title: Effects of soy protein isolate and moderate exercise on bone turnover and bone mineral density in postmenopausal women.
abstract: 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.
authors.affiliation: Division of Geriatrics and Nutritional Sciences, Department of Medicine, Washington University School of Medicine, St. Louis, MO, USA. elevans@uiuc.edu
authors.forename: Ellen M
authors.initials: EM
authors.lastname: Evans
authors.forename: Susan B
authors.initials: SB
authors.lastname: Racette
authors.forename: Rachael E
authors.initials: RE
authors.lastname: Van Pelt
authors.forename: Linda R
authors.initials: LR
authors.lastname: Peterson
authors.forename: Dennis T
authors.initials: DT
authors.lastname: Villareal
mesh_terms: 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
chemical_list: D007529:Isoflavones; D030262:Soybean Proteins