Dietary soy protein and isoflavones: minimal beneficial effects on bone and no effect on the reproductive tract of sexually mature ovariectomized Sprague-Dawley rats.
OBJECTIVE
The present study was conducted to determine the effects of dietary soy protein and isoflavones on bone and the reproductive tract in the absence of the ovary.


METHODS
Three-month-old Sprague-Dawley rats (n = 56) were either sham-operated or ovariectomized and then fed diets containing casein or soy protein +/- isoflavone extract for 12 weeks. The amounts of casein, soy protein, and extract (per kg diet) in each group were as follows: (1) Ovariectomy, 200 g of casein; (2) Ovariectomy+low soy, 100 g of casein + 100 g of soy protein; (3) Ovariectomy+high soy, 200 g of soy protein; (4) Ovariectomy+low extract, 200 g of casein + 17.2 g of extract; (5) Ovariectomy+high extract, 200 g of casein + 34.4 g of extract; (6) Ovary intact, 200 g of casein; (7) Ovariectomy+estradiol-17beta, 200 g of casein. Diet consumption, body weight, uterine weight, urine deoxypyridinoline, and bone mineral density of the femur and lumbar vertebrae were measured. The femur rigidity was evaluated by histomorphometry. The reproductive tract (uterus, vagina, and cervix) was studied histologically.


RESULTS
The Ovariectomy group showed significant increases in body weight, diet consumption, and deoxypyridinoline, decreases in uterine weight and bone mineral density, and negative changes in histomorphometry compared with the Ovary intact group. Neither soy protein nor extract diets abrogated these alterations, except for the Ovariectomy+high extract group that showed statistically significant positive changes in histomorphometric parameters. There were no histological differences in the reproductive tract among Ovariectomy, Ovariectomy+soy, and Ovariectomy+extract groups. The estradiol-17beta replacement abrogated ovariectomy-induced alterations.


CONCLUSIONS
Dietary intake of isoflavones by sexually mature ovariectomized rats has a minimal beneficial effect on bone with no effect on the reproductive tract.
Bahr
Janice M
JM
Department of Animal Sciences, University of Illinois, Urbana, IL 61801, USA. jbahr@uiuc.edu
Nakai
Masaaki
M
Rivera
Alexander
A
Walsh
Jane
J
Evans
Glenda L
GL
Lotinun
Sutada
S
Turner
Russell T
RT
Black
Molly
M
Jeffery
Elizabeth H
EH
D000818:Animals; D015519:Bone Density; D001842:Bone and Bones / Q000187:drug effects; D004032:Diet; D004195:Disease Models, Animal; D004958:Estradiol / Q000008:administration & dosage; D005260:Female; D005270:Femur Head; D006801:Humans; D007529:Isoflavones / Q000008:administration & dosage*; D008159:Lumbar Vertebrae; D015663:Osteoporosis, Postmenopausal / Q000517:prevention & control*; D010052:Ovariectomy; D008517:Phytotherapy; D010936:Plant Extracts / Q000008:administration & dosage; D051381:Rats; D017207:Rats, Sprague-Dawley; D030262:Soybean Proteins / Q000008:administration & dosage*; D014599:Uterus / Q000187:drug effects
D007529:Isoflavones; D010936:Plant Extracts; D030262:Soybean Proteins; D004958:Estradiol