Potassium

Potassium, with the chemical symbol K, is an alkali metal with atomic number 19. In its pure form it is silvery-white shiny and almost waxy. In air, it reacts very rapidly to form potassium oxide, and over a longer period of time it reacts with carbon dioxide in the air to form potassium carbonate, which is also known as potash (K2CO3). In the Earth's shell, it is the 7th most abundant element. It does not occur elementally in nature. The most important potassium compounds are potassium salts (e.g. KCl), potassium feldspar or the potassium mica. In the course of the earth's history, the potassium salt deposits were partially washed out and washed into the sea, hence the proportion of potassium salts in seawater. Potassium plays only a minor role in technology. For example, potassium compounds are used in soap production, in the glass and ceramics industries, or as drying agents in laboratories or in oxygen equipment. The element potassium was discovered and described in 1807 by the English chemist Sir Humphrey Davy (1778-1829) together with sodium in London. Its name is derived from the Arabic word Kalja = ash. In medicine, potassium permanganate (KMnO4) is of some interest as a special potassium compound. This substance is used for external application as an antiseptic in a concentration of 0.01-0.05% for disinfecting injuries because of its very strong oxidative effect, but it is increasingly being replaced by other active ingredients. However, a more common use is still as a disinfectant additive in rinses and baths.

Functions in the body

Potassium is an important electrolyte in the body, and is therefore also frequently measured routinely during blood tests. The potassium concentration in the serum must be between 3.5 and 5.5 mmol/l. Potassium is mainly, and in fact about 98%, present in the interior of cells. Potassium is also involved in the production of energy and in the water-electrolyte balance. Together with other electrolytes (charged particles) and molecules, it is essential in maintaining osmotic pressure in cells. Among other things, potassium is involved in the activation of some enzymes, in the biosynthesis of protein, and in carbohydrate metabolism and thus in energy production. Together with sodium, calcium and chlorine, potassium affects heart muscle activity and is responsible for the excitability of muscle and nerve cells. This occurs through the build-up of an electrical potential difference between the cell interior and the cell exterior. In this process, the cell interior of a heart cell is charged to about -70 mV and that of a muscle and nerve cell to about -90 mV relative to the cell exterior. For those who are particularly interested, this process can be explained as follows: The cells of the heart, like the skeletal muscle cells, have an electrical voltage between the cell interior and cell exterior. In skeletal muscle, the voltage between the cell interior and the cell exterior is about -90 mV (mV= millivolts) at rest, and in the heart it is about -70 mV, with the cell interior negatively charged relative to the cell exterior. Essentially responsible for this voltage is the property of the cell membrane to have different permeabilities for the different ions that are in the body. By means of chemical, mechanical or electrical stimuli, this permeability of the membrane can be changed. A skeletal muscle maintains its electrical tension permanently without external stimuli, e.g. nerve stimulation. This is different for the cells of the heart. To generate a voltage of -70 mV in the heart, there is a concentration difference of about 10 mmol/l = 0.23 g/ to 140mmol/l = 3.22 g/l for the Na+ ions between the cell interior and the cell exterior. Furthermore, there are also concentration differences for K+ and Cl- and a number of other ions. For example, the K+ concentration in the cell interior is 140 mmol/l = 5.47 g/l and in the extracellular space is 4 mmol/l = 0.16 g/l. In contrast to the skeletal muscle cell, the resting potential of -70 mV is not stable in cardiac cells . Small amounts, mainly Na+ enter the cell interior. This leads to a reduction of the voltage from -70 mV inside the cell to more positive values of e.g. -60 mV. The more positive (= lower negative) the cell interior becomes, the greater the permeability of the cell membrane for Na+ and the more positive in turn the cell interior becomes. From a threshold of about -50 mV, the permeability of the cell membrane changes very rapidly, allowing relatively more Na+ to enter in a very short time. This leads to a voltage reversal of +30 mV with respect to the cell exterior. During this process, Na+ permeability then decreases again and that for K+ and Cl- increases. K+ flows out of the cell and Cl- flows in. This occurs until the original state is restored, i.e. the cell interior again has a voltage of around -70 mV. It should be mentioned that the extremely small quantities of Na+ ions flowing into the cell and the K+ ions flowing out are always transported out or in again by means of so-called active processes.

Foods rich in potassium

Potassium is mainly found in cereals, vegetables and fruits. Chanterelles, for example, contain around 5 g of potassium per 100 g of dry matter. Fruit, especially bananas, green vegetables such as spinach, lettuce and parsley, wholemeal bread, meat and fish are good sources of potassium. For example, 100 g of banana contains about 400 mg (0.4 g) of potassium. It should be noted, however, that potassium goes into solution when food is prepared by prolonged soaking or boiling, and is thus discarded with the cooking water. In the case of kidney diseases, where the mineral balance is disturbed, one makes use of this fact. That is why vegetables and potatoes are left to soak for a long time when prepared for kidney patients. Potassium deficiency is not usually to be expected in a normal diet, since adults consume at least 2 g of potassium daily. Deficiency possibly occurs with malnutrition or nutritional deficiency. Patients suffering from certain cardiovascular diseases, such as high blood pressure, require slightly more than twice the normal daily amount and should therefore discuss their dietary habits with their attending physician or a nutritional counselor.

Hypokalemia, potassium deficiency

Hypokalemia is a decrease in blood serum potassium below 3.5 millimoles per liter (mmol/l). It is the most common form of electrolyte disorders. The causes of such potassium deficiency may include:

• Vomiting, diarrhea, misuse of laxatives.
• increased excretion via the kidneys, e.g. during therapy with diuretics
• Cushing's syndrome
• inflammatory bowel disease
• Alcohol abuse
• too much salt consumption
• Reduced intake of potassium, e.g. in nutritional disorders such as bulimia or potassium-free infusions.
• acute alkalosis (acid-base balance disorder)
• Distribution disorders as in insulin therapy or diabetic coma
• advanced age, dehydration due to insufficient fluid intake

Heavy sweating and physical exertion can cause a deficiency of potassium. This deficiency can cause a number of disturbances in the body that are relatively non-specific: for example, muscle weakness, fatigue, headaches, dizziness, nausea, cramps and fluctuating moods. Potassium deficiency also causes blood glucose levels to drop, resulting in symptoms of hypoglycemia. Furthermore, kidney dysfunction, cardiovascular problems (often characteristic ECG changes are found) and intestinal sluggishness due to reduced muscle tone can be the result of potassium deficiency.

Hyperkalemia, excess potassium

Hyperkalemia refers to elevated blood serum potassium levels above a value of 5.5 millimoles per liter (mmol/l). The causes of such an increase in potassium may be due to an increased intake, e.g. through infusions or blood transfusions. Furthermore, hyperkalemia can occur when potassium is increasingly released from body cells. This can be the case in hemolysis (destruction of red blood cells by destruction of their cell membrane), acidosis (hyperacidity in the blood), as well as in severe injuries, burns or infections. Kidney disease or potassium-sparing diuretics can also lead to elevated serum potassium levels. Dialysis patients are particularly susceptible to potassium overdoses, and eating too much banana can have serious consequences. With a few exceptions, the symptoms of hyperkalemia are essentially the same as those of hypokalemia described earlier. One exception, for example, is that an elevated potassium concentration results in diarrhea rather than constipation.

Potassium poisoning

In the case of potassium poisoning, bradycardia occurs, i.e. a reduced heart rate up to cardiac arrest, muscle weakness and confusion. Furthermore, speech and swallowing disorders occur. A lethal dose is considered to be about 10 to 20 g of potassium salts, e.g. KCL. As therapy, gastric lavage with physiological saline solution can be performed. Furthermore, cation exchangers or infusions with sodium hydrogen carbonate are used. In threatening cases, hemodialysis is performed. In the event of potassium poisoning, it is particularly important to monitor cardiac activity (ECG) and determine the potassium concentration in the blood.

Daily potassium requirement

The exact requirement for potassium cannot be clearly determined, as it depends on a number of parameters for each individual. For people over the age of 17, the minimum requirement is estimated as an average of around two grams of potassium per day. For children and adolescents, the requirement is one to two grams, according to the German Society for Nutrition. Infants need about 450 to 600 mg daily. Potassium is found in many foods. The daily requirement is therefore generally considered to be covered. Due to various conditions, however, there may be an additional need for potassium.

Demand in sport

When potassium leaves a cell, sodium migrates into the cell. In the process, the cells need the potassium for their growth and the synthesis of protein. For this reason alone, the mineral is of interest to anyone who wants to build their muscles.

Potassium and low carbohydrate diets

Diets that avoid foods rich in potassium, such as fruits and vegetables, can have problems. This is especially true of high-protein, low-carbohydrate diets - which, after all, are supposed to avoid fruits and vegetables. Their diet plans inevitably lead to high acidity in the body, which can cause muscle weakness during exercise and suppress protein synthesis. In the course of a low-potassium diet, the kidneys are also no longer able to conserve the mineral to a sufficient extent and secrete more and more potassium. This is already the case if you consume less than one gram a day - even then hypokalemia can occur. Its symptoms manifest themselves in muscle weakness, cardiac arrhythmias and glucose intolerance - all of which, of course, have a negative impact on your workouts. That's why many on a low-carb diet often feel weak and tired - as a result of insufficient potassium intake. There are also the natural diuretic effects that come from the low-carb diet: A general loss of water, which is particularly noticeable at the beginning of the diet. In addition, the body excretes various minerals along with the water - especially sodium and potassium.

Caution with potassium-sparing diuretics

Supplementation with pharmaceutical diuretics eliminates all minerals that hold water in the body - especially sodium - to get rid of the last excess water under the skin. This is why many bodybuilders take a high dose of potassium before their competitions, because the loss of potassium, calcium and magnesium can lead to muscle cramps, and that's the last thing you need on stage. With potassium sparing diuretics, the potassium (as the word also says) is spared. Under normal conditions, such potassium sparing drugs are not a problem either. However, it becomes dangerous when these diuretics are combined with potassium supplements! There is a high concentration of calcium in the blood (hyperkalemia) and this can lead to cardiac death if it is not detected in time.

Dosage

Even if the athlete excretes fewer minerals in sweat than the average person, this is not true for potassium and magnesium. A potassium deficiency is therefore widespread among athletes. The need is at least 3-5g a day to take with meals. In any case, one should avoid taking a potassium supplement on an empty stomach. This is because it signals the adrenal glands to release aldosterone, which in turn helps the kidneys to excrete potassium and retain sodium. This can lead to edema, the leakage of fluid from the vascular system. If the body retains proportionately more potassium than sodium, this aids in the secretion of excess sodium - which, on balance, means less water under the skin.