You finish a long run, strip off your shirt, and notice the white residue on your skin. That's salt. And salt is just one of several electrolytes your body loses every time you sweat – minerals that do a lot more than most runners realize.
Electrolytes don't get talked about as much as carbohydrates or protein, but they're quietly involved in almost everything that keeps you running well. Muscle contractions, fluid balance, nerve signalling, even how efficiently your heart beats. When they drop low enough, you feel it – and it's rarely subtle.
What Electrolytes Actually Are
Electrolytes are minerals that carry an electrical charge when dissolved in fluid. The ones that matter most for runners are sodium, potassium, magnesium, and calcium. Each plays a distinct role.
You track your miles.
We'll handle the meals.
Sodium is the most important one during a run. It's the primary electrolyte in your blood and the fluid surrounding your cells, and it's responsible for regulating fluid balance. When sodium drops – either from sweating heavily or drinking too much plain water without replacing what you've lost – cells can take on too much fluid. In mild cases, that causes bloating and a sloshing feeling. In more severe cases, it leads to hyponatremia, a dangerous condition where blood sodium falls low enough to affect brain function. [1]
Potassium works alongside sodium to maintain fluid balance inside and outside your cells, and it plays a direct role in muscle contraction. Low potassium is associated with cramping and a general sense of weakness, though the relationship between electrolytes and cramping is more complex than it's often presented. [2]
Magnesium supports muscle function, energy metabolism, and sleep quality – all things that matter for runners in heavy training. It's the electrolyte most commonly depleted in endurance athletes who don't pay attention to diet variety. [3]
Calcium is primarily known for bone health, but it also plays a role in muscle contraction and nerve transmission during exercise.
What Running Does to Your Electrolyte Balance
Every time you sweat, you lose electrolytes – primarily sodium, with smaller amounts of the others. The rate varies significantly between individuals. Some runners are heavy sweaters, some are salty sweaters (you can tell by the white marks on your kit), and some barely notice any loss on an easy 45-minute run.
The volume of sweat matters, but so does what you're drinking to replace it. Drinking large amounts of plain water without sodium to match dilutes your blood sodium concentration. This is counterintuitive – you can drink plenty and still create an electrolyte imbalance. It's one reason sports drink formulations exist: not just to add calories, but to replace what plain water can't.
For runs under an hour in moderate conditions, water is usually enough. For anything longer, or in heat and humidity, electrolyte replacement starts to matter — and sodium is the priority. [1] Research gives us specific targets: for runs of 60 to 90 minutes, aim for roughly 250 to 500 mg of sodium per 500ml of fluid. For efforts over 2 hours, that rises to 500 to 1,000 mg per 500ml, particularly in heat or if you are a heavy sweater. To put that in practical terms, a quarter teaspoon of table salt contains roughly 500 to 600 mg of sodium — the Maple Lemon Electrolyte Drink in Fuel is built around this range.
Food First
Most runners don't need to rely on supplements or sports drinks to maintain good electrolyte status. A varied diet with enough salt, plenty of vegetables, and foods like bananas, nuts, seeds, and leafy greens covers the basics well for everyday training.
Where food alone starts to fall short is during and immediately after very long runs or races in hot conditions, when losses are high and your ability to eat normally is limited. That's where a deliberate electrolyte strategy – adding salt to your during-run drink, reaching for an electrolyte drink post-run, or including salty real-food options – makes a practical difference.
The Maple Lemon Electrolyte Drink covers this well for during or after a run – simple ingredients, the right balance of sodium and carbohydrates:
Maple Lemon Electrolyte Drink
Cramps: The Complicated Part
The relationship between electrolytes and muscle cramping is widely misunderstood. The popular version of the story – that cramps are caused by sodium or potassium deficiency – is an oversimplification. The research suggests that exercise-associated muscle cramps are more likely related to neuromuscular fatigue than to electrolyte imbalance, though dehydration and low sodium can be contributing factors in some cases. [2]
The practical takeaway: don't assume that every cramp is an electrolyte problem, and don't assume that salty gels are a guaranteed fix. The best approach is to stay well-hydrated, replace electrolytes on longer efforts, and look at training load if cramping is a recurring issue.
The Simple Version
You don't need to overthink electrolytes. For most training runs, eating well and staying hydrated is enough. The moments when it genuinely matters are long runs in the heat, races, and back-to-back training days when cumulative sweat losses add up.
In those situations, the fix is straightforward: add sodium to your hydration, and don't rely on plain water alone when you're out for a long time. Foods naturally rich in potassium – bananas, sweet potatoes, avocado, leafy greens – and magnesium – nuts, seeds, dark chocolate, whole grains – are easy to work into everyday meals without overthinking it.
Electrolytes are not a magic performance lever. But ignoring them entirely on long hot runs is one of the more avoidable ways to have a bad day.
Recipes in Fuel.fit tagged for during-run and recovery use real-food electrolyte sources – because a pinch of salt and a splash of maple syrup goes a long way.
Sources
[1] Hew-Butler T, Verbalis JG, Noakes TD. Updated fluid recommendation: position statement from the International Marathon Medical Directors Association. Clin J Sport Med. 2006;16(4):283-292.
[2] Schwellnus MP. Cause of exercise associated muscle cramps (EAMC) – altered neuromuscular control, dehydration or electrolyte depletion? Br J Sports Med. 2009;43(6):401-408.
[3] Nielsen FH, Lukaski HC. Update on the relationship between magnesium and exercise. Magnes Res. 2006;19(3):180-189.
