Isoflavone-rich soy protein prevents loss of hip lean mass but does not prevent the shift in regional fat distribution in perimenopausal women.
OBJECTIVE
Menopause-induced estrogen deficiency increases the risk of cardiovascular disease, which is related to a shift in regional fat distribution. We tested the hypothesis that estrogen-like isoflavones in soy protein isolate (SPI+) would lessen both regional fat gain and lean loss compared with isoflavone-poor soy (SPI-).


METHODS
Perimenopausal participants (N = 69) were randomly assigned (double-blind) to 24 weeks of treatment (40 g soy or whey protein per day): SPI+ (n = 24), SPI- (n = 24), or whey control (n = 21); each participant had blood drawn in the fasted (12 hours) state, had physical activity assessed, and kept a 5-day food diary. Dual-energy x-ray absorptiometry was used to examine the effects of SPI+ on regional fat and lean tissue distribution changes in the waist, hip, and thigh regions.


RESULTS
Mean body mass increased (P < 0.01) in each group, but treatment had no effect on gain in overall body mass, fat mass, or lean mass using analysis of variance. In all treatment groups combined, lean mass increased in each region; fat mass increased only in the waist region. Treatment had an effect (P = 0.039) on hip lean mass and a marginal effect (P = 0.077) on thigh fat. Regression analyses revealed that SPI+ diminished the increase in thigh fat (P = 0.018) and heightened the increase in hip lean (P = 0.035) mass. Carbohydrate intake (P = 0.006) and cohort (reflective of season; P = 0.011) contributed to the gain in thigh fat. Total protein intake (P = 0.0012), plasma insulin (P = 0.0034), and physical activity (P = 0.047) contributed to the gain in hip lean mass.


CONCLUSIONS
Gain in hip lean mass was greater (P = 0.014) in SPI+ than other groups, but SPI+ did not reduce the disease-promoting menopausal shift in regional fat mass.
Moeller
Laura E
LE
Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA.
Peterson
Charles T
CT
Hanson
Kathy B
KB
Dent
Sarah B
SB
Lewis
Douglas S
DS
King
Douglas S
DS
Alekel
D Lee
DL
D000273:Adipose Tissue / Q000187:drug effects*; D000704:Analysis of Variance; D001823:Body Composition / Q000187:drug effects*; D001824:Body Constitution; D002979:Climacteric; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007529:Isoflavones / Q000494:pharmacology*; D008875:Middle Aged; D010349:Patient Compliance; D012044:Regression Analysis; D030262:Soybean Proteins / Q000494:pharmacology*
D007529:Isoflavones; D030262:Soybean Proteins