Potassium is an alkali metal which is found mainly as potassium chloride. In the body potassium is one of the main ‘electrolytes’ alongside sodium and chloride. These minerals carry an electrical charge.
Potassium carries a positive charge (it is known as a cation). Of around 115-150 g of potassium that is present in the body up to 98% is found within the cells.
Potassium and sodium are particularly linked. Together they help to maintain a normal water balance in the body.
Potassium is also involved in muscle contraction, sending nerve impulses and releasing energy during metabolism.
Most people have a potassium intake of between 3-4 g per day. It is estimated that around a quarter of this comes from dairy products and a quarter comes from plants and vegetables. Surprisingly one of the best sources of potassium in the human diet is coffee, with fruits, especially dried fruits, ranking next. Good potassium sources in the diet are:
- Instant coffee
- Dried peaches
- Leafy green vegetables, e.g. spinach, chard.
- Citrus fruits
- Dairy foods
Healthy individuals who eat a balanced diet rarely need to supplement their diets with potassium.
Absorption of potassium is very efficient. Some estimates state that up to 90% is absorbed. However as one of the most soluble of all minerals potassium is unfortunately lost through many cooking processes and the processing and manufacture of food.
Potassium is absorbed from the small intestine and requires no specific structures or mechanism. The process is passive diffusion. The amount that is absorbed is very dependent on the amount of potassium that is in the small intestine. Absorption will stop if the level in the intestine is lower than that in the bloodstream.
Most of the excess potassium is eliminated in the urine via the kidneys. Some is eliminated as sweat and when we perspire we should then try to replace lost potassium by drinking fruit juice.
Depletions of potassium can cause serious health problems. It is therefore vital that consistent levels of potassium are maintained.
Deficiency can lead to a variety of conditions:
- Muscle weakness
- Water retention
- Nausea and sickness
- Depression and mood changes
- Cardiac arrhythmia
- Reduced reflexes and even paralysis
Potassium deficiency is rare and does not occur under normal conditions. The most common causes of potassium deficiency are vomiting, diarrhoea and excessive sweating which can occur as a result of uncommon heat or exercise.
Potassium levels are also known to decrease through ageing and chronic illness. It is important that infants are monitored carefully if they suffer from diarrhoea because it is easy for them to become lacking in potassium.
Health conditions which can lead to lowered levels of potassium include diabetes and renal disease. Chronic potassium problems have also been noted in those with cancer, heart and liver disease.
Several drugs may also cause low levels of potassium; of most relevance are diuretics and laxatives.
In diagnosed cases of potassium deficiency the levels can be raised by increasing the intake of potassium rich foods in the diet, taking oral supplements or in severe cases, potassium-containing drugs.As previously mentioned sodium and potassium are very closely linked. Magnesium is also involved in maintaining the potassium levels in cells.