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What Are Electrolytes And Why Do You Need Them

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When a powerful thirst strikes after you’ve undertaken an especially energetic activity, the natural response is to reach for a glass of water. And that’s not a bad idea at all – no-one’s going to criticise you for drinking water – but sometimes your body needs more than H₂O alone. Sometimes, your body needs electrolytes.

Fortunately, electrolytes are not especially hard to come by. For all the info on what electrolytes do and why you need to replenish them after exercise, Coach spoke to Dr Ieva Alaunyte, registered nutritionist and senior scientist at Lucozade Sport (opens in new tab), at the launch of FitWater, an electrolyte-rich beverage.

What are electrolytes?

“To put it very simply electrolytes are minerals,” says Alaunyte.

“You find them in your diet. Sodium, magnesium, calcium and potassium are some of them.

“You also find electrolytes in every single cell of your body. Your skin, your muscle cells, your brain – they all contain electrolytes in the fluid.”

Why do you need electrolytes?

So electrolytes are everywhere, which is good, because without them our body would stop functioning.

“There many different types of electrolytes, and they have different functions in the body,” says Alaunyte.

“One of the main functions that they have is to monitor hydration and ensure that you are hydrated.”

Electrolytes also play an important role as communicators between cells – for example, they transmit electrical impulses from the brain that cause muscle contraction when you move.

Why are they especially important when you exercise?

Most of the time you don’t need to consider your electrolyte balance much because you’ll probably get everything you need from your daily meals, but that changes when you break a sweat.

“When you exercise you not only lose water but you also lose electrolytes,” says Alaunyte.

“You do get electrolytes from your everyday diet but people who exercise might need greater amounts of electrolytes, to replenish what they lose in sweat during exercise.

“Losing only 2% of your bodyweight through fluids can cause dehydration. Some of the symptoms of dehydration are headache, not being able to concentrate as well and your muscles not being as efficient. Overall you’ll find exercise harder and enjoy it less if you’re not fully hydrated.”

Naturally most people turn to water for hydration, but during strenuous activity drinking water alone can dilute your electrolyte levels further, and it can even lead to hyponatremia – low blood sodium. This sometimes affects amateur marathon runners who are worried about becoming dehydrated and glug down lots of water during the event.

How intense does your exercise need to be to make using an electrolyte drink worthwhile?

As soon as you start to sweat you start losing electrolytes. Whether you feel the need to replace them directly, rather than relying on your diet, will depend on the intensity of your workout (and when your next meal is).

“We are all very different, and it depends on how much you sweat, what environment you are exercising in, and the intensity of the exercise you are doing,” says Alaunyte.

“But usually during 30-60 minutes of moderate-intensity exercise you are likely to lose half a litre to a litre of body fluid. With that you will lose electrolytes, and you want to replenish what you lose.”

Do some people lose more electrolytes in their sweat than others?

“It depends how fit you are and your body composition. Also, some people just sweat more or sweat more electrolytes,” says Alaunyte.

If your sweat really stings your eyes and leaves white marks on your skin or clothes after exercise, you could well be a salty sweater, which means it may be worth paying closer attention to your electrolyte levels.

What are the different electrolytes that you need?

Until now we’ve taken electrolytes as one big happy family, but there are some that are especially important to replace when exercising.

“The electrolytes you lose in the greatest quantities in sweat are sodium and chloride, although you also lose others like calcium and magnesium,” says Alaunyte.

“They all have a function in hydration, but sodium is particularly important. Calcium is important for bones and muscle function, while magnesium helps prevent fatigue.”

How are electrolyte drinks different from sports drinks?

Sports drinks are designed to hydrate but also to provide energy for performance,” says Alaunyte.

“They contain electrolytes, but they also provide calories in the form of carbohydrates. For longer or harder exercise sports drinks can help to keep you going, but for low-intensity exercise, or if you don’t want the calories in sports drinks, an electrolyte drink like FitWater can help. A sports drink usually contains over 100 calories a bottle, while water has none.”

The Best Electrolyte Tabs And Powders

High5 Zero


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HIGH5 Zero Electrolyte Hydration Tablets Added Vitamin C, 3 x 20 Tubes (opens in new tab)

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Unless you’re regularly exercising in extreme conditions or consider yourself a prolific sweater, you don’t have to get too complex when picking out an electrolyte drink – just go for a flavour that appeals. These High5 Zero tabs are good value, come in three refreshing flavours, and contain 250mg of sodium in each serving.

Precision Hydration


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Precision Hydration Electrolyte Drink Mix - All Natural Multi Strength Electrolyte Powders - Individual Waterproof Servings - Gluten/Dairy Free, Hypotonic (1 Box (8 sachets), 500mg/l - Yellow) (opens in new tab)

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Precision Hydration’s sachets of electrolyte powder come in three serving sizes – 500mg, 1,000mg and 1,500mg of sodium per litre when mixed in 500ml water. Picking between the three comes down to the conditions you’ll be in, but also how salty a sweater you are. If you fancy that your sweat contains more salt than most (white residue on your skin or clothes after exercise is the giveaway), then the higher-strength sachets will be your best bet.

Nick Harris-Fry is a journalist who has been covering health and fitness since 2015. Nick is an avid runner, covering 70-110km a week, which gives him ample opportunity to test a wide range of running shoes and running gear. He is also the chief tester for fitness trackers and running watches, treadmills and exercise bikes, and workout headphones.