Isoflavone-rich soy protein isolate attenuates bone loss in the lumbar spine of perimenopausal women.
BACKGROUND
No published studies have directly examined the effect of soy protein with isoflavones on bone or bone turnover in perimenopausal women.


OBJECTIVE
Our objective was to determine the effects of 24 wk of consumption of soy protein isolate with isoflavones (80.4 mg/d) in attenuating bone loss during the menopausal transition.


METHODS
Perimenopausal subjects were randomly assigned, double blind, to treatment: isoflavone-rich soy (SPI+; n = 24), isoflavone-poor soy (SPI-; n = 24), or whey (control; n = 21) protein. At baseline and posttreatment, lumbar spine bone mineral density (BMD) and bone mineral content (BMC) were measured by using dual-energy X-ray absorptiometry. At baseline, midtreatment, and posttreatment, urinary N:-telopeptides and serum bone-specific alkaline phosphatase (BAP) were measured.


RESULTS
The percentage change in lumbar spine BMD and BMC, respectively, did not differ from zero in the SPI+ or SPI- groups, but loss occurred in the control group (-1.28%, P: = 0.0041; -1.73%, P: = 0.0037). By regression analysis, SPI+ treatment had a positive effect on change in BMD (5.6%; P: = 0.023) and BMC (10.1%; P: = 0.0032). Baseline BMD and BMC (P: < or = 0.0001) negatively affected the percentage change in their respective models; baseline body weight (P: = 0.0036) and bone-free lean weight (P: = 0.016) contributed positively to percentage change in BMD and BMC, respectively. Serum BAP posttreatment was negatively related to percentage change in BMD (P: = 0.0016) and BMC (P: = 0.019). Contrast coding using analyses of covariance with BMD or BMC as the outcome showed that isoflavones, not soy protein, exerted the effect.


CONCLUSIONS
Soy isoflavones attenuated bone loss from the lumbar spine in perimenopausal women.
Alekel
D L
DL
Department of Food Science and Human Nutrition, Human Metabolic Unit, Center for Designing Foods to Improve Nutrition, the Department of Statistics, Iowa State University, Ames 50011-1120, USA. alekel@iastate.edu
Germain
A S
AS
Peterson
C T
CT
Hanson
K B
KB
Stewart
J W
JW
Toda
T
T
D000328:Adult; D015415:Biomarkers; D001842:Bone and Bones / Q000378:metabolism; D004032:Diet; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007529:Isoflavones / Q000494:pharmacology*; D008159:Lumbar Vertebrae / Q000187:drug effects*; D008875:Middle Aged; D010024:Osteoporosis / Q000517:prevention & control*; D015663:Osteoporosis, Postmenopausal / Q000517:prevention & control; D010349:Patient Compliance; D017697:Premenopause; D030262:Soybean Proteins / Q000494:pharmacology*
D015415:Biomarkers; D007529:Isoflavones; D030262:Soybean Proteins