Hydration Blog

How can a sports drink possibly hydrate better than water?

Saturday, February 11, 2023

On 4th January 2012, the Advertising Standards Agency (ASA) met to consider complaints that Powerade ION4 as advertised by Jessica Ennis, World and European Heptathlon Champion, was making claims that were misleading.  According to the advert and Ennis’ testimonial it was claimed that Powerade ION4 ‘hydrates (me) better than water’.  The ASA considered evidence from Coca Cola Great Britain as well as published scientific evidence and experts and the hydration claim was accepted (see http://www.asa.org.uk/ASA-action/Adjudications/2012/1/Beverage-Services-Ltd/SHP_ADJ_156530.aspx for adjudication details.

How can anything possibly hydrate better than water? Surely hydration and water are synonymous? While intuitively one would think so, it’s not that simple.  For the body to be better hydrated the drink has to retained by the body.  When comparing to another drink this can be shown simply by an increase in body weight with less urine production.  A more complex method using blood sampling (Dill and Costill method) is used to show an increase in plasma volume.  The benefits of improved hydration in sport are indisputable, especially in the context of intense exercise as Coca Cola GB took great pains to explain during the adjudication.

Almost all scientific trials looking at which drink hydrates better involve a cross-over design.  An athlete is randomly exposed to one drink and tested under controlled conditions with a standard exercise regime often in a climate chamber.  The test is then repeated usually 2-3 weeks later with the second drink being evaluated.  Quite a few such trials have been published with convincing evidence that electrolyte containing drinks result in better retention as evidenced by increased body weight and plasma volume. The electrolyte responsible for this retention is sodium – in fact the only electrolyte so far recognized scientifically to confer any benefit in rehydration. The drinks also tend to typically contain around 6% carbohydrate for energy as well as promote water uptake in the gut.

Our own Precision Hydration trials in elite athletes have replicated these findings. 72 hrs ad libitum drinking of an electrolyte drink specific to sweat sodium losses compared to Evian water showed that our electrolyte drinks (H2ProHydrate) containing zero carbohydrates resulted in a weight gain of around 0.72 kg (1% increase) with the greatest fluid retention seen in those who lost most salt in their sweat (1.72%).  One would think that weight gain translated to poorer performance. But as published scientific evidence has shown, this increased fluid retention results in improved performance.  In our trials we saw a 7.3% power output increase across all the athletes while on H2ProHydrate with peak gains of 23% seen in high salt sweaters who retained the most fluid.

All in all the addition of electrolytes, primarily sodium, to water makes it a better hydrator than water alone by a magnitude of around 11-20% (although claims of up to 40% have been made by some).  Being better hydrated increases weight slightly but the performance gains seen far outweigh this.

So it is good to see that sometimes sports drink marketing messages are more than just hype – although the fact that people contest marketers claims so vigorously in court does go to show how much mistrust there is of advertising these days….even when it is telling the truth!

Dr Raj Jutley
Chief Medical Office

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