Soy isoflavones do not modulate circulating insulin-like growth factor concentrations in an older population in an intervention trial.
Insulin-like growth factors (IGF) are essential for normal growth and maintenance of lean muscle mass; however, high insulin-like growth factor-I (IGF-I) and low IGF binding protein-3 (IGFBP-3) levels are also associated with several cancers. To test the hypothesis that long-term soy isoflavone supplementation decreases circulating IGF-I concentrations, we conducted a controlled, parallel-arm, double-blind intervention study with 150 participants (85% men), 50-80 y old. Participants were randomly assigned to consume a soy beverage powder daily for 12 mo. The active treatment group (+ISO) received soy protein containing 83 mg isoflavones, whereas the comparison group (-ISO) received soy protein containing 3 mg isoflavones. Serum IGF-I and IGFBP-3 were measured by ELISA. Mean change in serum IGF-I concentrations was similar in the two groups (+1.4 nmol/L in +ISO, +1.2 nmol/L in -ISO; P = 0.74, 95% confidence interval -1.1, +1.5 nmol/L for the 0.21 nmol/L difference between groups), indicating no effect of the isoflavone intervention. Similarly, the changes in IGFBP-3 and the IGF-I/IGFBP-3 ratio were similar in both groups, again showing no effect of +ISO treatment. A 12 mo, 83 mg/d soy isoflavone intervention did not modulate serum IGF in an older, mostly male population.
Adams
Kenneth F
KF
Fred Hutchinson Cancer Research Center, University of Washington, Center for Health Studies, Group Health Cooperative, Seattle, WA, USA.
Newton
Katherine M
KM
Chen
Chu
C
Emerson
Scott S
SS
Potter
John D
JD
White
Emily
E
Lampe
Johanna W
JW
D000368:Aged; D004311:Double-Blind Method; D005006:Ethnicity; D005260:Female; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood* / Q000187:drug effects; D007334:Insulin-Like Growth Factor I / Q000187:drug effects / Q000378:metabolism*; D007529:Isoflavones / Q000493:pharmacokinetics / Q000494:pharmacology*; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D012959:Socioeconomic Factors; D013025:Glycine max; D014861:Washington
D018972:Insulin-Like Growth Factor Binding Protein 3; D007529:Isoflavones; D007334:Insulin-Like Growth Factor I