Monday, 27 August 2012

Rethinking the science of hydration

True or False?

  • Thirst is not a reliable gauge of a body's need for water
  • Urine colour is a reliable gauge of hydration (dark=dehydrated; light = well hydrated)
  • It is better to rehydrate with a sports drink after exercise than with water
  • We should weigh ourselves before exercise, and after. We must then drink enough fluid to make up for that weight loss to ensure complete rehydration 
  • Exercise-induced hyponatremia (low blood sodium) or electrolyte imbalances can be prevented (or avoided) by  drinking a sports drink during and/or after exercise rather than just water
  • People get sick and/or collapse due to dehydration during sporting events where fluid is provided. 

 I would have answered 'true' to most, if not all, of these statements. In fact, I learned that many of these statements are true in school. However, last month, BMJ published The truth about sports drinks that shed some light on the science behind dehydration and sports beverages. 

The article describes clever marketing tactics on the part of the sports drink industry, including providing funding to scientists and science journals. For example, they reveal that Medicine and Science in Sport and Exercise, one of the leading sport medicine and exercise science journals,  is owned by the American College of Sports Medicine that has financial ties to Gatorade and Powerade. Many of the editors on the editorial board have (and have had) ties with sports drink companies. 

The article explains that this marketing, and hijacking of the science of hydration, has undermined our confidence in our own thirst mechanisms. 'They' have us believe that our bodies are unable to tell us when we're thirsty; that not drinking enough before, during or after exercise, can make us very sick ; that rehydrating only with water rather than a sports drink can cause the potentially fatal hyponatremia. 

However, according to this article, there is no evidence that anybody has ever gotten ill due to dehydration during a sporting event when fluid was available. That is because our bodies tell us when it's thirsty, and we drink to satisfy our thirst. 
Simple as that. 
The article also explains that overhydration can lead to electrolyte imbalances and is potentially very dangerous, but can occur by drinking sports drinks just as it can by drinking too much water. 

I highly suggest you read the article- it's definitely interesting. 

Here's a bit more from Professor Tim Noakes, Discovery health chair of exercise and sports science at Cape Town University:

Thank you, Umang!