptoms in the context of osteoporosis, cancerous illnesses of colon, prostate and breast. Three main classes of phytoestrogens covers: isoflavones, lignans and coumestans. Selected nine major phytoestrogens had been analyzed simultaneously in the same foods. Questionnaire designed to determine intake frequency as well as amount of selected foods and the most common diseases presented in the population has been used to find relationships between dietary habits and health status. Evaluation of selected goals in the present study has been realized in cooperation with 140 respondents in retired age (divided into Males - covered by 34 individuals and Females - 106 individuals), comming from middle-north Slovakia region. On the base of collected data it can be concluded, that evaluated population is presented by high values of lignans intake and particularly secoisolariciresinol, mainly caused by relative high proportion of cereals and linseed in the diet. Furthermore, the relationship between phytoestrogens intake and eating habits as well as its contribution in protection against selected diseases was demonstrated.

Urinary phytoestrogens and cancer, cardiovascular, and all-cause mortality in the continuous National Health and Nutrition Examination Survey

PURPOSE

Experimental studies suggest that phytoestrogen intake alters cancer and cardiovascular risk. This study investigated the associations of urinary phytoestrogens with total cancer (n = 79), cardiovascular (n = 108), and all-cause (n = 290) mortality among 5179 participants in the continuous National Health and Nutrition Examination Survey (1999-2004).

METHODS

Urinary phytoestrogens were measured using high-performance liquid chromatography with tandem mass spectrometric detection. Survival analysis was performed to evaluate hazard ratios (HRs) and 95 % confidence intervals (CIs) for each of the three outcomes in relation to urinary phytoestrogens.

RESULTS

After adjustment for confounders, higher urinary concentrations of total enterolignans were associated with a reduced risk of death from cardiovascular disease (HR for tertile 3 vs. tertile 1 0.48; 95 % CI 0.24, 0.97), whereas higher urinary concentrations of total isoflavones (HR for tertile 3 vs. tertile 1 2.14; 95 % CI 1.03, 4.47) and daidzein (HR for tertile 3 vs. tertile 1 2.05; 95 % CI 1.02, 4.11) were associated with an increased risk. A reduction in all-cause mortality was observed for elevated urinary concentrations of total enterolignans (HR for tertile 3 vs. tertile 1 0.65; 95 % CI 0.43, 0.96) and enterolactone (HR for tertile 3 vs. tertile 1 0.65; 95 % CI 0.44, 0.97).

CONCLUSIONS

Some urinary phytoestrogens were associated with cardiovascular and all-cause mortality in a representative sample of the US population. This is one of the first studies that used urinary phytoestrogens as biomarkers of their dietary intake to evaluate the effect of these bioactive compounds on the risk of death from cancer and cardiovascular disease.

Pharmacokinetics and bioavailability of plant lignan 7-hydroxymatairesinol and effects on serum enterolactone and clinical symptoms in postmenopausal women: a single-blinded, parallel, dose-comparison study

Objective

7-Hydroxymaitairesinol (7-HMR) is a naturally occurring plant lignan found in whole grains and the Norway spruce (Piciea abies). The purpose of this study was to evaluate the bioavailability of a proprietary 7-HMR product (HMRlignan, Linnea SA, Locarno, Switzerland) through measurement of lignan metabolites and metabolic precursors.

Methods

A single-blind, parallel, pharmacokinetic and dose-comparison study was conducted on 22 post-menopausal females not receiving hormone replacement therapy. Subjects were enrolled in either a 36 mg/d (low-dose) or 72 mg/d dose (high-dose) regimen for 8 weeks. Primary measured outcomes included plasma levels of 7-HMR and enterolactone (ENL), and single-dose pharmacokinetic analysis was performed on a subset of subjects in the low-dose group. Safety data and adverse event reports were collected as well as data on hot flash frequency and severity.

Results

Pharmacokinetic studies demonstrated 7-HMR C_max = 757.08 ng/ml at 1 hour and ENL C_max = 4.8 ng/ml at 24 hours. From baseline to week 8, plasma 7-HMR levels increased by 191% in the low-dose group (p < 0.01) and by 1238% in the high-dose group (p < 0.05). Plasma ENL levels consistently increased as much as 157% from baseline in the low-dose group and 137% in the high-dose group. Additionally, the mean number of weekly hot flashes decreased by 50%, from 28.0/week to 14.3/week (p < 0.05) in the high-dose group. No significant safety issues were identified in this study.

Conclusion

The results demonstrate that HMRlignan is quickly absorbed into the plasma and is metabolized to ENL in healthy postmenopausal women. Clinically, the data demonstrate a statistically significant improvement in hot flash frequency. Doses up to 72 mg/d HMRlignan for 8 weeks were safe and well tolerated in this 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.

Dietary isoflavone intake is not statistically significantly associated with breast cancer risk in the Multiethnic Cohort

Given the high intake levels of soya and low incidence rates of breast cancer in Asian countries, isoflavones, substances with an oestrogen-like structure occurring principally in soyabeans, are postulated to be cancer protective. In the present study, we examined the association of dietary isoflavone intake with breast cancer risk in 84,450 women (896 in situ and 3873 invasive cases) who were part of the Multiethnic Cohort (Japanese Americans, whites, Latinos, African Americans and Native Hawaiians) with a wide range of soya intake levels. The absolute levels of dietary isoflavone intake estimated from a baseline FFQ were categorised into quartiles, with the highest quartile being further subdivided to assess high dietary intake. The respective intake values for the quartiles (Q1, Q2, Q3, and lower and upper Q4) were 0-< 3·2, 3·2-< 6·7, 6·7-< 12·9, 12·9-< 20·3, and 20·3-178·7 mg/d. After a mean follow-up period of 13 years, hazard ratios (HR) and 95% CI were calculated using Cox regression models stratified by age and adjusted for known confounders. Linear trends were tested by modelling continuous variables of interest assigned the median value within the corresponding quartile. No statistically significant association was observed between dietary isoflavone intake and overall breast cancer risk (HR for upper Q4 v. Q1: 0·96 (95% CI 0·85, 1·08); P trend = 0·40). While the test for interaction was not significant (P=0·14), stratified analyses suggested possible ethnic/racial differences in risk estimates, indicating that higher isoflavone intakes may be protective in Latina, African American and Japanese American women. These results are in agreement with those of previous meta-analyses showing no protection of isoflavones at low intake levels, but suggesting inverse associations in populations consuming high amounts of soya.

Soy intake and breast cancer risk: an evaluation based on a systematic review of epidemiologic evidence among the Japanese population

OBJECTIVE

We reviewed epidemiological studies of soy intake and breast cancer among Japanese women. This report is one among a series of articles by our research group, which is evaluating the existing evidence concerning the association between health-related lifestyles and cancer.

METHODS

Original data were obtained from MEDLINE searches using PubMed or from searches of the Ichushi database, complemented with manual searches. Evaluation of associations was based on the strength of evidence and the magnitude of association, together with biological plausibility.

RESULTS

Five cohort studies and six case-control studies were identified. Among the cohort studies, two studies observed that total soy intake (in terms of total amounts of soy foods or soy isoflavones) was associated with a moderate (0.5 ≤ relative risk ≤ 0.67 with statistical significance) or strong (relative risk ≤ 0.5 with statistical significance) risk reduction of breast cancer in postmenopausal women. Among the case-control studies, two studies reported a weak (0.67 ≤ odds ratio ≤ 1.5 with statistical significance or 0.5 ≤ odds ratio ≤ 0.67 without statistical significance) inverse association between total soy intake and the risk of breast cancer. In the former, this association was observed in all women combined-premenopausal and postmenopausal women-but in the latter, the association was confined to postmenopausal women. The associations of intakes of individual soy foods with the risk of breast cancer were generally null. There is some evidence that supports the biological plausibility of a protective effect of isoflavones on breast cancer risk.

CONCLUSIONS

We conclude that soy intake possibly decreases the risk of breast cancer among Japanese women.

Effects of short-term fructooligosaccharide intake on equol production in Japanese postmenopausal women consuming soy isoflavone supplements: a pilot study

BACKGROUND

Recent studies suggest that some of the clinical effectiveness of soy or daidzein, which is a type of isoflavone, may be attributed to a person's ability to produce equol from daidzein. Equol, which is a metabolite of one of the major soybean isoflavones called daidzein, is produced in the gastrointestinal tract by certain intestinal microbiota where present. Habitual dietary patterns may alter the intestinal bacterial profile, and influence the metabolism of isoflavones and the production of equol. Fructooligosaccharides (FOS) have a prebiotic activity as well as being a dietary fibre. The purpose of the present study was to determine whether FOS supplementation increases equol production in equol producers and stimulates equol production in equol non-producers in Japanese postmenopausal women.

METHODS

A soy challenge was used to assess equol-producer status prior to the start of the study in healthy postmenopausal Japanese women. The study involved 4 separate groups in randomised crossover design. First, subjects were classified as equol producers (n = 25) or non-producers (n = 18), and then they were randomly assigned to the FOS or control group. All subjects received a daily dose of 37 mg isoflavone conjugates in the capsule (21 mg aglycone form) and either FOS (5 g/day) or sucrose as control, in a randomised crossover study design. Equol -production was assessed by testing the serum and urine before and after the 2-week supplementation period.

RESULTS

The analyses were conducted on 34 subjects completed the study, 21 (61.8%) were classified as equol producers, and 13 (38.2%) as non-producers. Significant differences were observed in the interaction effect of time × equol state after 1 week of intervention (p = 0.006). However there were no effects after 2 weeks of intervention (p = 0.516). Finally, in both equol producers and non-producers, FOS supplementation did not affect the serum equol concentration or the urinary equol to daidzein concentration ratios.

CONCLUSIONS

We have reported that FOS intervention (5 g/day for 2 weeks) does not significantly modulate the capacity of intestinal microbiota to produce equol in postmenopausal Japanese women, in either equol producers or non-producers in this pilot study. Further larger investigations that explore the roles of specific intestinal microbiota in equol production will enable the establishment of dietary conditions that are required to enhance equol production.

Tools to evaluate estrogenic potency of dietary phytoestrogens:A consensus paper from the EU Thematic Network "Phytohealth" (QLKI-2002-2453)

Phytoestrogens are naturally occurring plantderived polyphenols with estrogenic potency. They are ubiquitous in diet and therefore, generally consumed. Among Europeans, the diet is rich in multiple putative phytoestrogens including flavonoids, tannins, stilbenoids, and lignans. These compounds have been suggested to provide beneficial effects on multiple menopause-related conditions as well as on development of hormone-dependent cancers, which has increased the interest in products and foods with high phytoestrogen content. However, phytoestrogens may as well have adverse estrogenicity related effects similar to any estrogen. Therefore, the assessment of estrogenic potency of dietary compounds is of critical importance. Due to the complex nature of estrogenicity, no single comprehensive test approach is available. Instead, several in vitro and in vivo assays are applied to evaluate estrogenic potency. In vitro estrogen receptor (ER) binding assays provide information on the ability of the compound to I) interact with ERs, II) bind to estrogen responsive element on promoter of the target gene as ligand-ER complex, and III) interact between the co-activator and ERs in ligand-dependent manner. In addition, transactivation assays in cells screen for ligand-induced ERmediated gene activation. Biochemical in vitro analysis can be used to test for possible effects on protein activities and E-screen assays to measure (anti)proliferative response in estrogen responsive cells. However, for assessment of estrogenicity in organs and tissues, in vivo approaches are essential. In females, the uterotrophic assay is applicable for testing ERa agonistic and antagonistic dietary compounds in immature or adult ovariectomized animals. In addition, mammary gland targeted estrogenicity can be detected as stimulated ductal elongation and altered formation of terminal end buds in immature or peripubertal animals. In males, Hershberger assay in peri-pubertal castrated rats can be used to detect (anti)androgenic/ (anti)estrogenic responses in accessory sex glands and other hormone regulated tissues. In addition to these short-term assays, sub-acute and chronic reproductive toxicity assays as well as two-generation studies can be applied for phytoestrogens to confirm their safety in long-term use. For reliable assessment of estrogenicity of dietary phytoestrogens in vivo, special emphasis should be focused on selection of the basal diet, route and doses of administration, and possible metabolic differences between the species used and humans. In conclusion, further development and standardization of the estrogenicity test methods are needed for better interpretation of both the potential benefits and risks of increasing consumption of phytoestrogens from diets and supplements.

Mammographic breast density and serum phytoestrogen levels

Some forms of estrogen are associated with breast cancer risk as well as with mammographic density (MD), a strong marker of breast cancer risk. Whether phytoestrogen intake affects breast density, however, remains unclear. We evaluated the association between serum levels of phytoestrogens and MD in postmenopausal women. We enrolled 269 women, ages 55-70 yr, who received a screening mammogram and had no history of postmenopausal hormone use. Subjects completed a survey on diet and factors related to MD and provided a blood sample for analysis of 3 phytoestrogens: genistein, daidzein, and coumestrol. We examined whether mean percent MD was related to serum level of phytoestrogens, adjusting for age and body mass index. Genistein and daidzein levels correlated with self-reported soy consumption. Mean percent MD did not differ across women with different phytoestrogen levels. For example, women with nondetectable genistein levels had mean density of 11.0% [95% confidence intervals (CI) = 9.9-12.4], compared to 10.5% (95% CI = 8.0-13.7) and 11.2% (95% CI = 8.7-14.6) for < and ≥ median detectable levels, respectively. In a population with relatively low soy intake, serum phytoestrogens were not associated with mammographic density. Additional studies are needed to determine effects of higher levels, particularly given patterns of increasing phytoestrogen intake.

Dietary lignan and proanthocyanidin consumption and colorectal adenoma recurrence in the Polyp Prevention Trial

Lignans and proanthocyanidins are plant polyphenols that have shown protective properties against colorectal neoplasms in some human studies. Using logistic regression, we estimated odds ratios (ORs) and 95% confidence intervals (CIs) to prospectively evaluate the association between lignan and proanthocyanidin intake, estimated from databases linked to a food frequency questionnaire, and adenoma recurrence in 1,859 participants of the Polyp Prevention Trial. Overall, individual or total lignans or proanthocyanidins were not associated with colorectal adenoma recurrence. However, in sex-specific analyses, total lignan intake was positively associated with any adenoma recurrence in women (highest vs. lowest lignan intake quartile OR = 2.07, 95% CI: 1.22-3.52, p trend = 0.004) but not in men (p interaction = 0.04). To conclude, dietary lignan and proanthocyanidin consumption were not generally related to colorectal adenoma recurrence; however, high lignan intake may increase the risk of adenoma recurrence in women.

Beyond overweight: nutrition as an important lifestyle factor influencing timing of puberty

Early onset of puberty may confer adverse health consequences. Thus, modifiable factors influencing the timing of puberty are of public health interest. Childhood overweight as a factor in the earlier onset of menarche has been supported by prospective evidence; nonetheless, its overall contribution may have been overemphasized, since secular trends toward a younger age at menarche have not been a universal finding during the recent obesity epidemic. Current observational studies suggest notable associations between dietary intakes and pubertal timing beyond contributions to an energy imbalance: children with the highest intakes of vegetable protein or animal protein experience pubertal onset up to 7 months later or 7 months earlier, respectively. Furthermore, girls with high isoflavone intakes may experience the onset of breast development and peak height velocity approximately 7-8 months later. These effect sizes are on the order of those observed for potentially neuroactive steroid hormones. Thus, dietary patterns characterized by higher intakes of vegetable protein and isoflavones and lower intakes of animal protein may contribute to a lower risk of breast cancer or a lower total mortality.

Legume, soy, tofu, and isoflavone intake and endometrial cancer risk in postmenopausal women in the multiethnic cohort study

BACKGROUND

Phytochemicals found in soy and other legumes have been speculated to reduce the risk of endometrial cancer; however, inconsistent findings have been reported in the few epidemiological studies conducted to date.

METHODS

We conducted a prospective analysis of 46 027 nonhysterectomized postmenopausal women who were recruited into the Multiethnic Cohort (MEC) Study between August 1993 and August 1996 and provided detailed baseline information on diet and other endometrial cancer risk factors. A total of 489 women diagnosed with incident endometrial cancer were identified through the Surveillance, Epidemiology, and End Results tumor registry linkages during a median follow-up period of 13.6 years. Cox proportional hazards models were used to estimate multivariable-adjusted relative risks (RRs) and 95% confidence intervals (CIs) for endometrial cancer associated with dietary intake of legumes, soy, and tofu, and for total isoflavones and specific isoflavones (daidzein, genistein, or glycitein). Truncated (age 50-89 years) age-adjusted incidence rates were calculated by applying age-specific rates within isoflavone quintiles to the overall MEC population eligible for endometrial cancer. To estimate the percentage of endometrial cancers that may have been prevented by consuming the highest quintile of total isoflavones, the partial population attributable risk percent was calculated.

RESULTS

A reduced risk of endometrial cancer was associated with total isoflavone intake (highest vs lowest quintile, ≥7.82 vs <1.59 mg per 1000 kcal/d, RR = 0.66, 95% CI = 0.47 to 0.91), daidzein intake (highest vs lowest quintile, ≥3.54 vs <0.70 mg per 1000 kcal/d, RR = 0.64, 95% CI = 0.46 to 0.90), and genistein intake (highest vs lowest quintile, ≥3.40 vs <0.69 mg per 1000 kcal/d, RR = 0.66, 95% CI = 0.47 to 0.91). No statistically significant association with endometrial cancer risk was observed for increasing intake of legumes, soy, tofu, or glycitein. Truncated age-adjusted incidence rates of endometrial cancer for the highest vs lowest quintile of total isoflavone intake were 55 vs 107 per 100 000 women per year, respectively. The partial population attributable risk percent for total isoflavone intake lower than the highest quintile was 26.7% (95% CI = 5.3% to 45.8%).

CONCLUSION

This study suggests that greater consumption of isoflavone-containing foods is associated with a reduced risk of endometrial cancer in this population of nonhysterectomized postmenopausal women.

Dietary intakes of total and specific lignans are associated with clinical breast tumor characteristics

Dietary lignans may affect breast cancer by modifying tumor characteristics likely to affect prognosis. We investigated usual dietary intakes of total and specific lignans with tumor characteristics in 683 women with breast cancer and 611 healthy women without breast cancer enrolled in the Data Bank and BioRepository at Roswell Park Cancer Institute (RPCI). Clinicopathologic data were abstracted from the RPCI breast cancer database. Dietary lignan intakes were calculated from FFQ. OR and 95% CI were estimated with logistic regression adjusting for potential confounders and stratified by menopausal status. Women in the highest compared to the lowest tertile of total lignan intakes had a 40-50% lower odds of breast cancer regardless of menopausal status and substantially reduced odds of an invasive tumor, especially among premenopausal women [OR 0.48 (95% CI 0.26-0.86)]. Lignan intakes were inversely associated with odds of grade 3 tumors among premenopausal women. Lignan intakes were inversely associated with risk of estrogen receptor (ER) negative (ER(-)) breast cancer among premenopausal women [OR 0.16 (95% CI 0.03-0.44)] and particularly triple negative tumors [ER(-), progesterone receptor negative, HER2 negative; OR 0.16 (95% CI 0.04-0.62)]. There were significant differences in the contribution to these effects by specific lignans, especially matairesinol and lariciresinol. In summary, in this case-control study of dietary lignan intakes and breast cancer, we found that higher lignan intakes were associated with lower risks of breast cancer with more favorable prognostic characteristics. Future investigations are warranted to explore the strong associations observed with ER(-) cancer in premenopausal women.

Endocrine disrupting activity in fruits and vegetables evaluated with the E-screen assay in relation to pesticide residues

Food is likely to be one of the most important routes of human exposure to endocrine disrupting compounds (EDCs). In the present study, we evaluated the total estrogenic activity of fruits and vegetables, which was calculated using the human breast cancer cell line (MCF-7 BUS) proliferation assay (E-screen), in relation to pesticide residues. We analysed 44 food samples, 30 fruits and 14 vegetables. Of these samples, 10 did not contain any pesticide residues. The other 34 samples contained from 1 to 7 pesticide residues in concentrations ranging from 0.03 to 1.91 ppm. Estrogenic activity was detected in the 59% of samples tested. The positive controls used were 17-β-estradiol (E2), the phytoestrogen genistein and the pesticide endosulfan. The average value of estradiol equivalency quantity (EEQ) for all positive samples was 0.15±0.32 μg/100g. A low correlation was found between the concentration of pesticide residues and the EEQ values (Spearman correlation r=0.376 and p=0.012). Using values obtained from the literature, we compared the estrogenic activity of food samples with the intrinsic content of phytoestrogens, but we found no correlations. Our results also suggested that the calculated intake of dietary EDCs might represent a concentration comparable to the normal endogenous estrogen concentration in human blood.

Risks and benefits of dietary isoflavones for cancer

A high intake of fruits and vegetables is associated with a lower risk of cancer. In this context, considerable attention is paid to Asian populations who consume high amounts of soy and soy-derived isoflavones, and have a lower risk for several cancer types such as breast and prostate cancers than populations in Western countries. Hence, interest focuses on soyfoods, soy products, and soy ingredients such as isoflavones with regard to their possible beneficial effects that were observed in numerous experiments and studies. The outcomes of the studies are not always conclusive, are often contradictory depending on the experimental conditions, and are, therefore, difficult to interpret. Isoflavone research revealed not only beneficial but also adverse effects, for instance, on the reproductive system. This is also the case with tumor-promoting effects on, for example, breast tissue. Isoflavone extracts and supplements are often used for the treatment of menopausal symptoms and for the prevention of age-associated conditions such as cardiovascular diseases and osteoporosis in postmenopausal women. In relation to this, questions about the effectiveness and safety of isoflavones have to be clarified. Moreover, there are concerns about the maternal consumption of isoflavones due to the development of leukemia in infants. In contrast, men may benefit from the intake of isoflavones with regard to reducing the risk of prostate cancer. Therefore, this review examines the risks but also the benefits of isoflavones with regard to various kinds of cancer, which can be derived from animal and human studies as well as from in vitro experiments.

Coffee consumption modifies risk of estrogen-receptor negative breast cancer

Introduction

Breast cancer is a complex disease and may be sub-divided into hormone-responsive (estrogen receptor (ER) positive) and non-hormone-responsive subtypes (ER-negative). Some evidence suggests that heterogeneity exists in the associations between coffee consumption and breast cancer risk, according to different estrogen receptor subtypes. We assessed the association between coffee consumption and postmenopausal breast cancer risk in a large population-based study (2,818 cases and 3,111 controls), overall, and stratified by ER tumour subtypes.

Methods

Odds ratios (OR) and corresponding 95% confidence intervals (CI) were estimated using the multivariate logistic regression models fitted to examine breast cancer risk in a stratified case-control analysis. Heterogeneity among ER subtypes was evaluated in a case-only analysis, by fitting binary logistic regression models, treating ER status as a dependent variable, with coffee consumption included as a covariate.

Results

In the Swedish study, coffee consumption was associated with a modest decrease in overall breast cancer risk in the age-adjusted model (OR_{> 5 cups/day} compared to OR_{≤ 1 cup/day}: 0.80, 95% CI: 0.64, 0.99, P trend = 0.028). In the stratified case-control analyses, a significant reduction in the risk of ER-negative breast cancer was observed in heavy coffee drinkers (OR_{> 5 cups/day} compared to OR_{≤ 1 cup/day} : 0.43, 95% CI: 0.25, 0.72, P trend = 0.0003) in a multivariate-adjusted model. The breast cancer risk reduction associated with higher coffee consumption was significantly higher for ER-negative compared to ER-positive tumours (P heterogeneity (age-adjusted) = 0.004).

Conclusions

A high daily intake of coffee was found to be associated with a statistically significant decrease in ER-negative breast cancer among postmenopausal women.

Breast cancer: a neglected disease for the majority of affected women worldwide

Recent progress with declines in mortality in some high-income countries has obscured the fact that for the majority of women worldwide who are newly diagnosed, breast cancer is a neglected disease in the context of other numerically more frequent health problems. For this growing majority, it is also an orphan disease, in that detailed knowledge about tumor characteristics and relevant host biology necessary to provide even basic care is absent. With the possible exception of nutritional recommendations, current international cancer policy and planning initiatives are irrelevant to breast cancer. The progress that has occurred in high-income countries has come at extraordinary fiscal expense and patient toxicity, which of themselves suggest nonrelevance to women and healthcare practitioners in middle- and low-income countries. The implications of these circumstances appear clear: if the promise of the now 60-year-old Declaration of Human Rights that the fruits of medical science accrue to all mankind is to be realized with respect to breast cancer, a basic and translational global research initiative should be launched.

Fermented and non-fermented soy food consumption and gastric cancer in Japanese and Korean populations: a meta-analysis of observational studies

Soy food is known to contribute greatly to a reduction in the risk of gastric cancer (GC). However, both Japanese and Korean populations have high incidence rates of GC despite the consumption of a wide variety of soy foods. One primary reason is that they consume fermented rather than non-fermented soy foods. In order to assess the varying effects of fermented and non-fermented soy intake on GC risk in these populations, we conducted a meta-analysis of published reports. Twenty studies assessing the effect of the consumption of fermented soy food on GC risk were included, and 17 studies assessing the effect of the consumption of non-fermented soy food on GC risk were included. We found that a high intake of fermented soy foods was significantly associated with an increased risk of GC (odds ratio [OR] = 1.22, 95% confidence interval [CI] = 1.02-1.44, I(2) = 71.48), whereas an increased intake of non-fermented soy foods was significantly associated with a decreased risk of GC (overall summary OR = 0.64, 95% CI = 0.54-0.77, I(2) = 64.27). These findings show that a high level of consumption of non-fermented soy foods, rather than fermented soy foods, is important in reducing GC risk.

Relation of isoflavones and fiber intake in childhood to the timing of puberty

BACKGROUND

It has been suggested that phytoestrogens and dietary fiber can affect puberty timing.

OBJECTIVE

We examined whether intake of isoflavone and fiber in healthy white children before their pubertal growth spurt [age at take-off (ATO)] was associated with puberty timing.

DESIGN

Multivariate regression analyses were performed in 227 DONALD (DOrtmund Nutritional and Anthropometric Longitudinally Designed) Study participants with 3-d weighed dietary records and information on potential confounders at baseline (1 and 2 y before ATO). In a subsample (n = 111), urinary isoflavones were determined in 24-h urine samples by gas chromatography-mass spectrometry analysis. Puberty timing was examined by using ATO and chronologic ages at pubertal stage 2 for breast development (B2) or gonadal development, peak height velocity (PHV), and menarche or voice break.

RESULTS

Girls whose diet was in the highest dietary isoflavone tertile experienced Tanner stage 2 for breast development ap 0.7 y later and reached PHV ap 0.6 y later than did girls whose diet was in the lowest isoflavone tertile [age (95% CI) at B2: 10.7 y (10.4, 10.9 y) compared with 10.0 y ( 9.7, 10.3 y), respectively; P for trend = 0.04; age at PHV: 11.9 y (11.6, 12.2 y) compared with 11.3 y (11.0, 11.6 y), respectively; P for trend = 0.04; adjusted for body mass index z score and fiber intake]. In boys, dietary isoflavones were not associated with pubertal markers. Urinary isoflavone and dietary fiber intakes were not associated with pubertal markers.

CONCLUSIONS

Girls, but not boys, with higher prepubertal isoflavone intakes appear to enter puberty at a later age. Fiber intake in this sample of healthy white girls and boys was not relevant for puberty timing.

Tea and coffee intake in relation to risk of breast cancer in the Black Women's Health Study

OBJECTIVE

Prospective studies of tea and coffee intake and breast cancer risk have yielded inconsistent results. None of these studies has reported separately on African-American women. We prospectively examined the relation of tea and coffee consumption to risk of breast cancer among 52,062 women aged 21-69 at enrollment in 1995 in the Black Women's Health Study.

METHODS

Dietary intake was assessed in 1995 and 2001 using a validated food frequency questionnaire. Cox proportional hazards models were used to estimate incidence rate ratios (IRR) and 95% confidence intervals (CI), adjusted for breast cancer risk factors.

RESULTS

During 12 years of follow-up through 2007, there were 1,268 incident cases of breast cancer. Intakes of tea, coffee, and caffeine were not significantly associated with the risk of breast cancer overall. The IRRs for consumption of ≥4 cups/day compared with none were 1.13 (95% CI 0.78-1.63) for tea and 1.03 (95% CI 0.77-1.39) for caffeinated coffee, and the IRR for the top quintile relative to the bottom quintile of caffeine intake was 1.04 (95% CI 0.87-1.24). Consumption of tea, coffee, and caffeine was not significantly associated with breast cancer risk according to menopausal status or hormone receptor status.

CONCLUSION

Our findings suggest that intakes of tea, coffee, and caffeine are not associated with the risk of breast cancer among African-American women.

Guidance from an NIH workshop on designing, implementing, and reporting clinical studies of soy interventions

The NIH sponsored a scientific workshop, "Soy Protein/Isoflavone Research: Challenges in Designing and Evaluating Intervention Studies," July 28-29, 2009. The workshop goal was to provide guidance for the next generation of soy protein/isoflavone human research. Session topics included population exposure to soy; the variability of the human response to soy; product composition; methods, tools, and resources available to estimate exposure and protocol adherence; and analytical methods to assess soy in foods and supplements and analytes in biologic fluids and other tissues. The intent of the workshop was to address the quality of soy studies, not the efficacy or safety of soy. Prior NIH workshops and an evidence-based review questioned the quality of data from human soy studies. If clinical studies are pursued, investigators need to ensure that the experimental designs are optimal and the studies properly executed. The workshop participants identified methodological issues that may confound study results and interpretation. Scientifically sound and useful options for dealing with these issues were discussed. The resulting guidance is presented in this document with a brief rationale. The guidance is specific to soy clinical research and does not address nonsoy-related factors that should also be considered in designing and reporting clinical studies. This guidance may be used by investigators, journal editors, study sponsors, and protocol reviewers for a variety of purposes, including designing and implementing trials, reporting results, and interpreting published epidemiological and clinical studies.

Factors to consider in the association between soy isoflavone intake and breast cancer risk

It has been suggested that soy isoflavones have protective effects against breast cancer. However, data from epidemiological studies are not conclusive. A recent meta-analysis showed that soy intake was inversely associated with breast cancer risk in Asian but not Western populations, which indicates that protection against breast cancer may require that women consume levels of soy typical in Asian diets. In addition to the amount of soy isoflavones consumed, the form and food source of isoflavones, timing of isoflavone exposure, estrogen receptor status of tumors, and equol-producer status and hormonal profile of individuals may modify the association between soy isoflavone intake and the risk of breast cancer. These factors might explain the heterogeneity of results from studies. This present report contrasts background data from Japanese and Western women to identify the potential modifying of these factors.

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.

Dietary intake and urinary excretion of lignans in Finnish men

Intake of lignans has been assessed in different study populations, but so far none of the studies has compared the daily intake of lignans and the urinary excretion of plant and enterolignans. We assessed the intake of lariciresinol, pinoresinol, secoisolariciresinol and matairesinol in 100 Finnish men consuming their habitual omnivorous diet, and measured the 24 h urinary excretion of plant and enterolignans to compare the intake and metabolism. Dietary determinants of lignan intake and their urinary excretion were also determined. The mean intake of lignans was 1224 (sd 539) mug/d, of which lariciresinol and pinoresinol covered 78 %. Almost half (47 %) of the intake of lignans was explained by the intake of rye products, berries, coffee, tea and roots. The urinary excretion of plant lignans corresponded to 17 % and enterolignans to 92 % of the intake of lignans. The urinary excretion of plant lignans was explained 14 % by the intake of rye products and intake of coffee, and consequently 3-7 % by the intake of water-insoluble fibre. The urinary excretion of enterolactone was explained 11 % by the intake of vegetables and rye products, 14 % by the intake of water-soluble fibre and only 4 % by the intake of lariciresinol. Although the assessed intake of lignans corresponded well with the urinary excretion of lignans, the enterolactone production in the human body depended more on the dietary sources of lignans than the absolute intake of lignans.

Soy consumption and prostate cancer risk in men: a revisit of a meta-analysis

BACKGROUND

Epidemiologic studies have shown that the consumption of soy foods may be associated with a reduction in cancer risk in humans.

OBJECTIVE

The purpose of this study was to conduct a meta-analysis on the association between soy consumption and prostate cancer risk in men.

DESIGN

We systematically reviewed studies obtained through a thorough Medline literature search and identified 15 epidemiologic publications on soy consumption and 9 on isoflavones in association with prostate cancer risk. We extracted the most adjusted relative risks (RRs) and odds ratios (ORs) of the highest and the lowest reported categories of intake from each study and conducted this analysis using a random-effects model in which studies with smaller SEEs are given greater weight in the summary measure.

RESULTS

Our analysis of studies on soy intake yielded a combined RR/OR of 0.74 (95% CI: 0.63, 0.89; P = 0.01). When separately analyzed, studies on nonfermented soy foods yielded a combined RR/OR of 0.70 (95% CI: 0.56, 0.88; P = 0.01) and those on fermented soy foods yielded a combined RR/OR of 1.02 (95% CI: 0.73, 1.42; P = 0.92). The analysis of studies on isoflavones yielded a combined RR/OR of 0.88 (95% CI: 0.76, 1.02; P = 0.09). Further separate analyses showed a combined RR/OR of 0.52 (95% CI: 0.34, 0.81; P = 0.01) from studies with Asian populations and 0.99 (95% CI: 0.85, 1.16; P = 0.91) from studies with Western populations.

CONCLUSIONS

The results of this analysis suggest that consumption of soy foods is associated with a reduction in prostate cancer risk in men. This protection may be associated with the type and quantity of soy foods consumed.

Isoflavones - Mechanism of Action and Impact on Breast Cancer Risk

Isoflavones are plant-derived substances with weak es-trogenic effects. Asian populations are high consumers of soy products which are rich in isoflavones. The lower breast cancer incidence in Asian women compared with Western women has been associated with the possibility of a preventive isoflavone effect on cancer risk. The aim of this review is to give an overview of current research data on the influence of isoflavones on the risk of primary breast cancer development as well as the risk of recurrence in breast cancer patients. Despite inconsistencies in the available data, an inverse correlation between isoflavone intake and risk of breast cancer is likely. However, a negative impact on breast cancer disease, especially on hormone receptor-positive tumors, cannot be excluded at present.

Food frequency questionnaires and overnight urines are valid indicators of daidzein and genistein intake in U.S. women relative to multiple 24-h urine samples

Data regarding convenient, valid methods for measuring U.S. isoflavone intake are limited. We evaluated a soy food questionnaire (SFQ), the Willett food frequency questionnaire (FFQ), and overnight urine samples relative to excretion in 24-h urine samples. We also described intake among women in a high-risk program for breast or ovarian cancer. Between April 2002 and June 2003, 451 women aged 30 to 50 yr with a family history of breast or ovarian cancer completed the SFQ and FFQ. Of them, 27 provided four 24-h and overnight urine specimens. In these women, 24-h sample measures were correlated with SFQ estimates of daidzein (Spearman r = .48) and genistein (r = .54) intake, moderately correlated with the Willett FFQ (daidzein r = .38, genistein r = .33), and strongly correlated with overnight urine excretion (daidzein r = .84, genistein r = 0.93). Among all 451 SFQ respondents, mean (median) daidzein and genistein intakes were 2.8 (0.24) and 3.9 (0.30) mg/day. Primary sources of both were soymilk, soy nuts, and tofu. We conclude that targeted soy food questionnaires, comprehensive FFQs, and multiple overnight urines are all reasonable options for assessing isoflavone intake in epidemiologic studies.

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.

Examining breast cancer growth and lifestyle risk factors: early life, childhood, and adolescence

The perinatal period, childhood, and adolescence are important intervals for breast cancer risk development. Endogenous estrogen exposure is thought to be highest in utero, and exposure to estrogens throughout life plays an important role in increasing breast cancer risk. Some evidence suggests that breast tissue is not fully differentiated until after the first full-term pregnancy; thus, breast tissue might be more susceptible to carcinogenic influences during early life and adolescence. Birth characteristics of the daughter, including gestational age, birth weight, and birth length are associated with maternal hormone levels during the index pregnancy, and birth size has been related to daughter's timing of puberty and adult breast cancer incidence. Furthermore, early life and adolescence are critical times for maturation of the hypothalamic pituitary ovarian axis, which regulates production of ovarian hormones including estrogen and progesterone. Childhood height, growth, diet, and body mass index (BMI) have also been associated with breast cancer risk later in life. Of the examined characteristics, we conclude that the available evidence is suggestive of a positive relationship of breast cancer risk with birth weight, birth length, and adolescent height, and an inverse relationship with gestational age and childhood BMI, although several inconsistencies exist in the literature. The best evidence for a relationship of adolescent diet and adult breast cancer risk is indirect, and the relationship of diet, weight status, and weight gain in childhood deserves further attention. The interaction of birth characteristics with established risk factors over the life course, such as age at menarche, in addition to gene-environment interactions, require more research. Further study is also needed to clarify the biologic mechanisms influencing the observed associations.

Coffee consumption and the risk of cancer: an overview

Habitual coffee drinking has been associated with a reduced risk of mortality and chronic diseases, including cancer. The favourable influence of coffee is supported by several plausible mechanisms due to the presence of a variety of biological compounds such as caffeine, diterpenes, caffeic acid, polyphenols as well as volatile aroma and heterocyclic substances. Current evidence suggests that coffee consumption is associated with a reduced risk of liver, kidney, and to a lesser extent, premenopausal breast and colorectal cancers, while it is unrelated to prostate, pancreas and ovary cancers. Coffee drinking may still help reduce death due to liver cancer.

Soy food and isoflavone intake in relation to semen quality parameters among men from an infertility clinic

BACKGROUND

High isoflavone intake has been related to decreased fertility in animal studies, but data in humans are scarce. Thus, we examined the association of soy foods and isoflavones intake with semen quality parameters.

METHODS

The intake of 15 soy-based foods in the previous 3 months was assessed for 99 male partners of subfertile couples who presented for semen analyses to the Massachusetts General Hospital Fertility Center. Linear and quantile regression were used to determine the association of soy foods and isoflavones intake with semen quality parameters while adjusting for personal characteristics.

RESULTS

There was an inverse association between soy food intake and sperm concentration that remained significant after accounting for age, abstinence time, body mass index, caffeine and alcohol intake and smoking. In the multivariate-adjusted analyses, men in the highest category of soy food intake had 41 million sperm/ml less than men who did not consume soy foods (95% confidence interval = -74, -8; P, trend = 0.02). Results for individual soy isoflavones were similar to the results for soy foods and were strongest for glycitein, but did not reach statistical significance. The inverse relation between soy food intake and sperm concentration was more pronounced in the high end of the distribution (90th and 75th percentile) and among overweight or obese men. Soy food and soy isoflavone intake were unrelated to sperm motility, sperm morphology or ejaculate volume.

CONCLUSIONS

These data suggest that higher intake of soy foods and soy isoflavones is associated with lower sperm concentration.

Oral antibiotics decrease urinary isoflavonoid excretion in children after soy consumption

How oral antibiotics (OABX) alter isoflavones (IFLs) in soy-consuming children is unknown. We evaluated OABX effects on urinary IFL excretion rates (UIERs) in 17 children, ages 4 to 17 yr, who provided 2 urine collections in pairs of a baseline urine and an overnight urine collection after consuming a body-weight-adjusted dose of soy nuts. The first collection was during OABX treatment for a bacterial infection and the second when healthy and off antibiotics. IFL food levels and UIERs were measured for nonmetabolites (NM), namely, daidzein, genistein (GE), and glycitein, and the metabolites (M) dihydrodaidzein, dihydrogenistein, equol, and O-desmethylangolensin (DMA), by liquid chromatography mass spectrometry. Urinary IFLs were hypothesized to change after OABX due to intestinal microflora alterations. A total of 11 children completed the study correctly. During OABX use, UIER (nmol/h/kg) for GE (6.4 +/- 1.0 vs. 10.1 +/- 1.6), all NM (27.5 +/- 4.8 vs. 36.2 +/- 4.7), and total IFLs (all NM + all M; 29.4 +/- 5.0 vs. 38.8 +/- 4.8) was reduced (P < 0.05) vs. when healthy. In contrast, a trend toward more DMA production during OABX was observed (1.2 +/- 0.6 vs. 0.4 +/- 0.3, P = 0.13). The reduction in urinary IFL appearance could be due to the changes of intestinal bacteria by OABX and/or due to processes related to the infection.

Isoflavones in children and adults consuming soy

Soy and their isoflavones (IFLs) are believed to protect against breast cancer, particularly when exposure occurs during childhood. Little is known about the bioavailability of IFLs in children and how this is affected by oral antibiotics (OABX). We measured IFLs by LC/MS and found that the urinary IFL excretion rate (UIER) reflects circulating IFLs accurately when area-under-curve (AUC) and identical time intervals are used (r=0.93; p<0.001). UIER in children and adults was determined when healthy and when on OABX by collecting urine in pairs of baseline and overnight specimen before and after consuming soy nuts, respectively. Compared to when healthy, children on OABX showed significantly decreased UIER but adults on OABX showed increased UIER (p<0.05). All 37 healthy children showed significantly higher UIERs compared to all 34 healthy adults. UIER is an adequate surrogate for determining IFL bioavailability and for measuring soy or IFL exposure in epidemiologic and other studies.

Urinary isoflavones are increased in adults, but decreased in children, consuming soy when on oral antibiotic therapy

The goal of this study was to evaluate how oral antibiotics (OABX) change the appearance of isoflavones (IFLs) in adults and children after soy consumption. The urinary IFL excretion rate (UIER) known to reflect circulating IFLs was hypothesized to change due to intestinal microflora changes by OABX. Subjects provided urine collections in pairs of a baseline urine and an overnight urine before and after consuming soy nuts first during OABX treatment and then again when healthy. During OABX versus when healthy, UIER (nmol/h/kg) in adults (n = 12) was increased (P < 0.05) for daidzein (35.2 +/- 7.2 vs. 18.9 +/- 2.4), daidzein + genistein + glycitein [nonmetabolites (NM); 42.6 +/- 8.0 vs. 23.6 +/- 2.9), and total isoflavonoids (Total IFLs; daidzein + genistein + glycitein + dihydrodaidzein + dihydrogenistein + equol + O-desmethylangolensin) (51.5 +/- 10.3 versus 29.6 +/- 4.7). In contrast, children (n = 7) showed reduced UIER (P < 0.05) when on OABX versus when healthy for daidzein (36.3 +/- 6.4 vs. 46.8 +/- 4.7), dihydrodaidzein (1.2 +/- 0.6 vs. 3.0 +/-1.1), NM (46.3 +/- 8.2 vs. 59.5 +/- 6.0), dihydrodaidzein + dihydrogenistein + equol + O-desmethylangolensin (1.0 +/- 0.8 vs. 4.3 +/- 1.3), and Total IFLs (48.2 +/- 8.5 vs. 63.8 +/- 6.4).

Intake of dietary phytoestrogen and indices of antioxidant and bone metabolism of pre- and post-menopausal Korean women

A group of 101 women, aged 40-65 years consisted of 48 premenopausal subjects and 53 postmenopausal ones living in Daegu and Gyeongbuk area in Korea were evaluated with their general characteristics, lifestyle factors, nutrient and phytoestrogen intakes, blood and urinary indices concerning antioxidant status and bone metabolism. Body mass index (BMI), waist hip ratio (WHR) and systolic blood pressure (SBP) of the postmenopausal women were significantly higher (23.8, 0.86, and 126.9 mmHg, respectively) than those of the premenopausal women (22.6, 0.82, and 115.9 mmHg; respectively). Nutrient intakes of the postmenopausal and premenopausal groups were not different except lower fat intake and higher dietary fiber and iron intakes in the postmenopausal group. Daily total phytoestrogen intake was significantly higher in the postmenopausal group (48.54 mg) than the premenopausal (31.41 mg) and was resulted mostly from higher intakes of daidzein and genistein from soy and soy products (45.42 mg vs 28.91 mg). Serum genistein level and excretion of enterolactone, major lignan metabolite, were not very different between the two groups. Serum retinal and α- tocopherol levels were higher in the postmenopausal group but TBARS levels were not different between the two groups. Serum osteocalcin (7.18 ng/mL) and urinary deoxypyridinoline (7.15 nmol/mmol creatinine), in the postmenopausal group were significantly higher than those in the premenopausal group (4.80 ng/mL, 5.95 nmol/mmol creatinine). Urinary excretion of enterolactone was positively correlated with serum osetocalcin in premenopausal women and serum genistein negatively correlated with the urinary DPD in postmenopausal women. Dietary phytoestrogen intake was negatively correlated with serum level of TBARS in all subjects. It is concluded that the effect of total phytoestrogen intake is beneficial on body antioxidant status in all middle-aged women regardless of menopause but the effect on bone metabolism appears different by the type of the phytoestrogen and the menopausal state.

Phyto-oestrogens and risk of prostate cancer in Scottish men

A population-based case–control study of diet, inherited susceptibility and prostate cancer was undertaken in the lowlands and central belt of Scotland to investigate the effect of phyto-oestrogen intake and serum concentrations on prostate cancer risk. A total of 433 cases and 483 controls aged 50–74 years were asked to complete a validated FFQ and provide a non-fasting blood sample. Multivariate logistic regression analysis found significant inverse associations with increased serum concentrations of enterolactone (adjusted OR 0·40, 95 % CI 0·22, 0·71] and with the consumption of soy foods (adjusted OR 0·52, 95 % CI 0·30, 0·91). However, no significant associations were observed for isoflavone intake or serum genistein, daidzein and equol. This study supports the hypotheses that soy foods and enterolactone metabolised from dietary lignans protect against prostate cancer in older Scottish men.

Isoflavones from soya foods are more bioavailable in children than adults

The purpose of the present study was to determine whether children experience a higher systemic exposure to isoflavonoids when consuming a body weight-adjusted dose of soya compared with adults. Forty study participants were recruited from a local Waldorf school, including twenty-one children and nineteen adults. Participants collected a baseline urine sample and ate immediately thereafter a body weight-adjusted dose of soya nuts (15 g/54.4 kg equivalent to 0.615 (SD 0.036) mg total isoflavones/kg) followed by a 12 h urine collection. Nineteen children and eighteen adults completed the protocol correctly (fourteen child-parent pairs). Children, compared with adults, showed a statistically significant (P < 0.05 by unpaired t test) higher urinary isoflavone excretion rate for daidzein (+39%), genistein (+44%), all non-metabolites (daidzein + genistein + glycitein; +41%) and total isoflavonoids (+32%). Isoflavones are more bioavailable in children v. adults. Urine is an excellent medium to determine systemic isoflavone exposure in children due to its non-invasiveness and high compliance, in particular when collected overnight; it also allows evaluation of completeness of specimen collection.

Diet and risk of ovarian cancer in the California Teachers Study cohort

Dietary phytochemical compounds, including isoflavones and isothiocyanates, may inhibit cancer development but have not yet been examined in prospective epidemiologic studies of ovarian cancer. The authors have investigated the association between consumption of these and other nutrients and ovarian cancer risk in a prospective cohort study. Among 97,275 eligible women in the California Teachers Study cohort who completed the baseline dietary assessment in 1995-1996, 280 women developed invasive or borderline ovarian cancer by December 31, 2003. Multivariable Cox proportional hazards regression, with age as the timescale, was used to estimate relative risks and 95% confidence intervals; all statistical tests were two sided. Intake of isoflavones was associated with lower risk of ovarian cancer. Compared with the risk for women who consumed less than 1 mg of total isoflavones per day, the relative risk of ovarian cancer associated with consumption of more than 3 mg/day was 0.56 (95% confidence interval: 0.33, 0.96). Intake of isothiocyanates or foods high in isothiocyanates was not associated with ovarian cancer risk, nor was intake of macronutrients, antioxidant vitamins, or other micronutrients. Although dietary consumption of isoflavones may be associated with decreased ovarian cancer risk, most dietary factors are unlikely to play a major role in ovarian cancer development.