Summer heat and electrolytes: sodium per serving compared

How much sodium do you lose training in a South African summer?

Anywhere from a few hundred to several thousand milligrams an hour, depending on who you are. Sweat sodium concentration commonly spans about 10 to 90 mmol/L between athletes (Baker, 2017 review), which is roughly 230 to 2 070 mg per litre at 23 mg of sodium per mmol. Sweat rates are often 0.5 to 2 L an hour and can pass 3 L an hour in heat.

A worked example, not a measurement: someone sweating 1 L an hour at 40 mmol/L loses about 920 mg of sodium an hour. Only a sweat-rate test (weigh yourself before and after a session) and signs like white salt marks on kit tell you where you sit.

Do you need electrolytes, or is water enough?

For sessions under an hour or two, water and normal meals cover most people. Electrolyte products earn their place during long efforts above 1 to 2 hours, especially in Durban or Lowveld humidity and on hot Cape Epic-style stages, and for heavy or salty sweaters. Cramps are multifactorial, so sodium is not a guaranteed fix, and the evidence that magnesium prevents exercise cramps is weak.

The bigger risk is overdrinking. Exercise-associated hyponatraemia (blood sodium below 135 mmol/L during or up to 24 hours after exercise) is mainly caused by drinking more hypotonic fluid than you sweat out. The 2015 consensus lists overdrinking, weight gain during exercise, events over 4 hours and a slower pace as risk factors. Sodium in your drink slows this but cannot prevent it if you overdrink. Drink to thirst. Nausea, headache, confusion or seizures during or after a long event need emergency care.

How much sodium is in popular South African electrolyte products?

Most sellers do not publish it. These are the figures we could find as of 27 October 2026:

Faithful to Nature's pages disagree on whether its R579 variety pack holds 20 or 40 sachets, which is why the REVIVE price is a band. Its pages state stevia leaf extract as the sweetener.

Sodium per serving is not published on the retailer pages we read for Biogen Electrolyte and Electrolyte Plus, USN Purefit Zero Hydrator, Nutritech Hydrate, Lifestyle Electrolyte Fizzy, Hydropop, Resurge, Kwench or the 32Gi Endure tub (the Dis-Chem page lists salt but no milligrams). REVIVE Raw's page gives sodium only per 100 g with no sachet weight. Check the pack, because a cheap sachet with unknown sodium is not cheap sodium.

What does the comparison tell you?

• Published sodium per serving differs about 50-fold. REVIVE's 1 000 mg suits long, hot, salty-sweat sessions; it is about 2.5 g of salt per sachet, so it is a lot for a casual jog.
• Rehidrat is an oral rehydration salt for diarrhoea and gastroenteritis. It carries about 12 g of sugars per sachet (our calculation), so it is not a sugar-free training drink.
• Revitalyte's page calls it an unregistered medicine not evaluated by SAHPRA.
• Energy gels are weak sodium sources at 20 to 29 mg: they replace carbohydrate, not salt. Electrolyte gels such as Biogen Cramp Care carry more (180 mg) but cost far more per milligram.

Can you make your own?

Yes. A level teaspoon of table salt holds roughly 2 300 mg of sodium, so a quarter teaspoon (about 575 mg) in a litre bottle supplies roughly half of a REVIVE sachet's sodium. Mix it consistently and rehearse it in training, because gut tolerance is individual.

Who should be careful with extra sodium?

Anyone with hypertension, kidney or heart disease, or on diuretics should ask a doctor before using high-sodium products. NSAID use is flagged in the hyponatraemia literature, though the link is unresolved. For children, water and food are normally enough.

How do you plan a hot session?

1. Weigh yourself before and after a 60-minute hot session, with fluid intake counted, to estimate sweat rate.
2. For efforts over 1 to 2 hours, add sodium from a product whose label you can read.
3. Sip to thirst; do not drink on a schedule beyond your sweat loss.
4. Rehearse race-day products in training.
5. Treat electrolyte products as sports foods (AIS Group A), not medicines.