Written By

Dr Emily Jevons

5 minutes

Most of what our body requires to function comes from small electrical charges sent across the body. Electrolytes are the essential minerals needed for this to occur, they will carry either a positive or a negative electrical charge when dissolved in water.

These electrical signals contribute to many factors including muscle contraction, nerve function and hydration. If our body wants to perform such functions effectively, we need to ensure our electrolyte stores are maintained through diet or supplementation. Vital electrolytes that we need to regularly consume include; sodium, calcium, potassium, bicarbonate, chloride, phosphate and magnesium.

So what happens if electrolyte stores are low? We can think of the human body as an electric battery, if the power of the battery is low, things will move slower (if at all) and less optimally. In the human body, we feel this as fatigue, headaches and dehydration.

If this occurs long-term, it can have more serious consequences.


One situation that can cause us to lose electrolytes, is exercise. When we exercise we lose electrolytes through our sweat, this in turn, contributes to dehydration. A reduction in as little as 2% of your body weight due to sweat loss can cause dehydration which will have a negative affect on your performance.

Specifically when we sweat, we mostly lose sodium, but we also lose potassium, magnesium and calcium in smaller quantities. The role of each of these electrolytes is summarised below:

SodiumSodium is the main electrolyte found in the fluid around our cells (extracellular fluid) which is where our sweat is drawn from giving it a key role in fluid balance. It also has a role in nutrient absorption in our gut, muscle contraction, cognitive function, and the transmission of nerve impulses.
PotassiumAlso known to help regulate fluid balance, muscle contraction, transmission of nerve impulses and can help support normal blood pressure.
MagnesiumMagnesium plays a major role in energy production and more than 300 biochemical reactions in the body. It also helps muscles contract and regulate blood sugar.
CalciumCalcium loss during sweat is minimal, but it is essential to maintaining overall health for bones and proper functioning of muscles and nerves.

On top of the importance for health, sodium and maintaining optimal fluid balance is also vital for performance. Although the impact will vary greatly between athletes, one study found that athletes who replaced their sodium during a middle distance triathlon finished 26 minutes (on average) faster than those who didn’t!

The amount of sodium you lose during exercise will vary between individuals but the ultimate need for replacing sodium during exercise comes down to fluid balance and maintaining appropriate osmolality (the bodies ratio of water and electrolytes).


The common dehydration mistake:

  • One of the biggest mistakes people make when trying to stay hydrated during exercise is over-watering.
  • This is what it says on the tin, where someone is drinking too much water leading to diluted levels of electrolytes. Low levels of sodium in the blood from taking on too much water can lead to hyponatremia which often presents itself as muscle cramps and fatigue.
  • You do need to replace lost water when exercising, but you also need to replace your electrolytes to help maintain this water-electrolyte balance.

Dietary deficiencies:

  • Electrolytes come from the foods such as potatoes (phosphorous and magnesium), leafy greens such as spinach or kale (calcium and magnesium) or coconut milk (sodium, potassium, calcium and magnesium) as just a few examples!
  • Whole foods do tend to be lower in sodium so we do need to consider adding salt (within reason) to some foods but most processed foods contain sodium already and extra won’t be needed.
  • For potassium and magnesium, you’ll find these rich in fruits, nuts and vegetables. If you follow a low carbohydrate diet, you may find it harder consume potassium-rich foods.


There are lots of foods-rich in electrolytes as mentioned above,  but these aren’t always the most accessible when exercising, which is where electrolyte supplements such as the SiS Hydro and SiS GO Electrolyte come in.

SIS HYDRO is an effervescent tablet that dissolves in water, each tablet contains 345mg Sodium, 269mg Chloride, 102mg Calcium, 65mg Potassium, 8.1mg Magnesium. 1 tablet should be mixed with 500ml of water, once prepared consume within 24 hours and don’t consume more than 4 per day.

SiS GO Electrolyte powder gives us a hydration solution but with easily digestible carbohydrates for energy as well. 1 serving of powder should be mixed with 500ml water to give appropriate concentrations of carbohydrate (36g as a 6% solution), sodium (20mmol/L) and fluid.


  1. Electrolytes are essential minerals that enable many key processes to occur within the human body such as muscle contraction and nerve impulse transmission.
  2. When we exercise, we lose water and electrolytes, mainly sodium, but also some potassium, magnesium and calcium. The amount of sodium you lose during exercise will vary between individuals but the ultimate need for replacing sodium during exercise comes down to fluid balance and maintaining appropriate osmolality (the bodies ratio of water and electrolytes).
  3. You can replace lost electrolytes through food or supplements such as the SiS Hydro or the SiS GO Electrolyte powder.


American College of Sport Medicine. 2009. ACSM position stand: Exercise and fluid replacement. Medicine and Science in Sport and Exercise 39 (2): 377 – 390.

Del Coso, J. et al. (2016). Effects of oral salt supplementation on physical performance during a half‐ironman: A randomized controlled trial. Scandinavian journal of medicine & science in sports26(2), 156-164.

Maughan R. J. and L. M. Burke. 2002. Sport nutrition. Handbook of sports medicine and sciences. Oxford: Black-well science.

O’Donnell M. J., et al. (2011). Urinary sodium and potassium excretion and risk of cardiovascular events. JAMA. Nov 23;306(20), 2229-38.

Piste, P., Sayaji, D. & Avinash, M. (2012) Calcium and its role in human body. Int J Res Pharm Biomed Sci, 4(2), 659-668.

Shirreffs, S. M., & Sawka, M. N. (2011). Fluid and electrolyte needs for training, competition, and recovery. Journal of sports sciences, 29(1), 39-46.

Written By
Dr Emily Jevons
Dr Emily Jevons
Emily has worked with Science in Sport since 2021. With a PhD in Exercise Physiology & Nutrition, she currently provides nutritional advice for endurance athletes. Emily not only understands the science behind performance nutrition solutions, but also the physiological and psychological demands of sport after competing competitively in swimming and triathlon for a number of years.
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