Potassium (K) is a 95% cation present inside cells. It is an essential trace element, therefore NOT replaceable or synthesizable by the body.
In the body of an adult there are about 110-140g of potassium, or 1,6-2 g of mineral per kg of body weight; of these 5,9 g / l are found dissolved in the intracellular fluids and only 137-215 mg / l are found in the extracellular fluid.
Functions of potassium
Its homeostasis is closely linked to that of sodium (extracellular electrolyte) and is maintained mainly thanks to the SODIUM-POTASSIUM pump. This trans-membrane structure represents a path for the passage of molecules against a concentration gradient, useful for controlling osmotic pressure and acid-base balance.
The extracellular portion of potassium is involved in the transmission of nerve impulses, muscle contraction and blood pressure regulation.
NB. The amount of potassium in the body is directly proportional to the cell mass, therefore, its body measurement is frequently used in estimating the individual lean mass.
The supply of potassium (K) with the diet occurs above all in an ionic form that is easily absorbed in the small intestine. Although there are three ways of excretion of potassium: intestinal, urinary and with sweat, it is essential to underline that potassium, due to its importance in the maintenance of numerous physiological processes, is a trace element subject to the control of renal filtration; this means that, although dietary variations or physiological losses that are more than significant may occur, the homeostasis of this electrolyte is guaranteed by the balance of the relationship between glomerular filtration and tubular secretion.
Potassium in food and diet
Potassium is an almost ubiquitous trace element in food, drinks and even water. In healthy subjects with ordinary physical activity, rather than the overall intake of potassium in the diet, it would be appropriate to consider the potassium / sodium RATIO (K: Na), a parameter that seems decidedly higher (therefore BETTER) in fresh foods, not processed and not preserved (fruit, vegetables and fresh meat).
The potassium intake with drinking water is variable (based on the quality of the water) but in any case not decisive with respect to the dietary one.
A sufficiently balanced and "average" diet rich in potassium brings from 3 to 5g / day, while its urinary excretion is around 2,3g / day. Knowing the renal saving mechanisms of potassium, which in case of need would drastically limit its elimination, these values allow us to deduce that a potassium intake of 3-5g / day may be more than sufficient for the homeostatic maintenance of essential functions.
NB. The potassium balance in athletes is completely outside the above values; we remind you that, despite it has been specified that NORMALLY the potassium quota eliminated by sweating can be defined as almost irrelevant, a sportsman (especially endurance) can be subjected to repeated changes in the water balance that reach 3-4% of their body weight . In this case it is essential to assess the extent of the overall dietary intake of potassium and possibly draw up a diet rich in trace elements; it is also possible and sometimes desirable to resort to hydro-saline dietary supplementation.
As anticipated, potassium is an almost ubiquitous mineral (it is found in many foods) but nevertheless it represents one of the most used nutrients in food supplementation; this means that many subjects, with their diet and supplements, take a higher amount of potassium than their own needs. However, assuming renal function is at least NORMAL, pathological excess potassium in the blood - termed hyperkalaemia or hyperkalaemia - is unlikely to say the least. Potassium intoxication can occur in the clinic by excessive enteral or parenteral administration at doses> 17,5 g / day (3 or 4 times the mean dose).
NB. Acute hyperkalemia can cause cardiac arrest.
Potassium deficiency, better defined as hypokalaemia, can occur via the gastrointestinal tract in the case of prolonged vomiting, chronic diarrhea or abuse of laxatives, or via the urinary route through the abuse of diuretics, in the presence of some types of chronic kidney disease or metabolic disorders such as diabetic acidosis. A similar disorder can induce electrical alterations of cell membranes causing: muscle fatigue, anorexia, nausea, inattention, apprehension, drowsiness and behavioral alterations.
NB. Hypokalaemia, in the most severe cases, can give rise to fatal cardiac arrhythmias and ileo-paralysis.
Diet rich in potassium and hypertension
Some studies have reported an inverse correlation between increased blood pressure and urinary excretion of potassium. It seems that a diet rich in potassium is essential for maintaining sodium homeostasis; in fact, subjects who do not reach satisfactory dietary levels of dietary potassium are not able to effectively eliminate sodium compared to those who have a diet rich in this mineral.
Ultimately, a potassium-rich diet can:
- Indiscriminately and significantly reduce mean systolic blood pressure
- Hypertension-related deaths are likely to decrease by up to 25%
NB. With a diet rich in fresh vegetables and fruit, it is also possible to reach a potassium intake higher than 10g / day.