A long-term study followed 8,894 men for prostate cancer diagnosis and mortality over at least two decades. The results showed that milk intake, especially in the first 20 years of life, was associated with an increased risk of prostate cancer. Daily milk consumption in adolescence was associated with a 3.2-fold risk of advanced prostate cancer later in life. Cows’ milk contains insulin-like growth factor 1 (IGF-1) which directly promotes cancer growth. High intake of animal fat has been also associated with increased testosterone levels and high testosterone levels may increase prostate cancer risk.
Torfadottir, J.E., et al., 2012. Milk Intake in Early Life and Risk of Advanced Prostate Cancer. American Journal of Epidemiology.175 (2) 144-153.