isoflavonoid levels in spot urine are associated with ...among study subjects, there were...

Vol. 7, /35-140, February /998 Cancer Epidemiology, Biomarkers & Prevention 135

3 The abbreviations used are: 0-DMA. O-desmethylangolensin: HPLC. high-

performance liquid chromatography; Cr. creatinine.

Isoflavonoid Levels in Spot Urine Are Associated with Frequency of

Dietary Soy Intake in a Population-based Sample of Middle-aged

and Older Chinese in Singapore1

Adeline Seow, Chen-Yang Shi, Adrian A. Franke,Jean H. Hankin, Hin-Peng Lee, and Mimi C. Yu2

Department of Community, Occupational and Family Medicine, National

University of Singapore, Singapore I 19074 IA. S., C-Y. S., H-P. LI; Cancer

Research Center of Hawaii, Honolulu, Hawaii 96813 IA. A. F., J. H. HI; and

USC/Norris Comprehensive Cancer Center, University of Southern California.

Los Angeles. California 90033 lM. C. Y.J

Abstract

Soy products contain high amounts of isoflavonoids,which have been shown to exhibit possible cancer-protective properties. Chinese populations in Asia, inparticular, have a high level of soy intake and a relativelylow risk of hormone-dependent cancers. In this study, weassessed the distributions of dietary soy isoflavonoids(daidzein, genistein, and glycitein) and urinary soyisoflavonoids and their metabolites (daidzein, genistein,glycitein, equol, and O-desmethylangolensin) among 147Singapore Chinese (76 men and 71 women) ages 45-74years, who are participants of the Singapore CohortStudy on diet and cancer. Urinary values were measuredfrom spot samples collected 10-20 months followingrecruitment, when usual dietary habits were assessed bya structured food frequency/portion size questionnaireadministered in person. Dietary levels of daidzein andgenistein were comparable within individuals and aboutseven times higher than the level of dietary glycitein. Allthree dietary isoflavonoids showed an approximately 3.5.fold difference between the 25th and 75th percentilevalues. Similarly, daidzein was the most abundant and

glycitein the least abundant of the five isoflavonoidcompounds in urine. There was a 4.9-fold differencebetween the 25th and 75th percentile values for the sumof the five urinary isoflavonoids. Among study subjects,there were statistically significant, dose-dependentassociations between frequency of overall soy intake andlevels of urinary daidzein (two-sided P 0.03) and sumof urinary daidzein, genistein, and glycitein (two-sidedP = 0.04). In contrast, there were no associationsbetween frequency of overall soy intake and levels of thetwo daidzein metabolites (equol and 0-desmethylangolensin) in urine (two-sided P 0.85 and

Received 4/28/97; revised 1 1/4/97; accepted 1 1/14/97.The costs of publication of this article were defrayed in part by the payment of

page charges. This article must therefore be hereby marked advertise,nent in

accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

I Supported by grant R35 CA53890 from the National Cancer Institute.

2 To whom requests for reprints should be addressed, at USC/Norris Compre-

hensive Cancer Center, University of Southern California, 1441 Eastlake Avenue,

Los Angeles. CA 90033-0800.

0.34, respectively). We suggest that within the range ofexposures experienced by Singapore Chinese, urinarylevel of daidzein or the sum of daidzein, genistein, andglycitein obtained from a spot sample can serve as abiomarker of current soy consumption in epidemiologicalstudies of diet-disease associations.

Introduction

Isoflavonoids are heterocyclic phenols that occur widely in

plants. The possible role of these compounds in reducing risksof cancers of the breast, prostate. and colon ( 1-3) has been a

subject of recent interest. Much of the evidence for the possibleprotective effect of isoflavonoids has come from in vitro andanimal studies (3, 4). These compounds exhibit estrogen orantiestrogen activity (5- 8) and are able to bind weakly toestrogen receptors (9, 10). Recent findings have also demon-

strated their ability to inhibit cell proliferation and angiogenesisand influence intracellular enzymes, protein synthesis, and

growth factor action (2, 1 1).Isoflavonoids in the diet originate mainly from soy prod-

ucts and, to a minor extent, from other beans and pulses (12).Soybeans, in particular, contain high amounts of the isofla-vones daidzein. genistein, and glycitein and are the primary

food sources of these compounds in humans. Daidzein is me-tabolized by intestinal bacteria to equol and 0-DMA,3 both ofwhich possess estrogenic activity (2, 13). Genistein is metabo-

lized to p-ethylphenol, which lacks either estrogenic or anties-trogenic effects (14).

Few studies have examined the effects of soy on cancerrisk in human populations. At the ecological level, Japanese and

Chinese have been cited as examples of population groups withhigh intakes of soy foods relative to those of Western popula-tions (I ). It is postulated that this may be one of the environ-

mental factors related to their lower risk of selected cancers,namely, cancers of the breast, colon, uterus, and prostate. Acase-control study among Singapore Chinese women in 1986-

1988 found that risk of breast cancer in premenopausal womenwas significantly and inversely associated with high intakes ofsoy protein, total soy products, and a high proportion of proteinfrom soy sources (15). No protective effect of high soy intakeon breast cancer risk was observed, however, in two case-control studies conducted in Shanghai and Tianjin, China, re-spectively ( 16). None of the three case-control studies was

designed to examine this specific diet/cancer relationship. Lim-itations of subjects’ recall and other methodological problemsmay contribute to the varying results of these case-control

studies.

on June 11, 2021. © 1998 American Association for Cancer Research. cebp.aacrjournals.org Downloaded from

http://cebp.aacrjournals.org/

136 Urinary lsollavonoids and Dietary Soy Intake

Recent developments in laboratory techniques such as gas

chromatography and HPLC have facilitated the application ofthese methods to the measurement of isoflavonoid compounds

in biological media, such as blood and urine. This, in turn, hasprovided investigators with a quantitative tool for examining

differences in soy intake between populations. Several studieshave shown that Japanese men and women who consume atraditional diet have high levels of isoflavonoids in both urineand plasma (4). Japanese women were found to excrete 10

times more daidzein and 20-30 times more equol and 0-DMAthan women in Boston and Helsinki (17, 18). In Western pop-

ulations, urinary excretion of isoflavonoids appears highestamong macrobiotic women who consume mainly cereals,grains, legumes, and vegetables for health reasons, followed byvegetarians, who in turn have higher levels than omnivores

(2. 19). Although studies among Chinese women have docu-

mented high soy intake (15. 16), no previous reports of urinaryisoflavonoid levels in this population are available.

Using a 3-day food diary. Adlercreutz et a!. (17) demon-strated a significant correlation between urinary excretion ofdaidzein, equol. and 0-DMA with intake of beans and pulses,

soy products, and boiled soybeans in 19 Japanese men andwomen. To our knowledge, no study has examined the rela-

tionship between individual urinary isoflavonoid levels andreported usual intake of soy in a population-based sample offree-living individuals.

Singapore is a small island republic with a resident pop-ulation of 2.9 million in 1995, of which 77.3% are ethnic

Chinese (20). Eighty-six % live in government-built publichousing estates. The diet consumed by Chinese in Singapore

remains similar in many ways to the traditional Chinese diet,particularly among older persons. At the population level, there

has been a change toward adoption of a more “Western” diet inrecent years (2 1 . 22). The incidence of hormone-dependent

cancers, such as breast and prostate cancer, is lower than inmost Western countries, although a significant rise has been

noted over the past 2 decades (23).Consumption of soybean products among Chinese in Sin-

gapore is relatively high. A variety of soy products are readilyavailable in local markets and food stores. These are primarilysoybean curd (tofu), soybean cake (taukwa), deep-fried soy-

bean cake (taupok), and dried soybean sheets (foojook). A

popular local dish, yong tau foo, contains a mixture of thesefour types of soy products.

The purposes of this study were (a) to define the ranges ofdietary and urinary (from spot samples) soy isoflavonoids in

Singapore Chinese, a population known to consume a variety ofsoy products, and (b) to determine whether soy isoflavonoidlevels in spot urine is associated with self-reported level of

usual consumption of soy products. A positive associationbetween intake frequency as assessed by a dietary question-naire, and urinary measurements of isoflavonoids will serve tovalidate the use of the latter as biomarkers of dietary soy

exposure in epidemiological studies of diet-disease associa-tions. Such results also validate the utility of the dietary ques-tionnaine in assessing intake levels of soy in the studied pop-ulation.

Materials and Methods

Study Population. Subjects were participants of the SingaporeCohort Study, a population-based prospective investigation ofdiet and cancer risk. The goal of the cohort study is to enroll60,000 Chinese men and women ages 45-74 years, dividedequally among each of the two major dialect groups (Hokkien

and Cantonese) in Singapore. Recruitment for the study beganin April 1993, and to date, more than S 1,000 subjects have beenenrolled. One year after commencement of the cohort study, a

3% random sample of subjects was recontacted and asked toprovide a blood and spot urine sample. The present data set

represents the first 147 subjects (76 males and 71 females)recruited into this substudy. The mean age at recruitment to thecohort study of the study subjects was 56.4 years. Most of theurine samples were collected between 10 and 20 months post-

recruitment to the cohort study (mean, 15.4 months).

Dietary Data. At recruitment, each subject completed, bymeans of an in-person interview, a structured questionnaire thatfocused on dietary habits during the past 12 months. Onehundred sixty-five food items were specified in the question-naire. For each of these food items, the respondent was asked

to select from eight frequency categories (ranging from “never”to “2 or more times a day”) and to indicate his/her usual servingsize from photographs of three portion size options. With re-

sped to soy intake, the list of foods included five groups of soy

foods commonly eaten in Singapore. The items were: yong taufoo (a mixed dish), and, separately, any tofu, taupok, taukwa,and foojook consumed other than in yong tau foo.

As part of the development of a Singapore Food Compo-sition Database, levels of daidzein, genistein, and glyciteinwere measured on four cooked samples each of various soyproducts purchased from different markets throughout Singa-pore in November 1995. These items were frozen immediately

following cooking and subsequently shipped to the Cancer

Research Center of Hawaii for chemical analysis in the labo-ratory of A. A. F. This recently completed Singapore Food

Composition Table provides the contents of various macro- and

micronutrients present in all major food items consumed inSingapore, including the soy products.4 Average daily intakes

of daidzein, genistein, glycitein, and soy protein were computedfor the 147 study subjects via linkage of nutrient contents in soyfoods with responses to the dietary questionnaire administered

in person at recruitment.

Urine Sample Collection. Spot urine samples were obtainedfrom the study subjects on randomly chosen dates, usually inthe morning (but not from first voids). The urine was collectedin a 250-ml plastic jar, of which 100 ml were transferred to a

conical flask containing 2 g of ascorbic acid. The acidified urinewas then aliquoted into five vials of 20 ml each and stored at-70#{176}C.All urine specimens were kept on ice immediately aftercollection and processed within 1 hour. The specimens re-mained frozen until analysis at the University of Hawaii Cancer

Research Center.

Laboratory Method. HPLC analysis for the common dietaryisoflavonoids daidzein, genistein, and glycitein and the daid-zein metabolites equol and 0-DMA was carried out based on

the method described by Franke and Custer (24, 25). Briefly,frozen urine aliquots were equilibrated to room temperature,vortex-mixed, and centrifuged at 850 X g for 20 mm. Seven-teen ml of the supernatant were mixed with 5 ml of 0.2 M

acetate buffer (pH 4.0) and 200 pA of flavone (60 ppm in 96%ethanol) as an internal standard and passed through a Cl8reversed-phase solid-phase extraction column (PGC Scientific,

Gaithersburg, MD). The column was then washed with 2 ml of

acetate buffer, and the compounds were eluted with 2.0 ml of

4 i. H. Hankin, S-H. Low, H-P. Lee, and M. C. Yu, The development of dietary

methodology for a prospective study of cancer in Singapore Chinese, submitted

for publication.



“ From the Singapore Food Composition Table.4

Cancer Epidemiology, Biomarkers & Prevention 137

100% methanol. The eluate was dried and incubated for 24 h at

37#{176}Cwith 50 p1 of glucuronidase (isolated from Escherichiacoli; 200 units/mI at 25#{176}C;Boehringer Mannheim, Indianapo-lis, IN) and with 50 �l of arylsulfatase (isolated from Helixpomatia; 5 units/ml at 25#{176}C;Boehringer Mannheim) in 0.2 M

phosphate buffer (pH 7.0). The hydrolyzed samples were mixed1 : 1 with 100% methanol before injection into the HPLC systemor storage at -20#{176}C.All HPLC analyses were carried out on a

Beckman “Gold” system (Fullerton, CA) using a NovaPak C18( 150 X 3.9 mm; inner diameter, 4 p�m) reversed-phase column(Waters, Milfond, MA) coupled to an Adsorbosphere Cl8(10 X 4.6 mm; inner diameter, S jtm) direct-connect guard

column (Alltech, Deerfield, IL). Elution was performed at aflow rate of 0.8 ml/min with the following linear gradient: A,

acetic acid/water (10:90; v/v); B, methanol/acetonitrile/dichlo-romethane (10:5:1; v/v/v); B in A (v/v), 5% for 5 mm, from S

to 45% in 20 mm, from 45 to 70% in 6 mm, and from 70 to 5%in 3 mm, with equilibration for 15 mm before subsequent

injection. Analytes were monitored by photodiode array detec-

tion at 260 and 280 nm during the entire HPLC run simulta-neously. Observed peaks were scanned between 190 and 400nm for identification purposes. Quantitation of observed signalswas performed using peak areas after calibration with authentic

standards.

Urinary Cr was measured at the laboratory of the Depart-ment of Community, Occupational and Family Medicine, Na-

tional University of Singapore, by the standard method on anAbbott autoanalyzer. Soy isoflavonoid levels are expressed as

nmol/mg creatinine (Cr).

Data Analysis. The standard � test was used to compare the

distributions of intake frequencies of the five soy foods betweenmale and female subjects. The distributions of both dietary and

urinary isoflavonoid levels in the study population were mark-edly skewed, which was corrected to a large extent on trans-formation to logarithmic values. Therefore, formal statisticaltestings were performed on logarithmically transformed values,and geometric (as opposed to arithmetic) means are presented.The product-moment correlation coefficient (r) was used toassess the degree of correlation between personal levels of

dietary and urinary isoflavonoids in the study subjects. TheANOVA method was used to compare urinary isoflavonoidlevels between male and female subjects and between subjectswith varying frequencies of soy intake. All Ps are two-sided,

and two-sided Ps of less than 0.05 were considered statistically

significant (26).

Results

Table 1 shows the protein and isoflavonoid contents of the four

major types of soy foods consumed in Singapore (and byChinese throughout the world). There is a wide variation innutrient content levels between these soy products, which ispartially due to their varying water contents. For 100 g ofcooked tofu, approximately 89 g are water. The comparablefigures for 100 g each of cooked taupok, taukwa, and foojook

are 59, 69, and 54 g, respectively. Within each of the four soyproducts analyzed, levels of daidzein and genistein were sim-

ilar, and both were about 7-10 times higher than the level of

glycitein.The distributions of intake frequencies and mean daily

intakes (in g) for the five groups of soy foods consumed bySingapore Chinese are shown in Table 2. Of the four types ofsoy products (tofu, taupok, taukwa, and foojook), tofu andtaukwa were considerably more common than foojook andtaupok. More than half of the subjects (56%) reported con-

Tab/e/Proteinand isoflavonoi

fro

d contents per

m Singapore”

100 g of cooke d soy products

Tofu Taupok Taukwa Foojook

Daidzein (mg)

Genistein (mg)

Glycitein (mg)

Protein (g)

12.4

I 1.9

1.5

8.1

7.2

8.3

0.7

14.0

3.7

14.1

2.1

16.2

23.2

28.8

3.5

22.3

sumption of tofu other than the yong tau foo dish (whichcontains all four types of soy products) at least once a week.The comparable proportion for taukwa was 43%. In contrast,

only 16% and 1 1% of subjects consumed “other taupok” and“other foojook,” respectively, on a weekly basis. We confirmedthat yong tau foo was a popular dish among Singapore Chinese.

Approximately one-third of our subjects consumed this specificdish at least once a week. Female and male subjects did notdiffer in their intake frequencies of these soy foods (all two-

sided Ps were greater than 0.05).Table 3 presents the percentile and geometric mean values

for dietary daidzein, genistein, and glycitein among study sub-jects. The three soy isoflavonoids exhibited comparable ranges

of exposure between subjects. There was an approximately3.5-fold difference between the 25th and 75th percentile values

of dietary daidzein, genistein, and glycitein. In terms of intakelevels of the three isoflavonoids within individuals, exposures

to daidzein and genistein were similar, and both were aboutseven times higher than glycitein (data not shown).

Table 3 also shows the percentile and geometric meanvalues for daidzein, genistemn, glycitein, and the two metabo-

lites of daidzein (equol and 0-DMA) in spot urine samplescollected from study subjects. There is considerable intenindi-vidual variation in values for each of the five urinary isofla-vonoid compounds. There was a 4.9-fold difference between

the 25th and 75th percentile values for the sum of the fiveurinary isoflavonoid compounds. Similar to the dietary results,urinary glycitein was the least abundant of the three parentisoflavonoid compounds; its mean value was one-third andone-half of the mean values for urinary daidzein and genistein,

respectively.

The distributions for each of the dietary and urinary isofla-vonoid compounds shown in Table 3 were similar between

males and females. Statistical comparisons by sex for individ-ual compounds and for sums of these compounds did not

demonstrate any differences in mean values.We examined the correlations between dietary and urinary

levels of daidzein, genistein, and glycitein through the compu-tation of product-moment correlation coefficients (r) between

paired dietary-urinary values among the 147 study subjects.None of the three weakly positive correlation coefficients wasstatistically different from 0.

We also examined the relationships between urinary levels

of soy isoflavonoids and usual intake frequencies of the fivemajor soy foods among our study subjects. For the four morecommon soy foods in Singapore (yong tau foo, other tofu, othertaupok, and other taukwa), there was little difference in urinary

levels of isoflavonoid compounds between subjects consuming

the given soy food at monthly frequency relative to less fne-

quent eaters. However, significantly higher levels of urinaryisoflavonoids were observed between weekly consumers of

yong tau foo, other taupok, and other taukwa compared to thosewho consumed these soy foods at monthly or less than monthly

frequencies (Table 4). Other foojook was not a common dietary



138 Urinary Isoflavonoids and Dietary Soy Intake

Table 2 Distributions of consu mption frequen cies and m can daily intakes of various so y foods amo ng 147 healthy subjects (Singa pore Coho a Study)

N

Males

(%) N

Females

(%)

Total

N (%)

Number of subjects 76 71 147

Yong tau foo

Rarely” 12 (l5.8)� II (15.5) 23 (15.7)

Monthly 37 (48.7) 39 (54.9) 76 (51.7)

Weekly 27 (35.5) 21 (29.6) 48 (32.7)

Mean daily intake (g) 10.3 7.5 8.9

Other tofu

Rarely 10 (13.2) 8 (11.3) 18 (12.2)

Monthly 25 (32.9) 22 (31.0) 47 (32.0)

Weekly 41 (53.9) 41 (57.7) 82 (55.8)


Other taupok

Rarely 40 (52.6) 34 (47.9) 74 (50.3)

Monthly 28 (36.8) 22 (31.0) 50 (34.0)

Weekly 8 (10.6) 15 (21.1) 23 (15.6)


Other taukwa

Rarely l8 (23.7) 9 (12.7) 27 (18.4)

Monthly 30 (39.5) 27 (38.0) 57 (38.8)

Weekly 28 (36.8) 35 (49.3) 63 (42.9)


Other foojook

Rarely 36 (47.4) 26 (36.6) 62 (42.2)

Monthly 37 (48.7) 32 (45.1) 69 (46.9)

Weekly 3 (3.9) 13 (18.3) 16 (10.9)


“ Rarely. less than once a month; monthly. one to three times a month; weekly.1’ Percentages may not add up to 100 due to rounding.

at least once a week.

Table 3 Geometric means and percentile values for dietary exposure and

urinary excretion of soy isoflavonoids among 147 healthy subjects (Singapore

Cohort Study)

PercentilesMean

25th 50th 75th

Dietary soy isoflavonoids

Weekly intake (mg) of:

Daid,ein 8.30 16.64 28.41 15.65

Genistein 8.38 16.58 29.56 15.90

Glycitein 1.06 2.14 3.87 2.31

Sum” 17.78 35.35 61.35 32.84

Urinary soy isoflavonoids

nmol/mg creatinine of:

Daidzein 0.42 1.37 4.35 1.92

Genistein 0.36 0.73 1.87 1.15

Glycitein 0.07 0.37 1.78 0.60

Equol 0. 14 0.60 1 .97 1.05

0-DMA 0.20 0.51 1.03 0.68

Sum’S 2.29 5.42 11.12 5.71

“ Sum of dietary daidzein, genistein, and glycitein.

I, Sum of the five isoflavonoid compounds measured in urine.

item among Singapore Chinese; only 10% of study subjects

(ii = I 6) consumed the food at least once a week, and 47% ateit one to three times pen month. Compared to subjects who

rarely ate other foojook, those who consumed this soy productat least once a month showed significantly elevated mean levelsof urinary daidzein and total urinary isoflavonoids (Table 4).

Because individuals who rarely ate one type of soy food

might be frequent consumers of one or more of the other fourtypes of soy foods, we further classified subjects into one ofthree frequency levels of overall soy intake as follows: the

lowest level consisted of subjects who consumed no more than

one type of soy food on a weekly basis, and the top level ofintake consisted of those who consumed at least four of the fivetypes of soy foods at least once a week. Table 5 shows thegeometric mean levels of the five urinary isoflavonoids within

each of the three levels of overall soy intake frequency. Therewere statistically significant, positive relationships between

overall soy intake frequency and urinary daidzein and sum ofurinary daidzein, genistein and glycitein. Figs. 1 and 2 show thescatter plots of urinary daidzein values and sum of urinary

daidzein, genistein, and glycitein values, respectively, amongstudy subjects according to their levels of overall soy intake

frequency. Neither of the two urinary metabolites, equol and0-DMA, showed a significant relationship with overall soyintake frequency.

Discussion

This study, for the first time, defines the ranges of dietary andurinary soy isoflavonoids in Singapore Chinese, a populationknown to consume a relatively high level of various soy prod-ucts. Our data on soy intake levels are compatible with reportedvalues on other Chinese populations, as well as earlier data

collected from healthy Singapore Chinese women. Specifically,

the median daily intake of soy protein among our male and

female subjects was 2.0 and 2.1 g, respectively. In Shanghai

and Tianjin, China, median intake levels among control sub-jects in two case-control studies of breast cancer were 3.5 and2.8 g, respectively (16). In an earlier case-control study ofbreast cancer in Singapore, we reported a median daily level of

2.5 g among control subjects (15).We did not observe a close correlation between quantita-

live levels of urinary isoflavonoids based on spot samples



Table 4 Geometric

intake frequencies

means (nmollmg Cr) of urinary soy isoflavonoids by

of various soy foods among 147 healthy subjects (Singapore

Cohort Study)

Geometric mean (nmol/mg Cr)

Less than At least Two-side P

weekly intake weekly intake

Table 5 Geometric means (nmol/mg Cr) of urinary soy isoflavonoids by

frequency of overall soy intake (Singapore Cohort Study)

Frequency of overall soy intake”Two-sided P

0-1 2-3 4-5 (linear trend)(a = 79) (a 55) (a 13)

Daidzein (1) 1.54 2.25 3.46 0.03

Genistein (2) 1 .07 1 .09 2.02 0.05

Glycitein (3) 0.51 0.66 0.92 0.11

(1) + (2) + (3) 2.86 3.59 5.89 0.04

Equol 0.79 1.55 0.87 0.85

0-DMA 0.54 0.88 0.77 0.34

Sum’� 4.65 6.90 8.80 0(34

Yong tau foo

Number of subjects 99 48

Daidzein 1.45 3.23

.E

.�

.�

.�

.�

I.�

j

60

50 -

40 -

30 -

20 -

10

0-

140 Urinary lsoflavonoids and Dietary Soy Intake

0�1. 2-3

Frequency of Overall Soy Intake

Fig. 2. Scatter plot of sum of urinary daidzein, genistein, and glycitein values

(nmol/mg Cr) among study subjects according to their levels of overall soy intake

frequency. The score represents the number of soy foods (of a total of five) that

were consumed on a weekly or daily basis.

individuals with varying underlying exposure. This is the casewith urinary daidzein and the sum of urinary daidzein, genis-tein, and glycitein in relation to soy intake in the present study.We observed mostly significant shifts in distributions between

frequent (i.e. , at least weekly) versus infrequent eaters of four

of the five types of soy food consumed by Singapore Chinese.We noted that individuals who rarely ate one type of soy food

might be frequent consumers of one or more of the other fourtypes of soy food. Therefore, we computed an overall soyfrequency score by summing the number of soy foods (total offive) consumed on a weekly basis. We found statistically sig-nificant, dose-dependent associations between the soy intakescore and levels of urinary daidzein and the sum of urinarydaidzein, genistein, and glycitein. Thus, our results suggest thatwithin the range of exposures experienced by Singapore Chi-nese, the urinary level of daidzein or the sum of daidzein,

genistemn, and glycitein obtained from a spot sample can serveas a biomarker of current soy consumption in epidemiologicalstudies of diet-disease associations.

Acknowledgments

We thank Siew-Hong Low for her efforts in supervising the Singapore Cohort

Study, Kazuko Arakawa for performing the data analysis. and Yuichiro Tanaka

for conducting the HPLC assays.

References

I . Persky. V.. and Van Horn, L. Epidemiology of soy and cancer: perspectives

and direction. J. Nutr., 125: 7095-7125, 1995.

2. Herman, C.. Adlercreutz, H., Goldin, B. R., Gorbach, S. L., HOckerstedt,

K. A. V., Watanabe, S., HSm#{228}l#{228}inen,E. K., Markkanen, M. H., MSkela, T. H.,WSh#{228}l#{228},K. T.. Base, T. A., and Fotsis, T. Soybean phytoestrogen intake and

cancer risk. I. Nutr., 125: 757S-770S, 1995.

3. Messina, M., Persky, V., Setchell, K. D. R., and Barnes, S. Soy intake and

cancer risk: a review of in vitro and in vivo data. Nutr. Cancer, 2/: 1 13-13 1, 1994.

4. Adlercreutz, H. Phytoestrogens: epidemiology and a possible role in cancer

protection. Environ. Health Perspect., 103(Suppl. 7): 103-1 12, 1995.

5. Baird, D. D., Umbach, D. M., Lansdell, L., Hughes, C. L., Setchell, K. D. R.,

Weinberg, C. R., Haney, A. F., Wilcox, A. J., and McLachlan, J. A. Dietary

intervention study to assess estrogenicity of dietary soy among postrnenopausal

women. J. Clin. Endocrinol. Metab., 80: 1685-1690, 1995.

6. Cassidy. A., Bingham, S., and Setchell, K. D. R. Biological effect of a diet of

soy protein rich in isoflavones on the menstrual cycle of premenopausal women.

Am. J. Clin. Nutr., 60: 333-340, 1994.

7. M#{228}kel#{228},S., Santti, R., Salo, L., and McLachlan, J. A. Phytoestrogens are

partial estrogen agonists in the male mouse. Environ. Health Perspect., /03(Suppl.

7): 123-127. 1995.

8. Verdeal, K., Brown, R. R., Richardson, T., and Ryan, D. S. Affinity ofphytoestrogens for the estradiol-binding proteins and effect of cournestrol on thegrowth of 7,l2-dimethylbenz(a)anthracene-induced rat mammary tumors. J. NatI.

Cancer Inst., 64: 285-290, 1980.

9. Martin, P. M., Horwitz, K. B., Ryan. D. S.. and McGuire, W. L. Phytoestrogen

interaction with estrogen receptors in human breast cancer cells. Endocrinology,

103: 1860-1867, 1978.

10. Zava, D. T., and Duwe, G. Estrogenic and antiproliferative properties of

genistein and other flavonoids in human breast cancer cells in vitro. Nutr. Cancer,

27: 31-40, 1997.

I I . Fotsis, T., Pepper. M., Adlercreutz, H., Base, T., Montesano, R., and

Schweigerer, L. Genistein: a dietary ingested isoflavonoid, inhibits cell prolifer-

ation and in vitro angiogenesis. J. Nutr., 125: 7905-7975, 1995.

-:i;-- 12. Franke, A. A., Custer, L. J., Cerna, C. M., and Narala, K. K. Quantitation ofphytoestrogens in legumes by HPLC. J. Agric. Food Chem., 42: 1905-1913,1994.

13. Setchell, K. D. R., Borriello, S. P., Hulme, P., Kirk, D. N., and Axelson, M.Nonsteroidal estrogens of dietary origin: possible roles in hormone-dependent

disease. Am. I. Clin. Nutr., 40: 569-578, 1984.

14. Price, K. R., and Fenwick, G. R. Naturally occurring oestrogens in foods: a

review. Food Additives Contamin., 2: 73-106, 1985.

15. Lee, H. P., Gourley. L., Duffy, S. W., Esteve, I., Lee, J., and Day, N. E.

Dietary effects on breast-cancer risk in Singapore. Lancet, 337: 1 197-1200, 1991.

16. Yuan, J-M., Wang, Q-S., Ross, R. K., Henderson, B. E., and Yu, M. C. Dietand breast cancer in Shanghai and Tianjin, China. Br. I. Cancer, 71: 1353-1358,

I 995.

17. Adlercreutz, H., Honjo, H., Higashi, A., Fotsis, T., H#{228}m#{228}l#{228}inen,E., Base-gawa, T., and Okada, H. Urinary excretion of lignans and isoflavonoid phy-

toestrogens in Japanese men and women consuming a traditional Japanese diet.

Am.J.Clin.Nutr.,54: 1093-1100, 1991.

I 8. Adlercreutz, H., Markkanen, H., and Watanabe, S. Plasma concentrations of

phyto-oestrogens in Japanese men. Lancet, 342: 1209-1210, 1993.

19. Adlercreutz, H., Fotsis, T., Bannwart, C., W#{228}h#{228}l#{228},K., M#{228}kela,T., Brunow,

G., and Hase, T. Determination of urinary lignans and phytoestrogen metabolites,

potential antiestrogens and anticarcinogens, in urine of women on various habit-

ual diets. J. Steroid Biochem., 25: 791-797, 1986.

20. Department of Statistics, Singapore. Yearbook of Statistics, p. 24. Singapore:

Ministry of Trade and Industry, 1995.

21. Lee, H. P., and Gourley, L. Food availability in Singapore 1961-1983:implications for health research. Food Nuts. Bull., 8: 50-54, 1986.

22. Lee, H. P., and Gourley, L. Fat and fibre in the Singapore diet. Ann. Acad.

Med. Singapore, /6: 408-41 1, 1987.

23. Chia, K. S., Lee, H. P., Scow, A., and Shanmugaratnam, K. Trends in cancer

incidence in Singapore 1968-1992. Singapore Cancer Registry Report No. 4.Singapore: Singapore Cancer Registry, 1996.

24. Franke, A. A., and Custer, L. J. High-performance liquid chromatography

assay of isoflavonoids and coumestrol from human urine. J. Chromatogr. B, 662:

47-60, 1994.

25. Franke, A. A., and Custer, L. I. Daidzein and genistein concentrations inhuman milk after soy consumption. Clin. Chem., 42: 955-964, 1996.

26. Snedecor. G. W., and Cochran, W. G. Statistical Methods, Ed. 6. Ames, IA:

The Iowa State University Press, 1967.



1998;7:135-140. Cancer Epidemiol Biomarkers Prev A Seow, C Y Shi, A A Franke, et al. middle-aged and older Chinese in Singapore.of dietary soy intake in a population-based sample of Isoflavonoid levels in spot urine are associated with frequency

Updated version

http://cebp.aacrjournals.org/content/7/2/135

Access the most recent version of this article at:

E-mail alerts related to this article or journal.Sign up to receive free email-alerts

Subscriptions

Reprints and

[email protected] at

To order reprints of this article or to subscribe to the journal, contact the AACR Publications

Permissions

Rightslink site. Click on "Request Permissions" which will take you to the Copyright Clearance Center's (CCC)

.http://cebp.aacrjournals.org/content/7/2/135To request permission to re-use all or part of this article, use this link


http://cebp.aacrjournals.org/content/7/2/135http://cebp.aacrjournals.org/cgi/alertsmailto:[email protected]://cebp.aacrjournals.org/content/7/2/135http://cebp.aacrjournals.org/

isoflavonoid levels in spot urine are associated with ...among study subjects, there were...

Documents