The Journal of Nutrition
Nutrition and Disease
Supplemental Dietary Racemic Equol Has
Modest Benefits to Bone but Has Mild
Uterotropic Activity in Ovariectomized Rats1–3
LeeCole L. Legette,4Berdine R. Martin,4Mohammad Shahnazari,4Wang-Hee Lee,5William G. Helferich,6
Junqi Qian,7David J. Waters,8Alireza Arabshahi,9Stephen Barnes,9Jo Welch,4David G. Bostwick,7
and Connie M. Weaver4*
4Department of Foods and Nutrition and5Department of Agricultural and Biological Engineering, Purdue University, West Lafayette, IN
47907;6Division of Nutritional Sciences, University of Illinois, Urbana, IL 61801;7Bostwick Laboratories, Richmond, VA 23060;
8Department of Veterinary Clinical Sciences, Purdue University, West Lafayette, IN 47907; and9Department of Pharmacology-Toxicology,
University of Alabama, Birmingham, AL 35294
Soy isoflavones and their metabolites, with estrogenic activity, have been considered candidates for reducing
postmenopausal bone loss. In this study, we examined the effect of dietary equol, a bioactive metabolite of the soy
isoflavone daidzein, on equol tissue distribution, bone parameters, and reproductive tissue activity using an adult
ovariectomized (OVX) rat model. An 8-wk feeding study was conducted to compare 4 dietary treatments of equol (0, 50,
100, 200 mg/kg diet) in 6-mo-old OVX female Sprague-Dawley rats. A dose response increase in tissue equol
concentrations was observed for serum, liver, kidney, and heart, and a plateau occurred at 100 mg equol/kg diet for
intestine. In OVX rats receiving 200 mg equol/kg diet, femoral calcium concentration was greater than those receiving
lower doses but was still less than SHAM (P , 0.05), and other bone measures were not improved. Tibia calcium
concentrations were lower in OVX rats receiving 100 and 200 mg equol/kg diet compared with the OVX control rats.
Trabecular bone mineral density of tibia was also lower in equol-fed OVX rats. At this dietary equol intake, uterine weight
was higher (P , 0.05) than in other OVX groups but lower than the SHAM-operated intact rats. The 200 mg/kg diet dose of
dietary equol significantly increased proliferative index in the uterine epithelium. Dietary equol had no stimulatory effect on
mild uterotropic effects. J. Nutr. 139: 1908–1913, 2009.
In 2002, results of the Women’s Health Initiative Study revealed
adverse effects of estrogen therapy, including increased risk
for cardiovascular disease and breast cancer, despite positive
benefits of reduced bone loss (1). This created interest in
alternative choices with bone protective effects such as soy
isoflavones and their metabolites (2). Soy isoflavones are
commonly referred to as phytoestrogens due to their chemical
structure, which is similar to estrogen. It has been postulated
that soy isoflavones exert their actions through binding with
estrogen receptor (ER)9-b (2) in osteoblast cells. This leads to
suppression of osteoclast differentiation via osteoprotegerin
(OPG) and subsequent inhibition of bone resorption (3).
Specifically, OPG competes with receptor-activated nuclear
factor k receptor (RANK) for binding to RANK ligand, which
is essential for osteoclast differentiation (3). A recent study
showed that administering soy isoflavone genistein to osteopenic
postmenopausal women for 2 y resulted in higher OPG: RANK
ligand ratios and femoral neck bone mineral density (BMD)
compared with a placebo group (4).
Some evidence suggests that soy isoflavone metabolites exert
more potent effects on bone than their parent precursors (5). In
1Supported by Purdue University, University of Alabama Botanical Center for
AgeRelated Diseases, and NIH
2Author disclosures: L. L. Legette, B. R. Martin, M. Shahnazari, W-H. Lee, W. G.
Helfreich, J. Qian, D. J. Waters, A. Arabshahi, J. Welch, and D. G. Bostwick, no
conflicts of interest. C. M. Weaver is on the board of Pharmavite; S. Barnes has a
U.S. patent on the use of conjugated isoflavones for prevention of osteoporosis.
3Supplemental Figure 1 is available with the online posting of this paper at jn.
* To whom correspondence should be addressed. E-mail: weavercm@purdue.
grants P50AT00477-01 andP50
9Abbreviations used: BMC, bone mineral content; BMD, bone mineral density;
ER, estrogen receptor; OPG, osteoprotegerin; OVX, ovariectomized; OVX-0,
ovariectomized rats receiving 0 mg equol/kg diet in an AIN-93M diet; OVX-50,
ovariectomized rats receiving 50 mg equol/kg diet in an AIN-93M diet;
OVX-100, ovariectomized rats receiving 100 mg equol/kg diet in an AIN-93M
diet; OVX-200, ovariectomized rats receiving 200 mg equol/kg diet in an AIN-93M
diet; pQCT, peripheral quantitative computed tomography; RANK, receptor
activated nuclear factor k receptor; mCT, micro computed tomography.
0022-3166/08 $8.00 ã 2009 American Society for Nutrition.
Manuscript received April 1, 2009. Initial review completed May 9, 2009. Revision accepted July 27, 2009.
First published online August 26, 2009; doi:10.3945/jn.109.108225.
particular, equol [7-hydroxy-3-(4-hydroxyphenyl)-chroman], a
metabolite derived from the soy isoflavone daidzein, has 80
times more ERb binding affinity than its parent compound (6).
Equol is produced by intestinal bacterial metabolism of
daidzein. After consumption of soy, the glycoside form of
daidzein, daidzin, is converted to the aglycone form, daidzein,
by enzymatic hydrolysis of the sugar group and daidzein is
further metabolized to equol. Thus, equol production is exclu-
sively dependent on the bacterial composition of intestinal
microbiota. Several bacteria (bifidobacteria and lactobacilli)
have been speculated to influence equol-producing ability (7). It
is estimated that only 30–50% of humans are equol producers
(8–10). The difference in equol-producing ability could explain
the inconsistencies among clinical studies of isoflavones (2,9).
Although rodents are equol producers, variability exists among
various strains. Ward et al. (11) examined the equol production
of 4 mouse strains, 2 inbred and 2 outbred, by providing the
same amount of daidzein (200 mg/kg diet) in the diet for 3 wk
and assessing serum equol levels. The outbred strains had an
almost 3- to 4-fold increase in serum equol levels and concurrent
lower serum daidzein levels compared with inbred strains
supplemented with daidzein (11).
There have been only a few studies that assessed the
biological effects of equol, due to its limited commercial
availability. Most studies have examined the effect of dietary
equol on reproductive tissues (12–14), and few have assessed the
impact on bone health (15,16). All studies had to use high doses
of equol ($400 mg/kg diet) to inhibit bone loss, which also
caused adverse effects on reproductive tissues. However, there is
currently no direct evidence supporting a positive action of
dietary equol on bone metabolism at physiological doses (0–250
Our aim was to determine the effect of dietary equol on bone
metabolism in ovariectomized (OVX) rats. Such a study became
feasible only with the recent capability to synthesize equol (6). A
dietary dose ranging study allowed insight into the potential
benefits of dietary equol supplement for those unable to produce
Materials and Methods
Rats. Seventy-eight virgin female Sprague Dawley rats (6 mo old) were
purchased from Harlan, of which 62 were OVX and 16 were SHAM
operated 2 d before shipment. Rats were housed in individual cages in a
temperature- and humidity-controlled room with lights on a 12:12-h on:
off cycle. An AIN-93M diet (17) and distilled water were provided ad
libitum for an acclimation period of 2 d. All procedures were approved
by and performed in compliance with the rules of Purdue University’s
Animal Care and Use Committee.
Diet and equol supplement. Equol powder (50% R-equol, 50% S-
equol; Supplemental Fig. 1) was produced as previously described (6)
and mixed evenly with AIN-93M base diet (17) ingredients (Dyets) at the
following concentrations: 0, 50, 100, and 200 mg/kg diet. Doses were
selected based on a pilot study in rats aimed to achieve serum human
equol levels, 0–1, 3–39, and 5–49 mmol/L, observed in postmenopausal
women in response to dietary soy isoflavones (0, 56, and 90 mg/d),
Study design. All OVX rats were weighed and assigned to 1 of the
following dietary treatments: OVX-0, OVX-50, OVX-100, and OVX-
200 to ensure similar mean body weight across OVX groups. Dietary
treatments consisted of an AIN-93M diet with 0 (n = 15), 50 (n = 16),
100 (n = 15), and 200 (n = 16) mg equol/kg diet, respectively. They were
pair-fed the mean intake of SHAM controls (n = 16; 0 mg/kg diet equol)
to avoid OVX-induced hyperphagia. After 8 wk of dietary treatment,
rats were killed by excess CO2. Blood was drawn via the portal vein and
serum was stored at 2808C for isoflavone analysis. Various tissues,
including kidney, liver, whole intestine, and heart (flushed with 50 mL
saline), were excised and stored at 2808C for isoflavone analysis. The
uterus and caudal mammary glands were collected and stored in 10%
buffered formalin for histopathologic examination and assessment of
epithelial proliferation. Right femurs and tibiae were wrapped in saline-
soaked gauze and stored at 2208C for evaluation of bone mechanical
properties. Left femurs and tibiae were collected and placed in 70%
ethanol and stored at 48C for scanning by peripheral quantitative
computed tomography (pQCT).
Serum and tissue equol measurement. Serum and tissue concentra-
tions of equol were quantified using a highly sensitive and specific
electrospray ionization liquid chromatography-multiple reaction ion
monitoring MS method as described previously (19). There were
modifications in conditions of chromatography as listed below. Chro-
matography was carried out on a 30- 3 2.0-mm i.d. Phenomenex
Phenyl-Hexyl column using mobile phase consisting of a gradient of 10–
80% acetonitrile in 10 mmol/L ammonium acetate over 5 min with a
flow rate of 0.4 mL/min. Equol was detected using the transition of its
m/z241 molecularionand itsm/z 119 fragmention.Tissuesampleswere
prepared by removing 0.2–0.250 g of tissue from sample and homog-
enization in 2 mL of an 80% methanol, 0.01% (wt:v) ascorbic acid
solution. Extraction techniques were described previously (19).
Bone density, size, and mechanical properties. Right femurs and
tibiae were measured for length and width at the midshaft using an ABS
digimatic solar caliper (Tri-State Instrument Service). Bone density was
measured by underwater weighing using a density determination kit
and Mettler Toledo analytical balance. Bone strength was assessed
using a 3-point bending test on a TA-XT2 Texture analyzer (Texture
pQCT measurements. pQCTanalysis was performed with the Stratec
peripheral quantitative computed tomograph (model Research SA+ of
Norland Stratec XCT, Stratec Electronics). Three cross-sectional sites
(1.0 mm thick) from distal, midshaft, and proximal sites of bones,
determinedat 12, 50, and 88% of the length of from distal,were scanned
using a 0.46-mm collimation (4 3 105counts/s) and a 0.08-mm voxel
size. Thresholds for segmentation of trabecular and cortical bone were
set at 300 mg/cm3and 900 mg/cm3, respectively.
Micro computed tomography measurements. Bone architecture
was assessed by micro computed tomography (mCT) analysis using a
Scanco microCT tomograph (mCT 40, Scanco Medical). Eight femurs
were randomly selected from each of the following groups: SHAM,
OVX-0, and OVX-200. Cancellous and cortical bone of femurs was
evaluated using methods and parameters described previously (20).
Cancellous bone at the distal femur was scanned with an isotropic
resolution of 16 mm obtained from 0.2 down the growth plate extended
for 62 slices. In the femur, 62 contiguous slices were contoured and
imaging proceeded proximally covering a distance of 1 mm.
Bone calcium content. After mechanical testing, right femurs and
tibias were dissolved in concentrated nitric acid overnight and analyzed
for total calcium content using atomic absorption spectrometry (PE
S100, Perkin Elmer).
Reproductive tissue analysis. The extent of epithelial proliferation in
mammary glands and uterine epithelium was determined by visually
scoringformalin-fixed tissuesections.Eachspecimen wasscored onscale
from 0 to 3, with 0 and 2 equivalent to the extent of epithelial
proliferation in OVX and SHAM controls, respectively. In addition to
visual scoring, the proliferative index in these tissues was determined by
proliferative cell nuclear antibody (PCNA) immunohistochemistry using
a technique previously reported (12). The proliferative index was defined
as the percentage of cells with unequivocal nuclear immunostaining.
Statistical analysis. Data were analyzed using SAS (version 9.1, SAS
Institute). The effect of equol on bone parameters was determined by
Dietary equol effect on ovariectomized rats1909
1-way ANOVA and multiple comparisons using Tukey’s test after
checking the normal distribution and constant variance assumptions of
ANOVA. In the case of nonnormal distribution (reproductive tissue
data), data underwent log transformation before analysis by 1-way
ANOVA and Tukey’s test. Significance was accepted at P , 0.05.
Body and uterine weight. All OVX groups except OVX-200
had significantly higher body weight than the SHAM despite
pair feeding. However, there was no significant effect of equol
supplementation on body weight of OVX rats (Fig. 1A). Dietary
intake was similar among all OVX groups, which were pair-fed
to the mean intake of SHAM rats. Feed efficiency ratios were
similar among OVX-0 (0.036 6 0.023), OVX-50 (0.046 6
0.020), and OVX-100 (0.035 6 0.023) but significantly higher
than for SHAM (0.090 6 0.019) and OVX-200 (0.210 6 0.024)
rats. Uterine weight in all OVX groups was significantly lower
than in SHAM rats (Fig. 1B). In OVX rats, the uterine weight
was greater only in the OVX-200 group (55% higher than
OVX-0; P # 0.05) but was still substantially less than in SHAM
(72% lower; P # 0.05).
Equol analysis. Equol levels of 50, 100, and 200 mg/kg diet of
OVX rats resulted in total serum (S/R) equol concentrations
increasing with increasing dose of dietary equol (Fig. 1C). Liver,
kidney, and heart tissue concentrations also increased with
increasing dose of dietary equol. Equol levels in the intestine
increased in all equol groups compared with OVX-0, but the
increase was not dose dependent (data not shown).
Bone calcium concentration, size, and mechanical prop-
erties. Femoral density measured by underwater weighing was
higher (P , 0.05) in the SHAM group than in the OVX groups
but was not affected by equol in the diet (Table 1). There were
no group differences in femoral length, width, or breaking force.
SHAM rats had higher (P , 0.05) femoral calcium concentra-
tion than OVX-0 (Fig. 1D). Among all OVX groups, only the
OVX-200 group maintained a femoral calcium concentration
similar to SHAM rats and higher (P , 0.05) femoral calcium
concentration than OVX-0 rats.
There was no significant decrease in tibial density in response
to ovariectomy, but the OVX-50 group had a lower tibia density
from SHAM. There were no group differences in tibia length,
width, or breaking force. SHAM rats had a significantly higher
tibia calcium concentration than all OVX rats. Among OVX
rats, OVX-100 and OVX-200 had significantly lower tibia
calcium concentrations than the OVX-0 and OVX-50 groups
pQCT measurements. In the midshaft femur and tibia, SHAM
rats had significantly higher total BMC than all OVX groups.
There were no differences among treatment groups for total
BMD, cortical BMD, and cortical thickness at the midshaft
femur and tibia.
For the distal femur, the SHAM group had significantly
higher total BMC, total BMD, trabecular BMD, and cortical
thickness than OVX-0 rats. There were no differences among
OVX rats at the distal femur.
At the proximal femur, the SHAM group had significantly
higher trabecular BMD than all OVX groups (Table 1).
operated and OVX rats fed diets containing various levels of equol (n = 15–16/group). Means without a common letter differ, P , 0.05.
Body weight (A), uterine weight (B), serum equol concentrations (C), and right femoral and tibia calcium concentration (D) in sham-
1910Legette et al.
Treatment groups did not differ for total BMD, cortical BMD,
and cortical thickness at the proximal femur.
At the proximal tibia, SHAM rats had significantly higher
total BMC than all OVX groups (Table 1). Among OVX rats, all
those fed dietary equol had significantly lower trabecular BMD
compared with OVX-0 rats. Treatment groups did not differ for
total BMD, cortical BMD, and cortical thickness at the proximal
mCT measurements. At the distal femur, the SHAM group had
significantly higher trabecular connectivity and significantly
lower trabecular spacing than the OVX-0 and OVX-200 groups
(Table 1). Treatment groups did not differ in cortical thickness,
porosity, and cortical BMD at the midshaft of the femur.
Evaluation of mammotropic and uterotropic effects of
equol. The SHAM group had significantly higher mammary
gland epithelial mass on visual scoring than all OVX groups
(Table 2). Among OVX groups, equol did not affect mammary
epithelial proliferation as evident by PCNA immunostaining
Based on visual scoring of histologic sections of the uterus,
the SHAM group had significantly greater uterine epithelial
mass than all OVX groups. OVX-200 rats had significantly
greater epithelial mass than OVX-0 and OVX-50 but not OVX-
100 rats. PCNA immunostaining showed SHAM control,
OVX-100, and OVX-200 rats had significantly higher uterine
epithelial proliferative index compared with the OVX-0 and
OVX-50 rats (Table 2). SHAM rats and OVX-200 rats had
significantly higher uterine stroma cell proliferative index than
OVX-0 and OVX-50 but not OVX-100 rats.
Because soy is the most abundant source of isoflavones in the
human diet, the 2 major soy isoflavones, daidzein and genistein,
have been extensively evaluated for their impact on mitigating
estrogen-related bone loss (11,21–24). Investigators have also
started to examine soy isoflavone metabolites, such as equol, as
potentially more biologically potent than their endogenous
precursors (6,9,25). Here, we show in OVX rats that dietary
intake of equol at a level of 200 mg/kg diet induces few changes
in bone calcium concentration, specifically a beneficial increase
in femoral calcium concentration but a negative decrease in tibia
calcium concentration. Furthermore, this level of dietary equol
intake exerted adverse effects in uterine, but not mammary,
tissue in OVX animals.
Few studies have characterized humans by their ability to
produce equol. Wu et al. (26) classified 68 study participants out
of 122 as equol producers based on conversion rate of daidzein
to equol present in fecal bacteria. They found that equol
producers had a significantly lower percent change in total hip
BMD after 24 wk of soy isoflavone treatment compared with
nonproducers. Similarly, Setchell et al. (2) observed a 2.4%
increase in lumbar spine BMD of equol producers (45% of
participants) after a 2-y intervention with soy isoflavones
compared with the 0.6% increase of nonproducers. Studies on
the direct effect of dietary equol on bone health have been
limited because of the high cost and limited availability of
commercial sources. Consequently, the few studies that exam-
ined the effects of equol in vivo have administered it by
subcutaneous injection or osmotic pump to conserve the
compound rather than via the more physiological route of
dietary intake (14,15). This may reflect the relationship between
a metabolite produced in vivo and its health effects but does not
address bioavailability of equol as a dietary supplement.
Administration of 0.5 mg/mL equol, but not 0.1 mg in 1 mL,
by osmotic pump inhibited OVX-induced bone loss of the whole
body, femur, and lumbar spine in ddY mice (27). In our study,
equol was fed to rats as a dietary supplement, so that serum
levels reflected digestion and absorption, relevant for designing a
Serum and most tissue concentrations of equol increased with
increasing dietary equol. Serum concentrations corresponded to
Bone characteristics of SHAM-operated and OVX rats fed diets containing various levels
SHAM OVX-0OVX-50 OVX-100OVX-200
Distal femur, pQCT
Total BMC, mmol Ca/g body wt
Trabecular BMD, mg/cm3
Bone volume/tissue volume
Trabecular connectivity density, 1/mm3
Trabecular number, 1/mm
Proximal femur, pQCT
Trabecular BMD, mg/cm3
Proximal tibia, pQCT
Total BMC, mmol Ca/g body wt
Trabecular BMD, mg/cm3
1.56 6 0.030a
1.51 6 0.030b
1.50 6 0.040b
1.50 6 0.030b
1.52 6 0.030b
1.50 6 0.040a
1.48 6 0.030ab
1.46 6 0.030b
1.46 6 0.050ab
1.48 6 0.030ab
0.414 6 0.082a
558 6 51.0a
0.337 6 0.051b
448 6 60.0b
0.307 6 0.025b
410 6 43.0b
0.319 6 0.042b
414 6 36.0b
0.321 6 0.041b
425 6 55.0b
0.250 6 1.00a
78.0 6 19.0a
4.28 6 0.550a
0.080 6 0.030b
19.0 6 11.0b
2.39 6 0.390b
0.090 6 0.050b
24.0 6 16.0b
2.61 6 0.520b
543 6 65.0a
481 6 36.0b
454 6 46.0b
466 6 54.0b
486 6 45.0b
0.270 6 0.033a
652 6 48.0a
0.255 6 0.035b
609 6 43.0b
0.255 6 0.038b
554 6 30.0c
0.263 6 0.087b
559 6 31.0c
0.230 6 0.025b
578 6 49.0c
1Values are means 6 SD, n = 15–16. Means without a common letter differ, P , 0.05.
2Bone density was calculated by underwater weighing.
3mCT measurements were only performed on SHAM, OVX-0 ppm, and OVX-200 ppm equol groups, n = 8.
Dietary equol effect on ovariectomized rats 1911
levels seen in previous studies with rodents receiving medium to
high doses of dietary daidzein (28–30). Serum concentrations
are also similar to levels in clinical participants (postmenopausal
women) from our laboratory, classified as equol producers, who
consumed between 120–150 mg isoflavones/d (20).
In this dose response study on the effect of dietary equol on
bone health, we found a modest effect on femoral calcium
concentration. In contrast, dietary equol appeared to have a
detrimental effect on tibia calcium concentration and trabecular
BMD at the proximal tibia. Whole bone measures of the femur
and tibia are largely cortical bone. Calcium absorption efficiency
tended to be greater (P = 0.07) in the OVX-100 (0.338 6 0.088)
and OVX-200 (0.352 6 0.124) groups than in the SHAM
(0.300 6 0.121), OVX-0 (0.280 6 0.103), and OVX-50
(0.020 6 0.037) groups. Skeletal site-specific results could be
attributed to a differential response between cortical and trabec-
ular bone. Alternatively, skeletal site-specific results could be due
todifferences inmechanicalloadingfortheanimalmodelused in
this investigation. In this animalmodel, the tibiaundergoes more
mechanical stress than the femur (31). Saxon et al. (32)
demonstrated that estrogen-like actions mediated through ERb
could inhibit bone formation under mechanical loading. Inves-
tigators applied daily loading to 16-wk-old mice with ERb null
mutations (ERb2/2) and found that ERb2/2mice had a 3.6-fold
increase in bone formation after mechanical loading compared
with wild type, ERb+/+, mice. Additional research should
examine the effect of estrogenic-like actions on bone mechanical
signaling and the subsequent impact on bone health.
Our results also showed that despite pair feeding, only the
highest dietary equol dose (200 mg/kg diet) helped maintain
body weight at SHAM levels, probably by exerting estrogen-like
effects on general metabolism. The highest dietary equol level
was also associated with increased uterine weight. The weight
differential between SHAM and OVX despite pair feeding (21)
and uterotropic effects of dietary equol (13) have been observed
previously. A risk factor associated with estrogen therapy or
compounds exerting estrogen-like effects is the growth stimula-
tion of reproductive tissue, especially uterus. Increased uterine
weight is a classical estrogen effect mediated by ERa (33–35). At
equol levels of 0.1 or 0.5 mg/d, no effect on uterine weight was
observed in OVX mice (27), whereas weight was increased in
mice receiving equol injections at 12 and 20 mg/kg body weight
per day (14). Similarly, Rachon et al. (15) observed increased
uterine weight as well as higher proliferation in uterine epithelial
cells after administrating 2 doses of racemic equol (50 and 400
mg/kg unpurified diet) for 3 mo to OVX Sprague Dawley rats. In
our study, only the highest dose of dietary equol, 200 ppm,
caused a significant increase (55%) in uterine weight compared
with the OVX control group as a reference as well as increased
epithelial proliferation. Findings of uterotropic effects from
dietary equol could be due to the fact that the only form of
synthesized equol available is the racemic mixture and the
R-equol isomer has an affinity for ERa, which is abundant in
reproductive tissue. Moreover, S-equol has a greater affinity for
ERb than R-equol (6). Recently, Heemstra et al. (36) developed
a method for total synthesis of S-equol. Future studies should
determine whether greater efficacy without uterotropic effects
will occur with dietary administration of S-equol.
Our findings demonstrate that a 200-mg equol/kg diet dose in
OVX rats has modest bone health benefits. Results also showed
that a 200-mg equol/kg diet dose did not induce changes in the
mammary epithelium but mildly stimulated the uterine epithe-
lium. Our study suggests that the benefit:risk ratio of racemic
equol has low promise as a commercial supplement. Given that S-
for ERb and not ERa compared with R-equol, future research
should establish whether S-equol would have greater bone
protective properties without reproductive tissue stimulation.
We thank Pamela Lachcik for technical assistance. L.L., B.M.,
and C.W. designed the research; L.L., M.S., W.L., J.W., A.A.,
J.Q., and D.B. conducted the research; L.L. and M.S. analyzed
the data. W.H., D.W., and S.B. provided essential materials.
L.L. and C.W. wrote the paper and had primary responsibility
for final content. All authors read and approved the final
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Reproductive tissue proliferation in SHAM-operated and OVX rats fed diets containing
various levels of equol1
SHAM OVX-0OVX-50 OVX-100 OVX-200
Epithelial PCNA, %
Stroma PCNA, %
1.94 6 0.570a
14.8 6 15.3a
0.53 6 0.740b
1.98 6 2.11b
0.38 6 0.50b
1.14 6 1.66b
0.47 6 0.510b
2.32 6 3.72b
0.94 6 0.570b
2.59 6 4.70b
1.94 6 0.770a
37.6 6 21.8a
19.2 6 21.1a
0.000 6 0.000c
1.14 6 2.09b
0.650 6 1.45b
0.130 6 0.340c
0.670 6 1.15b
0.920 6 1.92b
0.330 6 0.490bc
8.95 6 12.4a
2.67 6 2.99ab
0.750 6 0.580b
15.3 6 18.0a
4.18 6 3.98a
1Values are means 6 SD, n = 15–16. Means without a common letter differ, P , 0.05.
1912 Legette et al.
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Dietary equol effect on ovariectomized rats1913