Sodium (Na) is a vital element in the body as a part of common salt (sodium chloride – NaCl), and as such is found in every bodily fluid and tissue. It plays a vital part in electrical conduction in nerves, plays a role in muscle contraction and regulates the amount of fluid in the body. The more sodium in the body, the more fluid is retained by the kidneys, and vice versa. Dehydration may be due to lack of water or lack of salt (sodium).
The amount of sodium in the body is regulated by the hormone aldosterone, which is produced in the adrenal glands, which sit on top of each kidney. Salt is obtained from a very wide range of foods. Excess intake in the diet may increase blood pressure.
The recommended daily dietary intake is 140 mg. in infants, 1500 mg. in children and 2000 mg. in adults.
Blood tests can be performed to determine the level of sodium present. The normal range is from 135 to 145 mmol/L. Low levels of sodium (hyponatraemia) may be due to excess water intake, severe diarrhoea, kidney disease, an underactive thyroid gland, diabetes mellitus, Addison’s disease, and numerous other medical conditions. Medications such as diuretics, tricyclic antidepressants, carbamazepine, phenothiazines and clofibrate may also be responsible. An excessively low level of sodium (below 120 mmol/L) is fatal.
High levels of sodium (hypernatraemia) may be caused by dehydration, salt water drowning, uraemia, diabetes insipidus, an over active adrenal gland, excess salt intake and mechanical ventilation.