They say milk does a body good, but there has been some recent research showing that dairy may be causing some new and alarming problems.
Dairy products boost the amount of insulin-like growth factor (IGF-I) in the blood. In turn, IGF-I promotes cancer cell growth. A small amount is normally in the bloodstream, but several recent studies have linked increased IGF-I levels to prostate cancer and possibly to breast cancer as well. Milk does other mischief.
Prostate cancer is one of the most common malignancies worldwide, with an estimated 400,000 new cases diagnosed annually. Its incidence and mortality have been associated with milk or dairy product consumption in international and interregional correlational studies.
Two studies in northern Italy compared prostate cancer patients to hospital controls, finding increased risk of prostate cancer among those with the most frequent milk consumption. Similarly, a study at Roswell Park Memorial Institute in Buffalo, NY, found an increased risk of prostate cancer with the daily consumption of three or more glasses of whole milk, compared to never drinking milk. In Montevideo, Uruguay, a comparison of prostate cancer patients to hospital controls, most of whom had other forms of cancer, found an increased risk of prostate cancer associated with drinking two or more milk servings per day, compared to having less than one serving per day.
Men who choose to avoid dairy products reap other nutritional benefits, such as a reduction in total fat, saturated fat, and cholesterol intake. Unless they replace dairy products with calcium-fortified products or calcium supplements, they are likely to reduce their calcium intake in the process. However, a reduction in calcium intake may be an important mechanism by which reducing or avoiding dairy products reduces prostate cancer risk. Moreover, there is no apparent risk to moderate reductions in calcium intake. There is little evidence to suggest that a high intake of calcium from dairy or other sources reduces the risk of osteoporotic fractures among men.