A Dietary Intervention to Lower Serum Levels of IGF-I in Mutation Carriers.

Background: Insulin-like growth factor I (IGF-I) and other markers of insulin resistance (IRm) might influence the penetrance of gene mutation. In a demonstration project on mutation carriers we tested the effect of the 'Mediterranean diet', with moderate protein restriction, on serum levels of IGF-I and IRm.

Methods: 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 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 ( < 0.001), fat mass ( = 0.002), with reduced hip circumference ( = 0.01), triglycerides ( = 0.02) and IGF-I ( = 0.02) compared with controls. They also had a significantly higher levels of insulin-like growth factor-binding protein 3 (IGFI-BP3) ( = 0.03) and a lower IGF-I/IGFI-BP3 ratio ( = 0.04). The reduction of serum levels of IGF-I was significantly associated with the reduction in the consumption of animal products ( = 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.