With August football practice fast approaching, every coach's favorite cheer will be to "stay hydrated" and "keep urine clear" during the summer heat. In 2017, a University of Texas football coach created a urine-based "Longhorn Football Hydration Chart," which labeled players with yellow urine as "selfish teammates" and those with brown urine as "bad guys." This "hydration shaming" practice has permeated high school sports, thereby encouraging a sporting culture which equates superior performance with superior hydration.

Overzealous obedience to this hydration advice has uncovered a dark underbelly to superior hydration practices: overhydration. When high school football player Walker Wilbanks died in Mississippi in August 2014 from overhydration, the doctor said that the cause of death was an "unpredictable freak occurrence."

Two weeks prior, another high school football player from Georgia drank "two gallons of water and two gallons of Gatorade" after football practice to prevent muscle cramps and then died. Thus, over the last four years, two high school football players have died during August football practice from overhydrating—a medical condition known as exercise-associated hyponatremia.

The molecular and neural circuits that govern fluid intake (and micturition) in real-time are absolutely exquisite. It's remarkable to think that animals survive without water bottles and urine charts – they drink when they are thirsty, and we should too.

Too much water, too little salt

Hyponatremia is caused by drinking too much water or sports drinks, which dilutes blood salt levels below the normal range. Any sudden drop in blood salt levels, from drinking more than the body can excrete, can cause all cells in the body to swell. Brain swelling from hyponatremia can cause headaches and vomiting, while muscle cell swelling can trigger whole-body muscle cramping.

Dehydration is undeniably harmful to human health and performance. Wrestlers have died from trying to "make weight," through vigorous dehydration practices. A recent meta-analysis of 33 studies verified that more than 2% dehydration impairs cognition.

When do athletes and others need to drink?

So how much fluid should football players – and all other humans for that matter – drink? If you ask fluid balance experts who perform basic science research on the brain or kidney, or clinicians who specialize in fluid balance disorders, researchers who perform brain scans on dehydrated and overhydrated humans, or even worm investigators, they all agree that water balance is tightly regulated and that all land mammals need to drink when thirsty.

Drinking when you are thirsty is not "too late," because the thirst mechanism is hardwired into the nervous system to protect against scarcity. Thirst represents the highly individualized signal which protects the balance between water and salt regardless of size, activity or ambient temperature and is encoded in most invertebrate and all vertebrate DNA. Babies are born with this innate behavioral drive.

What's a football player to do?

Football players absolutely need water, but they should be warned not to overdo it. In the modern era, where the fluid is widely available, in order to stay adequately hydrated, the following must occur:

  1. A variety of fluids needs to be freely available to football players, and
  2. The players should be given the freedom to drink whenever they feel thirsty.

And when the players get hot, they need the opportunity to pour generous amounts of ice water over their heads instead of into their mouths to promote evaporative cooling, rather than dilute sodium levels. Better yet, they should be allowed to go inside and cool off.

We should recognize who the "true champions" may be with regards to most modern day hydration advice. According to the latest figures, bottled water sales have increased to US$18.5 billion dollars, up 8.8% from the previous year.