The effects of phytoestrogen isoflavones on bone density in women: a double-blind, randomized, placebo-controlled trial.
BACKGROUND
Isoflavone phytoestrogen therapy has been proposed as a natural alternative to hormone replacement therapy (HRT). HRT has a beneficial effect on bone, but few trials in humans have investigated the effects of isoflavones on bone.


OBJECTIVE
The objective of the study was to determine the effect on bone density of a red clover-derived isoflavone supplement that provided a daily dose of 26 mg biochanin A, 16 mg formononetin, 1 mg genistein, and 0.5 mg daidzein for 1 y. Effects on biochemical markers of bone turnover and body composition were also studied.


METHODS
Women aged 49-65 y (n = 205) were enrolled in a double-blind, randomized, placebo-controlled trial; 177 completed the trial. Bone density, body composition, bone turnover markers, and diet were measured at baseline and after 12 mo.


RESULTS
Loss of lumbar spine bone mineral content and bone mineral density was significantly (P = 0.04 and P = 0.03, respectively) lower in the women taking the isoflavone supplement than in those taking the placebo. There were no significant treatment effects on hip bone mineral content or bone mineral density, markers of bone resorption, or body composition, but bone formation markers were significantly increased (P = 0.04 and P = 0.01 for bone-specific alkaline phosphatase and N-propeptide of collagen type I, respectively) in the intervention group compared with placebo in postmenopausal women. Interactions between treatment group and menopausal status with respect to changes in other outcomes were not significant.


CONCLUSIONS
These data suggest that, through attenuation of bone loss, isoflavones have a potentially protective effect on the lumbar spine in women.
Atkinson
Charlotte
C
MRC Biostatistics Unit, Institute of Public Health, Robinson Way, Cambridge, United Kingdom.
Compston
Juliet E
JE
Day
Nicholas E
NE
Dowsett
Mitch
M
Bingham
Sheila A
SA
D000368:Aged; D015992:Body Mass Index; D015519:Bone Density / Q000187:drug effects*; D001842:Bone and Bones / Q000187:drug effects / Q000378:metabolism; D004311:Double-Blind Method; D004958:Estradiol / Q000097:blood; D005260:Female; D006801:Humans; D007529:Isoflavones / Q000494:pharmacology*; D008875:Middle Aged; D048789:Phytoestrogens; D028321:Plant Preparations / Q000494:pharmacology*
D007529:Isoflavones; D048789:Phytoestrogens; D028321:Plant Preparations; D004958:Estradiol