A new paper has found that the chemical citrate – a by-product of natural cell metabolism – is mixed with water to create a viscous fluid that is trapped between the nano-scale crystals that form our bones. This fluid allows enough movement, or 'slip', between these crystals so that bones are flexible, and don't shatter under pressure. It is the inbuilt shock absorber in bone that, until now, was unknown.
If citrate leaks out, the crystals – made of calcium phosphate – fuse together into bigger and bigger clumps that become inflexible, increasingly brittle and more likely to shatter. This could be the root cause of osteoporosis.