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Sodium – The Most Important Electrolyte for Hydration and Performance
Sodium is the most important extracellular cation and the crucial regulator of water balance, blood volume, and nerve function. In sports, adequate sodium intake – especially during intense sessions and in the heat – is critical for performance and safety.
Physiological Functions
- Osmolarity: Sodium largely determines the osmotic pressure in blood and body fluids
- Water Balance: Sodium attracts water → regulates cell volume and blood volume
- Action Potentials: Sodium influx through voltage-gated Na⁺ channels triggers action potentials in nerves and muscles
- Nutrient Absorption: Secondary active transport of many nutrients (glucose, amino acids) via sodium-coupled transporters (SGLT1, SNAT)
- Blood Pressure: Increased sodium intake increases blood volume → blood pressure rises in salt-sensitive individuals
Sodium in Sports: An Underestimated Electrolyte
Sodium is the electrolyte most concentrated in sweat. There are large individual differences among endurance athletes:
- “Salty Sweaters”: Lose 1,500–2,500 mg of sodium/L of sweat (white marks on dark clothing as an indicator)
- “Light Sweaters”: 500–800 mg of sodium/L of sweat
- During a marathon run (2–3 L of sweat): Sodium loss of 1,000–7,000 mg is possible
Hyponatremia – The Dangerous Side Effect of Too Much Water
Hyponatremia (serum sodium <135 mmol/L) occurs during sports when too much sodium-free water is consumed along with high sodium loss. Symptoms: nausea, headaches, confusion, cramps, in extreme cases unconsciousness and death. Particularly risky during long-distance runs and triathlons.
Prevention: Do not drink more than thirst dictates; use sodium-containing drinks or salt tablets during long events.
Recommendations for Sports and Everyday Life
| Situation | Sodium Recommendation |
|---|---|
| Normal daily life (DGE) | Max. 6 g table salt/day (= 2,400 mg sodium) |
| Training <60 min. | Water sufficient |
| Training 60–90 min. in heat | 500–700 mg sodium/h in drink |
| Endurance >2h | 700–1,000 mg sodium/h |
| Keto diet (first weeks) | Increased need: 3,000–5,000 mg/day |
Sodium and Blood Pressure
Approximately 25% of the population is “salt-sensitive” – for them, increased sodium intake leads to a measurable rise in blood pressure. For athletes with normal kidney function and a high sweat rate, higher sodium intake is generally safe. Individuals with hypertension or heart failure should discuss sodium intake with their doctor.
Frequently Asked Questions (FAQ)
Is sea salt healthier than table salt?
No – biochemically, sodium chloride is identical, whether from sea salt or rock crystal salt. Sea salt contains trace amounts of other minerals, but these are nutritionally irrelevant. Iodized table salt is better for iodine supply.
What is the best source of sodium for sports?
Sodium chloride (table salt), sodium citrate (better tolerated), or sodium phosphate. In electrolyte drinks, usually combined as sodium chloride + sodium citrate.
