Brooke Shields recently had a seizure as a result of overhydrating. At what point does H2O become dangerous?

In a new interview with Glamour, actress Brooke Shields revealed that she suffered from a seizure while in New York this past September.

“I was preparing for [a] show, and I was drinking so much water, and I didn’t know I was low in sodium,” she recalled. “I was waiting for an Uber. I get down to the bottom of the steps, and I start evidently looking weird, and [the people I was with] were like, ‘Are you OK?’”

The 58-year-old star remembers walking into a restaurant while in a daze right before “frothing at the mouth, totally blue, trying to swallow my tongue.” Candidly talking about the event on the record, Shields told the publication that she “drowned” herself by drinking too much water.

According to Dr. Jonathan Parker, a neurosurgeon at Mayo Clinic in Arizona, some seizures can be caused by excessive water drinking.

“A tonic-clonic seizure refers to a type of seizure during which you notice a stiffening and then a jerking of muscles,” he said. Parker explained that during such an episode, abnormal electrical activity in the brain spreads to both hemispheres, disrupts the natural order of things and causes unusual physical activity.

A tonic-clonic seizure can be provoked or unprovoked. “Unprovoked ones are the result of structural issues like tumors, prior stroke history, something you can’t pinpoint right away,” Parker said.

Provoked tonic-clonic seizures, on the other hand, can be caused by certain medications, brain trauma, excessive fever and electrolyte abnormalities. What happened to Shields likely belongs in the latter category of possibilities.

Parker explained that average potable, naturally occurring water is low on electrolytes. As a result, drinking too much of it can risk diluting the electrolytes present in the blood and affect blood sodium levels ― a drop that would cause a seizure.

“Your blood sodium level can drop dramatically if you drink excess water because [the water] boasts fewer electrolytes than your body and will therefore dilute what is in your blood,” he said.

How to tell if you’re drinking too much water

How much water is too much water? How can we avoid flooding our system?

According to Parker, “There are a lot of factors to keep in mind: your body size, how long you’ve been outside for, and if you’re sweating and losing liquid, for example,” he said, specifically noting that “it’s rare that people drink so much water as to cause an electrolyte abnormality that causes a seizure.”

According to the Mayo Clinic, the average, adequate amount of fluid intake is around 15.5 cups for men and 11.5 cups for women in temperate climates. This includes any type of fluid, though, including other beverages and hydrating foods.

Parker suggested paying attention to how thirsty you are when trying to gauge how much to actually hydrate.

“There’s no one-size-fits all amount of water you should or shouldn’t have, but you should drink for thirst,” he said. “If, for example, you’re drinking more than a liter an hour, but you’re sitting inside, you’re not sweating or losing liquid, and you’re not thirsty, then you might run into a problem.”

You can also look at your urine: If it’s light yellow or almost clear, you’re hydrated. Darker urine might be a sign you could use a little more H2O.

How to spot a tonic-clonic seizure

In her recounting of the medical event, Shields mentioned that the people around her noticed her looking “weird,” a description that Parker associated to the “aura” that certain patients have right before a seizure.

“Think of it as a warning sign, a funny feeling rising in the chest or the tingling in one part of the body, or a feeling of déjà vu,” Parker said. “Some of these things can be early warning signs that come up immediately before a seizure happens.”

In terms of treatment, the most successful way to avoid another tonic-clonic seizure is to “remove the provoking agent.” Whether that involves excessive hydration or a specific medication, simply avoiding the cause of the seizure would stop its recurrence.

Unprovoked seizures are a bit more complicated since they can’t be pinpointed to a specific action. In many such cases, medical experts would suggest taking epilepsy medication or, perhaps, surgery.

“If it’s provoked and you remove the cause, it’s unlikely you’ll have another seizure because you won’t engage with that cause again,” Parker said. “If it’s unprovoked, there is a risk it can happen again.”

Whatever the case may be, make sure to call a medical professional as soon as you experience any of the feelings described above.