Isolated Isoflavones do not affect the circulating insulin-like growth factor system in men at increased colorectal cancer risk
Vrieling, A. ; Rookus, M.A. ; Kampman, E. ; Bonfrer, J.M.G. ; Korse, C.M. ; Doorn, J. van; Lampe, J.W. ; Cats, A. ; Witteman, B.J.M. ; Leeuwen, F.E. van; van't Veer, L.J. ; Voskuil, D.W. - \ 2007
The Journal of Nutrition 137 (2007)2. - ISSN 0022-3166 - p. 379 - 383.
estrogen replacement therapy - red-clover - factor-i - postmenopausal women - binding protein-3 - soy protein - clinical characteristics - premenopausal women - antioxidant status - human health
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