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The purpose of electrolyte drinks

The sports nutrition market is packed with products claiming to assist running performance. Sometimes it can be difficult to make informed decisions about which products offer value for money and provide health and performance benefits. Electrolyte drinks are commonly marketed at runners and endurance sport enthusiasts but are they worth the money and are they really necessary?

What are electrolytes?

Electrolytes are vital to our health. Electrolyte is a term for salts, specifically ions, which are positively and negatively charged. This is important to enable cells such as nerve, heart and muscle cells to maintain voltages across membranes and to carry electrical impulses that enable cells to send messages back and forth between themselves to help you move, see, think and perform. They also regulate how and where fluids are distributed throughout the body.

A healthy and varied diet usually supplies an adequate amount of electrolytes. However, when we sweat, we lose electrolytes. The major electrolytes present in sweat are sodium, potassium, and chloride. Additional electrolytes include calcium, magnesium, phosphate, and bicarbonate, to name just a few. These electrolytes need to be replaced to help restore body fluid balance and maintain health.

How are electrolytes lost during exercise?

During exercise, core body temperature increases as the working muscles generate heat every time they contract. As a result, we begin to sweat and lose body water. The process whereby sweat evaporates from the surface of the skin helps cool the body by removing excess heat from the body. The main electrolytes lost in sweat are sodium and potassium. Potassium enables the movement of fluids and nutrients across cell membranes, therefore allowing them to carry on their metabolic activities such as contacting muscles. Without sufficient potassium, muscles cells can’t generate nerve impulses that control muscle contraction. Sodium also plays a role in muscle and nerve function and helps maintain fluid levels throughout the body.

How can electrolyte drink benefit runners?

Electrolyte drinks are useful for runners to allow replacement of the electrolytes (in particular, sodium and potassium) lost through sweat, which aids the following:

During post-exercise rehydration, the replacement of electrolyte losses, particularly sodium, must occur to fully restore fluid balance. Rehydrating with fluids low in electrolytes (e.g. water) can lower plasma sodium levels causing a reduced thirst and increased urine output resulting in decreased voluntary fluid intake and inadequate fluid retention. Although sodium can be replaced by eating salty foods (e.g. bread, breakfast cereal, pretzels), or adding salt to meals, electrolyte drinks with higher sodium content can be useful for rapidly restoring fluids and electrolytes.

There is some evidence, although controversial, that whole body sodium losses may be a cause of specific types of muscle cramps in some individuals. Electrolyte supplementation may be beneficial in these individuals.

When can an electrolyte drink benefit runners?

Proper hydration for running is essential to safety and performance, but when should runners look beyond just plain water to boost performance? Since electrolytes help your body retain fluids and may prevent muscle cramps, you need to replace them when running for longer than 90 minutes. Additional scenarios when electrolyte drinks are particularly beneficial to runners are when individuals have a high sweat rate or high sweat content, when runners are exercising in the heat and when the replacement of large electrolyte losses during ultra-endurance activities is required.

Are there any concerns when using an electrolyte drink?

In some situations, excessive salt supplementation during exercise may lead to gastrointestinal problems or cause further impairment of fluid balance. It’s vital that runners practice using an electrolyte drink in training, prior to competition.

Increasing the sodium content of a drink generally reduces the drink palatability and may interfere with the voluntary consumption of fluid. Caution should be taken to ensure drinking during exercise is sufficient to minimize fluid deficits. It may be beneficial to decrease the electrolyte content of the drink to increase its palatability if fluid deficits exceed 2% loss in body mass.

Finally, general guidelines for healthy eating suggest limiting the salt intake in your diet. Electrolyte replacement during and after sport may be considered as a special situation however, caution should be taken if you have previously been advised to reduce the salt in your diet due to health concerns.

Conclusion

How much salt you lose while exercising depends on how hard you are exercising, how much you are sweating, how hot it is, and how long you are working out. Electrolyte losses are highly specific to the individual so no specific answer exists about how much you will lose while exercising. However, during prolonged exercise and exercise in the heat, when electrolyte losses are usually greater, electrolyte drinks are beneficial in aiding fluid retention, stimulating the drive to drink and restoring electrolyte balance.