Hyponatremia

by Graeme Hilditch

The Dangers of Over-Hydration

As with so many aspects of nutrition, injury and training, a little knowledge can be a dangerous thing. This is particularly the case when it comes to hydrating the body – especially when it’s hot.

Although the message at last seems to have got through that taking on fluids before, during and after training is essential, sadly some runners have taken this piece of advice too far.

No matter what your level of running ability, it’s important to appreciate that there is a limit to how much fluid your body is able to store and once you pass that limit, drinking additional water is surplus to requirements.

In most cases, the result of drinking too much simply involves very frequent visits to the bathroom to pass out excess fluids, but if runners keep on drinking excessively once they are already hydrated, then they are at risk of water toxicity.

Over hydration (or water toxicity) can be far more serious than the risks of dehydration and for runners taking on long, hot and challenging training runs / races in the summer months, the risk of falling ill due to over hydration, although low, is very real if you are not aware of the dangers.

Leaching electrolytes.

So why and how can we end up with water toxicity? The answer is all to do with the essential salts contained within our cells.

One of the key ingredients in our blood is electrolytes (salts). Without the right balance of salts, our cells are unable to regulate their water content, which can lead to a condition known as Hyponatremia.

Although we usually consume sufficient quantities of salts to ensure this balance remains normal, an imbalance can be created if we consume either excessive quantities of water and / or combine it with a profuse amount of sweating.

By drinking too much water before and during a long run, on top of losing a lot of salt in our sweat, it can easily lead to a deficiency in blood electrolyte levels and severe ill health

Common symptoms of hyponatremia

The difficulty with accurately diagnosing a runner with hyponatremia is that the symptoms are fairly similar to those of hypoglycaemia (low blood sugar).

Nonetheless, the following symptoms should not be ignored as they could be a sign of hyponatremia:

  • Dizziness

  • Headaches

  • Muscle cramps

  • Nausea

  • Tiredness

  • Weakness

  • Confusion

  • Lack of consciousness

How much water is too much?

It is impossible to say how much water you would have to consume and how much you would have to sweat to suffer from hyponatremia, as it depends on your electrolyte levels in the first place.

However, by following these tips, you’ll significantly reduce your chances of contracting hyponatremia:

  • Stop drinking when you’re hydrated

  • Do not eat a low sodium diet during your training.

  • Drink sports drinks which contain “electrolytes” before and during and after a long or hard hot run in the heat.

  • Wear clothing to keep you cool.

Cases of hyponatremia are rare - but they do happen.

So, if you’re running a marathon this year and you find out conditions will be warm, it might be an idea to go over the advice in this post one more time.

By taking note of this advice, you’ll be doing everything you can to reduce your chances of falling ill.

Happy running.

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