The Dangers of Overhydrating

A top sports scientist explains the scary health hazards of over-hydration

As athletes, exercisers and lovers of spending time outside, we’re constantly warned against the dangers of becoming dehydrated.

It is for good reason; if you’re going to spend time getting sweaty, you’ll want to replace those fluids so that your body can continue functioning optimally. But what’s hardly ever brought to our attention is the fact that overhydrating—or in medical terms, hyponatraemia—is a health risk that is far more common and quite possibly even more detrimental.  

“I think that over-hydration has become more of an issue, ironically, because of the messages promoted by the sports drink and bottled water industries who have been very keen to point out the pitfalls of dehydration, as their products can provide a 'cure' for this,” says Andy Blow, co-founder and Sports Scientist at Precision Hydration and a Red Bull High Performance partner. “They’ve created a 'fear' of dehydration, whilst simultaneously failing to point out that over-drinking is also very harmful.”

Blow pointed out that the “beware dehydration” message has gained a lot of traction because athletes especially are often paranoid about how they can best optimize their performance. “Drinking a bit more, rather than not enough has become the norm,” he said.

Overhydrating is particularly problematic when excessive amounts of low-sodium fluids are consumed. Blow says that the sodium levels in our blood must be tightly regulated. If those levels drop too far below the optimal amount hyponatraemia occurs.

“This causes fluid to shift into the body's cell, making them swell up which can be especially problematic if it happens in the brain,” says Blow.

According to Blow, common signs of hyponatraemia include headaches, nausea, confusion, loss of energy, muscle twitching or cramps, and in advanced cases, seizures and coma. However, he says it can be hard to diagnose because other symptoms like low blood sugar, low blood pressure and fatigue are common issues that many athletes sometimes experience during exercise for reasons unrelated to overhydrating.

Since confusion and disorientation are both associated with hyponatraemia, Blow says it can be very difficult to self-diagnose. However, if you ever find yourself in a position where you may have accidentally overhydrated and think you may be at risk, he offered the following advice.

“If you think you are suffering with hyponatraemia, and have been drinking a lot, which is obviously implicated in it, you should stop consuming fluids, slow down or stop completely if you are exercising and try to get some salt into your system,” he said. “If all is well your body should start to dump fluid by making you urinate which will help you regain homeostasis. If treated by medical professionals who have properly diagnosed hyponatraemia with a blood test they will probably choose to treat it with a high concentration saline drip and in this instance recovery is often very rapid.”

As Blow mentioned earlier, swelling of the brain is the most serious health issue related to short-term hyponatraemia, which he says is the type that most commonly affects athletes and recreational exercisers.

“People suffering from chronic hyponatraemia due to other medical complications can suffer all sorts of neurological impairments manifesting itself in things like increased reaction times, decreased attention and difficulties with walking gait,” says Blow.

Similar to his advice about hydrating properly, Blow says that avoiding over-hydration is as simple as listening to your body’s cues.

“It really comes down to listening to your body, responding to thirst and if you are having to drink large volumes of fluid due to high sweat losses for prolonged periods of time, adding salt or electrolyte mixes with plenty of sodium in them to you drinks,” he said.

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