Sodium is an electrolyte which is found in all bodily fluids and is required for the normal function of the human body. Sodium is needed to regulate the amount of water in the body as well as to regulate blood pressure.
Sodium is an essential part of our diet and is needed to ensure the plasma volume of our blood is correct. Sodium is also involved in the transmission of nerve impulses and the normal functioning of our cells. Humans require 200-500mg of sodium per day.
However, the western diet usually means this amount is exceeded which can lead to various health problems. An increased sodium intake has been linked to an increase in blood pressure which is a risk factor for cardiovascular disease.
Hypernatraemia or high sodium levels are usually a result of increased water loss. Symptoms of hypernatraemia include:
The causes of water loss are varied and some which can result in hypernatraemia are:
A common cause of hyponatraemia or low sodium levels is vomiting and diarrhoea due to the loss of water and electrolytes which occurs during diarrhoea and vomiting. Drinking water while you are ill is therefore important to keep yourself hydrated and replace the water already lost. There are electrolyte replacement therapies available from your local pharmacy which can replace the electrolytes including sodium lost due to diarrhoea. If your sodium levels fall quickly then you may feel weak or tired and if severe enough you could fall into a coma. However, if your sodium levels fall slowly there may be no symptoms at all.
Excess fluids in the body can also be responsible for hyponatraemia. This can be caused by drinking too much water, kidney disease, liver cirrhosis, heart failure and malnutrition.
In the western world, our salt intake greatly exceeds what our body needs. A high intake can have a negative effect on our health so it is important to be aware of your individual sodium intake.
High blood pressure is a major risk factor for cardiovascular disease. An increased sodium intake has been linked with an increase in blood pressure, while a reduced sodium intake has the opposite effect.3 Therefore, there is a clear benefit of a decreased sodium intake. Studies have shown that a reduction in sodium can reduce blood pressure which ultimately means a lower risk of cardiovascular events such as heart attacks and strokes.3 The maximum salt (sodium chloride) an adult should consume is 6g per day, while the maximum amount of sodium is 2.5g. Food labels should have their sodium content stated on them for ease. Some labels use a traffic light system which makes sodium and sodium chloride levels easily identifiable.
High salt intake has been linked with dehydration. Dehydration can lead to cardiovascular events, too. Therefore, it is essential to keep yourself hydrated. However, you must get the balance correct because too much water can also have an adverse effect on your sodium balance.
Exercise is beneficial for all aspects of our health: mental, physical and social, but it is important we keep our sodium levels at optimum levels during physical activity. Long distance or endurance exercises can result in low sodium levels or hyponatraemia. One cause of this is a consumption of water or fluid but not electrolytes which exceeds the rate at which you are sweating. In other words, over drinking. So, it is essential that you are aware of your fluid and electrolyte intake during exercise. Likewise, you shouldn’t exercise and not keep yourself hydrated as this can have adverse effects, too.
 Lab Tests Online. (2012). Sodium Test. Available at: https://labtestsonline.org.uk/tests/sodium-test
 Aburto, N, J., Ziolkovska, A., Hooper, L., Elliot, P., Cappuccio, F, P and Meerpohl, J, J. (2013). Effect of Lower Sodium Intake on Health: Systematic Review and Meta-Analyses. BMJ: 346.
 Adrogué, H, J and Madias, N, E. (2000). Hypernatremia. The New England Journal of Medicine.
 Kooman, J, P., van der Sande, F, M and Leunissen, K, M. (2004). Sodium, Blood Pressure and Cardiovascular Pathology: Is It All Volaemia? Nephrology Dialysis Transplantation: 19(5), pp 1046-1049.
 British Heart Foundation. (2018). Salt. Available at: https://www.bhf.org.uk/heart-health/preventing-heart-disease/healthy-eating/salt
 Dmitrieva, N, I and Burg, M, B. (2015). Elevated Sodium and Dehydration Stimulate Inflammatory Signaling in Endothelial Cells and Promote Atherosclerosis. PLoS One: 10(6).
 Montain, S, J., Cheuvront, S, N and Sawka, M, N. (2006). Exercise Associated Hyponatraemia: Quantitative Analysis to Understand the Aetiology. Br J Sports Med: 40(2), 98-105.