Potassium is one of the main macroelements that we must take in with the diet. At the same time, our kidneys are perfectly capable of maintaining blood potassium values within the physiological range. Despite this, some foods, for example fruit, vegetables, legumes and lean meats, can allow you to take the right amount with your diet.
This aspect, associated with the right consumption of water, allows the kidneys to work at their best and ‘repays’ us by giving us all the energy we need in our busy days.
How many of you have not thought at least once in your life of taking a potassium tonic when they feel weak? And again, how many don’t associate the consumption of bananas with the need to counteract these deficiencies? Well, these are only two half-truths!
Clearly, in the event that physical activities are carried out that can lead to a greater excretion of this element, it is also necessary to correct the diet. An example above all? The practice of anaerobic sports.
What is potassium
Despite its infinitesimal dimensions, potassium is included in the category of food macroelements.
This occurs because this chemical element, together with other known ‘relatives’ such as sulphur, sodium, calcium or magnesium, is indispensable for our body.
Suffice it to say that it is one of the minerals most present in the cells of the human body, reaching quantities of about 180 g.
Despite this importance, our body always tends to eliminate the same amount of potassium with urine and feces, regardless of what we have introduced with the diet. It goes without saying that diets lacking in this element can cause a strong physiological deficiency known as malnutrition.
There are basically two organs responsible for managing potassium: the muscles and the liver. These are two real potassium warehouses capable of releasing it into the blood whenever it is needed.
Which organ allows it to be absorbed
Since it is a mineral that we can only take in with the diet, it goes without saying that the absorption of this element takes place in the intestine.
For greater precision, potassium is absorbed from the food bolus, in the first part of the intestine. I am referring in more detail to the duodenum and jejunum, intestinal segments responsible for the absorption of most nutrients.
How it is absorbed
Specifically, we speak of negative feedback regulation, as the higher the concentrations of potassium in the blood, the lower the efficiency with which this element is filtered at the renal level.
In addition, it should also be noted that blood potassium levels do not remain constant throughout the day.
In fact, in the hours of light, the potassium in the plasma tends to decrease and then increase again during the hours of darkness. So, this explains why we often feel more tired in the summer. We mustn’t be alarmed… we are physiologically predisposed to greater asthenia due to a normal reduction in the availability of this element.
Action of hormones on the uptake of potassium into cells
Some hormones show an action favoring the absorption of potassium into the cells or an opposite action.
In the first case, we speak of insulin and β-adrenergic catecholamines. In the second case, the reference is directed towards aldosterone.
In more detail, the first two hormones have an action that favors the entry of potassium into the muscle cell as they act directly on the sodium/potassium pump.
Instead, aldosterone stimulates the release of potassium outside the cell by reversing the polarity of the same pump.
What is potassium used for?
Its functions in the human body are innumerable and to name them all would be truly impossible.
Suffice it to say that this ion, having a key role in regulating the cellular balance, is part of infinite physiological processes.
Not surprisingly, the importance of potassium homeostasis is underlined by the fact that patients with high or low potassium die more from any cause. At this point, let’s do some clarity, trying to give an order of importance, on the main roles of potassium.
Regulation of membrane potential
It is a key aspect of the propagation process of electrical impulses. For example, it is enough to think that this regulation is the basis of the transmission of nerve and muscle impulses. To this, its cardiac activity is also added.
Indeed, even the contraction of the heart, being an involuntary muscle, is managed, among others, by this mineral salt. It is not uncommon to record cases of heart failure due to altered concentrations of this as well as other ions. So, summarizing some of the physiological functions related to the membrane potential, they include the control of:
- vascular tone.
- Blood pressure.
- Gastrointestinal motility.
Control of protein and glucose metabolism
Once the body has managed to assimilate sugars and proteins from the intestine, it must transport them to the cells.
Also in this process, potassium is actively involved. In fact, this ion specifically participates in two processes. First, it presides over the synthesis of proteins. Secondly, it contributes to the transformation of dietary sugars into reserve sugars.
I am referring precisely to glycogen, a form of sugar present in the liver and kidneys. It acts as an energy reserve during any physical activity.
Correct hormone secretion
It also actively helps our glands. In fact, many of them use it as an activator ion of some chemical steps necessary in the production of hormones.
Regulation of the movement of nutrients to and from cells
In chemistry, when a difference in the concentration of charges is created between one side and the other of a membrane, in the presence of water, we speak of osmotic potential.
In this regard, in the cells of living beings, this principle is the basis of the passage of nutrients through a membrane. And if we think of cells, the first membrane that comes to mind is the one that gives integrity to the cell itself.
Potassium is one of the major ions involved in the generation of this osmotic potential. Therefore, where there is potassium, there is also an active exchange of molecules entering and/or leaving the cells.
Balancing the acid-base balance
If you think of a ‘positive’ person, you immediately think that his alter ego is a ‘negative’ person. The same goes for electric charges. And as in the best of love stories, polar opposites attract. When this happens, i.e. a positively charged molecule and a negatively charged molecule join together, a molecule known as an acid-base is generated.
This mechanism, sometimes very complex, is one of the pillars of human physiology. In fact this system, known as a buffer, helps maintain the correct balance between acids and bases in our body.
And what does potassium have to do with it? Being one of the best known positively charged molecules in our body, it has a very important role in regulating the physiological acid/base balance. This role is performed together with sodium and its ‘opposite pole’, ie chlorine (Cl–).
Contrasts osteoporosis and kidney stones
We have seen that potassium helps regulate the excretion of liquids in the urine, supporting the kidneys.
Well, in this area, its presence reduces the risk of kidney stones and the possibility of bone loss (osteoporosis).
Contrast of water retention
As seen before, the distribution of charged molecules on the two sides of a membrane is at the basis of the generation of an osmotic equilibrium.
When this balance is broken, water moves to one side or the other of the membrane itself. This principle is the basis of water retention. In this pathological condition there is an imbalance between the amount of potassium found inside the cells (intracellular environment) and the amount of sodium present outside (extracellular environment).
In fact, an imbalance in favor of sodium generates a greater retention of water with consequent edema and swelling. In these cases, reducing sodium intake by increasing potassium intake can help counteract this phenomenon. How to do? Choose the right foods and avoid excessive salt additions to foods.
Daily requirement of potassium
The recommended daily requirement of potassium for adults is 3.9 g/day per day. But these quantities vary in the case of an infant, an infant or an adolescent.
In the case of an infant, a daily intake of approximately 0.7 g/day of potassium is sufficient. This quantity rises to 1.9 g/day between the ages of 1 and 3 years and to 2.3 g/day between 4 and 6 years.
A further increase is expected in the age group between 7 and 10 years (2.8 g/day of potassium) while from 11 years onwards, the requirement settles on the values expected for an adult.
It should be noted that no variations in potassium intake are recommended for pregnant or breastfeeding women.
It is a mineral salt abundant in nature. Therefore, it is easy to find variable concentrations of this element in an infinite number of foods.
For a detailed list of all foods and their potassium content, please refer to the attached table.
I give a brief summary of the same table below, listing the most common foods in the diet…