Effects of soy protein isolate and moderate exercise on bone turnover and bone mineral density in postmenopausal women.
OBJECTIVE
The aim of this study was to assess the independent and additive effects of soy protein isolate (SPI) and moderate-intensity exercise (EX) on bone turnover and bone mineral density (BMD).


METHODS
This study used a placebo-controlled, double-blind (soy), randomized 2 (SPI vs milk protein isolate [MPI]) x 2 (EX vs no EX) design. Sixty-one postmenopausal women were randomized, and 43 (62 +/- 5 y) completed the 9-month intervention (SPI, n = 10; MPI, n = 12; SPI + EX, n = 11; MPI + EX, n = 10). Serum C-terminal cross-linked telopeptides of type I collagen and serum bone-specific alkaline phosphatase were measured as markers of bone resorption and formation, respectively. BMD was measured by dual-energy x-ray absorptiometry.


RESULTS
At 9 months, SPI reduced serum C-terminal cross-linked telopeptides (-13.3% +/- 15.3% vs -1.5% +/- 21.0%; P = 0.02) and serum bone-specific alkaline phosphatase (-4.7% +/- 14.7% vs 6.5% +/- 17.7%; P = 0.02) compared to milk protein isolate. EX attenuated the reduction in serum C-terminal cross-linked telopeptides (-1.9% +/- 21.6% vs -12.4% +/- 15.3%; P = 0.04); however, no EX effects were apparent in serum bone-specific alkaline phosphatase at 9 months (2.8% +/- 16.1% vs -1.0% +/- 18.3%; P = 0.28). Neither SPI nor EX affected BMD at any site; however, change in BMD was related to change in fat mass (r = 0.40, P < 0.05).


CONCLUSIONS
In postmenopausal women (1) SPI reduces bone turnover with no impact on BMD over 9 months; (2) moderate-intensity endurance exercise training did not favorably alter bone turnover and had no impact on BMD; and (3) there were no additive effects of soy and exercise on bone turnover or BMD.
Evans
Ellen M
EM
Division of Geriatrics and Nutritional Sciences, Department of Medicine, Washington University School of Medicine, St. Louis, MO, USA. elevans@uiuc.edu
Racette
Susan B
SB
Van Pelt
Rachael E
RE
Peterson
Linda R
LR
Villareal
Dennis T
DT
D015502:Absorptiometry, Photon; D000368:Aged; D015519:Bone Density / Q000187:drug effects; D016723:Bone Remodeling / Q000187:drug effects; D004311:Double-Blind Method; D015444:Exercise; D005260:Female; D006801:Humans; D007529:Isoflavones / Q000008:administration & dosage* / Q000494:pharmacology; D008875:Middle Aged; D015663:Osteoporosis, Postmenopausal / Q000517:prevention & control; D017698:Postmenopause / Q000187:drug effects / Q000378:metabolism*; D030262:Soybean Proteins / Q000008:administration & dosage* / Q000494:pharmacology; D016896:Treatment Outcome; D016387:Women's Health
D007529:Isoflavones; D030262:Soybean Proteins