The brush border cells in the intestine use calcium and magnesium as a barrier to prevent absorbtion of heavy metals.
That means that if you get your first morning pH balanced out your exposure to metals is greatly reduced as you are excreting most of the metals through the gut. This is a godsend for people with amalgams.
Before any heavy metal detox program you should get your first morning pH balanced out. Otherwise you are going to be reabsorbing far more heavy metals than you should.