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.
Fred Hutchinson Cancer Research Center, University of Washington, Center for Health Studies, Group Health Cooperative, Seattle, WA, USA.
Kenneth F
KF
Adams
Katherine M
KM
Newton
Chu
C
Chen
Scott S
SS
Emerson
John D
JD
Potter
Emily
E
White
Johanna W
JW
Lampe
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