How Much Sodium Do You Actually Need in an Electrolyte Drink?

Jasmine Meagher, founder of Ritua
Jasmine Meagher, BSc Food Science and Nutrition
Founder, Ritua · 10 min read

Electrolyte drinks have turned into a numbers race. One brand puts 200 mg of sodium in a serve, another 500 mg, another 1,000 mg, and each implies its number is the correct one. The honest answer is that there is no single correct number. What you need depends on how much sweat you produce, how salty that sweat is, and how long you are out there, and all three vary enormously between people and from one session to the next.

So this article works through what the sweat research shows: how much sodium is in sweat, how wide the spread is, what sodium does once you drink it, and where the evidence says a high sodium drink earns its place. It also says the part supplement companies tend to skip. For a forty minute session in mild conditions, most people do not need anywhere near 1,000 mg of sodium.

What sodium actually does when you drink it

Sodium is the main solute in the fluid outside your cells, and your body defends its concentration closely. That one fact explains most of what sodium does in a drink. Take in plain water after a heavy sweat loss and blood sodium concentration falls slightly, the signal to hold onto water switches off, and the kidneys produce dilute urine. You drank the fluid, but a share of it leaves again. Adding sodium keeps blood sodium concentration up, keeps the retention signal on, and more of what you swallowed stays in you.

This has been tested directly. In a study by Shirreffs and Maughan in the American Journal of Physiology, volunteers were dehydrated by about 1.9 per cent of body mass in warm, humid conditions, then rehydrated with a volume equal to 150 per cent of what they had lost. The only variable was the sodium content of the drink: 0, 25, 50 or 100 mmol per litre. Urine production over the six hour recovery period was inversely related to how much sodium was ingested, and only on the 100 mmol per litre trial were participants in positive fluid balance at the end. Same volume of fluid, four different outcomes, driven by sodium.

The beverage hydration index trial in the American Journal of Clinical Nutrition found the same across 13 drinks in 72 participants: an oral rehydration solution produced significantly less urine over four hours than still water, while a conventional sports drink, juice, cola, tea and coffee did not differ from water. Be precise about what that means, though: it is a claim about fluid retention, not about protecting you from anything.

How salty is sweat, and how much does it vary?

Sweat begins nearly isotonic with blood plasma, around 135 to 145 mmol per litre of sodium, then sodium is reabsorbed as it travels up the sweat duct. That is why what reaches your skin is far less salty than plasma, and how efficiently you reabsorb is what separates a salty sweater from everyone else. Lindsay Baker's 2017 review in Sports Medicine lists what shifts it: exercise intensity, environment, heat acclimation, aerobic capacity, body size, protective equipment, sex, age, diet and hydration status.

The size of the spread is the most useful number in this conversation. A retrospective analysis of 506 athletes by Baker and colleagues in the Journal of Sports Sciences collected forearm patch samples across team and endurance sports in conditions from 15 to 50 degrees Celsius.

Across 506 athletes, forearm sweat sodium concentration averaged 43.6 mmol per litre but ranged from 12.6 to 104.8 mmol per litre. That is more than an eightfold difference between the least and the most salty sweater, or roughly 290 mg to 2,400 mg of sodium in every litre of sweat.

Forearm patches read higher than the body as a whole, so the study converted the results to predicted whole-body values using a published regression equation. Those averaged 35.9 mmol per litre and ranged from 18.2 to 70.8, about 420 to 1,630 mg of sodium per litre of sweat. Two people can do the identical session side by side and one loses four times as much sodium as the other. No number printed on a label is right for both.

Sweat rate and duration matter more than the label

Concentration is only half of it. What you lose is concentration multiplied by volume, and volume varies more widely still. In that same group of 506 athletes, whole-body sweating rate averaged 1.21 litres per hour with a range of 0.26 to 5.73. Then multiply by time, because twenty minutes and four hours are not the same problem. This is why the American College of Sports Medicine position stand on exercise and fluid replacement issues no universal sodium figure. It states that because there is considerable variability in sweating rates and sweat electrolyte content between individuals, customised fluid replacement programs are recommended.

For a sense of scale, Barnes and colleagues compiled sweat testing on 1,303 athletes and reported sodium loss per hour by sport: 55.9 mmol per hour in American football, 51.7 in endurance sport, 34.6 in soccer, 34.5 in basketball and 27.2 in baseball. One millimole of sodium is about 23 mg, so in label units those averages run from roughly 1,290 mg per hour down to 625 mg per hour. The standard deviations were large, so treat them as a scale, not a prescription.

When a higher sodium drink is warranted

More sodium makes sense when total loss is genuinely large: long duration, high sweat rate, hot or humid conditions, or repeated sessions in one day. The International Olympic Committee consensus paper on fluid and electrolyte needs puts daily losses for active athletes training in hot weather at 4 to 10 litres of water and 3,500 to 7,000 mg of sodium. At that end, replacement is arithmetic rather than marketing. The same paper notes that where there is no urgency, normal eating and drinking replaces it perfectly well, because sodium is not scarce in a normal diet. A concentrated drink earns its keep when fluid balance has to be restored inside 24 hours, or when the deficit is too large to eat your way out of before the next session. The Sports Dietitians Australia position statement on exercise in hot environments makes the same point: build the strategy from an individual assessment, not a default.

It also helps to understand why an electrolyte drink is more concentrated than sweat rather than matched to it. Ritua's Hydrate delivers 1,000 mg of sodium in a 500 ml serve, about 87 mmol per litre of made up drink, higher than the predicted whole-body sweat sodium of every athlete in the Baker dataset. It is not a like for like copy of sweat. It returns a useful amount of sodium in a volume you will actually finish, because almost nobody drinks litre for litre what they lose. That is also why the serve is more than some people need.

When 1,000 mg is more than you need

Here is the part worth saying plainly. Sweating at 0.5 litres per hour for 45 minutes is about 375 ml of sweat, and at the dataset average of 35.9 mmol per litre that is roughly 310 mg of sodium. A 1,000 mg serve is three times that. It will not harm a healthy person, but it is not replacing anything, and you should not be told that it is.

There is a dietary context too. The Australian and New Zealand Nutrient Reference Values set an Adequate Intake for sodium of 460 to 920 mg per day for adults and a Suggested Dietary Target of 2,000 mg per day for reducing chronic disease risk. A single 1,000 mg serve is half that target. The reference values do note that the Adequate Intake may not apply to highly active people such as endurance athletes or those doing heavy physical work in hot conditions. That caveat is the point: the honest way to use a high sodium drink is to know which group you are in on the day. A serve is not all or nothing either. Half a sachet in 250 to 300 ml of water scales it down sensibly.

Hyponatraemia, briefly and accurately

Sodium comes up in endurance circles mainly because of exercise associated hyponatraemia. The Third International Exercise Associated Hyponatraemia Consensus Development Conference statement defines it as a blood sodium concentration below the laboratory reference range, for most laboratories below 135 mmol per litre, occurring during or up to 24 hours after physical activity. Asymptomatic cases have been reported in 0 to 51 per cent of finishers depending on the event, with the highest rates in 161 km ultramarathons.

The consensus is explicit about cause. The primary mechanism is overconsumption of hypotonic fluids relative to exchangeable sodium, likely combined with non-osmotic vasopressin secretion. In plainer terms, the dominant risk factor is drinking more than you are losing over a sustained period. It is a dilution problem before it is a sodium deficiency problem. That is why the statement is careful about supplementation: sodium can attenuate the fall in blood sodium when fluid intake roughly approximates sweat losses during prolonged exercise, but cannot prevent the condition where fluid intake is persistently excessive. Sodium is part of the picture in long events. It is not a substitute for sensible drinking volumes, and no drink should be sold as though it were.

How to work out your own number

You do not need a laboratory for the part that matters most. Weigh yourself, with minimal clothing, before and after a typical session, accounting for anything you drank. Each kilogram lost is roughly one litre of sweat, so two or three sessions gives you a workable sweat rate, the variable that moves sodium loss the most. For saltiness, white salt marks on dark clothing or a gritty film on the skin point towards the higher end, and sweat patch testing gives an actual figure. Multiply sweat rate by session length by estimated concentration, then compare that to the label.

The bottom line

Sodium earns its place in a drink because it helps you hold onto the fluid you swallow. How much you need is set by your own sweat, not by whatever number the category has converged on this year. Predicted whole-body sweat sodium spans roughly a fourfold range between individuals, sweat rates more than twentyfold, and duration multiplies both. A high sodium serve suits long, hot, heavy sweating sessions and fast turnarounds between them, and it is more than you need for a short indoor session. Saying so describes who it is for.

If you do sit at the high loss end, Ritua Hydrate is formulated at 1,000 mg of sodium, 190 mg of potassium and 70 mg of magnesium per 5.5 g sachet in 500 ml of water, with no added sugar. It is a Formulated Supplementary Sports Food under FSANZ Standard 2.9.4, a category intended for people undertaking significant physical activity. If that is not you on a given day, half a serve or plain water is a sound answer.

The label conditions for that category apply and are worth reading: it is not suitable for children under 15 years of age or pregnant women, it should only be used under medical or dietetic supervision, and it is not a sole source of nutrition. If you have high blood pressure, kidney disease, or any condition where your sodium intake is being managed, raise the sodium content of any sports drink with your doctor first.

This article is general information, not medical advice, and is not a substitute for guidance from your doctor, particularly if you are managing an existing health condition or taking medication.

Jasmine Meagher, founder of Ritua

Jasmine Meagher

BSc Food Science and Nutrition · Founder, Ritua

Jasmine founded Ritua to bring evidence-based, TGA-compliant supplements to Australian women. She writes about the research behind every ingredient Ritua sells.

Common questions

Is 1,000 mg of sodium per serve too much?

It depends on your losses. Sweat sodium loss rates measured across 1,303 athletes averaged roughly 1,190 mg per hour in endurance sport and about 625 mg per hour in baseball, so 1,000 mg sits in a sensible range for a long or hot session. For a 40 minute indoor session at a modest sweat rate, where losses may be a few hundred milligrams, it is more than you need. Half a sachet is a reasonable way to scale it.

Why is an electrolyte drink saltier than sweat?

Because people rarely drink the full volume they sweat out. Predicted whole-body sweat sodium in the Baker dataset averaged 35.9 mmol per litre, while 1,000 mg in 500 ml is about 87 mmol per litre. A more concentrated drink returns a useful amount of sodium in a volume you will realistically finish. The trade off is that it is easy to take in more sodium than you actually lost.

Does sodium stop me getting cramp?

Ritua makes no claim of that kind, and this article deliberately does not make one. The research on exercise associated muscle cramp is contested and no consensus body currently endorses sodium as a preventive. What the evidence here covers is narrower and better established: sodium influences how much of the fluid you drink your body retains.

How do I know if I am a salty sweater?

White salt residue on dark clothing or a gritty film on the skin after a hard session is a rough indicator of the higher end of the range, though it is not a measurement. The research method is a standardised absorbent sweat patch, usually on the forearm, with the result converted to a whole-body estimate using a regression equation. Some sports science and performance clinics offer it.

Should I use an electrolyte drink every day?

Only if your daily sweat losses justify it. The Australian and New Zealand Nutrient Reference Values put the Suggested Dietary Target for sodium at 2,000 mg per day, while noting that the Adequate Intake may not apply to endurance athletes or people working hard in hot conditions. If you train long in the heat most days, regular use may make sense. If you do not, water and normal meals will usually cover it.

Does more sodium protect me from hyponatraemia in a long race?

Not on its own. The Third International Exercise Associated Hyponatraemia Consensus statement is clear that sodium supplementation can attenuate the fall in blood sodium when fluid intake roughly approximates sweat losses, but cannot prevent the condition when fluid intake is persistently excessive and produces fluid overload. The dominant risk factor is drinking more than you lose, so managing total fluid volume matters more than the sodium content of the drink.

Sources

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