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Sodium, Na, Na+, Natrium

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Although sodium is metal it is not found in nature in its free form, but just in compounds or ionic form. It was first isolated by Humphry Davy in 1807.

Sodium ions are needed in small amounts in plants and much more in humans duo to its important role.

Salt, which is the main source of sodium, had a very important role in people's lives in past, so it was used for payment of salaries. Thus, for example, the Roman soldiers sometimes in addition to other income received and a lump of salt.

Physiological role of sodium

In humans, sodium plays a key role in the regulation of blood volume, blood pressure, osmotic balance and maintain a constant pH.

Renin–angiotensin system - hormone system that regulates blood pressure and fluid balance influences the amount of sodium in the body. Lowering blood pressure, and serum sodium in the kidneys leads to the formation of renin. Renin is an enzyme that is known as angiotensin-converting-enzyme and mediates the regulation of extra cellular fluid volume (plasma, lymph, intestinal fluid), and arterial vasoconstriction. In this way, regulate blood pressure. Renin causes the production of aldosterone and angiotensin (hormones) that cause sodium excretion in the urine.

Increasing the concentration of sodium decreases renin formation and sodium returns to normal.

Sodium is also essential for the functioning of neurons and osmoregulation between cells and the extracellular fluid. In humans, this process is regulated by the Na+/K+ pump.

Metabolism

Sodium is the most abundant cation (positive ion) of extracellular fluid. The 15 liters of extracellular fluid (in a person of 70 kg) is about 50 g of sodium, or about 90% of the sodium in the body. Extracellular fluid perform the funcion of nutrient transport into cells and cellular waste from the cells.

Although the system for maintaining the balance of sodium and water in the body is complex, one of the main ways in which the human body control the lose of body fluids that osmoreceptors in the hypothalamus maintains the balance between sodium and water in the extracellular fluids. The relative loss of body water leads to a relative increase in the concentration of sodium and this is called sodium overdose and is manifested as thirst.

On the other hand, excess of body water caused by increased water intake will lead to sodium deficiency, which is registered by the hypothalamus, causing a decline in the secretion of the hormone vasopressin in the back lobe of the pituitary gland and consequently the loss of water in urine.

Food sources of sodium

Since plants contain small amounts of sodium, a diet that is based only on plant foods is low in sodium. Therefore, vegetarians recommended sodium intake through sea salt.

Sodium is much aboundant in sea salt.

A good source of sodium is canned food, sausage, fast food, a variety of snacks, spices.

Sodium is also present in meat, eggs, chicken, seafood, fish, and vegetables such as carrots, beets, cauliflower, celery.

Recommended daily allowance

The minimum physiological requirements for sodium in humans are 500 milligrams a day, but it is recommended intake to 2.3 grams per day. In many countries, people consume more than 3.4 grams per day, which can cause high blood pressure (hypertension).

Sodium deficiency - hyponatremia

Excess of water in body caused by increased water intake will lead to sodium deficiency - hyponatremia, which is felt by the hypothalamus, causing a decline in the secretion of the hormone vasopressin in the back lobe of the pituitary gland and consequently the loss of water in urine.

Hyponatremia is often a secondary phenomenon in other diseases where there is a build up of water in the body.

Symptoms include nausea, vomiting, headache, confusion, lethargy, fatigue, loss of appetite, restlessness, irritability, muscle weakness, cramps, and in severe cases, decreased consciousness and coma.

Many diseases are associated with hyponatremia: heart failure, impaired liver, kidney and lung.

Various neurological symptoms are accompanied by a lack of sodium.

Overdose - hypernatremia

The relative loss of body water leads to a relative increase in the concentration of sodium and this condition is called hipernatemia, manifested as thirst.

It is often in dehydrated individuals (eg, people who have been rescued from the sea or desert) observed a high concentration of sodium in the blood. The return of these people to normal should be gradual because too rapid treatment of hipernatremia leads to brain damage caused by swelling of cells.

Hypernatremia usually occurs due to water loss from the body and is therefore often referred to as the less precise term dehydration. Water is lost from the body in several ways: the sweat, breath, feces and urine. It is rarely that sodium overdose occur in excessive intake of sodium (e.g. in cases when drinking sea water).

Symptoms of hypernatremia are lethargy, weakness, irritability, neuromuscular irritability, oedema, coma.

References

Malhotra V.K., 1998, “Biochemistry for Students. 10th Ed,” Jaypee Brothers Medical Publishers (P) Ltd, New Delhi, India. [Web Reference]

Soetan K.O., Olaiya C. O. and Oyewole O.E., 2010, “The importance of mineral elements for humans, domestic animals and plants-A review,” African Journal of Food Science; 4(5): 200-222. [Web Reference]

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