You have probably heard that you should drink milk because it builds strong bones. This is true because milk and other dairy products are good sources of calcium, which is necessary for strong bones. Studies have shown that children ages 3–13 who don't drink milk break their bones more easily. But as we will see, it takes much more than calcium to make strong bones. Calcium adds strength to bones because it is a mineral. Minerals are naturally occurring chemical elements and compounds that are solid and crystalline (made of orderly crystals). In bones, calcium is combined with the elements phosphorus, hydrogen, and oxygen to form a very hard crystal called hydroxyapatite.
But strong bones require more than hardness. If bones were made out of pure hydroxyapatite (like the enamel of our teeth) they would be very hard but brittle and would actually fracture more easily.
[Read the rest of the article at Answers in Genesis.]