In our second post, we showed how clever marketing campaigns helped spark a dramatic shift in these generally accepted principles. In an effort to increase sales of their hydration beverage, Gatorade touted the dangers of dehydration and its (supposed) side effects: heat stroke and muscle cramps.
In this post we will look at these claims, as well as the science behind them.
We’ll start with the US Military. According to Tim Noakes, about 30 years ago the military also began adhering to the “more is better” hydration theory. Military guidelines were written, stating that soldiers should drink 1.9 liters per hour, which would help ward off dehydration and heat sickness. However, over the course of several decades, these recommendations had caused about 100 hospitalizations per year, and at least six deaths.
As Noakes writes, however, the military quickly realized their mistake,
"Because of its exquisite monitoring system, within a few years of producing the wrong guidelines, they realized they had it wrong."
By 1998 the hydration guidelines were cut in half, to what Noakes considers much more reasonable levels. But what does that really tell us? We all know that too much water can be potentially dangerous, but isn’t the risk of overhydration less concerning that the dangers of dehydration?
If you listen to marketing campaigns run by the sports drink industry, then the answer is a resounding “yes.” After all, industry-funded researchers have been studying the effects of dehydration for nearly 50 years. Establishments like the Gatorade Sports Science Institute have continued to churn out studies that stress the dangers of dehydration, promoting the practice to essentially drink as much as you can.
Well, according to the British Medical Journal, these “studies” don’t tell us much. In a 2012 investigation into the world of hydration research, the BMJ had this to say, “As it turns out, if you apply evidence based methods, 40 years of sports drinks research does not seemingly add up to much, particularly when applying the results to the general public.”
There were many problems with the claims made by sports drinks, as well as the methodology for their studies. Investigators looked into the industry-sponsored studies from the years 1971-2012, the results from which were used to support more than 431 performance-enhancing claims made about 104 products. 75% of the studies were rated “low in quality”. Only 2.7% of the studies were judged to be of high quality and also at a low risk for bias.
The BMJ researchers took particular interest in a claim that you’ve probably heard before: Drink before your feel thirsty.
At the time of the BMJ’s investigation, Gatorade’s website stated:
“Your brain may know a lot, but it doesn’t know when you’re body is thirsty. You need to drink during exercise before you feel thirsty in order to get enough fluids in your body to maintain your performance level.”
You’ve probably heard it since you were a child in gym class. By the time you feel thirsty you’re already dehydrated. Well, the evidence - and the British Medical Journal - disagrees. Investigators reported:
“Drinking according to thirst sensations (as opposed to drinking more or less frequently) was associated with better sports outcomes. One of the studies in the review found that exercise induced dehydration of up to 2.3% of body weight significantly improved performance. The explanation for how exercise induced dehydration might improve performance is straightforward: you carry less weight, and you don’t have to interrupt your exercise.
Although we could not find a report in the medical literature of dehydration being a direct cause of death in marathon runners, we did find overhydration was responsible for several deaths. By following advice to “drink before thirst,” many athletes are drinking too much, which does not help performance and puts them at risk.”
The researchers concluded that our brains ultimately do know when to hydrate, and its the best and safest gauge we have. In our next and last post on the subject, we’ll explore some of the other dangers of overhydration, including muscle cramps.