Does Coffee render Calcium in Milk useless?

I usually drink Milk Coffee because I don't really like plain milk, even with sugar. But according to other internet sources, I've heard that you lose four to five milligrams of Calcium with each cup of coffee. I still don't understand why or whether it's from the Milk or actually from your bones (which I find weird for some reason...) but this is a negligible amount and won't affect my bones or Calcium levels adversely if the caffeine is reducing Calcium levels in my bones..., but does this mean that even Milk Coffee is not a substitute for a higher Calcium intake at all? Would it help if I drank decaffeinated coffee with milk? I really couldn't find a clear answer online, so I thought I'd ask someone here... :)