NEW YORK • Elite runners often turn to sports drinks to keep essential minerals in balance, but a new study shows these products can actually contribute to a dangerous medical condition when temperatures are high.
The best way to avoid life-threatening hyponatremia - when the body's sodium levels dip dangerously low - is by training better, keeping fit, and avoiding excess water or sports-drink consumption, researchers report in the Clinical Journal of Sports Medicine.
"There have been recorded fatalities in people who did nothing but drink electrolyte-containing sports drinks," said co-author Grant Lipman, a clinical professor of emergency medicine at the Stanford University School of Medicine and director of Stanford Wilderness Medicine.
"The trick is to listen to your body and drink only when you are thirsty. It's important to realise that sports drinks won't protect you and might even harm you."
Endurance athletes have long been cautioned to protect themselves from dehydration and its accompanying high sodium levels, but the concern should be exercise-associated hyponatremia (EAH), which can be fatal, Dr Lipman said.
In fact, 14 deaths from EAH have been documented since 1985.
To look at the impact of electrolyte supplements on the health of endurance athletes, Lipman and colleagues recruited 266 ultra-marathoners from RacingThePlanet's week-long events, which involved running 240km over seven days across rough terrain in extreme weather conditions at deserts around the world.
Each of the volunteers ran in one of five different races in 2017 in South America, Namibia and Mongolia.
Before the races, Lipman and his colleagues asked the volunteers what electrolyte supplements they planned to use, how often they planned to take them and what their drinking strategy was.
In particular, with regard to drinking strategies, the researchers wanted to know if the runners planned to drink at regular intervals or when they were thirsty. The vast majority of runners said they used electrolyte supplements.
At the beginning of each event, the researchers collected data, including blood samples that would be tested for sodium levels, and measured the runners' weights.
At the end of the races, before the runners hydrated or rested, the researchers once again weighed them and drew blood samples.
When the researchers analysed their data afterwards, they found that 41 of the runners had salt imbalances upon finishing the races: 11 had too little sodium and 30 were dehydrated and had too much sodium in their blood.
Several factors predisposed runners to developing EAH: higher temperatures during the race, a shorter time training in preparation for the race, higher weight at the outset and taking five to six hours longer than other competitors to finish the race.
Another important factor was over-hydration - consuming too much water or sports drink.
Lipman notes that one popular sports drink has six times less salt than is found in the blood of a healthy person, so consuming this drink will also dilute salt levels in the blood.
While experts have known for years about the risk for EAH, the new study provides some actual data, said Dr Melissa Leber, an associate professor of orthopaedics and emergency medicine at the Icahn School of Medicine at Mount Sinai, in New York City.
The best way to avoid EAH is to carefully prepare for races, said Leber, who was not involved in the new research.
"You should have a fluid replacement plan based on your average sweat rate," she explained.
"If you are going to be doing these (ultra-marathons), you need to be taking straight salt tablets at a rate that will be based on how much you are losing."
Though most people don't know their sodium levels are dangerously low until they are already in trouble, there are some warning symptoms that include confusion, nausea, muscle cramping, dizziness, fatigue and headaches, Leber said.
If the condition is not reversed, an athlete can develop respiratory distress and, sometimes as a result, encephalopathy, or brain disease.
"The end result is coma and death," she said.
REUTERS
