title: Combination of soy protein and high dietary calcium on bone biomechanics and bone mineral density in ovariectomized rats.
abstract: OBJECTIVE
  To determine if feeding soy in combination with a high-calcium diet would preserve bone mineral density and biomechanical bone strength to a greater extent than either soy or calcium alone.
  
  
  METHODS
  Rats were sham-operated (n = l0) and fed a control diet (AIN93G containing 0.2% calcium, 20% casein) or ovariectomized (n = 40) and randomized to one of the following diets (n = 10 per group): control, high calcium (2.5% calcium, 20% casein), soy (0.2% calcium, 20% soy protein), or soy plus high calcium (2.5% calcium, 20% soy protein) for 8 weeks. Bone mineral density of femurs and lumbar vertebrae 1 through 6 were measured by dual energy x-ray absorptiometry. Biomechanical strength properties of femurs and the fifth lumbar vertebrae were measured by three-point bending and compression, respectively.
  
  
  RESULTS
  The dietary combination of soy and high calcium did not result in higher femur bone mineral density compared with other ovariectomized groups, and there were no differences in femur yield load or peak load among groups. In contrast, soy plus high calcium resulted in a higher (P < 0.05) vertebral bone mineral density compared with all other ovariectomized groups. Vertebral strength was preserved among rats fed either soy plus high calcium, soy, or high calcium whereas the ovariectomized group fed a control diet had lower (P < 0.05) vertebral strength than the sham-operated group.
  
  
  CONCLUSIONS
  Bone mineral density of the lumbar spine was the only bone outcome that significantly benefited from the combination of soy and high calcium compared with soy or high calcium alone.
authors.affiliation: Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Pearl L
authors.initials: PL
authors.lastname: Breitman
authors.forename: Debbie
authors.initials: D
authors.lastname: Fonseca
authors.forename: Wendy E
authors.initials: WE
authors.lastname: Ward
mesh_terms: D015502:Absorptiometry, Photon; D000818:Animals; D001696:Biomechanical Phenomena; D001835:Body Weight / Q000502:physiology; D015519:Bone Density; D002136:Calcium, Dietary / Q000008:administration & dosage*; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000502:physiology*; D007529:Isoflavones / Q000008:administration & dosage; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000502:physiology*; D010052:Ovariectomy; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D030262:Soybean Proteins / Q000008:administration & dosage*
chemical_list: D002136:Calcium, Dietary; D007529:Isoflavones; D030262:Soybean Proteins