Electrolytes and Running: Essential Science or Clever Marketing?

Hydration is a fundamental part of running.

But recently there has been a noticeable shift in how hydration is being sold to runners. Electrolytes are no longer presented as something useful in specific situations. They are now marketed as essential, something you supposedly need every single day simply because you run.

Walking around the National Running Show, the sheer number of companies selling daily electrolyte supplements really started to irritate me. Sachets costing up to two pounds per serving, often little more than flavoured salt, and in some cases bundled into subscriptions so you never miss your daily dose of daily flavoured salt.

To be clear, this is not an argument against electrolytes. They have a role. But running is already expensive, and if we are going to tell runners they need something daily, that claim should stand up to scrutiny. So it is worth being honest about when electrolytes are useful, when they might help, and when you are probably just wasting money.

When you strip away the marketing, the science is far less dramatic.

What electrolytes actually do

Electrolytes are minerals, primarily sodium, potassium, magnesium, calcium and chloride, that help regulate fluid balance, nerve conduction and muscle contraction (Sawka et al., 2007).

When you sweat, you lose both water and electrolytes, but sodium is by far the most significant loss (Maughan and Shirreffs, 2008). In long or hot runs, this loss can matter.

However, most people already consume plenty of electrolytes through their normal diet, particularly sodium. Western diets are not sodium deficient (McLean, 2014). The assumption that runners are routinely electrolyte depleted simply because they run is not supported by evidence.

Do daily electrolyte supplements improve performance?

The short answer is that there is no strong evidence that they do.

Research consistently shows that routine electrolyte supplementation does not improve endurance performance in athletes who are otherwise well nourished.

A prospective study of ultramarathon runners found no association between sodium supplementation and race performance (Hoffman and Stuempfle, 2015). Interestingly, runners who lost more body mass during the race, in other words became more dehydrated, often performed better than those who consumed more fluid and sodium.

Similarly, studies examining high sodium intake during endurance exercise have failed to demonstrate consistent improvements in thermoregulation, cardiovascular strain or performance outcomes (Hew-Butler et al., 2015).

In practical terms, taking electrolyte drinks or capsules every day is unlikely to make you faster if your basic hydration and nutrition are already adequate.

When electrolytes can be useful

Electrolytes do have a clear role when physiological demand increases.

During prolonged exercise, particularly in hot or humid conditions, sweat losses can be substantial. In these situations sodium helps maintain plasma volume, electrolytes improve fluid retention compared to water alone, and sodium stimulates thirst, supporting voluntary fluid intake (Sawka et al., 2007).

This can help reduce symptoms such as dizziness, nausea and excessive fatigue late in long events (Maughan and Shirreffs, 2008).

Even here, it is important to be precise. Electrolytes primarily support hydration status rather than directly enhancing performance. They help prevent problems rather than create performance gains.

Situations where supplementation may make sense

Electrolyte supplementation may be appropriate during long runs or races lasting over ninety minutes, in hot or humid conditions, during multi day or ultra endurance events, when food intake is limited, for runners with very high sweat rates, and during recovery after prolonged heavy sweating.

These are context specific uses, not evidence for daily supplementation regardless of training load or environment.

Can electrolytes be harmful?

Yes, and this is where nuance matters.

Excess electrolyte intake without equivalent fluid loss can contribute to electrolyte imbalances and gastrointestinal distress (Shirreffs and Maughan, 2006). Chronically high sodium intake may also place unnecessary strain on cardiovascular and renal systems in individuals who are not deficient.

At the other extreme, excessive fluid intake, often encouraged by aggressive hydration messaging, can dilute blood sodium levels and lead to exercise associated hyponatremia, a potentially life threatening condition (Noakes et al., 2005; Hew-Butler et al., 2017).

Ironically, this condition is more commonly linked to over drinking than to sodium deficiency.

What most runners actually need

For the majority of runners doing short to moderate training sessions, running in temperate conditions and eating a normal mixed diet, daily electrolyte supplementation is unnecessary.

Electrolytes are readily available from food including fruit and vegetables, dairy, nuts and seeds, and salted foods such as bread, soups and sauces.

For most days, water plus food is sufficient.

So is this mostly marketing?

For daily use in most runners, yes.

The claim that all runners need electrolytes every day is not supported by evidence. What is supported is targeted use during long, hot or high sweat sessions.

Electrolytes can improve hydration maintenance, reduce discomfort in demanding conditions and help runners complete long efforts more comfortably. They are a tool, not a requirement.

Bottom line

Electrolyte supplements are not necessary on a daily basis for most runners. They do not inherently improve performance, and they are unlikely to provide additional health benefits if you are already eating a balanced diet and training in mild conditions. They can, however, be useful in specific, demanding situations such as long runs, hot weather, or high sweat losses.

Use them when the situation calls for it, not because a stand at a running expo, an advert on social media, or a well-lit influencer with a discount code told you that you need daily electrolytes to be a “serious” runner.

Running is already expensive. Your hydration strategy does not need to be.

References

Hew-Butler, T., Rosner, M.H., Fowkes-Godek, S. et al. (2015) Statement of the Third International Exercise-Associated Hyponatremia Consensus Development Conference. Clinical Journal of Sport Medicine, 25(4), pp.303–320.

Hew-Butler, T., Loi, V., Pani, A. and Rosner, M.H. (2017) Exercise-associated hyponatremia: 2017 update. Frontiers in Medicine, 4, 21.

Hoffman, M.D. and Stuempfle, K.J. (2015) Sodium supplementation and exercise-associated hyponatremia during prolonged exercise. Medicine and Science in Sports and Exercise, 47(9), pp.1781–1787.

Maughan, R.J. and Shirreffs, S.M. (2008) Development of individual hydration strategies for athletes. International Journal of Sport Nutrition and Exercise Metabolism, 18(5), pp.457–472.

McLean, R. (2014) Measuring population sodium intake: a review of methods. Nutrients, 6(11), pp.4651–4662.

Noakes, T.D., Sharwood, K., Speedy, D. et al. (2005) Three independent biological mechanisms cause exercise-associated hyponatremia. British Journal of Sports Medicine, 39(12), pp.852–858.

Sawka, M.N., Burke, L.M., Eichner, E.R. et al. (2007) Exercise and fluid replacement. Medicine and Science in Sports and Exercise, 39(2), pp.377–390.