Can the Body Store Sodium? A Deep Dive into Pre-Marathon Nutrition Strategy

When preparing for an endurance event like a marathon, most athletes are well-versed in the concept of carbohydrate loading, increasing glycogen stores to optimise performance. But what about sodium? Can the body store sodium in the same way? And is there any benefit to “sodium loading” in the days leading up to a race?

As a nutritionist I decided to do a little bit of research of my own. Let’s dive into the science behind sodium regulation, its role in endurance performance, and whether you should consider sodium loading before your next race.

⚖️ Understanding Sodium and the Body

Sodium is an essential electrolyte, a mineral that helps regulate fluid balance, nerve function, and muscle contractions. It plays a particularly important role during prolonged physical activity, where fluid and electrolyte losses can impact performance and even lead to serious complications like hyponatremia (low blood sodium).

🧬 But can sodium be stored?

Unlike carbohydrates, which are stored in the body as glycogen in the liver and muscles, sodium is not stored in a reservoir. Instead, your body maintains tight control over sodium concentration through a dynamic balance involving:

• The kidneys (which regulate sodium excretion in urine)

• Hormones like aldosterone and antidiuretic hormone (ADH)

• Sweat glands, which lose sodium during physical exertion

  
  

Any excess sodium you consume is typically excreted within hours to a day, either through urine or sweat. So, no, sodium cannot be stored in the way that fuels like glycogen can.

🏃‍♂️ Sodium and Endurance: Why It Still Matters

During endurance events like marathons, sodium becomes a key player. Here's why:

• You can lose 500–2,000 mg of sodium per hour of intense exercise, depending on sweat rate, environment, and individual variation.

• Sodium loss can lead to muscle cramps, fatigue, and impaired performance.

• In extreme cases, low sodium combined with over-hydration can lead to exercise-associated hyponatremia, which is dangerous and potentially life-threatening.

That’s why maintaining electrolyte balance before and during the event is critical.

🧂 What Is Sodium Loading?

Sodium loading is the practice of intentionally increasing sodium intake in the 1–2 days before an endurance event, with the goal of:

• Expanding plasma volume (the fluid portion of your blood)

• Enhancing thermoregulation and sweat capacity

• Improving hydration status

• Potentially reducing the risk of hyponatremia during prolonged exercise

  
  

While not universally practiced or needed, sodium loading can offer performance benefits, particularly in hot and humid conditions or for salty sweaters.

✅ Sodium Loading Protocol (Evidence-Informed)

Here’s a commonly used and researched approach:

⏳ Timing:

Begin 1–2 days before the event.

🧪 Dosage:

Consume 500–1,500 mg of sodium per day, spread out in meals or in a sodium-rich electrolyte drink.

• This is above typical dietary intake but should be adjusted based on individual sweat rate and tolerance.

• For context, 1 tsp of table salt (NaCl) contains about 2,300 mg of sodium.

  
  

🧴 Fluid Consideration:

Pair sodium intake with fluids to ensure hydration without over-dilution.

• Use electrolyte drinks like Hydralyte Sport, LMNT, Precision Hydration, or similar.

• Avoid excessive plain water intake during this time to reduce hyponatremia risk.

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⚠️ Important Considerations

Sodium loading is not for everyone. Here’s what to watch out for:

🔹 Potential Side Effects:

• Temporary fluid retention or bloating

• High blood pressure symptoms (especially in salt-sensitive individuals)

• Stomach discomfort if dosed too aggressively

  
  

🔹 Who Should Avoid It?

• Individuals with hypertension, kidney disease, or salt sensitivity

• Those who haven’t tested sodium intake during training

• Athletes with very low sweat sodium loss

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Always trial sodium strategies during training, never for the first time on race week.

🥇 Carb Loading vs. Sodium Loading: Key Differences

Factor	Carb Loading	Sodium Loading
Stored in Body?	Yes – as glycogen	No – regulated, not stored
Purpose	Energy storage for endurance	Optimise hydration & balance
When to Start	2–3 days before event	1–2 days before event
Risks	Temporary weight gain, GI issues	Bloating, elevated BP
Best For	All endurance athletes	Heavy sweaters, hot races

🧠 Final Takeaways

• The body does not store sodium in the traditional sense, but increasing sodium intake strategically before an event may enhance hydration and endurance.

• Sodium loading can be a valuable tool for endurance athletes, but it must be personalised, trialed in advance, and done with a clear understanding of your sweat rate, sodium loss, and overall health.

• For many athletes, a combination of pre-race sodium intake and ongoing electrolyte management during the race is the most effective strategy.

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📣 Need Personalised Guidance?

If you're training for an endurance event and want a tailored hydration and nutrition plan, consult with an accredited sports nutritionist or dietitian. Sweat testing and individual assessment can make all the difference in your performance and safety on race day.

Hope this was helpful!