When I was on coffee, I used to get feeling of calcium insuffiency, like
aching calves.(even when on supplements) Now I feel great off of the coffee.
(even with no calcium supplements)

 I think the 1200 mg recommendation is because most people on SAD are
leaching so much calcium due to caffeine, sodium, etc.

I have also had a similar explanation given to me, but only once.  Your
>explanation makes it clearer.  Apparently the parathyroid glands control
>this mechanism.  I was told that high calcium levels in the blood cause the
>paras to shut down the bone-building process, thinking there is plenty of
>calcium in the blood...and leeching it out.  Your diabetes analogy sounds
>right on...a kind of calcium insensitivity!  Thank you.