Electrolytes

What you actually lose in sweat

The electrolyte category is built on an implied claim: that exercise depletes a range of minerals that must be replaced from a specific product. The numbers do not support that.

Sweat sodium concentration varies considerably between people — from roughly 0.5 g to over 2 g per litre — which is why some people see visible salt marks on their clothing and others never do. Everything else on the list is present in amounts that a normal diet replaces without thought.

When you genuinely need them

Yes:

• Sessions over about 90 minutes, especially with heavy sweating.
• Hot or humid conditions, indoors or out.
• Heavy sweaters. If your clothes are soaked and you see salt residue, you lose sodium at the high end of the range.
• Endurance events, where both fluid and sodium losses are large and prolonged.
• Two sessions in a day with little recovery time.
• Very low-carbohydrate diets. These increase sodium excretion, and much of what is called "keto flu" is sodium depletion.
• After vomiting or diarrhoea, where oral rehydration solutions are genuinely medically useful.
• If you cramp regularly — the evidence is weaker than the folklore, but sodium is a reasonable thing to try.

No:

• A 45–75 minute indoor lifting session.
• Daily use "for hydration" while eating a normal diet containing salt.
• As a substitute for drinking water.
• To fix fatigue that is actually caused by poor sleep or under-eating.

What to use

In order of cost-effectiveness:

1. Salt in water. Roughly a quarter to a half teaspoon (around 500–1,000 mg sodium) per litre. Functionally equivalent to most commercial products. Add squash or juice if the taste is unpleasant.
2. Salt plus carbohydrate for long sessions. Sodium and glucose are co-absorbed, which speeds fluid uptake — this is the actual science behind sports drinks.
3. A standard sports drink. Around 500 mg sodium and 30–60 g carbohydrate per litre. Reasonable for endurance work.
4. Electrolyte tablets or powders. Convenient and portable. Check the sodium content — many contain only 200–300 mg per serving, which is below what a sweaty hour costs you.
5. Oral rehydration solutions. Higher sodium, designed for illness. Genuinely the right tool for gastrointestinal illness.

Not worth it: coconut water (high potassium, low sodium — the wrong way round for sweat replacement), "trace mineral" drops, and premium electrolyte brands whose sodium content is lower than a pinch of table salt.

How much sodium, and the salt-is-bad question

There is genuine tension here that deserves an honest answer rather than a fitness-industry one.

• Public health guidance is to limit sodium — under 2.3 g a day, or around 6 g of salt, primarily for blood pressure and cardiovascular risk.
• Athletes losing 1–2 litres of sweat a session have genuinely higher needs. Someone training hard in heat may lose 1–2 g of sodium in a session.
• Both can be true. Replacing sweat losses is not the same as habitually eating a high-sodium diet on top of normal requirements.
• If you have high blood pressure, this is a conversation for your doctor, not a decision to make from a supplement label.
• For most people training an hour indoors, a normal diet already contains plenty of sodium and no addition is needed.

The practical position: add sodium in proportion to what you actually lose, not as a daily habit because a brand suggested it.

Cramp, and why sodium may not fix it

Exercise-associated muscle cramp is widely attributed to electrolyte loss and dehydration. The evidence for that is weaker than the confidence with which it is stated.

• The leading alternative explanation is altered neuromuscular control — muscle fatigue disrupting the balance between excitatory and inhibitory reflexes.
• Cramp often occurs in people who are not dehydrated, and in muscles that were working hardest rather than throughout the body.
• Fatigue and unaccustomed intensity are better predictors than fluid status.
• Sodium may still help some people, particularly heavy sweaters in heat, and it is cheap and harmless to try.
• Stretching the cramping muscle is the most reliable acute treatment, which fits the neuromuscular explanation better than the electrolyte one.

If cramp is frequent and severe, the more productive interventions are usually reducing the jump in training load and improving conditioning for the specific activity.

Common questions

Do I need electrolytes for a normal gym session?

No. Water is sufficient for an hour indoors — see hydration and performance.

Which electrolyte actually matters?

Sodium. The others are lost in trivial amounts.

Is a pinch of salt really equivalent to a branded product?

For sodium content, often yes — and sometimes more than it. Check the label.

Is coconut water a good electrolyte drink?

Not for sweat replacement. High in potassium, low in sodium, which is the wrong ratio.

Do electrolytes help with hangovers?

Rehydration helps generally. The alcohol effects are not an electrolyte problem — see alcohol and training adaptation.

Will electrolytes stop my cramps?

Possibly, for heavy sweaters. Fatigue is a better-supported cause.

Can I have too much sodium?

Yes, chronically, particularly with high blood pressure. Replace losses rather than adding habitually.

What about on a low-carb diet?

Sodium needs genuinely rise. Adding salt is sensible here.

The practical version

• Sodium is the only electrolyte lost in meaningful quantities in sweat.
• Potassium, magnesium and calcium sweat losses are trivial and covered by food.
• Water is sufficient for indoor sessions under about 90 minutes.
• A quarter to half teaspoon of salt per litre matches most commercial products.
• Sodium plus carbohydrate speeds fluid absorption — the real science behind sports drinks.
• Cramp is better predicted by fatigue than by electrolyte status.