How much sodium do I need?

In this series of blog posts we’ve discussed what sodium is, what it does in the body, how it’s lost in sweat, and how to quantify those losses. In this post, we’ll discuss how to decide if sodium needs replacing during exercise, and whether a targeted approach is necessary or not.

Sodium decision chart

Why do we need to replace sodium?

As discussed in a previous post, sodium consumed during exercise may have benefits in terms of:

  • improving the taste of drinks

  • maintaining blood sodium concentration and osmolarity

  • increasing blood volume retention

Currently there is minimal if any evidence that sodium replacement can actually improve exercise performance, at least exercise of less than 4 hours.

Note that for the reasons described above, the first does not require sweat sodium testing, simply ‘season to taste’. The second reason is where quantifying sweat sodium losses might be potentially helpful. So when does it matter?

Predicting sodium replacement needs