Excessive consumption of milk is associated with a host of western lifestyle diseases. It is not a 'natural food'. Drinking milk is only natural for any species during infancy, and never into adulthood. Add to this the fact that human beings are the only species that drinks hormonal mammary gland fluids from another species and it becomes easy to see that drinking cows milk is entirely 'unnatural' for humans!
According to Dr. Michael Greger, "Consumption of cow's milk can upset our body's hormonal balance." This increases our levels of Insulin Like Growth Factor-1 (IGF-1), which promotes the growth of cancerous tumors. Check out Dr. Greger's two minute video clip regarding the dangers associated with dairy products.
Some other articles and blogs that might interest you:
1) Dairy Products Promote Prostate Cancer
2) Dairy Intake Blocks Antioxidant Absorption
3) Avoid the Negative Effects From Dairy by Choosing Plant Foods for Calcium