title: Isolated isoflavones do not affect the circulating insulin-like growth factor system in men at increased colorectal cancer risk.
abstract: Epidemiological studies show that increased insulin-like growth factor (IGF)-I concentrations are related to increased colorectal cancer risk. A reduced colorectal cancer risk has been associated with isoflavones, which might affect the IGF-system because of their weak estrogenic activity. We conducted a randomized, placebo-controlled, double-blind crossover study to investigate the effect of an 8-wk isolated isoflavone supplementation (84 mg/d) on serum concentrations of total IGF-I, free IGF-I, total IGF-II, IGF binding protein (BP)-1, IGFBP-2, and IGFBP-3. Additionally, we investigated whether IGF-system component differences were related to concentrations of the more potent estrogenic isoflavone metabolite, equol. Our study population consisted of 37 men with a family history of colorectal cancer or a personal history of colorectal adenomas. Isoflavone supplementation did not significantly affect serum total IGF-I concentrations (relative difference between serum total IGF-I concentrations after isoflavone supplementation and after placebo: -1.3%, 95% CI -8.6 to 6.0%). Neither free IGF-I, nor total IGF-II, IGFBP-1, IGFBP-2, or IGFBP-3 concentrations were significantly altered. Interestingly, the change in serum IGF-I concentrations after isoflavone supplementation was negatively associated with serum equol concentrations (r=-0.49, P=0.002). In conclusion, isolated isoflavones did not affect the circulating IGF-system in a male high-risk population for colorectal cancer. However, to our knowledge, this is the first study that suggests isoflavones might have an IGF-I lowering effect in equol producers only. This underlines the importance of taking into account equol status in future isoflavone intervention studies.
authors.affiliation: Division of Experimental Therapy, Department of Epidemiology, The Netherlands Cancer Institute, Amsterdam, The Netherlands.
authors.forename: Alina
authors.initials: A
authors.lastname: Vrieling
authors.forename: Matti A
authors.initials: MA
authors.lastname: Rookus
authors.forename: Ellen
authors.initials: E
authors.lastname: Kampman
authors.forename: Johannes M G
authors.initials: JM
authors.lastname: Bonfrer
authors.forename: Catharina M
authors.initials: CM
authors.lastname: Korse
authors.forename: Jaap
authors.initials: J
authors.lastname: van Doorn
authors.forename: Johanna W
authors.initials: JW
authors.lastname: Lampe
authors.forename: Annemieke
authors.initials: A
authors.lastname: Cats
authors.forename: Ben J M
authors.initials: BJ
authors.lastname: Witteman
authors.forename: Flora E
authors.initials: FE
authors.lastname: van Leeuwen
authors.forename: Laura J
authors.initials: LJ
authors.lastname: van't Veer
authors.forename: Dorien W
authors.initials: DW
authors.lastname: Voskuil
mesh_terms: D000328:Adult; D000368:Aged; D015179:Colorectal Neoplasms / Q000097:blood* / Q000503:physiopathology*; D018592:Cross-Over Studies; D019587:Dietary Supplements; D004311:Double-Blind Method; D006801:Humans; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000378:metabolism; D018971:Insulin-Like Growth Factor Binding Protein 2 / Q000378:metabolism; D018972:Insulin-Like Growth Factor Binding Protein 3; D018969:Insulin-Like Growth Factor Binding Proteins / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D007335:Insulin-Like Growth Factor II / Q000378:metabolism*; D007529:Isoflavones / Q000494:pharmacology*; D008297:Male; D008875:Middle Aged; D012307:Risk Factors
chemical_list: C032231:IGFBP1 protein, human; C515497:IGFBP3 protein, human; D018970:Insulin-Like Growth Factor Binding Protein 1; D018971:Insulin-Like Growth Factor Binding Protein 2; D018972:Insulin-Like Growth Factor Binding Protein 3; D018969:Insulin-Like Growth Factor Binding Proteins; D007529:Isoflavones; C487928:Promensil; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II