In 30 seconds
- Potassium is the dominant mineral inside your cells: an adult of about 80 kg has about 140 g. EFSA recommends 3,500 mg a day.
- Little is lost in sweat: about 140-200 mg per litre, compared with 230-2,070 mg of sodium.
- During intense effort, potassium leaves the muscle and its concentration outside the fibres can more than double. It is one of the factors in fatigue.
- Interval training improves how muscle handles it: in a 7-week study, the trained leg lasted 28% longer.
Potassium is the mineral in charge inside your cells, and without it your nerves and muscles do not work. You lose little of it in sweat: what matters is eating enough and understanding what happens to it in your muscles when you push hard. This is what the studies say.
What potassium does
It is the most abundant positively charged ion inside cells. There it is about 30 times more concentrated than outside, and that difference is what allows nerve impulses to be transmitted, muscles to contract and the kidneys to work 2. It is maintained by a pump in the cell membrane, the sodium-potassium pump.
An adult of about 80 kg has around 140 g of potassium. You absorb 85-90% of what you eat, and the kidneys get rid of the excess 2.
European regulations authorise three claims for potassium 3: “Potassium contributes to normal functioning of the nervous system.” “Potassium contributes to normal muscle function.” “Potassium contributes to the maintenance of normal blood pressure.” A varied and balanced diet and a healthy lifestyle are important.
Potassium a day
The recommendation compared with actual intake
How much you need and where to find it
EFSA sets an adequate intake of 3,500 mg a day for adult men and women, and 4,000 mg while breastfeeding. It bases this on potassium's effects on blood pressure and stroke risk 1.
It is not that easy to reach. In the US, men have on average about 3,000 mg a day and women about 2,300 mg 2. These are some of the richest sources 2:
| Food | Potassium |
|---|---|
| Dried apricots (half a cup) | 755 mg |
| Cooked lentils (1 cup) | 731 mg |
| Medium baked potato, without skin | 610 mg |
| Orange juice (240 ml) | 496 mg |
| Medium banana | 422 mg |
| Low-fat milk (240 ml) | 366 mg |
| Raw spinach (2 cups) | 334 mg |
| Grilled chicken breast (85 g) | 332 mg |
| Cooked salmon (85 g) | 326 mg |
Source: US National Institutes of Health (NIH), based on the USDA database.
A plate of lentils, a banana and a potato already add up to more than 1,700 mg. Pulses, fruit, vegetables and dairy are your foundation.
Level of evidence by outcome
| Outcome | Evidence | What the data show |
|---|---|---|
| Nerve and muscle function | High | Function recognised by European regulations. |
| Losses in sweat | High | Sweat contains little potassium, similar to blood: about 3.6-5.2 mmol per litre. |
| Fatigue during intense effort | Moderate | Potassium leaving the muscle contributes to fatigue; training improves how it is controlled. |
| Blood pressure | Moderate | Reductions of about 4.5 mmHg in systolic pressure across 25 trials; other, stricter analyses do not confirm them. |
| Cramps | No clear effect | It is not considered a key mineral in exercise-associated cramps. |
The rating is our own, based on the number of studies, their quality and the consistency of the results.
The key studies
| Study | Type | Sample | Outcome |
|---|---|---|---|
| EFSA, 2016 | Reference values | European adults | Adequate intake of 3,500 mg a day, because of its effects on blood pressure and stroke risk. 1 |
| Sejersted and Sjøgaard, 2000 | Review | Exercise physiology | During intense effort, potassium outside the muscle fibre can more than double. It may contribute significantly to fatigue. 5 |
| Nielsen et al., 2004 | Trial | 6 men, about 7 weeks | Interval training increased sodium-potassium pumps by up to 29%. The trained leg lasted 28% longer to exhaustion. 6 |
| Baker and Wolfe, 2020 | Review | Sweat composition | Sweat contains 3.6-5.2 mmol of potassium per litre, similar to blood. Sodium ranges from 10 to 90 mmol per litre. 4 |
| Miller et al., 2022 | Review | Exercise-associated cramps | Potassium is not considered a key mineral in cramps. Eating a banana did not raise blood potassium until 60 minutes later. 8 |
| 2017 meta-analysis, cited by the NIH | Meta-analysis | 25 trials | Higher potassium intake lowered systolic pressure by 4.48 mmHg and diastolic pressure by 2.96 mmHg. 2 |
How much you lose in sweat
Much less than people usually think. Sweat contains potassium at a concentration similar to that of blood, while sodium and chloride are by far the most concentrated minerals 4:
| Mineral | Concentration | In mg per litre |
|---|---|---|
| Potassium | 3.6-5.2 mmol/L (sometimes 2-8) | 140-200 mg (80-310 mg) |
| Sodium | 10-90 mmol/L | 230-2,070 mg |
Source: Baker and Wolfe, 2020. Conversion: 1 mmol of potassium = 39.1 mg; 1 mmol of sodium = 23 mg.
If you sweat 1.5 litres in a long session, you lose about 200-300 mg of potassium. A medium banana contains 422 mg 2. The mineral you really need to watch with sweat is sodium: we explain it in sodium and performance and in how much salt you lose when you sweat.
Potassium, in mmol per litre
Potassium at rest and at the point of fatigue
What happens to potassium when you push hard
This is where it gets interesting. Each contraction lets some potassium out of the muscle fibre. During intense effort, the concentration outside the fibre can more than double 5. In a trial with leg exercise, it reached about 9-10 mmol per litre at the point of fatigue 6. In the blood, at rest, it is between 3.5 and 5.5 5.
When you stop, it falls very quickly, and even stays below normal for 10-15 minutes 5. Researchers believe these changes may contribute significantly to muscle fatigue during intense effort 5.
It is not all negative: moderate rises in potassium during exercise appear to benefit several systems in the body. It is a large loss of balance between the inside and outside of the fibre that is associated with fatigue 7.
About 7 weeks of intervals
Trained muscle handles potassium better
Training improves how you handle it
The good news is that muscle adapts. In one study, six men trained just one leg with very intense one-minute bouts, for about 7 weeks. The trained leg increased its sodium-potassium pumps by up to 29% and accumulated less potassium outside the fibre at the same workload. And it lasted 28% longer to exhaustion 6.
It is one of the reasons why interval training improves your tolerance of hard efforts. If you do CrossFit or HIIT, you will find everything in our nutrition guide for high-intensity training.
Potassium and cramps
This is the banana myth. The most comprehensive review of exercise-associated cramps says that potassium is generally not considered a key mineral in this problem 8. And in a study with dehydrated people, eating a banana did not raise blood potassium until 60 minutes later, too late for a cramp 8.
The explanation with the most support is fatigue of the muscle and of its nervous control. You will find it in muscle cramps during exercise.
Potassium and blood pressure
This is the benefit with the most studies outside sport. In a meta-analysis of 25 trials, higher potassium intake lowered blood pressure by 4.48 mmHg systolic and 2.96 mmHg diastolic 2. A Cochrane review with six high-quality trials found no significant reductions, so the effect is not settled 2.
In follow-up studies, every additional 1,640 mg of potassium a day was associated with a 21% lower risk of stroke 2.
Safety
- Healthy people: the kidneys get rid of the excess. A diet low in potassium rarely causes low blood potassium on its own; the usual causes are diarrhoea, vomiting, some diuretics or sweating very heavily 2.
- Risk of high potassium: chronic kidney disease, some blood pressure medicines and potassium-sparing diuretics 2.
- Sodium-free salt substitutes: they can contain between 440 and 2,800 mg of potassium per teaspoon 2.
If you have kidney disease or take blood pressure medication, check with your doctor before taking supplements or sodium-free salt substitutes.
The potassium in Nitrus
Nitrus Isotonic contains five minerals per serving: 195 mg of sodium, 148 mg of potassium, 143 mg of calcium, 110 mg of phosphorus and 23 mg of magnesium. Those 148 mg are similar to the amount lost in a litre of sweat. And each serving adds carbohydrates, all 13 vitamins, BCAAs and taurine.
The foundation of your potassium intake is still on your plate. Nitrus is for your training sessions and your hot days.
Frequently asked questions
What does potassium do?
It is the most abundant mineral inside your cells. It maintains the difference in charge between the inside and outside of the cell, which is what allows nerve impulses to be transmitted and muscles to contract. It also plays a part in the kidneys and in blood pressure.
How much potassium do I need a day?
EFSA sets an adequate intake of 3,500 mg a day for adult men and women, and 4,000 mg while breastfeeding. The easiest way to get there is with pulses, potatoes, fruit, vegetables, dairy, meat and fish.
Do you lose a lot of potassium when you sweat?
Not much. A litre of sweat contains about 140-200 mg of potassium, while sodium ranges from 230 to more than 2,000 mg. A medium banana, with 422 mg, covers the potassium in more than two litres of sweat.
Do bananas stop cramps?
There is no evidence that they do. The reference review on cramps does not consider potassium a key mineral, and eating a banana did not raise blood potassium until 60 minutes later, too late for a cramp.
Are potassium supplements dangerous?
In healthy people, the excess is passed in urine. But if you have kidney disease or take blood pressure medication or potassium-sparing diuretics, check with your doctor before taking supplements or sodium-free salt substitutes.
Sources
- EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA). Dietary reference values for potassium. EFSA Journal. 2016;14(10):4592. View publication
- Office of Dietary Supplements, National Institutes of Health. Potassium: fact sheet for health professionals. View publication
- Commission Regulation (EU) No 432/2012 establishing a list of permitted health claims made on foods. View publication
- Baker LB, Wolfe AS. Physiological mechanisms determining eccrine sweat composition. Eur J Appl Physiol. 2020;120(4):719-752. View publication
- Sejersted OM, Sjøgaard G. Dynamics and consequences of potassium shifts in skeletal muscle and heart during exercise. Physiol Rev. 2000;80(4):1411-1481. View publication
- Nielsen JJ, Mohr M, Klarskov C, Kristensen M, Krustrup P, Juel C, Bangsbo J. Effects of high-intensity intermittent training on potassium kinetics and performance in human skeletal muscle. J Physiol. 2004;554(Pt 3):857-870. View publication
- Lindinger MI, Cairns SP. Regulation of muscle potassium: exercise performance, fatigue and health implications. Eur J Appl Physiol. 2021;121(3):721-748. View publication
- Miller KC, McDermott BP, Yeargin SW, Fiol A, Schwellnus MP. An evidence-based review of the pathophysiology, treatment, and prevention of exercise-associated muscle cramps. J Athl Train. 2022;57(1):5-15. View publication
Information based on published studies. It does not replace the advice of a doctor or registered dietitian. The results describe what was measured in each study, not the properties of any specific product.
