Sodium and salt: a key mineral for athletes

The WHO recommends limiting salt intake to 5 grams per day, which is equivalent to approximately 2000 mg of sodium. This reference mainly applies to the general population. But as soon as you run a marathon, go on bike rides, or traverse mountainous terrain, the situation changes completely. Your needs can climb well above the norm, sometimes two to three times more, because you lose a significant amount of sodium through sweat.

However, a deficit of this mineral during exercise promotes early fatigue, nausea, confusion, digestive problems, and, in the most severe cases, hyponatremia. Hence the importance of anticipating your actual sodium needs to maintain your performance while staying safe.

Sodium and salt: what's the difference?

Do not confuse sodium and salt. These two terms do not refer to the same thing.

Table salt, which you use in cooking as a flavor enhancer, is actually sodium chloride (NaCl). It is mainly composed of chlorine (Cl) and sodium (Na). 

Sodium, which is often indicated on the labels of certain food products, is an electrolyte. It is present as ions (Na⁺) in the body and is involved in several vital functions. 

Sodium is a component of salt: it represents approximately 40% of its total mass. In other words, there are approximately 400 milligrams of sodium in 1 gram of salt.

For an athlete, the important thing is not the salt itself, but the quantity of sodium available and its effect on performance.

Why is sodium essential for athletes?

Sweat losses vary greatly from person to person. Some studies estimate that an athlete can lose 0.5 to 2 liters of sweat per hour, with a highly variable concentration of 230 to over 2000 mg of sodium per liter.

Without compensation, your blood volume gradually decreases and your heart has to work harder to supply your muscles with oxygen and nutrients. In this way, you tire more quickly and your exercise tolerance decreases.

A recent review published in Performance Nutrition also confirms that sodium intake before, during, and after exercise helps to limit the effects of dehydration, promotes water retention, rapid rehydration, and the restoration of lost electrolytes. 

In short, sodium is involved in maintaining fluid balance, intestinal absorption of certain nutrients, nerve impulse transmission, and muscle contraction. 

What are the sodium requirements based on physical activity?

These figures are indicative: always adjust your sodium intake to your sweating, effort intensity, climatic conditions, and personal tolerance.

Should you supplement with sodium?

Sodium supplementation is not always necessary. It becomes relevant when the body's natural compensatory capacities become limited.

When can supplementation be useful?

This is often the case in four specific situations. 

• Efforts exceeding 90 minutes (Marathon, trail running, triathlon, long-distance cycling): beyond this duration, your cumulative losses become significant and difficult to compensate for solely through food.
• Training or competition in hot weather: Heat increases your sweat production. Your sodium losses can thus double or triple compared to a temperate climate.
• "Heavy sweater" profile: Some people naturally produce more sweat. If you notice white deposits on your clothes, it's crystallized sodium. You probably belong to this category, and your needs are therefore higher than average.
• Insufficient dietary intake: If your daily diet is low in sodium, you start with limited reserves. This becomes problematic during intense training phases when needs increase.

Risks associated with poor sodium management

An isolated excess can cause digestive problems (nausea, diarrhea), a temporary increase in blood pressure, or uncomfortable water retention (feeling of bloating, temporary weight gain). These effects are generally transient in healthy individuals.

The real danger is related to hyponatremia (blood sodium concentration < 135 mmol/L), often caused by excessive consumption of pure water without electrolytes during prolonged efforts. 

Symptoms include: confusion, severe nausea, swelling, and, in the most critical cases, seizures or cerebral edema, requiring emergency hospitalization.

Sodium and the athlete's daily diet

Sodium primarily comes from table salt, prepared meals, and certain processed foods. The goal is to maintain a regular intake without chronic excess.

• Prioritize naturally salty sources: seaweed, olives, shellfish, celery, aged cheeses, quality cured meats (in moderation).
• Salt your meals normally the day before and the day of a big effort to anticipate your losses.
• Eat a salty dish after exercise to quickly restore your electrolyte balance. Examples: homemade vegetable broth, miso soup, rice bowl with soy sauce, cheese omelet.
• Avoid low-salt diets without professional advice: active athletes have increased needs.
• Limit ultra-processed products: although their sodium content is high, their nutritional quality remains low (poor in micronutrients, rich in additives).

Common sodium mistakes made by athletes

Mistake #1: Drinking only water on long outings. Beyond 90 minutes, pure water gradually dilutes your blood sodium, and the risk of hyponatremia increases proportionally to the amount of water ingested without electrolytes. Alternate pure water with electrolyte drinks, or add a pinch of salt to your water bottle.

Mistake #2: Banning salt for fear of hypertension. This recommendation mainly concerns sedentary individuals or those with confirmed cardiovascular diseases. An active and healthy athlete should not completely eliminate salt.

Mistake #3: Using a new product on race day. Your digestive system may react poorly to a new formulation. Test your sodium consumption strategy during training, several weeks before the big day. Replicate race conditions with intensity, heat, and timing.

Testimonials and expert recommendations

Experts agree: proper sodium management is essential to compensate for sweat losses.

According to Nina S. Stachenfeld, researcher at John B. Pierce Laboratory and Yale School of Medicine: "sodium intake during or after exercise stimulates thirst and helps the kidneys retain water."

Controlled studies show that sodium-enriched drinks reduce the risk of hyponatremia and support maintaining performance. The effect is particularly marked beyond 2 hours of continuous effort.

A dramatic event marked collective awareness of the importance of sodium in athletes. At the 2002 Boston Marathon, 13% of the 488 runners tested had hyponatremia. A 28-year-old female runner died of hyponatremic encephalopathy after consuming large amounts of water without sodium compensation.

FAQ

What is the role of sodium in the human body?

This mineral regulates hydration, supports nerve transmission, and participates in muscle contraction.

Why is sodium important for endurance athletes?

Sodium compensates for sweat losses, maintains fluid balance, and helps stabilize performance during prolonged efforts.

How much sodium should an athlete consume per day?

Basic needs range from 1500 mg at rest to 2500-3000 mg during regular training. During exercise, add 300 to 600 mg per hour. A very active athlete can thus reach 4000-5000 mg per day without problems.

What is the difference between sodium and table salt?

Salt contains sodium, but only sodium affects hydration and muscle function. One gram of salt provides 400 mg of sodium.

What happens if you lack sodium during a marathon?

A lack of sodium leads to several effects: performance drop, risk of hyponatremia and cramps. In severe cases, cerebral edema.

Is salt dangerous for athletes' health?

Salt is not necessarily a danger for active athletes as long as recommended doses are respected. In case of high blood pressure or other cardiac/renal pathology, consult a professional before increasing your intake.

Should salt tablets be taken during trail running or marathons?

Yes, especially in hot weather or in case of heavy sweating. Always accompany them with sufficient water to avoid digestive issues.

Conclusion

Sodium is a real ally for endurance athletes when managed intelligently and judiciously. Understanding your individual losses, adapting your intake according to the context (duration, intensity, climate), and avoiding extremes (deficiency as well as excess) allow you to simultaneously optimize your hydration, recovery, and performance.

Bibliography

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