Background: Insulin-like growth factor I (IGF-I) and other markers of insulin resistance (IRm) might influence the penetrance of BRCA gene mutation. In a demonstration project on BRCA mutation carriers we tested the effect of the 'Mediterranean diet', with moderate protein restriction, on serum levels of IGF-I and IRm.
Methods: BRCA mutation carriers, with or without breast cancer, aged 18⁻70 years and without metastases were eligible. After the baseline examinations, women were randomized to an active dietary intervention or to a control group. The intervention group attended six full days of life-style intervention activities (cookery classes followed by lunch, sessions of walking for 45 min and nutritional conferences) over the next six months.
Results: 213 BRCA mutation carriers completed the six-month study. Women in the intervention group (110) showed major changes in all the parameters under study. They significantly lost weight (p < 0.001), fat mass (p = 0.002), with reduced hip circumference (p = 0.01), triglycerides (p = 0.02) and IGF-I (p = 0.02) compared with controls. They also had a significantly higher levels of insulin-like growth factor-binding protein 3 (IGFI-BP3) (p = 0.03) and a lower IGF-I/IGFI-BP3 ratio (p = 0.04). The reduction of serum levels of IGF-I was significantly associated with the reduction in the consumption of animal products (p = 0.04).
Conclusions: Women in the intervention group showed significant improvements in IGF-I and in other IRm that might influence the penetrance of BRCA mutations.
Keywords: BRCA genes; IGF-I; diet; mutation carriers; penetrance.