Antiresorptive effects of phytoestrogen supplements compared with estradiol or risedronate in postmenopausal women using (41)Ca methodology.
BACKGROUND
Reduction of ovarian estrogen secretion at menopause increases net bone resorption and leads to bone loss. Isoflavones have been reported to protect bone from estrogen deficiency, but their modest effects on bone resorption have been difficult to measure with traditional analytical methods.


METHODS
In this randomized-order, crossover, blinded trial in 11 healthy postmenopausal women, we compared four commercial sources of isoflavones from soy cotyledon, soy germ, kudzu, and red clover and a positive control of oral 1 mg estradiol combined with 2.5 mg medroxyprogesterone or 5 mg/d oral risedronate (Actonel) for their antiresorptive effects on bone using novel (41)Ca methodology.


RESULTS
Risedronate and estrogen plus progesterone decreased net bone resorption measured by urinary (41)Ca by 22 and 24%, respectively (P < 0.0001). Despite serum isoflavone profiles indicating bioavailability of the phytoestrogens, only soy isoflavones from the cotyledon and germ significantly decreased net bone resorption by 9% (P = 0.0002) and 5% (P = 0.03), respectively. Calcium absorption and biochemical markers of bone turnover were not influenced by interventions.


CONCLUSIONS
Dietary supplements containing genistein-like isoflavones demonstrated a significant but modest ability to suppress net bone resorption in postmenopausal women at the doses supplied in this study over a 50-d intervention period.
Weaver
C M
CM
Department of Foods and Nutrition, Purdue University, West Lafayette, Indiana 47907-2059, USA. weavercm@purdue.edu
Martin
B R
BR
Jackson
G S
GS
McCabe
G P
GP
Nolan
J R
JR
McCabe
L D
LD
Barnes
S
S
Reinwald
S
S
Boris
M E
ME
Peacock
M
M
D000368:Aged; D000704:Analysis of Variance; D050071:Bone Density Conservation Agents / Q000494:pharmacology / Q000627:therapeutic use*; D001862:Bone Resorption / Q000517:prevention & control*; D002118:Calcium / Q000378:metabolism; D002132:Calcium Radioisotopes / Q000378:metabolism*; D018548:Cotyledon; D018592:Cross-Over Studies; D019587:Dietary Supplements; D004958:Estradiol / Q000494:pharmacology / Q000627:therapeutic use*; D012968:Etidronic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D005260:Female; D019833:Genistein / Q000494:pharmacology / Q000627:therapeutic use; D006801:Humans; D007529:Isoflavones / Q000097:blood / Q000494:pharmacology / Q000627:therapeutic use*; D016014:Linear Models; D008525:Medroxyprogesterone / Q000494:pharmacology / Q000627:therapeutic use*; D008875:Middle Aged; D015663:Osteoporosis, Postmenopausal / Q000517:prevention & control*; D048789:Phytoestrogens / Q000494:pharmacology / Q000627:therapeutic use*; D028321:Plant Preparations / Q000494:pharmacology / Q000627:therapeutic use; D029908:Pueraria; D000068296:Risedronic Acid; D016037:Single-Blind Method; D013025:Glycine max; D016896:Treatment Outcome; D029921:Trifolium
D050071:Bone Density Conservation Agents; D002132:Calcium Radioisotopes; D007529:Isoflavones; D048789:Phytoestrogens; D028321:Plant Preparations; D004958:Estradiol; D019833:Genistein; D008525:Medroxyprogesterone; D000068296:Risedronic Acid; D012968:Etidronic Acid; D002118:Calcium