If I was to be asked “what is the most frequent question you get in relation to heat stress?” I could respond without hesitation. It would have to be “What should you drink?” This is a question that has been heavily researched over the years, just type in heat stress & fluids or drinks into a search engine and watch it go ballistic. So why should a topic that is so well studied and discussed still cause so much confusion? My response here could easily be the beginning of a long and involved discourse but I will try to keep it to one page. I will give you a few references at the end to hunt down should you need more detail.
First off, the most cost efficient and effective solution for me is just plain cool water. I can already see some sports drink suppliers starting to warm up the keyboard and ready to fire away the numerous references of studies done demonstrating the benefits of electrolyte supplement drinks. Now I am not challenging the validity of these products as they do have their place in the rehydration process. I have a colleague who suffered terribly and ended up in hospital in Africa despite maintaining their hydration level with water. And we have probably all heard about “hyponatraemia” the water sickness. There’s also a great study done by two medicos from Brisbane in relation to this and the Kokoda trail (see link below).
However, I would still challenge the difference in normal scenarios and the cost benefit analysis of the requirement of such a product as a replacement for water. And let’s face it, whether we like it or not, in industry in particular you need to be able to demonstrate there is a recoverable benefit for the additional cost.
For what it’s worth (and I profess no medical expertise here), this is what I recommend for the average person. In the majority of cases plain cool water will suffice. Our diets are already heavily loaded with salt and if you are acclimatised the hormone aldosterone will help reduce salt lost in the sweat.
If however you do anticipate a heavy day in the heat be it at work or in sport I suggest an electrolyte drink before you start, then another electrolyte drink half way through and then at the end of the session. In between just keep re-hydrating with plain water. Not rocket science. Bear in mind that individuals do vary and illnesses can also have an impact.
There is one other aspect I will touch on before I finish. A lesson learned from experience. If the water tastes unpleasant you are fighting an uphill battle. This is where I find the electrolyte additives on the market have an additional value. If it tastes good they will drink it. And also bear in mind, it doesn’t matter how scientifically precise the osmolality of the drink is or “how much quicker it is absorbed” etc. If it tastes like camel sweat NO ONE WILL DRINK IT. Never underestimate the importance of palatability.
I have not touched on the rehydration “icy poles” now available (I love them in summer but that is purely a throw back to my childhood), maybe a topic for another day.
Want to know more, here’s a start?
Clapp, A, Bishop, PA, Smith, JF, Lloyd, LK & Wright, KE (2002). A Review of Fluid Replacement for Workers in Hot Jobs. Am Ind Hyg Assoc J, 63: pp 190-198.
Nevola, VR, Staerck, J, Harrison, M., (2005). Commander’s Guide: Drinking for optimal performance during military operations in the heat. Defence Evaluation and Research Agency Centre for Human Sciences, Farnborough,
Kenefick, RW & Sawka, MN (2007). Hydration at the Work Site. J Am College Nutrition, 26(5); pp 597S–603S.
Sawka MN, Burke LM, Eichner ER, Maughan RJ, Montain SJ & Stachenfeld NS (2007). American College of Sports Medicine position stand. Exercise and fluid replacement. Med Sci Sports Exerc, 39(2): pp 377-390.