(Medical Xpress) -- While people have been told for years about the importance of milk in a diet for children, a new study published in the American Journal of Epidemiology says that milk consumption in large quantities in adolescence can increase the risk of advanced prostate cancer.
The study was led by Johanna E. Torfadottir from the University of Iceland. The research team followed 8,894 men that were born between 1907 and 1935. These men came from different areas of Iceland where regular milk consumption varied based on availability in the area. They followed these men for 24 years.
Throughout those 24 years, 1, 123 men developed prostate cancer with 371 of those being advanced prostate cancer.
Their study results showed that those men that lived in the capital, where milk was scarce at the time, were 29 percent less likely to be diagnosed with advanced prostate cancer. For those men that were born before 1920 and lived in rural areas and consumed regular amounts of milk, the risk was as much as 64 percent higher than those in the capital.
While this study was observational and does not show a direct cause between milk and prostate cancer, other studies have shown there may be a link. Researchers D. Margel and N.E. Fleshner from the University of Toronto published a study in BMJ Open linking the estrogen found in cow milk to an increased risk of prostate cancer.
Another study published in the November 2011 issue of Nutrition and Cancer shows that cow milk promoted the growth of LNCaP prostate cancer cells by 30 percent.
The Western diet is far richer in milk and dairy products than other developing countries. This may explain why the risk of prostate cancer is also higher in the West than other countries.
Researchers do not believe that this is enough to recommend that teenage boys reduce their milk consumption. There are many health benefits that milk does provide during adolescence and these benefits need to be weighed against the risks.
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More information: Milk Intake in Early Life and Risk of Advanced Prostate Cancer, Am. J. Epidemiol. (2011) doi:10.1093/aje/kwr289
The authors investigated whether early-life residency in certain areas of Iceland marked by distinct differences in milk intake was associated with risk of prostate cancer in a population-based cohort of 8,894 men born between 1907 and 1935. Through linkage to cancer and mortality registers, the men were followed for prostate cancer diagnosis and mortality from study entry (in waves from 1967 to 1987) through 2009. In 20022006, a subgroup of 2,268 participants reported their milk intake in early, mid-, and current life. During a mean follow-up period of 24.3 years, 1,123 men were diagnosed with prostate cancer, including 371 with advanced disease (stage 3 or higher or prostate cancer death). Compared with early-life residency in the capital area, rural residency in the first 20 years of life was marginally associated with increased risk of advanced prostate cancer (hazard ratio = 1.29, 95% confidence interval (CI): 0.97, 1.73), particularly among men born before 1920 (hazard ratio = 1.64, 95% CI: 1.06, 2.56). Daily milk consumption in adolescence (vs. less than daily), but not in midlife or currently, was associated with a 3.2-fold risk of advanced prostate cancer (95% CI: 1.25, 8.28). These data suggest that frequent milk intake in adolescence increases risk of advanced prostate cancer.