Sugar

Refined sugar (like white sugar) has a high acid-forming effect on the body.  If the body is too acidic, it leaches calcium from the bones to neutralize the acid.  This causes weaker bones. 

The more I read I'm amazed how bad refined sugar is for us.  I was just reading today that sugar feeds the bad bacteria in the intestines.  I've also been reading how sugar increases inflammation in the body.