Soy isoflavone supplementation and bone mineral density in menopausal women: a 2-y multicenter clinical trial.
BACKGROUND
Isoflavones are naturally occurring plant estrogens that are abundant in soy. Although purported to protect against bone loss, the efficacy of soy isoflavone supplementation in the prevention of osteoporosis in postmenopausal women remains controversial.


OBJECTIVE
Our aim was to test the effect of soy isoflavone supplementation on bone health.


METHODS
A multicenter, randomized, double-blind, placebo-controlled 24-mo trial was conducted to assess the effects of daily supplementation with 80 or 120 mg of soy hypocotyl aglycone isoflavones plus calcium and vitamin D on bone changes in 403 postmenopausal women. Study subjects were tested annually and changes in whole-body and regional bone mineral density (BMD), bone mineral content (BMC), and T scores were assessed. Changes in serum biochemical markers of bone metabolism were also assessed.


RESULTS
After study site, soy intake, and pretreatment values were controlled for, subjects receiving a daily supplement with 120 mg soy isoflavones had a statistically significant smaller reduction in whole-body BMD than did the placebo group both at 1 y (P < 0.03) and at 2 y (P < 0.05) of treatment. Smaller decreases in whole-body BMD T score were observed among this group of women at 1 y (P < 0.03) but not at 2 y of treatment. When compared with the placebo, soy isoflavone supplementation had no effect on changes in regional BMD, BMC, T scores, or biochemical markers of bone metabolism.


CONCLUSIONS
Daily supplementation with 120 mg soy hypocotyl isoflavones reduces whole-body bone loss but does not slow bone loss at common fracture sites in healthy postmenopausal women. This trial was registered at clinicaltrials.gov as NCT00665860.
Wong
William W
WW
US Department of Agriculture/Agricultural Research Service, Children's Nutrition Research Center, Baylor College of Medicine, Houston, TX 77030, USA. wwong@bcm.edu
Lewis
Richard D
RD
Steinberg
Francene M
FM
Murray
Michael J
MJ
Cramer
Margaret A
MA
Amato
Paula
P
Young
Ronald L
RL
Barnes
Stephen
S
Ellis
Kenneth J
KJ
Shypailo
Roman J
RJ
Fraley
J Kennard
JK
Konzelmann
Karen L
KL
Fischer
Joan G
JG
Smith
E O'Brian
EO
D000328:Adult; D015519:Bone Density / Q000187:drug effects*; D002118:Calcium / Q000494:pharmacology; D019587:Dietary Supplements; D004305:Dose-Response Relationship, Drug; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D006801:Humans; D007529:Isoflavones / Q000008:administration & dosage / Q000494:pharmacology*; D008875:Middle Aged; D010919:Placebos; D017698:Postmenopause / Q000187:drug effects; D013997:Time Factors; D014807:Vitamin D / Q000494:pharmacology; D047071:beta-Glucans / Q000008:administration & dosage / Q000494:pharmacology*
D007529:Isoflavones; D010919:Placebos; D047071:beta-Glucans; C508230:soy isoflavone aglycone; D014807:Vitamin D; D005640:Follicle Stimulating Hormone; D002118:Calcium