Postmenopausal bone mineral density in relation to soy isoflavone-metabolizing phenotypes.
OBJECTIVE
Intestinal bacterial metabolize the soy isoflavone daidzein to O-desmethylangolensin (O-DMA) or equol. Some individuals do not excrete O-DMA or equol after soy consumption, suggesting they do not harbor bacteria capable of producing these metabolites. The aim of this study was to evaluate bone mineral density (BMD) in relation to presence of these urinary metabolites.


METHODS
BMD, determined by whole-body dual X-ray absorptiometry scan, was age-adjusted and evaluated in relation to O-DMA-producer and equol-producer phenotypes in 92 postmenopausal women, aged 50-75 years. Women consumed supplemental soy foods (daidzein source) for 3 days and collected a first-void urine sample on the fourth day in order to determine metabolic phenotypes.


RESULTS
In O-DMA producers (n=76) compared to O-DMA non-producers (n=16), greater total, leg and head BMD (p<0.05) were observed. Total BMD among the O-DMA producers (geometric mean=1.04 g/cm2) was 6% greater than total BMD among the O-DMA non-producers (geometric mean=0.98 g/cm2). Total and site-specific BMD did not differ between equol producers (n=24) and non-producers (n=68) (p>0.05). In exploratory analyses, among regular soy consumers, spinal BMD was 20% lower among the equol producers than non-producers, whereas, among soy non-consumers, no such difference was observed (p-interaction<0.05). Among equol producers, circulating estrone and free estradiol concentrations were inversely or not associated with total BMD, whereas, among equol non-producers, these hormones were positively associated (p-interaction<0.05).


CONCLUSIONS
Our results provide evidence that intestinal bacterial composition may influence BMD in postmenopausal women. Further studies characterizing associations of intestinal bacterial profiles with BMD are warranted.
Frankenfeld
Cara L
CL
Cancer Prevention Program, Fred Hutchinson Cancer Research Center, 1100 Fairview Ave N., M4-B402, PO Box 19024, Seattle, WA 98109-1024, USA.
McTiernan
Anne
A
Thomas
Wendy K
WK
LaCroix
Kristin
K
McVarish
Lynda
L
Holt
Victoria L
VL
Schwartz
Stephen M
SM
Lampe
Johanna W
JW
D015502:Absorptiometry, Photon; D000368:Aged; D015415:Biomarkers; D015519:Bone Density; D060754:Equol; D005260:Female; D006801:Humans; D007422:Intestines / Q000382:microbiology*; D007529:Isoflavones / Q000378:metabolism* / Q000652:urine; D008875:Middle Aged; D015663:Osteoporosis, Postmenopausal / Q000209:etiology / Q000378:metabolism / Q000517:prevention & control; D010641:Phenotype; D048789:Phytoestrogens / Q000652:urine; D017698:Postmenopause; D030262:Soybean Proteins / Q000008:administration & dosage / Q000737:chemistry / Q000378:metabolism*
C007610:4',7-dihydroxy-3,4-dihydroisoflavone; D015415:Biomarkers; D007529:Isoflavones; D048789:Phytoestrogens; D030262:Soybean Proteins; D060754:Equol; C004742:daidzein; C050052:O-desmethylangolensin