Do I need additional electrolytes?

Walk through the start area of any race and you'll see it: athletes dropping electrolyte tablets into every bottle “just to be safe.” Electrolyte supplements have become one of the biggest trends in sports nutrition, and they are often treated as something you can never get enough of. But is that actually true? Or are most athletes taking far more electrolyte than they actually need? In this blog we dig into the science behind electrolytes, with a specific focus on sodium, and give you a simple step-by-step plan to work out whether additional sodium actually makes sense for you.

What are electrolytes, and why does sodium matter most?

Electrolytes are minerals that carry an electrical charge once dissolved in the fluids of the body: sodium, potassium, chloride, magnesium and calcium are the best-known examples. They play a role in fluid balance, the transmission of nerve signals and muscle contractions. Of all these electrolytes, sodium is lost by far the most through sweat, and it is also the one that nearly all commercial ‘electrolyte’ products are actually built around. That is why sodium deserves most of the attention in this blog.

How much sodium do you actually lose in sweat?

The amount of sodium in your sweat differs enormously between individuals, and this appears to be largely genetically determined. On average, sweat contains around 0.8 grams of sodium per litre, but this ranges from as little as 0.25 grams to as much as 2 grams per litre between people. Additionally, we need to take into account the sweat rate, which itself can range from less than half a litre to several litres per hour, depending on factors such as intensity and temperature. This illustrates how total sodium losses vary hugely from one athlete (and one session) to the next. For most training sessions under roughly 90 minutes in moderate conditions, total sodium losses stay relatively modest and are easily replaced through a normal diet: most Western diets already contain more than enough sodium. Moreover, our kidneys keep the sodium in your blood within a very narrow range. Once you have taken in enough, they get rid of the rest in your urine, and they adjust for what you already lost in sweat.

What about the other electrolytes?

Potassium, magnesium, calcium and chloride are also lost through sweat, but in much smaller amounts than sodium. Deficiencies of these electrolytes are rare in athletes, and a normal, varied diet is more than sufficient to replenish them. The often-heard link between, for example, magnesium and muscle cramps is much weaker in the scientific literature than popular belief suggests. In practice, the ‘electrolyte question’ for most athletes really comes down to a sodium question.

Does sodium actually improve performance?

Sodium plays a genuine physiological role: it helps maintain blood sodium concentration and osmolality, and supports the retention of fluid in the body. However, there is currently minimal evidence that sodium supplementation directly improves performance, at least during exercise shorter than about 3 to 4 hours. What sodium reliably does is improve the taste of a sports drink and support your thirst response, meaning you are more likely to keep drinking, and staying adequately hydrated is what ultimately matters for performance.

When does additional sodium actually matter?

Recent modelling research shows that the risk of your blood sodium concentration dropping during exercise mainly depends on three factors: the total sweat losses, what percentage of your sweat fluid losses you actually drink back, and how salty your sweat is. When we start exercising and sweating we will lose fluids and sodium. However, the amount of fluid that we will lose, is always higher than the amount of sodium. Even if you are a very ‘salty sweater’. This means that the sodium concentration in your blood will increase, even if the total amount of sodium decreases a little bit. The image below illustrates this.

Blood sodium concentration typically only drops in a meaningful way when all of these are high at the same time: losing a lot of sweat for a prolonged duration (3-4+ hours), replacing more than roughly 70-80% of these losses, combined with an above-average sweat sodium concentration. In practice, this combination is mostly only realistic during ultra-endurance exercise, where the duration is long enough, and there is enough opportunity to drink large volumes of fluid. During most training sessions and races under about 3 hours, the total fluid loss you need to replace to avoid meaningful dehydration is relatively small. In these situations additional sodium is unnecessary, and simply choosing a drink that tastes good to you (‘season to taste’) is all you need.

For example, imagine an athlete competing in a 6-hour ultra-endurance event, such as a mountain bike race in hot, humid conditions. This athlete sweats heavily and makes a conscious effort to drink frequently to stay hydrated, replacing nearly 90% of their fluid losses. Being both a "salty sweater" and drinking high volumes of fluid puts this athlete’s blood sodium concentration at a genuine risk of dropping. In this specific scenario, additional sodium would be highly beneficial to maintain a stable blood sodium concentration. In contrast, consider an athlete during a 1-hour run or 2-hour bike ride. Even if this person is a "salty sweater", his or her total sweat and sodium losses remain relatively small due to the shorter duration. In these shorter sessions, their body's internal stores and normal dietary intake are more than sufficient to manage fluid balance without needing extra sodium supplementation.

Step-by-step plan: do you need additional sodium during your session?

Use the flow below to quickly work out where you stand.

Do I need additional sodium before or after my session?

Even if you don’t have to replace sodium during your workout, hard and/long training sessions can induce significant sodium losses. Replacing these losses before and especially afterwards is important. As already mentioned, a typical Western diet contains more than enough sodium. Therefore, if you train 2-3x per week, you don’t have to worry about additional sodium intake. It will automatically be replaced through your normal diet. However, if you train most days of the week and have high sweat/sodium losses day after day, with limited time to recover in between, it might become more challenging to replace your sodium needs through your regular diet. Therefore, especially endurance athletes with frequent and prolonged training sessions (in the heat) could benefit from added sodium before and/or after their workouts. Adding an Amacx Hydro Tab to your glass or bottle of water in the hours after training, provides an easy solution for that.

For the majority of athletes, during the majority of their training sessions, additional sodium is simply unnecessary. Save the deliberate, targeted use of sodium for the moments where it actually counts: long, hot, high-sweat-rate sessions where you know you are a salty sweater, and where you are actually drinking enough fluid to need it.

Summary

• Electrolytes are minerals with an electrical charge; sodium is lost by far the most through sweat and deserves most of the attention.
• Potassium, magnesium, calcium and chloride are lost in much smaller amounts and are easily replenished through a normal diet.
• Sweat sodium losses vary hugely between individuals and depend on both sweat rate and sweat sodium concentration.
• There is currently minimal evidence that sodium supplementation directly improves performance in exercise under about 3-4 hours. Its main benefits are improving taste and stimulating fluid intake.
• Blood sodium concentration only drops meaningfully when you replace more than ~70% of your fluid losses and have an above-average sweat sodium concentration – mostly relevant in ultra-endurance exercise.
• For sessions under 3 hours, a normal diet is enough. Only in long, hot, high-sweat-rate sessions where you are a known ‘salty sweater’ is targeted sodium (e.g. Amacx Hydro Tabs) worth considering.
• Additional sodium before or after your workout could be beneficial, especially if you have full weeks of training with limited recovery time in between the sessions.