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Potassium

What is potassium?

Potassium is an essential mineral for the body. Potassium affects the metabolism of the heart, muscles, kidneys and central nervous system as well as the transmission of nerve impulses.

Together with sodium, potassium affects blood pressure and the body’s fluid balance. Sodium and potassium work together and the balance between them is important.

After calcium and phosphorus, potassium is the most common mineral in the body.

There are about 130–170 grams of potassium in the body. Most of this can be found in the intracellular fluid. Only a few per cent is outside the cells in the bloodstream, where its concentration is strictly regulated.

The role of potassium in the body

Potassium is a mineral, which means that it is essential for humans. 99% of potassium in the body can be found inside cells. The majority of potassium is in muscle cells, but about 20 per cent is located in red blood cells and in bone and liver cells.

Together with sodium, potassium transports water, sugar and waste through cell walls. In addition, they affect blood pressure and the body’s fluid balance. These functions depend on the balance between sodium and potassium.

Swedes consume more sodium than recommended intake as table salt. Excessive salt intake increases blood pressure and causes swelling and the recommendation is to reduce the intake of salt through nutrition. However, the role of potassium is often forgotten in this process. An imbalance between sodium and potassium is usually the cause of symptoms.

Potassium is also involved in the transmission of nerve impulses and the regulation of muscle contraction.

The nervous system acts as a messenger between the brain and the body. The messages are transmitted as a nerve impulse and contribute to regulating, among other things, heart rate, reflexes and muscle contraction. Imbalanced potassium levels in the body can weaken muscle contraction and are particularly harmful to the heart.

The kidneys regulate the excretion of potassium in urine. A small amount of potassium is also eliminated through stool.

Which foods are good sources of potassium?

Many foods are high in potassium. Potassium can be obtained, for example, from:

• avocados
• bananas
• milk
• white beans
• spinach
• berries
• watermelon.

The body regulates the level of potassium in blood

The body does not produce potassium, so it must be obtained through food.

• There is always enough potassium in food and dietary potassium deficiency is not recognised as a condition.
• If you are healthy, high intake of potassium does not raise the level of potassium in the blood above the normal level.
• Correspondingly, unvaried nutrition or diets do not lead to potassium deficiency in the body.
• Potassium supplements should not be used just in case without a good reason.

The amount of potassium obtained from food does not affect the amount of potassium in blood as the body regulates this level. Healthy kidneys effectively regulate the excretion of potassium so that, during low potassium intake, the kidneys deposit potassium in the body and, during higher intake, potassium is excreted in the urine.

However, the blood potassium level must remain within certain limits in order for the body to function normally.

Excessively high or low potassium levels may be a sign of an illness. An excessively high or low blood potassium level is usually caused by a kidney problem or by certain medications. Potassium deficiency can also be a result of excessive sweating, vomiting, diarrhoea or an eating disorder. Heavy use of laxatives or diuretics can also cause potassium deficiency. On the other hand, certain diuretics may also cause high potassium levels.

What are the potential symptoms of potassium deficiency?

Potassium deficiency can cause the heart to enlarge and wear out, reducing cardiac contractility. This condition is called heart failure, which means that the heart is unable to pump enough blood to the brain, other organs and muscles.

Athlete’s potassium intake (sweating and potassium)

Heavy physical activity causes profuse sweating. The body excretes water and minerals with sweat. Sweating is affected by diet, body composition, genes and adapting to the climate during exercise. Therefore, there can be large individual differences between people.

In general, the heavier the physical activity, the more potassium is removed from the body. The role of potassium is to feed the muscles while they contract continuously during exercise. The body excretes potassium through urine and sweat throughout the physical effort. Therefore, there is not enough potassium to regulate blood pressure and transfer nerve impulses.

Low potassium symptoms

Potassium deficiency due to physical activity and sweating may cause:

• muscle cramps
• slow reflexes
• nausea
• rapid heart rate
• vomiting.

Endurance athletes in particular must take care of the adequate intake of potassium due to sweating.

Why is the body’s potassium value examined?

The potassium test makes it possible to examine potential fluid and electrolyte imbalances in the body. Excessively high or low potassium levels may be a sign of illness or caused by a medication.

The level of potassium is checked with a blood test.

Potassium reference value P-K

The reference levels may vary depending on the laboratory and the test analysis method.

High potassium

High potassium levels can be caused by, for example:

• potassium-binding diuretics
• acidosis, i.e. excessive acidity of body fluids
• tissue damage such as burns
• diabetes
• Addison’s disease

Hyperkalemia

Hyperkalemia, high blood potassium, is usually caused by an acute kidney disease. High potassium levels make the heart susceptible dysfunction and cause muscle weakness.

Low potassium

Low potassium levels can be caused by, for example:

• low potassium intake
• magnesium deficiency
• excessive non-renal excretion of potassium: diarrhoea, vomiting and excessive sweating

Hypokalemia

Hypokalemia, low blood potassium, is usually caused by the use of diuretics. Diuretics increase urine output, resulting in a higher than normal excretion of potassium. Hypokalemia makes the heart susceptible to arrhythmia and causes muscle weakness.

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