[utensil4778]

For anyone else wondering: your body is continually pulling calcium from your bones for metabolic processes. Usually it gets replaced when you consume something with calcium in it.

It makes sense to have somewhere to store extra nutrients so you can keep functioning for a long time between taking in those specific nutrients again.

Your body does this with a lot of your organs. Fat is obviously calorie storage, but muscles can also be resorbed for energy under starvation conditions (or just when they're under used). Your kidneys can resorb water from stored urine, and your intestines pull most water out of what you consume. Most neurotransmitters and hormones get recycled at various rates and turned into new molecules.

I'm sure there's more, but that's all I know of offhand.