Sarah Di Lorenzo: Electrolytes, sports drinks, coconut water explained — when do you need them for hydration?

Walk into any supermarket or scroll social media and there’s a bottle for every hydration mood, electrolyte sachets, “clean” sports drinks, coconut water cartons, hydrogen water, and alkaline water — all promising to out-hydrate plain old tap water. As a nutritionist, I get asked about this constantly.

For most people, most of the time, water is genuinely enough. Unless you’re sweating heavily, exercising hard for more than an hour, dealing with heat stress, or recovering from a bout of gastro, your kidneys are remarkably good at holding your electrolyte balance steady on their own as long as you’re eating regular meals. A normal Australian diet already supplies more than enough sodium and potassium to cover everyday losses. In fact, most of us are consuming almost double the recommended sodium intake before we’ve even considered a sports drink. But I want to give you the definition of electrolytes before I go on.

An electrolyte is a mineral that carries an electrical charge when dissolved in a fluid like blood, sweat or the water inside and around your cells. That charge is what allows the body to run its most essential processes.

Electrolytes in the body

Sodium regulates fluid balance and blood pressure; the main electrolyte lost in sweat.

Potassium controls muscle contractions (including your heartbeat) and nerve signals.

Chloride works with sodium to maintain fluid balance and stomach acid.

Calcium muscle contraction, nerve signalling, blood clotting, bone strength.

Magnesium muscle relaxation, energy production, more than 300 enzyme reactions.

Phosphate energy storage, bone structure.

Bicarbonate keeps blood pH stable.

What they actually do

• Fire nerve signals — every thought, movement and heartbeat depends on electrolytes shifting across cell membranes.
• Contract and relax muscles including your heart and diaphragm.
• Hold water in the right places — inside cells, in your bloodstream, in the spaces between.
• Keep blood pH in a narrow range so enzymes can function.
• Move nutrients into cells and waste products out.

The word comes from the Greek elektro- (electric) and lytos (able to be dissolved) literally “something that dissolves and conducts electricity”.

When you dissolve salt (sodium chloride) in water, it splits into sodium and chloride ions, each carrying a charge and that’s an electrolyte solution.

So electrolytes are the charged minerals that keep your nerves firing, your muscles contracting, your heart beating, and your fluids balanced. You lose them in sweat, urine, vomit and diarrhoea which is why replacing them matters in those specific situations, and why food (not just drinks) is where most of us get them from every day.

So when do electrolyte drinks actually earn their place? Sports drinks and electrolyte mixes are formulated to replace what you lose through sweat mainly sodium, with smaller amounts of potassium and chloride.

This matters most during prolonged, intense or hot-weather exercise, where sweat losses can be substantial.

A litre of sweat can contain 400mg to 1000mg of sodium, so a well-formulated electrolyte drink (usually 300–700mg of sodium per litre) is genuinely doing a job here.

The trade-off is that many mainstream sports drinks carry a hefty sugar load, often 30g to 60g per bottle which is the equivalent of a can of soft drink.

They’re a tool for specific situations, not a daily habit.

Coconut water sits in the middle. It’s naturally rich in potassium, around 400mg per cup which is more than a banana and contains smaller amounts of sodium, magnesium and calcium. Clinical research comparing coconut water to conventional sports drinks after exercise has found it can rehydrate reasonably well, performing comparably on rehydration markers in several trials.

But coconut water’s sodium is often much lower than a sports drink or an oral rehydration formula, which limits how well it replaces heavy salt losses during long, hot sessions. It also contains naturally occurring sugars, about 6g per cup, which add up if you’re drinking it daily. Think of it as sitting somewhere between water and a sports drink.

Most Australians already eat too much sodium and not enough potassium which is the exact opposite of what our bodies thrive on. Swapping a sugary soft drink for coconut water is a smart move, even outside exercise contexts.

A practical way to think about it is that water is genuinely sufficient, and adding a squeeze of lemon or a few mint leaves makes it more interesting. Light activity, a walk, a mild sweat or wanting something more interesting than water, then coconut water is a reasonable middle ground. For long, hard, hot or heavily sweaty sessions of an hour plus, an electrolyte or sport drink with adequate sodium does the job better.

Check the label and choose one with at least 300mg sodium per serve and lower sugar. where possible.

When recovering from vomiting or diarrhoea, this is where a proper oral rehydration solution beats anything on the sports drink shelf.

One caveat worth flagging is that anyone with kidney disease, on blood pressure medication or diuretics, or managing a heart condition should check with their doctor before regularly using high-potassium or high-sodium hydration products.

The bottom line for most healthy adults is don’t let clever branding and marketing convince you that everyday water needs to be upgraded.

Save the electrolyte drinks for when your body is actually asking for them and drink the water in-between, and be sure to get a good quality one that is a true electrolyte product.