Nutrition glossary
What are electrolytes?
Electrolytes are minerals, such as sodium, potassium and magnesium, that carry an electric charge when they dissolve in your body's fluids. They control how much water sits inside and outside your cells, and they let your nerves fire and your muscles, including your heart, contract.
The main electrolytes and what each one does
Your blood, sweat and urine all contain electrolytes. Your kidneys keep the levels in a narrow range, flushing out extra and holding on to more when you run low.
| Electrolyte | Main job | Everyday sources |
|---|---|---|
| Sodium | Holds water in your blood and around cells; nerve signals | Table salt, bread, cheese, soups, processed foods |
| Potassium | Works opposite sodium inside cells; heart rhythm, muscle contraction | Potatoes, beans, bananas, yogurt, leafy greens |
| Chloride | Partners with sodium for fluid balance; part of stomach acid | Table salt, salted foods |
| Magnesium | Muscle and nerve function, energy use, steady heartbeat | Nuts, seeds, beans, whole grains, spinach |
| Calcium | Bones and teeth, muscle contraction, blood clotting | Milk, yogurt, cheese, fortified plant milks, tofu set with calcium |
| Bicarbonate and phosphate | Keep your blood's acid level steady; energy storage | Made and balanced by your body; phosphate is in most protein foods |
Food sources: you probably eat more than you think
Most people get plenty of sodium without trying. In the US the general limit is 2,300 mg of sodium a day, and in the UK it is 6 g of salt, which is about the same. Most of it comes from bread, cheese, ready meals and restaurant food, not the salt shaker.
Potassium is the one many people fall short on. A few easy examples:
- A medium banana gives you roughly 400 mg.
- A medium baked potato with the skin on gives you more, often around 900 mg.
- A pot of plain yogurt adds potassium and calcium at the same time.
Magnesium comes mostly from plant foods like almonds, pumpkin seeds, oats and black beans. A mix of fruit, vegetables, beans, dairy and whole grains covers most of your electrolytes.
Signs your levels may be low
In healthy people eating normally, levels rarely drop far. It usually takes a trigger: heavy sweating, vomiting or diarrhoea, some medicines (especially water pills called diuretics), kidney problems, or a sudden drop in food intake.
- Low sodium can cause headache, nausea, tiredness and, when severe, confusion. Drinking huge amounts of plain water during long endurance events is a known cause.
- Low potassium can cause weakness, muscle cramps, constipation and a fluttering or irregular heartbeat.
- Low magnesium can cause twitching, cramps and fatigue.
Get medical help quickly for confusion, fainting, a racing or irregular heartbeat, or vomiting and diarrhoea that you can't keep fluids down through. If you have kidney disease or heart failure, or take diuretics or blood pressure tablets, talk to your doctor before using electrolyte supplements or salt substitutes, because too much potassium can be as dangerous as too little.
When sports drinks help, and when they're pointless
For a 30-minute run, a gym class or a normal day at a desk, water is enough. A sports drink just adds sugar you don't need, often 30 g or more in a bottle.
They can make sense when you exercise hard for more than about an hour, especially in heat, or when you are a heavy, salty sweater (white marks on your clothes are a clue). For vomiting or diarrhoea, a pharmacy oral rehydration solution is a better choice than a sports drink, because it has more salt and less sugar.
Electrolytes and keto flu
When you cut carbs sharply, as on a keto diet, your insulin levels fall and your kidneys let go of more sodium and water. You also stop eating many potassium-rich foods such as potatoes, beans and fruit. In the first week, that can show up as a dull headache, tiredness, dizziness when you stand up and leg cramps at night, often called keto flu.
Many people feel better with an extra cup of salty broth a day and by leaning on low-carb, potassium-rich foods like avocado, spinach, mushrooms and plain yogurt. If you take blood pressure medicine or have kidney problems, check with your doctor before adding salt.
Common questions
What are electrolytes in simple terms?
They are minerals like sodium, potassium, calcium and magnesium that dissolve in your body's water and carry a small electric charge. That charge lets your nerves send signals and your muscles contract, and it helps your body decide where water goes.
Do I need electrolyte drinks every day?
Most people don't. A normal diet with fruit, vegetables, dairy or fortified alternatives, beans and whole grains supplies what you need. Drinks and tablets are mainly useful for long, sweaty exercise or recovering from a stomach bug.
Is it possible to have too many electrolytes?
Yes. Too much sodium over time raises blood pressure for many people, and very high potassium can upset heart rhythm, especially in people with kidney disease. That is why supplements are not a good idea without a reason.
Related
If you are starting a low-carb plan, read about ketosis, net carbs and the range of low-carb diets. For a lower-sodium, potassium-rich way of eating, see the DASH diet. For the basics of a balanced plate, try healthy eating basics, or browse the full nutrition glossary.