Digestive Health

Updated 06 August 2014

Why electrolytes are so important

There is much talk about electrolytes and how important it is to not lose or overdo them. But do you know what electrolytes actually are and why they are so vital to the body?

I recently realised that I seem to be warning the public about not depleting their electrolytes all the time, but that most people are probably not really acquainted with the idea of what electrolytes are and why they should be so important and why one should not lose or overdo them! So let’s have a look at what electrolytes are and what roles they play in the human body and why it is so vital not to lose them through the overuse of diuretics (water pills) and laxatives and excessive water intake or to ingest such excessive quantities that they also make us very ill.

What are electrolytes?

Electrolytes are chemical elements or minerals such as sodium, potassium, magnesium and calcium, as well as salts including chloride, bicarbonate and phosphates. Electrolytes can either be simple salts, for example sodium chloride, or complex organic molecules.

These electrolytes have the capacity to undergo a process called disassociation which turns them into substances called ions which carry positive or negative charges. In chemical reactions, 1 quantity (a milliequivalent or mEq) of an ion with a positive charge (also called an anion) will combine with 1 mEq of an ion with a negative charge (also called a cation) (Mahan et al, 2012).

The reason why it is important that cations and anions should balance each other out in the human body is that they are found both inside the cells and outside the cells. For example, it is important that a balances must be maintained between the fluid surrounding a body cell and the fluid inside a body cell. If this balance is disturbed, then the cell may lose some of its fluid and become dehydrated which in extreme cases can lead to damage or death of the cell.

According to Mahan and her coauthors (2012), the most important electrolytes on the outside of the cells are sodium, calcium chloride and bicarbonate. The most important electrolytes inside the cells are potassium, magnesium and phosphate.

Vital functions

Electrolytes perform so many vital functions in the human body that if we lose too much of one or all electrolytes we will probably die and if there is a buildup of any one electrolyte it will seriously disturb the normal function of the body.

This delicate balance that controls and maintains practically all of our body functions, can easily be disrupted by the following factors:
  • Excessive intake of liquids, including water. It stands to reason that electrolytes (usually minerals and salts) need to dissolved in liquid so that they can disassociate and form ions, but if you drink more liquid than necessary, your kidneys will excrete this fluid in the form of urine and along with the fluid you will lose your vital electrolytes. This is the reason why it is recommended that people should drink adequate quantities of water and other fluids, but not to overdo their water intake to such an extent that they lose vital electrolytes and become ill.

  • Excessive losses of electrolytes due to abuse of diuretics and laxatives. Diuretics or water pills cause the kidneys to excrete more urine and this can therefore lead to increased loss of electrolytes, particularly potassium. Consequently you may have noticed that some diuretics are labelled as ‘potassium-sparing’ which means that such diuretics do not deplete your potassium stores and cause a potassium imbalance.

In addition to losing water and electrolytes by the action of diuretics, laxatives also tend to lead to increased losses of fluid and electrolytes if they induce constant diarrhoea. Laxative abuse is common for various reasons such as chronic constipation (particularly in women) and overuse in slimming. Bulimic patients also often use laxatives to purge themselves after they have eaten vast quantities of food.

In each case repeated use of harsh laxatives can cause extreme loss of body fluids leading to dehydration and loss of vital electrolytes that can lead to a whole range of negative side-effects such as dizziness, tiredness and exhaustion, fainting, heart arrhythmias and even heart failure, confusion and in severe cases to death.

The most important electrolytes

The most important electrolytes are calcium, sodium, potassium, and magnesium. To underline their significance we need to consider their most important functions and the recommended quantities that we should eat on a daily basis.

1) Calcium

People are generally aware of the fact that most of the calcium in the human body is found in the skeleton and the teeth (99%), but what may not be as well known, is that the remainder occurs in our bodies as ionised calcium (an electrolyte). As a cation, ionised calcium is called the “second messenger” which means that it reacts to changes in calcium levels inside the cells. It regulates cell function, the heartbeat and blood clotting (Mahan et al, 2012).

The Recommended Daily Allowance (RDA) for calcium is between 1000 and 1300 mg per day (Mahan et al, 2012) which can be supplied by milk and dairy products (our richest sources of readily available calcium), green vegetables such as collard greens, nuts, tinned fish if one eats the bones, and calcium-extracted tofu which is made from soy beans.
2) Sodium

Sodium is the most important ion in the fluid outside the cells and therefore regulates the volume of liquid inside the cells and also the volume of plasma in blood. Sodium is vital to both nerve and muscle function and it helps to control and maintain the acid-base balance of the body. When patients develop severe hyponatremia (low sodium levels) they may suffer from seizures and coma, and they may even die due to a lack of sodium (Mahan et al, 2012).

At present there is no RDA for sodium, but the Institute of Medicine in the USA has published so-called Dietary Reference Intakes (DRIs) of 1.2 to 1.5 gram per day (Mahan et al, 2012). Most people obtain much higher quantities of sodium from their diets by way of table salt, salt-containing foods and also medicines that contain sodium. Because excessive sodium intake is linked to development of high blood pressure or hypertension and other diseases of lifestyle, it has been recommended that the upper limit of sodium intake should not exceed 2 g per day which represents a sodium chloride (table salt) intake of not more than 5 g per day (WHO, 2012). In countries such as South Africa, it is now mandatory that manufacturers must reduce the salt (sodium) content of certain foods (Government Gazette, 2012).

3) Magnesium

Most of the magnesium in the human body is also located in bone, but about 1% of  magnesium is found in the fluids outside the cells. Magnesium is regarded as one of the most important cofactors in enzyme reactions, so if our magnesium levels are dangerously low, it can have life-threatening consequences (Mahan et al, 2012).

The RDA for magnesium varies between 310 and 420 mg per day depending on age and gender. The most important sources of magnesium in the diet are green leafy vegetables, legumes (cooked or canned dry beans, lentils, peas or soybeans) and unprocessed or whole grains and cereals and products made from these grains such as wholewheat breads and crackers, wholegrain breakfast cereals, unsifted flour and brown rice.

4) Potassium
Potassium is the most important cation in the fluid inside the cells. Together with sodium, potassium is responsible for maintaining both the acid-base balance, and the water balance of the body. In regard to maintenance of the water balance it is important to prevent dehydration on the one hand and water intoxication on the other hand. Potassium together with calcium, helps to regulate nerve and muscle activity in the body. Insufficient potassium intake can interfere with the storage of glycogen (the primary source of energy for muscle activity) (Mahan et al, 2012).

A deficiency (hypokalaemia) and an excess (hyperkalaemia) of potassium can have severe and even fatal effects on the function of the heart.

No RDA has been specified for potassium, but an intake of at least 4700 mg per day has been suggested for adults. Potassium is found in most foods with fruits, vegetables, fresh meat and dairy products acting as primary sources of the mineral. Despite the fact that potassium is found in such abundance in common foods, research indicates that up to 50% of adults in the USA do not obtain the suggested 4700 mg per day from their diets (Mahan et al, 2012). 

It is important to maintain sensible electrolyte and water intakes so that you ingest neither too much nor too little of these vital components that keep our bodies in balance.
References: (Government Gazette (2012). Regulations relating to the reduction of sodium in certain foodstuffs & related matters. No. R533, 11 July 2012. No. 35509, pp. 3-8. Government Printer, Pretoria; Mahan LK et al (2012).Krause’s Food and the Nutrition Care Process,13th Edition. Elsevier, USA; WHO (2012). WHO. Guideline: Sodium intake for adults and children. Geneva, WHO, 2012.)


Dr Ingrid van Heerden is a registered dietician and holds a doctoral degree in Nutrition and Biochemistry. She believes that "we are what we eat" and offers free nutrition and weight loss advice via her DietDoc service on Health24.com. Read more of her articles.


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Dr. Estelle Wilken is a Senior Specialist in Internal Medicine and Gastroenterology at Tygerberg Hospital. She obtained her MBChB in 1976, her MMed (Int) in 1991 and her gastroenterology registration in 1995.

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