Assessing the accuracy of a food frequency questionnaire for estimating usual intake of phytoestrogens

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.

Development of an Assay for Soy Isoflavones in Women's Hair

Soy isoflavones, at adequate dosages, have estrogenic and anti-thyroidal effects in animals and humans, which can either be beneficial or adverse, depending on the consumer’s physiological status. Hence, this study presents an assay of soy isoflavones in hair, aiming to give new information about a person’s exposure to isoflavones, when health issues related to estrogenic or thyroidal effects are observed. Aqueous or organic extraction procedures following acidic, basic, or enzymatic digestions were tested on 60 hair samples (from volunteers) from a hairdresser, and a clinical trial 2017T2-29. The acidic digestion method was the most efficient regarding isoflavones. A specific inquiry was developed to assess the dietary habits of French consumers based on the analysis of 12,707 food labels from France. It was used to check for the reliability of the new assay method. A score for the consumer exposures to isoflavones was built considering, among other parameters, soy-based diets and foodstuff containing soy as an ingredient, i.e., “hidden-soy”. The correlation between this score and isoflavone measurements in hair reached 0.947; p < 0.001. Therefore, providing that relevant data are considered to assess isoflavone exposure, hair that smoothens daily isoflavone intake variations, is a relevant tissue to assess human isoflavone exposure for subsequent health analyses.

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.

Higher intake of dietary n-3 PUFA and lower MUFA are associated with fewer menopausal symptoms

OBJECTIVE

This study aimed to investigate the association between dietary fat quality and menopausal symptoms.

METHODS

We carried out a cross-sectional study with 393 Iranian postmenopausal women. Dietary intakes and menopausal symptoms were assessed, using a validated food frequency questionnaire and a menopausal rating scale (MRS) questionnaire, respectively. Participants were divided into low and high total MRS and its domain scores.

RESULTS

Women in the highest quartiles of monounsaturated fatty acids (MUFA) had higher somatic symptoms compared with women in the lowest quartile (odds ratio [OR] 3.41; 95% confidence interval [CI] 1.17-9.95). Women in the highest quartiles of n-3 polyunsaturated fatty acids (PUFA) (OR 0.58; 95% CI 0.32-1.05), eicosapentaenoic acid (EPA) (OR 0.66; 95% CI 0.37-1.20), and n-3:n-6 PUFA ratio (OR 0.49; 95% CI 0.25-0.97) had lower somatic symptoms compared to the lowest quartiles. The OR for psychological symptoms decreased from the lowest to the highest quartiles of n-3 PUFA (OR 0.47; 95% CI 0.20-1.11) and n-3:n-6 PUFA ratio (OR 0.46; 95% CI 0.24-0.86). Higher intakes of EPA (OR 0.53; 95% CI 0.29-0.99) and docosahexaenoic acid (OR 0.51; 95% CI 0.27-0.95) were found to be related with fewer urogenital symptoms.

CONCLUSION

Consuming diets low in MUFA intake, but high in n-3 PUFA, and with a more favorable ratio of n-3:n-6 PUFA may be helpful for improving menopausal symptoms.

A Multicomponent Behavioral Intervention to Reduce Stroke Risk Factor Behaviors: The Stroke Health and Risk Education Cluster-Randomized Controlled Trial

BACKGROUND AND PURPOSE

The Stroke Health and Risk Education Project was a cluster-randomized, faith-based, culturally sensitive, theory-based multicomponent behavioral intervention trial to reduce key stroke risk factor behaviors in Hispanics/Latinos and European Americans.

METHODS

Ten Catholic churches were randomized to intervention or control group. The intervention group received a 1-year multicomponent intervention (with poor adherence) that included self-help materials, tailored newsletters, and motivational interviewing counseling calls. Multilevel modeling, accounting for clustering within subject pairs and parishes, was used to test treatment differences in the average change since baseline (ascertained at 6 and 12 months) in dietary sodium, fruit and vegetable intake, and physical activity, measured using standardized questionnaires. A priori, the trial was considered successful if any one of the 3 outcomes was significant at the 0.05/3 level.

RESULTS

Of 801 subjects who consented, 760 completed baseline data assessments, and of these, 86% completed at least one outcome assessment. The median age was 53 years; 84% subjects were Hispanic/Latino; and 64% subjects were women. The intervention group had a greater increase in fruit and vegetable intake than the control group (0.25 cups per day [95% confidence interval: 0.08, 0.42], P=0.002), a greater decrease in sodium intake (-123.17 mg/d [-194.76, -51.59], P=0.04), but no difference in change in moderate- or greater-intensity physical activity (-27 metabolic equivalent-minutes per week [-526, 471], P=0.56).

CONCLUSIONS

This multicomponent behavioral intervention targeting stroke risk factors in predominantly Hispanics/Latinos was effective in increasing fruit and vegetable intake, reaching its primary end point. The intervention also seemed to lower sodium intake. Church-based health promotions can be successful in primary stroke prevention efforts.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01378780.

Improving the estimation of flavonoid intake for study of health outcomes

Imprecision in estimating intakes of non-nutrient bioactive compounds such as flavonoids is a challenge in epidemiologic studies of health outcomes. The sources of this imprecision, using flavonoids as an example, include the variability of bioactive compounds in foods due to differences in growing conditions and processing, the challenges in laboratory quantification of flavonoids in foods, the incompleteness of flavonoid food composition tables, and the lack of adequate dietary assessment instruments. Steps to improve databases of bioactive compounds and to increase the accuracy and precision of the estimation of bioactive compound intakes in studies of health benefits and outcomes are suggested.

Measuring exposure to the polyphenol metabolome in observational epidemiologic studies: current tools and applications and their limits

Much experimental evidence supports a protective role of dietary polyphenols against chronic diseases such as cardiovascular diseases, diabetes, and cancer. However, results from observational epidemiologic studies are still limited and are often inconsistent. This is largely explained by the difficulties encountered in the estimation of exposure to the polyphenol metabolome, which is composed of ~500 polyphenols distributed across a wide variety of foods and characterized by diverse biological properties. Exposure to the polyphenol metabolome in epidemiologic studies can be assessed by the use of detailed dietary questionnaires or the measurement of biomarkers of polyphenol intake. The questionnaire approach has been greatly facilitated by the use of new databases on polyphenol composition but is limited by bias as a result of self-reporting. The use of polyphenol biomarkers holds much promise for objective estimation of polyphenol exposure in future metabolome-wide association studies. These approaches are reviewed and their advantages and limitations discussed by using examples of epidemiologic studies on polyphenols and cancer. The current improvement in these techniques, along with greater emphasis on the intake of individual polyphenols rather than polyphenols considered collectively, will help unravel the role of these major food bioactive constituents in disease prevention.

Relationship between dietary phytoestrogens and development of urinary incontinence in midlife women

OBJECTIVE

Because exogenous estrogen treatment has been associated with a higher risk of urinary incontinence, our objective was to evaluate the longitudinal relationships of dietary phytoestrogen intakes (isoflavones, coumestans, and lignans) and the development of incontinence in midlife women transitioning through menopause.

METHODS

The Study of Women's Health Across the Nation (SWAN) Phytoestrogen Study was developed within SWAN, a community-based, multisite, multiracial/ethnic, prospective cohort study. SWAN interviewers administered a food consumption assessment at baseline and on follow-up visits 5 and 9. The SWAN Phytoestrogen Study created a phytonutrient database that allowed estimation of the usual daily intakes of four isoflavones, four lignans, and coumestrol. On an annual self-administered questionnaire, participants reported on the frequency and type of incontinence. We used discrete proportional hazards models to evaluate whether the estimated daily intake of each phytoestrogen class on the visit previous to the first report of incontinence was associated with the development of monthly or more incontinence versus remaining continent.

RESULTS

We found no association or patterns of association between developing any, stress, or urge incontinence and the reported daily dietary intake of isoflavones, coumestrol, and lignans on the visit previous to the onset of incontinence.

CONCLUSIONS

The results of this longitudinal study provide important information to better understand estrogenlike substances in the continence mechanism of midlife women. Our study shows that neither high nor low dietary intakes of isoflavones, coumestrol, and lignans prevent stress or urge incontinence. Future studies should evaluate whether serum levels of phytoestrogens or their metabolites impact incontinence symptoms.

Association of dietary soy genistein intake with lung function and asthma control: a post-hoc analysis of patients enrolled in a prospective multicentre clinical trial

BACKGROUND

Broad dietary patterns have been linked to asthma but the relative contribution of specific nutrients is unclear. Soy genistein has important anti-inflammatory and other biological effects that might be beneficial in asthma. A positive association was previously reported between soy genistein intake and lung function but not with asthma exacerbations.

AIMS

To conduct a post-hoc analysis of patients with inadequately controlled asthma enrolled in a prospective multicentre clinical trial to replicate this association.

METHODS

A total of 300 study participants were included in the analysis. Dietary soy genistein intake was measured using the Block Soy Foods Screener. The level of soy genistein intake (little or no intake, moderate intake, or high intake) was compared with baseline lung function (pre-bronchodilator forced expiratory volume in 1 second (FEV(1))) and asthma control (proportion of participants with an episode of poor asthma control (EPAC) and annualised rates of EPACs over a 6-month follow-up period.

RESULTS

Participants with little or no genistein intake had a lower baseline FEV(1) than those with a moderate or high intake (2.26 L vs. 2.53 L and 2.47 L, respectively; p=0.01). EPACs were more common among those with no genistein intake than in those with a moderate or high intake (54% vs. 35% vs. 40%, respectively; p<0.001). These findings remained significant after adjustment for patient demographics and body mass index.

CONCLUSIONS

In patients with asthma, consumption of a diet with moderate to high amounts of soy genistein is associated with better lung function and better asthma control.

Effect of exercise training combined with isoflavone supplementation on bone and lipids in postmenopausal women: a randomized clinical trial

We determined the effects of 2 years of exercise training and soy isoflavone supplementation on bone mass and lipids in postmenopausal women provided with calcium and vitamin D. Women were randomized to four groups: exercise training (Ex); isoflavone supplementation (Iso: 165 mg/d [105 mg/d aglycone equivalent]); combined Ex and Iso (ExIso); and placebo (control). Exercise included resistance training (2 days/week) and walking (4 days/week). Our primary outcomes were lumbar spine and hip bone mineral density (BMD). Secondary outcomes included hip geometry, tibia and radius speed of sound (SOS), dynamic balance (6 m backward tandem walking), blood lipids, mammography, and endometrial thickness. A total of 351 women (Ex = 86, Iso = 90, ExIso = 87, control = 88) were randomized, with 298 analyzed at 2 years (Ex = 77, Iso = 76, ExIso = 72, control = 73). There was a significant interaction for total hip BMD (p < 0.001) such that ExIso had a greater rate of decrease (absolute change [95% confidence interval] = -0.018 [-0.024, -0.012] g/cm(2) ) than either the Ex or Iso groups alone (-0.005 [-0.01, 0.001] and -0.005 [-0.011, 0.001] g/cm(2) , respectively). There were no differences between groups for changes in lumbar spine BMD and minimal significant changes in hip geometric properties and bone SOS. Exercise groups improved dynamic balance as measured by a decrease in backward tandem walking time over 6 m (p = 0.017). Isoflavone groups decreased low density lipoproteins (Iso: -0.20 [-0.37, -0.02] mmol/L; ExIso: -0.23 [-0.40, -0.06] mmol/L; p = 0.003) compared to non-isoflavone groups (Ex: 0.01 [-0.16, 0.18] mmol/L; control: -0.09 [-0.27, 0.08] mmol/L) and had lower adverse reports of menopausal symptoms (14% versus 33%; p = 0.01) compared to non-isoflavone groups. Isoflavone supplementation did not increase endometrial thickness or abnormal mammograms. We conclude exercise training and isoflavone supplementation maintain hip BMD compared to control, but these two interventions interfere with each other when combined. Isoflavone supplementation decreased LDL and adverse events related to menopausal symptoms.

Associations between flavonoids and cardiovascular disease incidence or mortality in European and US populations

Twenty publications from twelve prospective cohorts have evaluated associations between flavonoid intakes and incidence or mortality from cardiovascular disease (CVD) among adults in Europe and the United States. The most common outcome was coronary heart disease mortality, and four of eight cohort studies reported significant inverse associations for at least one flavonoid class (multivariate adjusted p(trend) < 0.05). Three of seven cohorts reported that greater flavonoid intake was associated with lower risk of incident stroke. Comparisons among the studies were difficult because of variability in the flavonoid classes included, demographic characteristics of the populations, outcomes assessed, and length of follow-up. The most commonly examined flavonoid classes were flavonols and flavones combined (11 studies). Only one study examined all seven flavonoid classes. The flavonol and flavone classes were most strongly associated with lower coronary heart disease mortality. Evidence for protection from other flavonoid classes and CVD outcomes was more limited. The hypothesis that flavonoid intakes are associated with lower CVD incidence and mortality requires further study.

The Live Well, Be Well study: a community-based, translational lifestyle program to lower diabetes risk factors in ethnic minority and lower-socioeconomic status adults

OBJECTIVES

We evaluated a community-based, translational lifestyle program to reduce diabetes risk in lower-socioeconomic status (SES) and ethnic minority adults.

METHODS

Through an academic-public health department partnership, community-dwelling adults at risk for diabetes were randomly assigned to individualized lifestyle counseling delivered primarily via telephone by health department counselors or a wait-list control group. Primary outcomes (6 and 12 months) were fasting glucose level, triglycerides, high- and low-density lipoprotein cholesterol, weight, waist circumference, and systolic blood pressure. Secondary outcomes included diet, physical activity, and health-related quality of life.

RESULTS

Of the 230 participants, study retention was 92%. The 6-month group differences for weight and triglycerides were significant. The intervention group lost 2 pounds more than did the control group (P=.03) and had decreased triglyceride levels (difference in change, 23 mg/dL; P=.02). At 6 months, the intervention group consumed 7.7 fewer grams per day of fat (P=.05) and more fruits and vegetables (P=.02) than did control participants.

CONCLUSIONS

Despite challenges designing effective translational interventions for lower-SES and minority communities, this program modestly improved some diabetes risk factors. Thus, individualized, telephone-based models may be a promising alternative to group-based interventions.

Development of an updated phytoestrogen database for use with the SWAN food frequency questionnaire: intakes and food sources in a community-based, multiethnic cohort study

Phytoestrogens, heterocyclic phenols found in plants, may benefit several health outcomes. However, epidemiologic studies of the health effects of dietary phytoestrogens have yielded mixed results, in part due to challenges inherent in estimating dietary intakes. The goal of this study was to improve the estimates of dietary phytoestrogen consumption using a modified Block Food Frequency Questionnaire (FFQ), a 137-item FFQ created for the Study of Women's Health Across the Nation (SWAN) in 1994. To expand the database of sources from which phytonutrient intakes were computed, we conducted a comprehensive PubMed/Medline search covering January 1994 through September 2008. The expanded database included 4 isoflavones, coumestrol, and 4 lignans. The new database estimated isoflavone content of 105 food items (76.6%) vs. 14 (10.2%) in the 1994 version and computed coumestrol content of 52 food items (38.0%), compared to 1 (0.7%) in the original version. Newly added were lignans; values for 104 FFQ food items (75.9%) were calculated. In addition, we report here the phytonutrient intakes for each racial and language group in the SWAN sample and present major food sources from which the phytonutrients came. This enhanced ascertainment of phytoestrogens will permit improved studies of their health effects.

An assessment of potential exposure and risk from estrogens in drinking water

BACKGROUND

Detection of estrogens in the environment has raised concerns in recent years because of their potential to affect both wildlife and humans.

OBJECTIVES

We compared exposures to prescribed and naturally occurring estrogens in drinking water to exposures to naturally occurring background levels of estrogens in the diet of children and adults and to four independently derived acceptable daily intakes (ADIs) to determine whether drinking water intakes are larger or smaller than dietary intake or ADIs.

METHODS

We used the Pharmaceutical Assessment and Transport Evaluation (PhATE) model to predict concentrations of estrogens potentially present in drinking water. Predicted drinking water concentrations were combined with default water intake rates to estimate drinking water exposures. Predicted drinking water intakes were compared to dietary intakes and also to ADIs. We present comparisons for individual estrogens as well as combined estrogens.

RESULTS

In the analysis we estimated that a child's exposures to individual prescribed estrogens in drinking water are 730-480,000 times lower (depending upon estrogen type) than exposure to background levels of naturally occurring estrogens in milk. A child's exposure to total estrogens in drinking water (prescribed and naturally occurring) is about 150 times lower than exposure from milk. Adult margins of exposure (MOEs) based on total dietary exposure are about 2 times smaller than those for children. Margins of safety (MOSs) for an adult's exposure to total prescribed estrogens in drinking water vary from about 135 to > 17,000, depending on ADI. MOSs for exposure to total estrogens in drinking water are about 2 times lower than MOSs for prescribed estrogens. Depending on the ADI that is used, MOSs for young children range from 28 to 5,120 for total estrogens (including both prescribed and naturally occurring sources) in drinking water.

CONCLUSIONS

The consistently large MOEs and MOSs strongly suggest that prescribed and total estrogens that may potentially be present in drinking water in the United States are not causing adverse effects in U.S. residents, including sensitive subpopulations.

Relative androgen excess during the menopausal transition predicts incident metabolic syndrome in midlife women: study of Women's Health Across the Nation

OBJECTIVE

During the menopausal transition, total testosterone (T) remains unchanged, whereas estrogen decreases markedly, creating a state of relative androgen excess. We hypothesized that change in the T-to-estradiol (T/E2) ratio during the menopausal transition would be associated with incident metabolic syndrome.

METHODS

The association between incident metabolic syndrome and total E2, total T, sex hormone-binding globulin, the free androgen index, baseline total T/E2 ratio, and the change of this ratio over time was evaluated in a multiethnic cohort of 1,862 premenopausal and perimenopausal women without diabetes enrolled in the Study of Women's Health Across the Nation.

RESULTS

New cases (n = 257) of metabolic syndrome were identified in the cohort during 6,296 woman-years of follow-up. The age-adjusted total T/E2 ratio increased by 10.1% per year during the 5 years of follow-up. Neither baseline nor change in E2 was associated with incident metabolic syndrome. Low sex hormone-biding globulin, free androgen index, and high total T at baseline all increased the risk of metabolic syndrome, but their change over time did not. Both baseline total T/E2 ratio (1.41; 95% CI = 1.17-1.69; P < 0.001) and its rate of change (1.24; 95% CI = 1.01-1.52; P < 0.04) were associated with increased incident metabolic syndrome independent of ethnicity.

CONCLUSIONS

The interaction between T and E2 during the menopausal transition, rather than the individual change of each over time, is a factor in the determination of risk of developing metabolic syndrome during the menopausal transition. This relationship was independent of ethnicity and other factors associated with prevalent metabolic syndrome before the onset of the menopausal transition.

Urinary isoflavones and their metabolites validate the dietary isoflavone intakes in US adults

BACKGROUND

Isoflavones are derived from dietary sources and considered to promote health by preventing the onset of such chronic diseases as cardiovascular disease, cancer, and osteoporosis. Valid and reliable estimation of isoflavone intake is a prerequisite to establishing biological functions of isoflavones on health risks.

OBJECTIVE

This study aimed to validate the approach of estimating dietary isoflavone intake with respective urinary isoflavone concentrations in US adults.

DESIGN

Data from the US Department of Agriculture isoflavone database and dietary recalls of 2,908 US adults with urinary isoflavone data in the 1999-2002 National Health and Nutrition Examination Survey were used.

RESULTS

Dietary isoflavone was consumed by only 35% of adults in a day with an average intake of 3.1 mg/day, which resulted in a mean intake of 1.0 mg/day for all US adults. The isoflavone intakes were from genistein (55%), diadzein (35%), glycitein (7%), biochanin A (2%), and formononetin (2%). Both daily total and energy adjusted isoflavone intake differed by race/ethnicity subgroups (P<0.05) and was associated positively with income (P<0.01) and inversely with body mass index (P<0.05). Geometric mean urinary isoflavone concentration was 5.0 ng/mL among isoflavone consumers and the urinary genistein and daidzein excretion correlated with their isoflavone intake levels (P<0.01).

CONCLUSIONS

In large population-based studies, estimated dietary isoflavone intake can be validated by urinary isoflavones. Further studies are needed at an individual level to validate dietary isoflavone intake by urinary isoflavone concentration.

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.

Soy isoflavones and risk of cancer recurrence in a cohort of breast cancer survivors: the Life After Cancer Epidemiology study

Soy isoflavones, structurally similar to endogenous estrogens, may affect breast cancer through both hormonally mediated and non-hormonally related mechanisms. Although the effects of soy are not well understood, some breast cancer survivors increase their soy intake post-diagnosis in attempt to improve their prognosis. Therefore, we examined the role of soy isoflavone intake and the risk of breast cancer recurrence by hormone receptor status, menopausal status, and tamoxifen therapy. A cohort of 1,954 female breast cancer survivors, diagnosed during 1997-2000, was prospectively followed for 6.31 years and 282 breast cancer recurrences were ascertained. Isoflavone intake was assessed by mailing modified Block and supplemental soy food frequency questionnaires to participants, on average 23 months post-diagnosis. Risk of breast cancer recurrence, measured by hazard ratios (HR) and 95% confidence intervals (CI), was estimated using multivariable delayed entry Cox proportional hazards models. Suggestive trends for a reduced risk of cancer recurrence were observed with increasing quintiles of daidzein and glycetin intake compared to no intake among postmenopausal women (P for trend: P = 0.08 for daidzein, P = 0.06 for glycetin) and among tamoxifen users (P = 0.10 for daidzein, P = 0.05 for glycetin). Among postmenopausal women treated with tamoxifen, there was an approximately 60% reduction in breast cancer recurrence comparing the highest to the lowest daidzein intakes (>1,453 vs. <7.7 microg/day; HR, 0.48; 95% CI, 0.21-0.79, P = 0.008). Soy isoflavones consumed at levels comparable to those in Asian populations may reduce the risk of cancer recurrence in women receiving tamoxifen therapy and moreover, appears not to interfere with tamoxifen efficacy. Further confirmation is required in other large prospective studies before recommendations regarding soy intake can be issued to breast cancer survivors.

Validation of a food frequency questionnaire for assessing dietary soy isoflavone intake among midlife Chinese women in Hong Kong

Substantial evidence suggests that soy isoflavones may protect against certain chronic diseases. This study aims to assess the reproducibility and validity of a 47-item semiquantitative soy FFQ (SFFQ) designed to measure the usual intake of soy isoflavones among 145 Chinese mid-life women in Hong Kong. Reproducibility of the SFFQ was assessed by the stability of dietary intake obtained at baseline (SFFQ0) and at 13-mo follow-up (SFFQ1). Relative validity was measured by comparing data collected from SFFQ1 with those derived from 23-d, 24-h dietary recalls (DR) collected during the same 1-y validation period. Isoflavone intake was calculated using analytical values from the Chinese University of Hong Kong Soy Isoflavone Database. A total of 3,217 DR were successfully obtained. The median (interquartile range) absolute intake estimated by the SFFQ1 was 0.91 (-2.7 to 6.8) mg aglucon equivalents/d higher than the 6.3 (3.7-10.7) mg aglucon equivalents/d measured by the DR (P < 0.0057; Wilcoxon's Signed Rank test). Bland-Altman analysis further demonstrated the presence of significant proportional bias between methods among Cantonese women with above-median intake (Spearman correlation coefficient; r = 0.44; P = 0.0005). Nonetheless, the intraclass and Pearson correlation coefficients, respectively, were 0.84 and 0.72 for non-Cantonese and 0.65 and 0.50 for Cantonese, showing moderate to good levels of reproducibility and validity of the SFFQ (difference between 2 intraclass correlation coefficients, P = 0.09; difference between 2 Pearson r, P = 0.16). The unadjusted and BMI-adjusted correlations were of similar magnitude. The SFFQ is a reasonably valid instrument for assessing dietary soy isoflavone exposure in Hong Kong Chinese mid-life women.

Assessment of dietary isoflavone intake among middle-aged Chinese men

We evaluated the reproducibility and validity of the FFQ used in the Shanghai Men's Health Study (SMHS) for assessing dietary isoflavone intake, using multiple 24-h dietary recalls (24-HDR) and urinary isoflavones as the reference criteria, with data from the dietary validation study of the SMHS. A total of 196 study subjects completed the 24-HDR and 2 FFQ and donated a quarterly spot urine sample during the 1-y study period. Levels of urinary isoflavones were measured in a random sample of 48 study participants. The correlation coefficient between the 2 FFQ administered 1 y apart was 0.50 for soy protein intake and ranged from 0.50 to 0.51 for isoflavone intake. The correlations of isoflavone intake from the second FFQ with those from the multiple 24-HDR ranged from 0.38 (genistein) to 0.44 (glycitein), and the correlations with urinary isoflavone levels were 0.48 for total isoflavones, 0.44 for daidzein, 0.42 for genistein, and 0.54 for glycitein. The intraclass correlation coefficients for the 4 spot urine samples were 0.36, 0.42, and 0.40 for daidzein, genistein, and glycitein, respectively, and 0.62, 0.68, and 0.55 for their metabolic products equol, dihydrodaidzein, and O-desmethylangolensin, respectively. These results suggest that the SMHS FFQ can reliably and accurately measure usual intake of isoflavones, and that the levels of isoflavones in urine samples are relatively stable among men in Shanghai.

Feasibility of a low-fat/high-fiber diet intervention with soy supplementation in prostate cancer patients after prostatectomy

OBJECTIVES

To evaluate the feasibility and long-term compliance with a low-fat diet supplemented with soy protein in men at increased risk for recurrence after radical prostatectomy.

DESIGN

Randomized, control study.

SETTING

Academic center in USA.

SUBJECT

Forty men who had undergone radical prostatectomy and were at increased risk for recurrence.

INTERVENTION

Low-fat (15% fat), high-fiber (18 g/1000 kcal) diet supplemented with 40 g soy protein isolate (n=26) was compared to USDA recommended diet (n=14).

RESULTS

Over 4 years, subjects in the intervention group but not in the control group made and sustained significant changes in their diet as measured by the dietary assessment instruments and urinary isoflavone excretion. In the intervention group, dietary fat intake was reduced from 33.46+/-1.27% energy/day to 21.04+/-1.74% (P<0.05), fiber intake increased from 14.6+/-1.06 to 21.05+/-2.29 g/day. The insulin growth factor-1 (IGF-1) level was decreased from 260.4+/-8.6 ng/ml at baseline to 220.5+/-7.9 ng/ml at 6 months (P<0.05) in the intervention group with no significant change in the control group. An ex vivo assay demonstrated inhibition of LNCaP cell growth (-20.0+/-7.7%, P<0.05) by sera from patients in the intervention group after 6 months of dietary change compared to baseline.

CONCLUSION

These data suggest that long-term low-fat dietary interventions as part of prospective randomized trials in prostate cancer survivors are feasible, and lead to reductions in circulating hormones or other growth factors stimulating prostate cancer growth ex vivo.

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.

Frequency of soy food consumption and serum isoflavone concentrations among Chinese women in Shanghai

Objective:

The food-frequency questionnaire (FFQ) can be an efficient tool to evaluate dietary intake in large, population-based studies, especially for specific foods. The objective of this study was to validate the assessment of soy and isoflavone (daidzein and genistein) intakes, measured by an FFQ, by comparing intakes with serum isoflavone concentrations.

Design and setting:

Soy and isoflavone intakes and serum isoflavone concentrations were determined as part of a case–control study of dietary factors and risks of benign breast disease and breast cancer. The FFQ, administered during an in-person interview, included six soy-specific line items. Blood was drawn within one week of FFQ completion.

Subjects:

In total, 1823 women living in Shanghai, People's Republic of China.

Results:

In this population, soybean milk, fresh bean curd and other bean foods were eaten once per week, and fermented bean curd, fried bean curd puff and soybeans were eaten less than once per week. A significant linear trend (P > 0.01) in serum isoflavone concentrations across increasing categories of soy and isoflavone intakes was observed, indicating that soy and isoflavone intakes, measured by the FFQ, well distinguished serum isoflavone concentrations. Linear trends were also observed in both case and control groups in stratified analyses, suggesting little differential bias by case–control status.

Conclusions:

The results suggest that the FFQ provides a useful marker of soy food consumption and isoflavone exposure in this population.

Soy isoflavones attenuate bone loss in early postmenopausal Chinese women : a single-blind randomized, placebo-controlled trial

BACKGROUND

Previous studies show that daily doses of 40-99 mg soy isoflavones produce inconsistent effects on preventing estrogen-related bone loss in postmenopausal women.

AIM OF THE STUDY

To examined the bone-sparing effect of isoflavones at a higher dose in early Chinese postmenopausal women.

METHODS

A total of 90 eligible women aged 45-60 years were randomly assigned to three treatment groups (30 subjects/group) with daily dosages of 0 (placebo), 84 and 126 mg isoflavones for 6 months. Further inclusion criteria included body mass index <30 kg/m(2) and Kuppermann Climacteric Scale >15. Bone mineral density (BMD) of the spine and hip were measured using dual- energy X-ray absorptiometry at 0 and 6 months. Serum osteocalcin, bone-specific alkaline phosphatase (BAP) and urinary deoxypyridinoline were examined at 0, 3 and 6 months.

RESULTS

Mean percent changes in BMD at the lumbar spine (p = 0.114) and femoral neck (p = 0.053) increased with the supplementations of soy isoflavones after adjusting for age, years since menopause, body weight and height, dietary intakes of isoflavones, calcium and protein, physical activities and baseline BMD at the relevant sites. We observed significantly dose-dependent linear relationship between the supplemental isoflavones and percent changes of BMD at the spine (p = 0.042) and femoral neck (p = 0.016) post-treatment, and urinary total deoxypyridinoline (p = 0.014) at 12 weeks but not at 24 weeks after adjusting for the above factors. No significant difference in percent changes in serum osteocalcin (p > 0.05) and BAP (p > 0.05) was found among the three treatment groups at 12-week and 24-week post-treatment.

CONCLUSION

There is a significantly dose-dependent effect of soy isoflavones on attenuating bone loss at the spine and femoral neck possibly via the inhibition of bone resorption in non-obese postmenopausal Chinese women with high Kuppermann Scale.

Phytoestrogen Exposure, Polymorphisms in COMT, CYP19, ESR1, and SHBG Genes, and Their Associations With Prostate Cancer Risk

Prospective phytoestrogen exposure was assessed using both biomarkers and estimates of intake in 89 British men recruited into the Norfolk arm of the European Prospective Investigation into Cancer and Nutrition study, men who subsequently developed prostate cancer. Results were compared with those from 178 healthy men matched by age and date of recruitment. Levels of seven phytoestrogens (daidzein, genistein, glycitein, O-desmethylangolensin, equol, enterodiol, and enterolactone) were measured in spot urine and serum samples. Five single-nucleotide polymorphisms in COMT, CYP19, ESR1, and SHBG genes were genotyped. Urinary levels of all phytoestrogens correlated strongly with serum levels. Correlation coefficients ranged from 0.63 (glycitein) to 0.88 (daidzein) (P < 0.001). Urinary and serum levels correlated significantly with isoflavone intake assessed from food diaries (R = 0.15-0.20; P < 0.05) but not with that from a food-frequency questionnaire. Odds ratios for phytoestrogen exposure, as assessed using the four methods, were not significantly associated with prostate cancer risk (P = 0.15-0.94). Men with the CC genotype for the ESRI PvuII polymorphism had significantly higher risk for prostate cancer compared with men with the TT genotype [adjusted odds ratio = 4.65 (1.60-13.49); P = 0.005]. Our results utilizing a combined prospective exposure provide no evidence that phytoestrogens alter prostate cancer risk in British men, whereas the C allele for the PvuII polymorphism may be associated with increased risk.

Validity and reliability of a quantitative food frequency questionnaire measuring n-3 fatty acid intakes in cardiac patients in the Midwest: a validation pilot study

The purpose of this pilot study was to test the validity and reliability of a quantitative n-3 fatty acid food frequency questionnaire (FFQ) for later use with larger groups of individuals. A convenience sample of heart patients provided dietary data via three 24-hour food recalls and FFQs. Participants were women (n=17) and men (n=11), 43 to 77 years of age. The association of mean daily intake of n-3 fatty acids obtained using food recalls and the FFQ was assessed by Pearson correlation. The reliability of the FFQ was assessed using coefficient alpha. Correlation of n-3 fatty acid intake using the food recalls and the FFQ was r=0.42 (P<0.05). The coefficient alpha for the test-retest of the FFQ was .83. The top two foods, walnuts and flaxseed, contributed 58% of the n-3 fatty acid intake, and the third food, salmon, contributed 5%. This quantitative n-3 FFQ is a valid instrument for use in place of food recalls for estimating n-3 fatty acid intakes in heart patients and is a reliable instrument to estimate n-3 fatty acid intakes from plant, animal, and seafood sources. The FFQ should be tested in a larger population. Registered dietitians can use this FFQ to screen for intakes, educate patients on food sources, and measure change in intakes after nutrition intervention.

Dietary genistein intake and cognitive performance in a multiethnic cohort of midlife women

OBJECTIVE

To examine the relationship between food frequency questionnaire estimated isoflavone intakes and cognitive performance.

DESIGN

The Study of Women's Health Across the Nation (SWAN), is a multiethnic, community based, longitudinal study of women aged 42 to 52 years at entry. Dietary isoflavone intakes were estimated from an interviewer-administered food frequency questionnaire at baseline. Intakes of genistein and daidzein were highly correlated (r = 0.98); therefore, analyses were conducted using genistein only. The SWAN includes white, African American, Hispanic, Chinese, and Japanese women; this analysis was performed only in the latter two ethnic groups because the others had minimal genistein intake (median, <4 microg/day). Cognitive function tests were measured at the fourth annual follow-up visit using the East Boston Memory Test (Immediate and Delayed), Symbol Digit Modalities Test, and Digit Span Backward Test. Ethnicity-specific general linear models were used to examine the relationship between each of these cognitive tests and energy-adjusted genistein intake controlling for age, menopause stage, ever-use of any hormones, and current use of any hormones.

RESULTS

Among 195 Japanese and women and 185 Chinese women, median intakes of genistein (mug/day) were 6,788 and 3,534, respectively. No associations between genistein intake and measures of cognitive performance were found in either ethnic group.

CONCLUSIONS

Our results did not support the hypothesis that genistein intake, at the levels consumed by the study sample, benefits cognitive performance. It also possible that the bioavailability of genistein in food sources is insufficient to exert a neurophysiological effect or that the potential effect of genistein is only manifest in low-estrogen states; the current study is not able to address these possibilities.

Reliability and validity of an assessment of usual phytoestrogen consumption (United States)

OBJECTIVE

To evaluate the reliability and validity of a food-frequency questionnaire (FFQ) and database designed to quantify phytoestrogen consumption.

METHODS

This study included 195 members of the California Teachers Study (CTS) cohort who, over a 10-month period, completed four 24-h dietary recalls, a pre- and post-study FFQ, and provided two 24-h urine specimens. Participants (n = 106) in a parallel study (and 18 women who dropped out of the long-term study) completed a single recall and FFQ, and provided one 24-h urine specimen. Urinary phytoestrogens were determined using liquid chromatography-mass spectrometry. Reliability and validity were evaluated using Shrout-Fleiss intraclass correlations and energy-adjusted deattenuated Pearson correlations, respectively.

RESULTS

Correlations reflecting the reproducibility of the FFQ phytoestrogen assessment ranged from 0.67 to 0.81. Validity correlations (FFQ compared to dietary recalls) ranged from 0.67 to 0.79 for the major phytoestrogenic compounds (i.e., daidzein, genistein, and secoisolariciresinol) and 0.43 to 0.54 for the less common compounds. Compared to urinary levels, validity correlations ranged from 0.41 to 0.55 for the isoflavones and 0.16 to 0.21 for total lignans.

CONCLUSION

Our isoflavone assessment is reproducible, valid, and an excellent tool for evaluating the relationship with disease risk in non-Asian populations. Further research is needed before these tools can accurately be used to assess lignan consumption.

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.

Phytoestrogens and prostate cancer risk

BACKGROUND

Phytoestrogens are natural plant substances. The four main classes are isoflavones, flavonoids, coumestans, and lignans. Phytoestrogens have anti-carcinogenic potential. For evaluation of the effect of phytoestrogens on prostate cancer risk, we reviewed analytical epidemiological data.

METHODS

Up to now, there are few studies that have assessed the direct relation between the individual dietary intake of soy products and other nutrients with phytoestrogens and the risk of prostate cancer. We decided to review analytical epidemiological studies providing data on (a) dietary soy intake or flavonoids intake, (b) urinary excretion of isoflavones or lignans, or (c) blood measurements of isoflavones or lignans. Soy is used as a marker for isoflavone intake.

RESULTS

Overall, the results of these studies do not show protective effects. Only four of these studies are prospective, and none of them found statistically significant prostate cancer reductions. Two prospective studies measured flavonoid intake and one reported a preventive effect on prostate cancer for the assumption of myricetin. One study assessed enterolactone concentrations in three different countries and showed no reduction in prostate cancer occurrence.

CONCLUSION

Few studies showed protective effect between phytoestrogen intake and prostate cancer risk.

A semiquantitative food frequency questionnaire is a valid indicator of the usual intake of phytoestrogens by south Asian women in the UK relative to multiple 24-h dietary recalls and multiple plasma samples

We investigated the relative validity of an interview-administered FFQ to estimate phytoestrogen intake among South Asian women in the UK. A population-based sample of 108 healthy South Asian women completed random repeated monthly 24-h recalls [with a subsample (n = 58) also providing multiple plasma samples] over a period of 1 y followed by administration of the FFQ. The FFQ produced slightly higher estimates of phytoestrogen intake than the 24-h recalls, but the percentage of women classified into the same +/- 1 quartile by the 2 methods was high for all phytoestrogens (from 81 to 94%) with only a small percentage (<5%) being misclassified into extreme opposite quartiles. Energy-adjusted Spearman correlations coefficients between the estimates obtained by the FFQ and the 24-h recalls were 0.55 for genistein, 0.60 for daidzein, 0.70 for secoisolariciresinol, and 0.63 for matairesinol (all P < 0.001). Spearman correlation coefficients between the FFQ estimates and plasma levels were 0.21 (P = 0.12) for genistein, 0.32 (P = 0.02) for daidzein and 0.10 (P = 0.43) for enterolactone; the corresponding values for the 24-h recalls compared with plasma levels were 0.43 (P < 0.001), 0.40 (P = 0.002), and 0.08 (P = 0.50), respectively. The method of triads was used to estimate the validity coefficients (VCs) between the estimates provided by each assessment method and "true intake." The FFQ had the highest VC for lignans (0.91 vs. 0.73 for 24-h recalls and 0.11 for plasma samples) and satisfactory VCs for both genistein (0.46 vs. 0.95 and 0.45, respectively) and daidzein (0.67 vs. 0.83 and 0.45, respectively). This FFQ is thus a relatively valid tool with which to estimate phytoestrogen intake among South Asian women in the UK.

Lifestyle and demographic factors in relation to vasomotor symptoms: baseline results from the Study of Women's Health Across the Nation

Results of recent trials highlight the risks of hormone therapy, increasing the importance of identifying preventive lifestyle factors related to menopausal symptoms. The authors examined the relation of such factors to vasomotor symptoms in the multiethnic sample of 3,302 women, aged 42-52 years at baseline (1995-1997), in the Study of Women's Health Across the Nation (SWAN). All lifestyle factors and symptoms were self-reported. Serum hormone and gonadotropin concentrations were measured once in days 2-7 of the menstrual cycle. After adjustment for covariates using multiple logistic regression, significantly more African-American and Hispanic and fewer Chinese and Japanese than Caucasian women reported vasomotor symptoms. Fewer women with postgraduate education reported vasomotor symptoms. Passive exposure to smoke, but not active smoking, higher body mass index, premenstrual symptoms, perceived stress, and age were also significantly associated with vasomotor symptoms, although a dose-response relation with hours of smoke exposure was not observed. No dietary nutrients were significantly associated with vasomotor symptoms. These cross-sectional findings require further longitudinal exploration to identify lifestyle changes for women that may help prevent vasomotor symptoms.

On food frequency questionnaires: the contribution of open-ended questions and questions on ethnic foods

BACKGROUND

Epidemiologic studies of diet must balance the goal of comprehensiveness with that of minimizing subject and study burden. Information on the impact of certain additional questionnaire elements may aid in such decisions.

METHODS

We administered a food-frequency questionnaire in a large multiethnic cohort of women (Study of Women's Health Across the Nation) in 1996-1997. Ancillary questionnaires asked about "any other foods you eat at least once a week" and about consumption of 8-16 ethnic foods included for respondents of Hispanic, Chinese, or Japanese ethnicity. We assessed the impact of these 2 ancillary questionnaires by examining the mean nutrient amount they contributed and their effects on rank-order correlations and categorizations of nutritional estimates. We examined the impact of ethnic foods both within the relevant ethnic group and among non-Hispanic whites.

RESULTS

Rank-order correlations (rs) between nutrient estimates with and without the open-ended question were 0.99 for almost all nutrients and all ethnic groups. Nutrient amounts added by the open-ended question rarely exceeded 2% of the total. Weighted kappa statistics for quintile classifications were greater than 0.9. Similarly, asking white respondents about ethnic foods added little to nutrient estimates, and all correlations between estimates with and without the ethnic foods were at least 0.95. The effect of ethnic foods on nutrient means within the relevant ethnic group was more substantial, although most correlations between estimates with and without the added foods were still above 0.9.

CONCLUSIONS

Open-ended food questions added little to nutrient estimates or rankings in any of the ethnic groups. Specific questions about ethnic foods were useful only within ethnic groups, for which they increased mean nutrient estimates and had modest impact on ranking.

Phytoestrogen Concentrations in Serum and Spot Urine as Biomarkers for Dietary Phytoestrogen Intake and Their Relation to Breast Cancer Risk in European Prospective Investigation of Cancer and Nutrition-Norfolk

Subjects of this study consisted of 333 women (aged 45–75 years) drawn from a large United Kingdom prospective study of diet and cancer, the European Prospective Investigation of Cancer and Nutrition-Norfolk study. Using newly developed gas chromatography/mass spectrometry and liquid chromatography/mass spectrometry methods incorporating triply 13C-labeled standards, seven phytoestrogens (daidzein, genistein, glycitein, O-desmethylangolensin, equol, enterodiol, and enterolactone) were measured in 114 spot urines and 97 available serum samples from women who later developed breast cancer. Results were compared with those from 219 urines and 187 serum samples from healthy controls matched by age and date of recruitment. Dietary levels were low, but even so, mean serum levels of phytoestrogens were up to 600 times greater than postmenopausal estradiol levels. Phytoestrogen concentrations in spot urine (adjusted for urinary creatinine) correlated strongly with that in serum, with Pearson correlation coefficients &gt; 0.8. There were significant relationships (P &lt; 0.02) between both urinary and serum concentrations of isoflavones across increasing tertiles of dietary intakes. Urinary enterodiol and enterolactone and serum enterolactone were significantly correlated with dietary fiber intake (r = 0.13–0.29). Exposure to all isoflavones was associated with increased breast cancer risk, significantly so for equol and daidzein. For a doubling of levels, odds ratios increased by 20–45% [log2 odds ratio = 1.34 (1.06–1.70; P = 0.013) for urine equol, 1.46 (1.05–2.02; P = 0.024) for serum equol, and 1.22 (1.01–1.48; P = 0.044) for serum daidzein]. These estimates of risk are similar to those established for estrogens and androgens in postmenopausal breast cancer but need confirmation in larger studies.

Validation of a soy food-frequency questionnaire and evaluation of correlates of plasma isoflavone concentrations in postmenopausal women

BACKGROUND

Soy foods may have various health benefits, but little is known about the patterns and correlates of soy consumption among postmenopausal women in the United States.

OBJECTIVE

We assessed the reliability and validity of a soy food-frequency questionnaire (FFQ) and examined demographic, lifestyle, and dietary correlates of plasma isoflavone concentrations in postmenopausal women.

DESIGN

In this cross-sectional study, soy isoflavone intake and plasma isoflavone concentration were analyzed in 96 postmenopausal women aged 50-79 y; the data were obtained at 2 visits that were 1 wk apart. Intake was determined with a 20-item soy FFQ and a comprehensive FFQ that included questions about tofu and soymilk. Fasting plasma daidzein and genistein concentrations were determined with liquid chromatography-mass spectrometry.

RESULTS

Intraclass correlations between week 1 and week 2 values were >0.98 for both the soy and comprehensive FFQs. Median reported isoflavone intake was <2 mg/d. Pearson's product-moment correlation coefficients relating isoflavone intakes with plasma isoflavone concentrations ranged from 0.35 to 0.43. Plasma isoflavone concentrations were positively associated with age, fiber consumption, servings of fruit and vegetables, and dietary supplement use and were inversely associated with caffeine consumption; no associations with body mass index, education, dietary beliefs, activity level, alcohol intake, or fat intake were observed.

CONCLUSIONS

Within a population with low soy consumption, the soy FFQ and comprehensive FFQ showed good reliability and moderate validity. Associations of plasma isoflavone concentrations with other dietary behaviors suggest that these compounds may serve as biomarkers of health behaviors in populations with low soy consumption.

Validation of a soy questionnaire with repeated dietary recalls and urinary isoflavone assessments over one year

This study assessed the validity and reliability of a 12-item soy questionnaire designed for use in cancer prevention research. The questionnaire measures soy intake over the past year. Subjects were 199 healthy 35- to 46-yr-old premenopausal women participating in an ongoing soy intervention study. Soy questionnaire estimates of isoflavone intake over 1 yr were compared with individual and combined estimates from two reference measures covering the same period: three or four repeated 24-h recalls and one or two repeated urine analyses. The sensitivity and specificity of the soy questionnaire in classifying high vs. low exposure (high exposure = soy intervention group membership) were comparable with 24-h recalls and were superior to urine analyses (sensitivity = 94.8%, 97.9%, and 71.1%; specificity = 95.1%, 97.1%, and 90.3% for the soy questionnaire, 24-h recalls, and urine analyses, respectively). Soy questionnaire isoflavone estimates were highly correlated with the combination of the two reference measures for the entire study population. Its brevity, ease of administration, and good measurement properties over a 1-yr period make the soy questionnaire well suited to the needs of researchers who wish to identify high and low consumers of soy foods, especially in populations who consume traditional Asian soy foods.

Validation of a soy food frequency questionnaire with plasma concentrations of isoflavones in US adults

OBJECTIVE

To validate assessment of soy intake using food frequency questionnaires (FFQs) compared with plasma isoflavone (genistein and daidzein) concentrations.

DESIGN

Cross-sectional analysis of soy isoflavone intake and plasma analysis of isoflavones.

SUBJECTS

77 men and women, age range 20 to 40 years, recruited from the Seattle metropolitan area.

MAIN OUTCOME MEASURES

Isoflavone intake was determined from responses to a 40-item soy FFQ and from tofu and soymilk intake assessed as part of a comprehensive FFQ used for the Women's Health Initiative (WHI FFQ). Isoflavone concentrations in fasting blood samples were determined by liquid chromatography-mass spectrometry.

STATISTICAL ANALYSES

Correlation coefficients were calculated for: a) isoflavone intake assessed by the soy FFQ and the WHI FFQ, b) intake assessed by the soy FFQ and plasma isoflavone concentrations, and c) intake assessed by the WHI FFQ and plasma isoflavone concentrations.

RESULTS

Isoflavone intake was highly correlated between the soy FFQ and the WHI FFQ (r = 0.84). Genistein and daidzein intakes determined by the soy FFQ were significantly correlated with plasma concentrations (r = 0.53 and 0.45, respectively). Isoflavone intake assessed from the WHI FFQ was also correlated with plasma concentration (r = 0.46 and 0.45). Soymilk and tofu were the two major contributors to isoflavone intake (38.6%).

CONCLUSIONS

A soy-specific, 40-item FFQ assessed isoflavone intake with good validity. Isoflavone intake assessed by the WHI FFQ (tofu and soymilk) had lower correlations with plasma concentrations compared with the soy FFQ. Nonetheless, assessment of the two foods is a reasonably good marker for soy food consumption in this sample.

Dietary soy isoflavones and bone mineral density: results from the study of women's health across the nation

Isoflavones are naturally occurring selective estrogen receptor modulators, with potential bone protective effects. To study the relation between soy isoflavone intake and bone mineral density (BMD), the authors analyzed baseline data from the Study of Women's Health Across the Nation, a US community-based cohort study of women aged 42-52 years. Their 1996-1997 analysis included African-American (n = 497), Caucasian (n = 1,003), Chinese (n = 200), and Japanese (n = 227) participants. Genistein and daidzein intakes were highly correlated (r = 0.98); therefore, analyses were conducted by using genistein. Median intakes of genistein (measured in micrograms/day) by African Americans and Caucasians were too low to pursue relational analyses further. For Chinese and Japanese women, median genistein intakes were 3,511 and 7,151 microg/day, respectively. Ethnic-specific, linear models were used to predict BMD as a function of energy-adjusted tertile of intake, controlled for relevant covariates. For Chinese women, no association between genistein and BMD was found. Premenopausal, but not perimenopausal, Japanese women whose intakes were greater had higher spine and femoral neck BMD. Adjusted mean spinal BMD of those in the highest tertile of intake was 7.7% greater than that of women in the lowest tertile (p = 0.02); femoral neck BMD was 12% greater in the highest versus the lowest tertile (p < 0.0001).

Validity and reproducibility of a self-administered food-frequency questionnaire to assess isoflavone intake in a japanese population in comparison with dietary records and blood and urine isoflavones

Valid food-frequency questionnaires (FFQ) need to be developed to assess isoflavone intake in investigations of its possible association with the lower incidence of breast and prostate cancer in Asian countries. We investigated the validity and reproducibility of isoflavone (daidzein and genistein) intakes from self-administered semiquantitative FFQ used in the JPHC Study (Japan Public Health Center-based Prospective Study on Cancer and Cardiovascular Diseases). We also investigated the number of food items that would be sufficient to ensure validity and reproducibility. We collected FFQ, dietary records (DR), blood and urine samples from 215 subjects among JPHC Study participants, estimated isoflavone intakes from FFQ and DR, and measured serum isoflavone concentration and urine isoflavone excretion. For daidzein, mean intakes estimated from FFQ and DR, serum concentration and urine excretion were 18.3 mg/d, 14.5 mg/d, 119.9 nmol/L and 17.0 micromol/d and for genistein, 31.4 mg/d, 23.4 mg/d, 475.3 nmol/L and 14.2 micromol/d, respectively. Results were similar when analyzed by sex. Spearman correlation coefficients for daidzein of energy-adjusted intakes from FFQ with those from DR, serum concentration and creatinine-adjusted urinary excretion were 0.64, 0.31 and 0.43, respectively. Correlations between two FFQ estimates with a 1-y interval were 0.76. Results were similar for genistein. The shorter version of the FFQ with three items (natto, miso and tofu for miso soup) showed a similar correlation. The original FFQ and the shorter versions have sufficient validity and reproducibility to be used in epidemiologic studies.