Science Questions

Does too much calcium make your bones brittle?

Sun, 17th Jan 2010

Listen Now    Download as mp3 from the show Does farting make you weigh less?

Question

Liam asked:

Does too much calcium make your bones brittle?

Answer

The answer is, yes it does, surprisingly. Calcium links up with phosphates to make the chemical "apatite" (calcium phosphate), one of the hardest chemicals we know, which is what makes bones hard and stony, and tough.

But if you have too much calcium, that can be as bad as having too little, as in condition osteoporosis where the bones actually begin to lose their calcification and the matrix of the bone, which makes them weak and more likely to break. Thereís also another disease called "osteomalacia" where you have too little just of the calcium and that also makes bones weak. 

But some people actually lay down too much calcium in bone, a condition called "osteopetrosis" from "petros" as in stony.  This is where people can have say, five times the amount of calcium in their bones that they should have.  Itís a genetic condition.  Itís very rare and I think it also goes by the name "Albers-Schonberg disease" or something like that, but itís very rare. 

In these individuals, the cells that break down bone, called "osteoclasts", don't work properly.  This is because the way bone is normally formed involves an equilibrium between laying down new bone and breaking down old bone, and thatís how bones are continuously remodelled. 

So if you shift that equilibrium on one direction or the other, you either lose or gain bone. And what scientists have found is that in people who have osteopetrosis, the osteoclasts that normally breakdown bone cannot work properly.  They have a deficiency of an enzyme called "carbonic anhydrase" and you need that to break down the calcium phosphate, the apatite, in order to remodel the bone. 

As a result, they just keep on making their bones get harder and harder, and harder.  Eventually they go beyond the point of this being beneficial and the bones become less flexible and more likely to break, so they get very brittle.

Multimedia

Subscribe Free

Related Content

Not working please enable javascript
EPSRC
STFC
Genetics Society
ipDTL