What Are Electrolytes?

Electrolytes are minerals that carry an electrical charge when dissolved in body fluids. The main electrolytes discussed in hydration and sports nutrition include sodium, potassium, chloride, magnesium and calcium.

They contribute to normal processes including fluid balance, nerve signalling and muscle function. Electrolytes are supplied through food and fluids and are naturally present throughout the body.

What does the term electrolyte mean?

Chemically, an electrolyte is a substance that forms electrically charged particles, called ions, when dissolved in water.

In the body, electrolytes are dissolved in blood and other fluids. Their electrical charge allows them to take part in processes involving fluid balance, nerve impulses and muscle contraction.

What are the main electrolytes?

Sodium

Sodium is found mainly in the fluid outside the body's cells. It plays an important role in extracellular fluid balance and is generally the main electrolyte lost through sweat during exercise.

The amount of sodium lost varies considerably between people because both sweat rate and sweat sodium concentration differ. [1][2]

Potassium

Potassium is found mainly inside cells. It plays an important role in the distribution of body fluids, nerve impulse transmission and muscle contraction. [3]

Chloride

Chloride is a negatively charged electrolyte found mainly in fluid outside cells. Its balance in the body is closely related to sodium.

Sodium and chloride are also the two components of ordinary dietary salt. [4]

Magnesium

Magnesium contributes to electrolyte balance and normal muscle and nervous-system function. It is also involved in many enzyme-controlled reactions throughout the body. [5][6]

Calcium

Calcium is widely associated with bones and teeth, but it also contributes to normal muscle function and neurotransmission. [6]

What do electrolytes do in the body?

Electrolytes do not all perform the same job, but together they are involved in several normal processes throughout the body.

They contribute to:

• Maintaining fluid balance inside and outside cells
• Transmitting nerve impulses
• Normal muscle function
• Maintaining the electrical and chemical gradients across cell membranes

Sodium and potassium, for example, are distributed differently across the cell membrane. Sodium is found mainly in fluid outside cells, while potassium is found mainly inside cells.

These differences are important for normal cellular, nerve and muscle function. Magnesium and calcium also have important roles in normal muscle and nervous-system function. [3][5][6][7]

Why are electrolytes relevant during exercise?

Exercise can increase the loss of both water and electrolytes through sweat.

Sodium is generally the main electrolyte lost through sweat, although the amount lost varies considerably between people.

Total losses depend on factors including:

• How much someone sweats
• The sodium concentration of their sweat
• Exercise duration
• Exercise intensity
• Temperature and humidity
• Individual physiology and heat acclimatisation

This means two people completing the same session can experience different fluid and sodium losses. The same person can also experience different losses from one session to another. [1][2]

Electrolyte replacement therefore becomes a practical consideration in some training situations, but this does not mean every workout requires an electrolyte supplement.

Where do electrolytes come from?

Electrolytes are not found only in sports drinks or supplements. They are naturally obtained through everyday food and drink.

Different foods provide different minerals. Examples include:

• Sodium and chloride from salt and foods containing salt
• Potassium from foods including potatoes, fruit, vegetables, beans, lentils and dairy products
• Magnesium from foods including nuts, seeds, legumes, whole grains and green leafy vegetables
• Calcium from foods including milk, yoghurt and cheese, as well as fortified foods and some vegetables

A varied diet can therefore provide substantial amounts of the electrolytes the body requires during normal daily life. [4][7][8][9][10]

Electrolyte supplements are another way of providing specified amounts of these minerals, usually in a format designed to be consumed with fluid.

Do you need an electrolyte supplement?

Not automatically.

Many people obtain electrolytes through their normal diet, and water alongside normal meals may be sufficient for many shorter, easier or lower-sweat training sessions.

An electrolyte-containing drink may become more relevant when:

• Exercise is prolonged
• Conditions are hot or humid
• Sweat losses are high
• An individual loses relatively large amounts of sodium through sweat
• Several sessions are completed close together
• There is limited time to eat, drink and recover before the next session

These are considerations rather than universal rules.

The usefulness of an electrolyte supplement depends on the individual, the session, the conditions and the wider diet rather than simply whether someone is exercising. [1][2]

Are electrolytes the same as hydration?

No.

Hydration refers to the body's water balance. Electrolytes are charged minerals that are involved in fluid regulation as well as other functions including nerve signalling and muscle function.

Water remains essential. Electrolytes do not replace the need to consume sufficient fluid.

The relationship becomes more relevant during exercise because sweat can remove both water and electrolytes from the body.

For a more detailed explanation, read: How Do Electrolytes Help With Hydration?

Key takeaways

• Electrolytes are minerals that carry an electrical charge when dissolved in body fluids.
• Sodium, potassium, chloride, magnesium and calcium are among the electrolytes commonly discussed in hydration and sports nutrition.
• Electrolytes are involved in fluid balance, nerve signalling and normal muscle function.
• Electrolytes are obtained through normal food and drink as well as electrolyte supplements.
• Water and electrolytes can both be lost through sweat during exercise.
• Sweat and sodium losses vary considerably between people and sessions.
• Not every workout requires an electrolyte supplement.

Related guides

For more detail on fluid balance and exercise hydration, read: How Do Electrolytes Help With Hydration?

For a deeper explanation of sodium losses through sweat, read: Sodium and Exercise Hydration

Sources

1. McDermott BP, Anderson SA, Armstrong LE, et al. National Athletic Trainers' Association Position Statement: Fluid Replacement for the Physically Active. Journal of Athletic Training. 2017;52(9):877–895.
2. Baker LB. Sweating Rate and Sweat Sodium Concentration in Athletes: A Review of Methodology and Intra/Interindividual Variability. Sports Medicine. 2017;47(Suppl 1):111–128.
3. European Food Safety Authority. Dietary Reference Values for Potassium. EFSA Journal. 2016;14(10):4592.
4. European Food Safety Authority. Dietary Reference Values for Chloride. EFSA Journal. 2019;17(9):5779.
5. European Food Safety Authority. Dietary Reference Values for Magnesium. EFSA Journal. 2015;13(7):4186.
6. European Commission. Commission Regulation (EU) No 432/2012 establishing a list of permitted health claims made on foods.
7. European Food Safety Authority. Dietary Reference Values for Sodium. EFSA Journal. 2019;17(9):5778.
8. National Institutes of Health, Office of Dietary Supplements. Potassium — Health Professional Fact Sheet.
9. National Institutes of Health, Office of Dietary Supplements. Magnesium — Health Professional Fact Sheet.
10. National Institutes of Health, Office of Dietary Supplements. Calcium — Health Professional Fact Sheet.