title: Dietary soy protein and isoflavones have no significant effect on bone and a potentially negative effect on the uterus of sexually mature intact Sprague-Dawley female rats.
abstract: OBJECTIVE
  To evaluate the effect of dietary soy protein and isoflavones on bone and the reproductive tract in premenopausal rats.
  
  
  METHODS
  Three-month-old intact Sprague-Dawley female rats (N = 50) were fed diets containing casein, soy protein, or casein with isoflavone extract for 12 weeks. The amount of casein, soy protein, and extract (per kilogram diet) in each group was: (1) 200 g casein (control); (2) 100 g casein plus 100 g soy protein (low soy); (3) 200 g soy protein (high soy); 4) 200 g casein plus 17.2g extract (low extract); and (5) 200 g casein plus 34.4 g extract (high extract). Diet consumption, body weight, uterine wet weight, urinary deoxypyridinoline concentration, and bone mineral density of the femur and lumbar vertebrae were measured. Femur rigidity was evaluated by histomorphometry. The uterus and vagina were studied histologically.
  
  
  RESULTS
  Rats in all treatment groups had lower body weights and lower deoxypyridinoline concentrations compared with controls, but none of the differences was statistically significant. There was no significant difference in femur and lumbar bone mineral density, uterine wet weights, or histomorphometry between the control and treatment groups. Histologically, uteri and vaginae were normal in all groups except that 1 of 10 rats in the high-soy group and 2 of 10 rats in the high-extract group showed extensive squamous metaplasia in the uterine gland.
  
  
  CONCLUSIONS
  These results suggest that dietary isolated soy protein and isoflavones have no effect on bone and the vagina during premenopausal period, but may have an adverse effect on the uterus.
authors.affiliation: Departments of Animal Sciences, University of Illinois, Urbana, IL, USA.
authors.forename: Masaaki
authors.initials: M
authors.lastname: Nakai
authors.forename: Leslie
authors.initials: L
authors.lastname: Cook
authors.forename: Leah M
authors.initials: LM
authors.lastname: Pyter
authors.forename: Molly
authors.initials: M
authors.lastname: Black
authors.forename: Jean
authors.initials: J
authors.lastname: Sibona
authors.forename: Russell T
authors.initials: RT
authors.lastname: Turner
authors.forename: Elizabeth H
authors.initials: EH
authors.lastname: Jeffery
authors.forename: Janice M
authors.initials: JM
authors.lastname: Bahr
mesh_terms: D000596:Amino Acids / Q000652:urine; D000818:Animals; D015415:Biomarkers / Q000652:urine; D001835:Body Weight; D015519:Bone Density / Q000187:drug effects*; D001842:Bone and Bones / Q000187:drug effects / Q000473:pathology; D004032:Diet; D005260:Female; D006801:Humans; D007529:Isoflavones / Q000008:administration & dosage / Q000494:pharmacology*; D009929:Organ Size; D017697:Premenopause / Q000652:urine; D051381:Rats; D017207:Rats, Sprague-Dawley; D030262:Soybean Proteins / Q000008:administration & dosage / Q000494:pharmacology*; D014599:Uterus / Q000187:drug effects* / Q000473:pathology; D014621:Vagina / Q000187:drug effects / Q000473:pathology
chemical_list: D000596:Amino Acids; D015415:Biomarkers; D007529:Isoflavones; D030262:Soybean Proteins; C036020:deoxypyridinoline