Sodium and its importance for humans

Sodium is an indispensable mineral for the human organism. An optimal supply of sodium is important to bind fluids in the body and to keep metabolic processes running. Fluctuating levels impair the function of the brain in particular. Especially for older people, disturbances in the sodium balance are risky, in severe cases even life-threatening.

Sodium is a chemical element with the symbol Na. Depending on how it combines with other elements, it also changes its properties. As a metal, sodium is soft, silvery white, shiny and reactive. If sodium is put into water in this form, it starts to burn and can explode. In contrast, it is harmlessly available to the body in the form of sodium salts.

Sodium is one of the most important electrolytes for humans. All cells depend on this mineral. Together with other minerals, it regulates blood pressure, heart rhythm and the transmission of electrical signals in nerve and muscle cells. Sodium also plays an important role in regulating the water balance and ensures a balanced acid-base balance. Sodium levels are regulated by the kidneys. If there is too much sodium in the blood, our body increases excretion via the urine. If the intake is too low or the loss is too high, sodium is reabsorbed.

According to the German Nutrition Society (Deutsche Gesellschaft für Ernährung e. V.), adults need an average of 1500 mg of sodium per day. If the sodium level in the blood is low, this is called hyponatremia. Increased sodium levels are called hypernatremia.

We supply our body with sodium in different amounts through food and drinks. The most important source of sodium for humans is sodium chloride, a compound of sodium and chloride (NaCl). In common parlance, it is called table salt or table salt. In addition to its use in cooking and seasoning, sodium is also used for preservation and is therefore present in processed foods. Bread and rolls, salami, cheese, ketchup, sauerkraut, salted herring and savoury biscuits, sauces, preserves and ready meals are particularly high in sodium. You can find information on how much salt is contained in the product on the nutrition label of the food packaging.

A short-term overdose due to an increased salt intake is harmless for healthy people, as it is excreted again via the kidneys. In this way, our body maintains a constant sodium level. But what happens when this balance is disturbed?

Decreased sodium levels are mainly caused by pre-existing conditions (such as hypothyroidism or adrenal insufficiency) or by taking certain medications (for example, dehydrating tablets, antidepressants or antihypertensives). A low-sodium diet, fasting cures or gastrointestinal diseases are also possible triggers. In rare cases, sodium deficiency can be caused by tumours that produce the hormone ADH (antidiuretic hormone) or similar substances. These cause increased sodium excretion.

One third of sodium is stored in the bones and can be mobilised in case of deficiency. However, if there is too little of it in the body, it tries to compensate for the sodium deficiency by sucking water out of the blood. This increases the intracranial pressure. The consequences are headaches,  mental confusion, memory problems and dizziness. This increases the risk of falls. Low blood pressure can also be the result of an undersupply of sodium.

Causes of elevated sodium levels are severe fluid loss through sweating, high fever, gastrointestinal diseases and dehydrating medications, or reduced sodium excretion due to pre-existing conditions (such as poorly controlled diabetes). In addition, an extremely high salt intake in the diet or insufficient fluid intake through drinks can cause an excess.

Especially as we get older, the body's ability to maintain the balance of fluid and sodium decreases. Many seniors feel less thirst and forget to drink. In addition, their bodies generally contain less water compared to young people. When there is a lack of fluid, the kidneys reduce excretion, which leads to an increase in the concentration of sodium in the blood. This leads to a condition called hypernatremia.

The symptoms depend on how pronounced the excess sodium is. In the early stages, our body shifts water out of the cells into the extracellular space, creating a feeling of thirst. Later, restlessness or lethargy, states of confusion, movement disorders or seizures occur. Severely increased sodium concentrations lead to life-threatening symptoms. The cells, especially the brain cells, become dehydrated. This can lead to impaired consciousness and even coma.

The two minerals are unequally distributed in the organism. Sodium is outside the cells, whereas potassium is inside the cells. The potassium concentration is lower than the sodium concentration, which ensures an osmotic balance. The uneven distribution is the basis for the function of many organs, for example the irritability of the nerves and muscles. The body's cells represent a kind of "mini-battery" for energy production. However, due to the modern diet, sodium intake tends to be too high and potassium intake too low, which can lead to fatigue and muscle weakness, among other things.

In case of deficiency symptoms or complaints that indicate high sodium levels, a doctor must be consulted for further clarification and treatment. He or she can carry out a physical examination and  talk to the patient to find out what triggers could be responsible for the symptoms (for example, changes in dietary habits). If he suspects a disturbed sodium level, he will order a blood sample to be taken. Sodium can also be measured in the urine. The normal value in the blood serum is 135 to 145 mmol/l, the optimal sodium level in 24-hour urine is 120 to 220 mmol/l.

The subsequent therapy depends on the cause. Normalisation of the sodium concentration can be achieved by administering fluid in the form of drinks, infusions, medication or a reduced or increased sodium intake with food.

As we age, we become more sensitive to fluctuations in sodium levels. Both decreased and increased values lead to physical and mental complaints. Regular monitoring of blood levels is therefore advisable, especially for seniors.