Are dietary influences on the risk of prostate cancer mediated through the insulin-like growth factor system?

Objectives To investigate whether dietary factors that appear to affect the risk of prostate cancer may be similarly associated with serum levels of insulin-like growth factor 1 (IGF-1). Patients and methods In the context of a case-control study, 112 men were admitted to three teaching hospitals in Athens, Greece, for disorders other than cancer. Sociodemographic data and detailed histories of smelting, alcohol and coffee consumption were recorded. A validated food-frequency questionnaire was administered by an interviewer and serological measurements of IGF-1 and its binding protein-3 conducted. Results IGF-1 declined significantly by almost 25% among men aged > 75 years and there was a small reduction in IGF-1 levels with increased alcohol intake, with a mean (95% confidence interval, CI) change of -1.6 (-2.2 to -0.9)% for an increment of one drink per day, There was no evidence for an effect of either smelting or coffee consumption on IGF-1 level. Among foods, the consumption of cooked tomatoes was substantially and significantly inversely associated with IGF-1 levels, with a mean (95% CI) change of -31.5 (-43.1 to -7.9)% for an increment of one serving per day. Conclusions The strongest known dietary risk factor for prostate cancer (lycopene deficit, as reflected in a reduced intake of cooked tomatoes) and an important endocrine factor in the aetiology of this disease (IGF-1) seem to be related in a way that suggests that at least one, and perhaps more, exogenous factors in the development of prostate cancer may be mediated through the IGF-1 system.