It’s impossible to go online without seeing an advert for an electrolyte supplement aimed at runners. We are constantly being told that we’re leaving performance on the table if we don’t consume these packets of salt. Is any of this true, or just marketing hype? We’re here to find out…
What actually are electrolytes?
Electrolytes are minerals that carry electric charge when they are dissolved in water. Your body uses electrolytes to control all sorts of functions that require electrical signals. This includes things like fluid balance, nerve signals, and muscle contractions. Electrolytes have also become extremely popular to put in a small packet to dissolve in your drink that costs a lot of money and doesn’t taste very nice.
The main electrolytes are:
Sodium (Na⁺): Helps regulate fluid balance and is essential for nerve signals and muscle contractions.
Potassium (K⁺): Helps your muscles contract, your nerves function, and your heart beat normally.
Chloride (Cl⁻): Helps maintain fluid balance and supports digestion and acid-base balance.
Magnesium (Mg²⁺): Supports muscle and nerve function and is involved in energy production.
Calcium (Ca²⁺): Helps muscles contract, nerves communicate, and bones maintain their strength.
Phosphate: Helps produce energy and is an important component of bones, teeth, and cells.
Bicarbonate: Helps keep your blood and body fluids at the correct acidity (pH).
All of those functions sound very important which can make it feel tempting to buy the overpriced horrible tasting drink mixture. When you sweat during exercise, you lose both water and electrolytes, particularly sodium. This can make it seem even more tempting to buy the magic electrolytes. Of course, as runners, we sweat a lot.
Electrolytes are minerals/ions dissolved in body fluids.
If I don’t drink electrolytes in an overpriced packet, how will my body get them?
If you eat a balanced and varied diet, the chances are you don’t actually need to consume supplementary electrolytes, even as a runner.
Sodium: Found in table salt, bread, cheese, sauces and processed foods.
Potassium: Found in potatoes, bananas, beans, lentils, dairy, fruit and vegetables.
Chloride: Found mainly in table salt, processed foods, dairy and vegetables.
Calcium: Found in dairy, fortified plant milks, tofu, canned fish and leafy greens.
Magnesium: Found in nuts, seeds, whole grains, legumes, dark chocolate and leafy greens.
Phosphate: Found in meat, dairy, fish, eggs, legumes, nuts and whole grains.
Bicarbonate: Produced naturally by the body rather than obtained significantly from food.
On top of this, your body also stores much more of the electrolytes that are lost in sweat than it’s possible to lose in a run. Most people store between 90 and 100g of sodium in their body and only the saltiest sweaters on earth lose less than 3g/hour of sodium. We’re sure you can do the maths on that, but even if you’re running for 5 hours, that’s only around 15% of what’s stored and you can make that back up after the race with a couple of Pot Noodles.
Most recreational runs don't require any expensive electrolyte products. For ordinary training, drinking according to thirst and eating a normal balanced diet is generally enough; electrolyte replacement becomes more relevant during prolonged exercise of over 5 hours, extremely heavy sweating, heat, or unusually salty sweat - but even then, it’s rarely actually needed.
But the supplement people told me it helps performance:
Sports nutrition brands spent years telling us that we needed to get our sweat tested and personalise our hydration strategy according to how salty our sweat is. Many of these brands completely forgot about electrolytes when they realised they could make more money selling us overpriced sugar (that we do, at least, actually need) rather than overpriced salt.
The evidence is mixed because sodium replacement during exercise can be useful in some situations, but the benefits are often overstated by the brands selling the products. Some leading sports nutritionists have even begun arguing that any supplementary sodium is completely useless - though this isn’t the prevailing opinion amongst scientists in general.
Studies investigating sodium supplementation during endurance exercise have produced inconsistent results. In controlled conditions, adding sodium to a drink doesn't reliably improve endurance performance compared with consuming an appropriate amount of fluid without additional sodium.
This makes sense because your body already has a large sodium reservoir, and most normal diets provide plenty of sodium.
Sodium is physiologically important, and sodium replacement can be useful during prolonged exercise with substantial sweating. But evidence that routinely consuming large amounts of sodium during exercise improves performance is inconsistent at best. For ordinary training, most runners can obtain sufficient electrolytes from their normal diet, while during long or hot events the need for deliberate sodium and fluid replacement becomes more relevant, but not enough to sustain an entire industry.
Electrolytes are real. The claim that every run requires an electrolyte product is not supported by the evidence and for the majority of runners, electrolyte supplementation is a waste of money.
But what about cramping?
Cramping is actually where the electrolyte narrative gets particularly divorced from reality, because the evidence doesn't support the simple idea that you lose sodium, you cramp, take electrolytes, the cramps stop. Yet, for some reason, this appears to be a widespread belief. Cramping is extremely multifactorial and actually quite a complex phenomenon we don’t seem to know a huge deal about.
One thing is for sure, athletes that are well prepared for race day are much less likely to cramp. Instead of wasting your money on electrolytes, spend it on a training plan that will prepare you as best as possible? Just one packet of popular electrolytes will buy you around 3 months of training with The Running Algorithm. That’s enough time to improve by around 5%.
