Potassium in foodstuffs and beverages

Potassium was discovered in 1807 by Sir Humphry Davy, who isolated it from caustic potash (KOH) by electrolysis.  Potassium is the seventh most occurring element in the earth´s crust and makes up about 2.4% of its constituents by weight.

Natural sources of potassium

Many potassium minerals can be found in ancient lakes and sea beds and often form rather extensive deposits from which potassium and its salts can easily be obtained.  In Northern Germany, for example, potash deposits which can extend of up to 1000m, were formed some 250 million years ago during the zechstein era of the upper permian age, when a shallow tropical ocean evaporated.

Potassium is also found in existing oceans, however, compared to sodium, is present only in relatively small amounts.

A physiologically available form of potassium is present in many foodstuffs, particularly unprocessed fruits and vegetables.

Heating food may cause the leaching of a noticeable portion of the potassium.  Steaming or short frying maintains higher mineral concentrations in foods.  Generally, fruits tend to provide larger amounts of potassium because they are usually consumed unprocessed.

Potassium and diet

Before the evolution of agricultural communities, humans lived as hunters and gatherers and sustained mainly on fruits, vegetables, roots, seeds and nuts, as well as on considerably large amounts of meat. The dietary potassium supply of human ancestors used to be more than sufficient (> 200 mmol/day) because of the high potassium content of many fruits and vegetables.

Dieses aus Pflanzen stammende Kalium spielt bei der Neutralisierung metabolischer nichtkarbonischer Säuren eine wichtige Rolle. Der menschliche Körper verfügt über verschiedene Mechanismen der metabolischen Säure entgegenzuwirken. Obwohl metabolische Säure teilweise direkt durch die Nieren eliminiert wird, reicht die Ausscheidung über den Urin allein nicht aus.

The plant-originating potassium plays an important role in the neutralization of metabolic non-carbonic acid. The human body utilizes several mechanisms to compensate metabolic acid.  Although metabolic acid is partially eliminated directly by the kidneys, urinary excretion alone is insufficient.

Potassium and bone density

A major part of metabolic acid is neutralized by alkaline calcium salts from the skeleton, the body’s largest mineral reservoir.  Provided that an individual develops acid continuously through a regular diet, this process results in a constant leaching of calcium from the skeleton and the calcium salts used in the acid elimination are eventually excreted by the kidneys.

This hard tissue re-absorption may result in reduced bone density, which may contribute to osteoporosis.

An effective acid-base regulator is the buffering of metabolic non-carbonic acid with potassium bicarbonate.  The plant-originating potassium mentioned above, plays an important role in this process.  Much of the potassium in fruits and vegetables comes as potassium malate and potassium citrate.  These cations are turned into bicarbonate, whereas it is still not fully understood which tissues are responsible for this transition.  The metabolic product, KHCO₃, is able to neutralize non-carbonic acid from the protein metabolism, minimizing urinary loss of calcium from the bones.

Potassium and blood pressure

Blood pressure regulation depends on many different factors.  It is widely accepted that potassium plays a key role in blood pressure modulation.  The currently observed level of foods low in potassium and high in sodium is commonly considered to lead to an elevated blood pressure.  On the opposite, moderately excessive dietary potassium does apparently not pose a concern to healthy adults. Based on a number of studies demonstrating an inverse correlation between a potassium supplementation and blood pressure, authors frequently recommend a professionally controlled supplementation of affected individuals with potassium.

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