The science of saline – why can we drink pure water, but when we put water into our bodies in other ways, like an IV, must we add minerals to it?

Question

The science of saline – why can we drink pure water, but when we put water into our bodies in other ways, like an IV, must we add minerals to it?

In: 480

Answer 1

It’s all about tonicity which is a fancy way of saying concentration of stuff (e.g., electrolytes). Nature likes for concentrations to be equal, so if you inject pure water into your veins, the water (no stuff) will enter your cells (lots of stuff) to try to equalize the concentrations. The problem is, if too much water enters your cells, they’ll burst and die. If you add enough stuff to the water so that the concentrations are equal, the water will stay in your veins without going into your cells.

If you have too much stuff in the water, you can also cause water to leave your cells (like pouring salt on a slug), which would cause them to shrivel up.