There really isn't a great deal new here. In t'old days when working reet 'ard in warm weather we consumed "salt tablets" dissolved in water. Yes!
Perspiration is more than H20 - there are salts and electrolytes there too. So? what's the message here?
Easy - don't go lite - go smart! There are very pleasant ways to increase electrolyte levels when working 'ard in summer sun. One of my faves is a lovely little pack of olives...