What is milk pure substance and why?

The basic fluid in milk is water but added to the water are proteins, sugars and fats. This makes milk a mixture of substances not a pure substance.http://wzus1.ask.com/r?t=p&d=us&s=usseo&c=qasp&app=a16&dqi=&askid=&l=dir&o=0&oo=0&sv=0a5c404a&ip=0e666c24&id=014B3730032E5F393D262D6B99CE67AC&q=Is-Milk-a-Pure-Substance&p=1&qs=121&ac=169&g=18efhRmp51WQXe&cu.wz=0&en=af&io=0&ep=&eo=&b=qai&bc=&br=&tp=top&ec=3&pt=%20Read%20More%20»&ex=&url=&u=Is_Milk_pure_substance