In the fitness world, we’re often advised to drink plenty of water to stay hydrated. Advertisements for electrolyte-enhanced sports drinks abound, and stainless steel bottles have practically morphed into an athleisure fashion accessory. Although a tall glass of ice-cold H20 feels divine after that HIIT workout, in some cases downing too much of the stuff can lead to serious health consequences. The risk is rare, but it’s real. We asked experts to explain hyponatremia, or water poisoning, and how to avoid it.
What is hyponatremia?
Here’s how it works: Your body strives to maintain the perfect balance between sodium and water. Sodium is a mineral as well as an electrolyte, crucial for maintaining blood pressure. It also helps nerves and muscles function properly.
Normally when we drink water during a workout, the amount is small enough for the body to handle—a few sips here, a couple chugs there. But when large volumes of water are taken in, “it can disrupt the delicate sodium balance,” says ACE-certified personal trainer Pete McCall, host of the All About Fitness podcast. The amount of sodium in your body’s fluids drops below normal, prompting water to move into the cells in an effort to balance things out. As a result, the cells swell with excess water. Brain cells are especially susceptible. “You can essentially drown your brain and organs,” McCall says. No surprise, then, that hyponatremia is also called water intoxication or water poisoning.
It sounds scary, and it is. Not only can hyponatremia cause confusion, headache, appetite loss, muscle weakness, cramping, and vomiting, but it can also be life-threatening if not swiftly treated.
Who is at risk?
Fortunately, hyponatremia is not a risk for most people, even avid exercisers, says George Chiampas, D.O., medical director for the Bank of America Chicago Marathon. “It’s sometimes seen in endurance events—half or full marathons or ultra-type events,” he says. “But for 30 or 60 minutes of exercise, even intense exercise, the risk is extremely low. You simply don’t have enough time to drink the large amount of water that would be required to cause hyponatremia.”
For these individuals, McCall says drinking three to six ounces every 15 minutes or so should be more than adequate, hydration-wise, and shouldn’t pose any risks. But if you’re not thirsty, don’t force yourself. Click here for more info on how much water you really need.
But what if you are gearing up for an endurance event? The key, Dr. Chiampas says, is having a proper hydration plan. “Sometimes runners will start over-hydrating days before an event occurs, so before they even start running the race, they already have a low salt content in their body.” Then as they begin running the race, water stations are positioned throughout the course, causing their sodium content to drop even more.
Dr. Chiampas says that thin women with a low body mass index who run longer than four hours tend to be at highest risk.
How do I make a hydration plan?
To formulate a safe hydration plan, Dr. Chiampas recommends this protocol for anyone working out longer than an hour at a time: First, step on a scale naked and capture your weight. Next, complete your workout, drinking water as you normally would. When finished, weigh yourself naked once again (you’ll want to peel off any sweat-soaked clothing). “If you are appropriately hydrated, you should not have lost more than two percent of your body weight,” he says. Gained weight? You’re drinking too much. Lost more than two percent? You’re not drinking enough.
It’s also important to swig electrolyte-enhanced water or drinks such as Gatorade during marathons, triathlons, and other endurance events, especially if it’s hot or humid outside, which promotes further sodium loss via sweating. Dr. Chiampas adds that if you’re a “salty sweater”—salt is visible on your clothing or skin post-workout. If your skin has a chalky sensation from lingering sodium, you may need extra salt during your endurance events. Talk to your health care provider for more guidance.