ACTIVE INGREDIENTS / Potassium

Potassium is the main intracellular cation; it is essential, since it cannot be replaced by other elements. A 70 kg man contains about 140 g. potassium, of which at least 95% is located in the cells. The remainder is in the extracellular liquid at a concentration of 3.3-5.5 mEq (137-215 mg/l). One milliequivalent of potassium (mEq.) corresponds to 39 mg.


WHY IS IT NECESSARY?

Potassium plays an essential role for the body and contributes to most vital functions. It calibrates the water content of cells and regulates osmotic pressure. Along with sodium and chloride it regulates cellular acid-base balance: in metabolic acidosis, potassium is released by cells, while in alkalosis the opposite occurs.

  • In balance with calcium and magnesium, it contributes to the regularity of the main cellular functions and, above all, to the excitability of muscles, heart and nervous system;

  • it is indispensable to the myocardium, on which it exercises direct action;

  • activates enzymatic systems by intervening in the formation of proteins;

  • participates in the synthesis of glycogen and, therefore, in the production of energy.


HOW IS IT TAKEN?

Potassium, being an essential constituent of all living cells, is contained in all foods. Potassium-rich food sources are fresh non-preserved foods such as fruit, vegetables and fresh meat.

  • 100 g. fresh vegetables contain 200-400 mg. potassium; 

  • 100 g. fresh fruit contain 100-200 mg. potassium; 

  • 100 g. bananas contain 380 mg. potassium;

  • 100 g. chocolate contain 420 mg. potassium;

  • 1 liter of wine contains 1040 mg. potassium;

  • 1 liter of Coca-Cola contains 520 mg. potassium.


HOW MUCH IS IT NEEDED?

The supply of normal and balanced feed ranges from 2 to 4 g. per day. Although the recommended daily dose (RDA) is not established, an average dose of 80 mEq/day (3.2 g/day) in adults may be recommended.

In addition, since prolonged doses of more than 150 mEq/day (5.9 g/day) may be hazardous in subjects with impaired kidney function (Swales 1991), and since there are no apparent benefits with greater amounts in healthy subjects, a contribution of 150 mEq/day (5.9 g) can be considered a maximum intake.

These levels correspond to those recommended by the European Commission (1993).


WHEN IS IT LACKING?

Plasma potassium deficiency (hypokalaemia) is relatively frequent and may be due to a food imbalance or a high loss of fluid at the gastrointestinal or urinary levels.

The main causes of a potassium deficiency are:

  • prolonged vomiting;

  • chronic diarrhea;

  • abuse of laxatives;

  • low-sodium diet;

  • prolonged intake of cortisone;

  • diabetic acidosis;

  • use of diuretics;

  • treatment with carbonic anhydrase inhibitors (acetazolamide).


HOW DOES IT WORK?

Potassium, that is, potassium concentration in the blood, is the only available data on the body's potassium balance. However, it is somewhat unreliable because virtually all potassium is found in the cells and its blood concentration cannot provide a reading of its possible intracellular deficiency. Indeed, a decrease in the potassium reserve of cells may accompany normal or even increased potassium. However, its decrease generally indicates a total potassium deficiency that must be corrected.


WHAT HAPPENS IN CASES OF MAGNESIUM DEFICIENCY?

Potassium deficiency can cause:

  • Cardiac disorders (heart dilation, irregular ECG, arrhythmias);

  • Weakness and decreased muscle tone;

  • Cramps;

  • Stomach relaxation, loss of tone in intestine and gall bladder, resulting in constipation;

  • Intense fatigue;

  • Behavioral changes: inability to focus, apprehension and drowsiness;

  • Anorexia, nausea;

  • Acid-base balance alterations: cell dehydration and swelling.


AND IF IT IS PRESENT IN EXCESS?

In the presence of normal kidney function it is almost impossible to induce excess potassium intake. Acute potassium intoxication may occur due to excessive enteral or parenteral potassium administration at levels greater than 450 mEq (17.5 g/day). Acute hyperkalaemia may cause cardiac arrest.


WHEN IS IT PRESCRIBED?

In all cases of hypokalaemia, of any origin: gastric, renal, pharmacological (medications that result in loss of it, such as diuretics, laxatives and corticoids), and in case of increased need (intense physical activity, profuse sweating, etc.).


POTASSIUM AND HYPERTENSION

Several studies have shown that it is not so much excess of dietary salt (sodium chloride) that promotes hypertension, but the imbalance of potassium/sodium in diet. The eating habits of industrialized countries include too much sodium and too little potassium.

Naturally, the sodium/potassium ratio must be more slanted in favor of potassium (for example, in potatoes it is 130/1, in oranges 263/1 and in bananas even 440/1).

There is an inverse correlation between increased blood pressure and potassium intake or the ratio of sodium/potassium urinary excretion. Indeed, adequate potassium intake is necessary to maintain an effective sodium homeostasis.

  • It has been shown that young healthy subjects with low potassium intake (10 mEq/day) were less able to eliminate their sodium load when they assumed 90 mEq/day (3.5 g) of potassium (Krishna et al., 1989).

  • Increased potassium intake at 65-100 mEq reduces blood pressure in individuals with regular blood pressure and hypertension, and increases urinary sodium excretion (Cappuccio et al., 1991).

  • It has been calculated that an increase in potassium intake of 60 to 80 mEq/day (from 2.3 to 3.1 g/day) should result in the reduction of 4 mmHg of the mean systolic pressure, and lead to a reduction of 25% of hypertension-related deaths (Rose, 1986).