Calcium and Magnesium are both Alkaline Minerals, so they both may neutralize body Acids!
Magnesium may neutralize 1.4 times as many Acids as what Calcium may do so!
And because of this difference in neutralizing power, this may be how come the body may need much more Calcium in the long run!
It may be because of this power of neutralization, that the magnesium may solve the problem of cramps under conditions where the body is too short of Magnesium because of too much excess Proteins of the Funny protein kind, but "IF" the body does not have enough Calcium to begin with , then "NO" amount of magnesium may completely solve the problem!
As people who have taken much magnesium over the years and not enough calcium, may be able to tell you it is so!