As we approach warmer weather, we wanted to discuss proper hydration, hydration fallacies, and potential dangers associated with over-hydrating. This is especially important for those of us training for endurance races.
The lessons learned in the endurance community to can be used to employ an effective hydration strategy. Many of the issues and complications that occur during and after endurance events are not associated with dehydration. Rather, they are cause by Exercise-associated Hyponatremia. This occurs when sodium levels fall below the normal blood sodium range of 135-145 mmol/L (millimoles per liter).
How does the happen?
For years endurance athletes, and every athlete for that matter, have been told to continuously drink water and sports beverages. The problem with consuming high quantities of these liquids before and during activity is that they lead to the dilution of the body’s blood sodium levels. As a person continues to consume liquids and sodium levels drop, water is driven into the cells and can cause the lungs to fill with fluid, the brain to swell, and multiple other issues.
This occurs during sport and exercise because the body goes into protection mode due to the possibility of losing fluid through sweat. The body will secrete a hormone, vasopressin, which is an antidiuretic that helps the body retain fluid. When we are not active, our body will not secrete this hormone, we will just make more frequent trips to the bathroom.
What, and how much, should I consume?
At first glance, it would appear that consuming sports drinks would help us avoid these risks; however, this is not the case. Sports drinks are not salty enough to maintain the proper sodium levels. As mentioned above, normal blood sodium levels are somewhere in the range of 135-145 mmol/L. Sodium concentration in Gatorade is 19 mmol/L. This means that the consumption of Gatorade will contribute to the further dilution of blood sodium.
For athletes with high levels of daily exercise or training, the loss of sodium can be significant. One way to counter that is to consume salty foods or soups between training sessions. Mid-workout sodium supplements do not help maintain sodium levels; whatever is ingested gets excreted. According to Dr. Martin Hoffman “one man ran 100 miles in 18 hours and took 7,000mg of supplemental sodium. When he collapsed at the end of the race, his blood sodium was 127 mmol/L, well below the normal range.”
For the average person who exercises on a daily basis at normal levels, the loss of sodium can normally be replenished through normal nutrition.
When to consume
According to Mitchell Rosner, a nephrologist and professor of medicine at the University of Virginia, habitual exercisers should weigh themselves before and after a workout to get a sense of how much they sweat. Once you know how much you sweat, you should drink that much after exercise. You will not be at risk for hyponatremia because, as highlighted above, your body is no longer secreting vasopressin, so the main side effect if you overhydrate is a greater number of visits to the restroom.
Another, simple approach, is to drink to thirst and to not pre-hydrate. According to Dr. Tamara Hew-Butler “ Your body is really well adapted… For us, thirst is like your real-time calculator for everybody. Thirst is going to save you from dehydration and hyponatremia. It’s the best thing that is going to keep you in the middle.”
This is not to say you shouldn’t consume water or sports drinks during sport or training. This is to say that most people get into trouble by consuming too much. Listen to your body, be prepared, and have fun.