Do You Need Electrolytes Every Day? What the Evidence Shows for Healthy Adults

How a simple question about a packet for your water bottle led us to laboratory tests, more than a million blood donors, and the unexpectedly important role of an ordinary lunch.

Imagine a normal working day. You sit at a computer, go out for lunch, and occasionally pour yourself some water or tea. No marathon, no heat exposure, no illness. Do electrolytes belong in this picture: a powder, tablet, or ready-made drink promising more effective hydration?

The promise sounds convincing. Sodium, potassium, and magnesium are essential. We lose them with water. Why not replace them proactively, especially if the drink really does make you feel better?

We started with a fairly narrow question: what does an electrolyte drink add for a healthy person who eats normally, is not overheating, and is not losing large amounts of fluid? It seemed that a few comparisons with water should settle the issue.

The studies created an unexpected difficulty. They showed quite convincingly that the drinks do something. It was much harder to decide what that effect actually meant. And when we tried to verify the most obvious explanation, we had to abandon several of our own assumptions.

What are electrolytes, and what does an electrolyte drink actually do?

Electrolytes are substances that form electrically charged particles, or ions, in solution. In nutrition, the term usually refers to sodium, potassium, chloride, magnesium, and calcium. They are involved in nerve and muscle function, fluid balance, and many other physiological processes.

But biological necessity does not by itself prove that an extra dose is useful. Oxygen is also essential, yet a healthy person sitting at a desk does not therefore need an oxygen cylinder.

The word “hydration” creates additional confusion. It can mean water intake, the body’s overall water state, or the result of a particular laboratory test. It is easy to move from one meaning to another without noticing.

We therefore separated three questions. Does the drink change how the body handles water? Does it correct a shortage of water or minerals? And does the person benefit in a way that matters, for example with less fatigue, less dizziness, or better performance?

The first answer appeared quickly. The second and third questions became the real story.

Do electrolyte drinks retain more water than plain water?

In a 2016 experiment by Ronald Maughan and colleagues, healthy men who started in a normally hydrated state drank 1 litre (34 US fl oz; 35 UK fl oz) of a beverage within 30 minutes. Researchers then collected urine for four hours. The drinks included water, milk, tea, coffee, a sports drink, and an oral rehydration solution, or ORS.

After water, mean urine mass over four hours was 1,337 g (47.2 oz). After ORS, it was 1,038 g (36.6 oz). The difference was about 300 g (10.6 oz). Milk also reduced urine output compared with water, while the tested sports drink did not show a statistically convincing advantage.

This is a real effect. But note what it does not mean. Even after ORS, participants excreted roughly as much urine during the observation period as the amount they had consumed in the experiment. The kidneys were drawing water from the body’s total water pool, not from a separately labelled litre that had just been swallowed. The result therefore describes a difference between conditions, not proof that the body “kept the whole drink”.

Measurements of this kind led to the Beverage Hydration Index, or BHI. In simplified form, it is the ratio of urine output after water to urine output after another beverage over the same time period.

If water produces 1 litre (34 US fl oz; 35 UK fl oz) of urine and another drink produces 800 ml (27 US fl oz; 28 UK fl oz), the second drink has a BHI of 1.25. This is only an illustrative calculation. It means lower urine output in that test. It does not mean the person became “25% better hydrated” in every meaningful sense.

The name of the metric sounds broader than the measurement itself. BHI can compare short-term responses to beverages, but by itself it tells us nothing about headache, mental clarity, or health one year later.

Electrolytes work, but what does “better hydration” mean?

In a subsequent controlled study, researchers independently varied sodium, sugar, and caffeine content. Solutions containing 27 and 52 mmol of sodium per litre reduced urine output more than solutions containing 7 and 15 mmol/L. In nutritional units, 27-52 mmol/L is about 620-1,200 mg of sodium per litre.

So the effect cannot simply be explained by attractive packaging: the composition of a drink really can change what happens to the fluid afterwards. But 27-52 mmol/L is not a universal threshold above which any product becomes “effective”. Other ingredients, the amount consumed, the person’s starting state, and the timing of measurement all matter.

Sugar and protein also have effects. They can alter gastric emptying, absorption, and subsequent water excretion. A multicomponent drink therefore cannot automatically credit all of its advantage to electrolytes unless the experiment separates the effects of the components.

This raises the next question: where is the water that has not yet appeared in urine?

In a 2022 study with 22 participants, an isotonic drink produced an approximately 106 ml (3.6 US fl oz; 3.7 UK fl oz) better calculated fluid balance by the fourth hour. However, bioelectrical impedance, which estimates body composition from the body’s electrical properties, did not detect convincing differences in total, intracellular, or extracellular water.

This does not prove that there was no difference. The instrument may simply have been unable to detect a small effect, and some fluid could still have been in the gastrointestinal tract. But the experiment also did not support the stronger claim that “less urine means the cells received more of the water they needed”.

It would also be wrong to dismiss BHI as an empty metric. In another experiment involving younger and older participants, some beverages maintained estimated plasma volume better. The physiological effect may extend beyond urine output. The point is narrower: moving from an effect to a benefit requires another layer of evidence.

A room thermometer can accurately show that the temperature increased. Whether that change helps the person in the room depends on whether they were cold in the first place.

Do electrolyte drinks still work when you eat normally?

After the first studies, an appealing hypothesis emerged. Drinking 1 litre (34 US fl oz; 35 UK fl oz) in a short period, on an empty stomach, followed by several hours without normal food does not look much like a day at a computer. Food already contains salt, potassium, carbohydrate, and protein. Perhaps adding an ordinary lunch would make the advantage of a special drink disappear.

The test was inconvenient for this hypothesis.

In a Singapore crossover study, 49 healthy men spent eight hours in an air-conditioned environment with almost no physical activity. Each participant completed both conditions: distilled water and an isotonic drink. Standardised breakfast, lunch, and a snack were provided. Drinking volume was almost identical, about 1.94 litres (66 US fl oz; 68 UK fl oz).

The difference remained: about 243 ml (8.2 US fl oz; 8.6 UK fl oz) of urine. Normal meals therefore do not necessarily eliminate the effect of the drink.

We recalculated the drink composition for the volume actually consumed. Participants received approximately 930 mg sodium, 270 mg potassium, and 116 g (4.1 oz) sugar, equivalent to about 466 kcal. This is our arithmetic based on the published mean intake and the stated composition, not a new analysis of individual participant data.

No convincing between-condition differences were found in changes in total body water by bioelectrical impedance or in serum osmolality, a measure of the concentration of dissolved particles. Better performance or reduced fatigue was not a demonstrated outcome. The trial also compared complete beverages, so the effect of sodium cannot be separated from the effect of sugar.

We therefore had to abandon our first neat hypothesis. A special drink can alter short-term fluid balance even when ordinary food is present. But the question became more precise: why does an already normally hydrated person need to retain those additional few hundred millilitres?

What happens after four hours: do the kidneys catch up?

Another explanation then appeared. Perhaps electrolytes simply delay water excretion. Over 24 hours, the kidneys may catch up and the early difference may disappear.

That is plausible. Plausibility, however, is not a measurement.

We found a 24-hour study in 34 healthy men in which beverage composition did not substantially change final hydration measures. However, the comparison involved water and combinations with cola, diet cola, and orange juice. This is not a precise electrolyte-powder-versus-water test. Treating it as definitive proof that the effect disappears would be too convenient.

Longer studies of salt do not give a simple answer either. In a DASH-Sodium analysis, 412 adults with blood pressure ranging from high-normal to hypertensive levels were studied. Higher sodium intake increased thirst. On the control diet it was associated with greater 24-hour urine volume, whereas on the DASH diet there was no convincing change in urine volume. The pattern looked nothing like constant “locking” of water inside the body.

In long-term controlled-feeding experiments during a simulated space mission, the picture became even more complex. With more salt, men drank less while the mechanisms of water conservation changed. This was a small and highly specific sample, so the result cannot be transferred directly to an everyday electrolyte packet. It demonstrates something more general: water and sodium balance is a feedback-regulated system, not a tank containing a salty sponge.

Over a period of days, thirst, renal sodium excretion, urine concentration, and fluid distribution can all change. A four-hour observation therefore cannot automatically be extrapolated to a month of daily use.

In the studies we reviewed, we did not find a precise answer to how much additional water remains after 24-72 hours when an ordinary dose of electrolytes is added to a normal diet. Claiming that the entire difference must disappear by midnight would be just as unjustified as promising persistent “super-hydration”.

Do electrolytes prevent fainting? Evidence from 1.4 million blood donors

To escape the circle of intermediate laboratory measures, we needed a study with an outcome that matters directly to people. For example: does the drink help prevent fainting?

Such a study exists, and it is far larger than most hydration experiments.

In STRIDES, published in 2026, researchers studied prevention of vasovagal reactions during blood donation, episodes of weakness and sometimes fainting associated with a reflex fall in blood pressure and/or heart rate. The study covered 1,379,095 donors and 4,134,712 donations across 73 centres in England. One comparison was 500 ml (17 US fl oz; 18 UK fl oz) of an isotonic drink versus 500 ml (17 US fl oz; 18 UK fl oz) of ordinary water before blood donation.

There was no convincing reduction in reactions involving loss of consciousness: odds ratio 0.98, with a 95% confidence interval of 0.92-1.04. The central estimate is almost exactly no difference, while the interval is compatible with either a small benefit or a small worsening.

This does not mean that more than a million people were individually randomised between two drinks. The study used a cluster design, with conditions changing across centres and time periods. Nor did it test treatment of dehydration or every form of low circulating volume.

But for this specific practical task, the result is important: replacing water with an isotonic drink before donation did not produce a meaningful additional benefit. Physiological plausibility alone was not enough.

At this point, “does the drink retain water?” stopped being the main question. The more important question became: what event is that retention supposed to prevent, and does it actually prevent it?

Is it useful to drink electrolytes every day?

Long-term use could theoretically produce effects that short laboratory studies miss. We looked for such a test and found a four-week study of a commercial electrolyte drink.

Forty men and women were assigned to four groups: placebo, or one, two, or three servings per day. The tested formula provided 510 mg sodium and 380 mg potassium per serving. The study primarily assessed safety and tolerability.

After correction for multiple comparisons, no statistically significant differences remained in the evaluated outcomes. For a small short-term trial, this is reassuring regarding tolerability. But ten people per group and four weeks cannot exclude rare or long-term adverse effects.

The main limitation is simpler: a safety study does not become a benefit study. It did not show that healthy participants had more energy, thought more clearly, or experienced fewer headaches. The study was partly funded by Liquid I.V.; this was disclosed in the publication.

Industry funding does not automatically invalidate data. But correct data can still answer a narrower question than the marketing claim. It matters whether a study measured product tolerability, urine output, or an improvement that is genuinely important to the person drinking it.

Could healthy people still have a hidden electrolyte deficiency?

After these findings, a strong counterargument remained. Limited evidence for benefit does not mean ordinary people never have inadequate mineral intake. Perhaps electrolyte drinks help a subgroup that small studies failed to identify.

Here we had to separate three states that are often compressed into the single everyday word “deficiency”: low dietary intake, depletion of body stores, and a pathologically low blood concentration. They are related, but they are not the same thing.

Sodium in a blood test is not a meter for how much salt you ate

Blood sodium concentration depends on the relationship between water and dissolved substances. Low blood sodium, or hyponatraemia, can occur when water is excessive relative to the body’s capacity to excrete it, in disease, or because of medications. It is not simply a laboratory test of whether a person salts their lunch enough.

In the EFSA scientific opinion on dietary reference values for sodium, the mechanisms of sodium conservation and the rarity of ordinary dietary sodium deficiency are discussed explicitly. The kidneys can reduce sodium losses when intake falls. This does not make regulation infallible, but the hypothesis of widespread hidden sodium deficiency in normally eating healthy people requires its own evidence.

Fatigue, or feeling better after a salty drink, is not by itself such evidence.

Potassium made us revise an overly simple conclusion

Potassium is more complicated. A normal blood result does not guarantee optimal intake because most potassium is inside cells and its blood concentration is tightly regulated. The US National Institutes of Health describes both the rarity of hypokalaemia caused solely by low intake in healthy people and the limitations of a blood test for assessing total potassium status.

In a controlled experiment with deliberate potassium restriction, healthy men showed changes in renal sodium handling and blood pressure. This is a causal signal that mineral composition of the diet matters even outside exercise-related losses. But the study examined very low potassium intake, so it does not prove that every person eating a normal diet benefits from an extra gram.

Similarly, a study of potassium from potatoes and potassium gluconate found good bioavailability from both sources but no convincing dose-dependent benefit for blood pressure over the short five-day study periods. It does not exclude a longer-term effect. It does show that food potassium was not inherently inferior to potassium from a supplement.

This forced us to revise our initial idea that “the body will regulate everything” as too crude. The body may maintain a normal blood result while diet quality still matters. But it does not follow that the best solution is a drink that simultaneously adds sodium.

The salt substitute used in the SSaSS trial had a different logic: part of the sodium was replaced with potassium rather than simply adding both. Among 20,995 people at high cardiovascular risk, this reduced strokes and other adverse outcomes. The size of that benefit cannot be transferred to young healthy people, and the trial cannot be treated as evidence that electrolyte water is beneficial.

Potassium deserves a separate article. For the present question, the important distinction is this: building a nutritionally adequate diet and slowing the excretion of recently consumed water are different tasks. Potassium supplements and salt substitutes also require particular caution in kidney disease and when taking medications that reduce potassium excretion.

Magnesium has its own difficulty because body stores are hard to assess with a single test. We discussed this in our article on magnesium and sleep. The presence of magnesium on a label does not establish that the dose or the product solves a specific problem.

Does drinking lots of water flush out electrolytes?

The most interesting alternative hypothesis came from user discussions. People described a similar sequence: they started drinking more, began urinating more often, added electrolytes, and then felt that water no longer “went straight through”.

This is a useful observation for forming a question. But the explanation that “water washed out the minerals and the powder put them back” needs independent testing.

In a small controlled study by Shore and colleagues, nine healthy participants received fixed amounts of sodium and potassium. During the water-loading condition, total water intake including food reached 6.8 litres per day (1.8 US gal; 1.5 UK gal), compared with 2.7 litres per day (0.71 US gal; 0.59 UK gal) during the control period. The regimen continued for four days.

Urine volume increased greatly, the urine became more dilute, and vasopressin signalling, which helps the body conserve water, decreased. Yet daily sodium and potassium excretion did not increase relative to baseline.

The kidneys were excreting mainly the excess water. They did not behave like a leaking bucket from which minerals escaped uncontrollably with every additional litre.

This was a small experiment, and 6.8 litres per day (1.8 US gal; 1.5 UK gal) was an experimental condition, not a safe universal target. But it directly demonstrates why high urine volume cannot automatically be interpreted as evidence of electrolyte loss.

A real danger does exist when water is consumed too quickly. In an experiment with intensive water loading, water entered the body faster than participants could excrete it and blood sodium concentration fell. The mechanism here is dilution by excess water, not necessarily the loss of a large amount of sodium.

The distinction matters. If a person is drinking more than they need, the ability of a beverage to reduce subsequent urine output does not prove that retaining that water was beneficial.

For a fuller discussion of why a fixed target in litres may not always be useful, and what “water requirement” actually means, see our guide How Much Water Should You Drink?

Why do some people feel better after electrolytes?

A person can accurately notice an improvement and still be wrong about the mechanism. This does not dismiss personal experience. It is simply the familiar problem of changing several variables at the same time.

An electrolyte packet changes more than sodium. It changes taste, sometimes sugar intake, the amount of fluid consumed, and expectations. If the bottle remained full all day without the powder but became pleasant enough to drink with it, the benefit may have come from drinking enough water. If the person had not eaten for a long time, a sweet drink also provides energy. If they began drinking at the worst point of a headache, part of the later improvement might have occurred without the intervention.

There may also be a genuine individual difference in blood-pressure or blood-volume regulation. Such a condition does not disappear because the person considers themselves healthy.

In the literature we reviewed, we did not find a convincing trial in healthy people during an ordinary sedentary day that separated all of these components at once: matched taste and volume, electrolytes independently varied, sugar independently varied, comparable expectations, and measurements of fatigue, concentration, and general well-being.

It is therefore unjustified to say either “it is all placebo” or “if it helps, there must have been a deficiency”. The observed effect and the explanation for that effect are two separate questions.

The same caution applies to coffee. In a controlled comparison of coffee and water in habitual coffee drinkers, moderate coffee consumption did not worsen hydration measures. The mere fact that someone drinks coffee in the morning does not prove that electrolytes must be replaced afterwards. Large single doses of caffeine and individual responses are separate questions.

When are electrolytes useful without exercise?

By this point, the phrase “without exercise” had started to become misleading. A sedentary person can sweat heavily in heat, become ill, fast, or have impaired circulatory regulation. The absence of a workout tells us surprisingly little about water and electrolyte balance.

Heat, sauna, and gastrointestinal illness

With substantial sweating, water is lost together with electrolytes. Exercise is not required. How much should be replaced depends on the duration of losses, food intake, and environmental conditions. One short sauna session is not equivalent to many hours of work in the heat.

For diarrhoea, oral rehydration solutions are well developed. Their composition is designed for a specific task: replacing water and salts while using intestinal absorption mechanisms. The WHO ORS formula contains, per 1 litre (34 US fl oz; 35 UK fl oz), 75 mmol sodium, 20 mmol potassium, and 75 mmol glucose, approximately 1,725 mg sodium, 782 mg potassium, and 13.5 g (0.48 oz) glucose.

A sports drink with a similar-sounding name is not necessarily equivalent to this solution. And the effectiveness of ORS during real fluid losses does not imply that healthy people should drink it every day.

Dizziness on standing: real physiology, but not a simple diagnosis

When a person stands up, some blood shifts downward. Vascular and nervous-system regulation normally compensates. In some disorders of this compensation, additional fluid and sodium can genuinely help.

In a crossover study in postural orthostatic tachycardia syndrome, or POTS, 14 women with POTS were studied for six days each under very low and very high sodium intake. Higher sodium intake increased plasma volume and reduced the excessive rise in heart rate on standing. However, values did not normalise to those of healthy controls, and the small experiment did not show a convincing improvement in the overall symptom score.

This is a real exception, but it is not a test of an ordinary office electrolyte packet. The sodium doses were extremely different: 10 versus 300 mmol per day, approximately 230 versus 6,900 mg. Such regimens should not be transferred directly into unsupervised everyday use.

Then came an unexpected turn: ordinary water can also rapidly affect vascular regulation. In a small randomised study of nine patients with orthostatic hypotension, plain water produced a larger short-term increase in blood pressure than salt water. After 30 minutes, the mean rise in systolic pressure was 37 versus 18 mm Hg.

This was a very specific patient group, and the finding does not refute possible longer-term effects of salt. It does show how poorly a universal ladder of “water is good, water plus electrolytes is even better” describes real physiology.

Repeated near-fainting needs an explanation, not simply a powder selected by trial and error. The same symptom can result from different mechanisms, and improvement after a drink does not establish a diagnosis.

Older adults: more attention to drinking does not automatically mean more salt

Age seemed an especially plausible exception. In a classic experiment after 24 hours without water, older men felt less thirst and drank less than younger men despite more pronounced changes in water balance.

But additional sodium does not follow automatically from this observation. Inadequate water intake and combined loss of water and salt are different states.

The ESPEN guideline on nutrition and hydration in older people makes this distinction explicitly. When dehydration results from inadequate drinking, the task is to provide fluid; sports drinks and ORS are not indicated for that specific problem. Access to drinks, assistance, and whether the person is willing to drink are important. Vomiting, diarrhoea, or other ongoing losses create a different situation.

Increased vulnerability to dehydration therefore does not automatically equal a need for an electrolyte supplement.

Fasting and abrupt carbohydrate restriction

Finally, an otherwise ordinary sedentary day changes substantially when a person stops eating normally.

Studies of low-carbohydrate diets have observed early changes in sodium and water excretion. This makes some reports of weakness at the beginning of fasting or a sudden dietary change physiologically plausible. But a plausible loss mechanism does not establish a universal electrolyte regimen, nor does it explain every symptom.

There is another issue. The kidneys need dissolved substances, including products of protein metabolism, in order to excrete water. Very sparse food intake reduces this solute load. The combination “I am barely eating but still drinking a lot for health” is therefore physiologically different from the same water intake during a normal diet.

In a published clinical case, hyponatraemia developed in the context of low solute intake; increasing protein improved the capacity to excrete water. This is a single observation, not a treatment recipe. Its value is mechanistic: the problem may arise from the combination of food intake and drinking rather than from the absence of a special powder.

We therefore did not place fasting in the same evidence category as rehydration for diarrhoea. Questions remain about dose, composition, and which people, if any, benefit. Attempting to correct possible hyponatraemia with salt on your own can be dangerous because both the cause and the speed of correction matter.

What is actually inside an electrolyte packet?

After the physiology, we returned to the shop shelf. The phrase “I drink electrolytes” turned out to say very little about the actual exposure.

Two formulas from official product labels, checked while preparing this article, make the point clearly:

The sodium content per serving differs by about 18-fold. The first product nevertheless contains more potassium. This is not a quality ranking. It simply shows that products sold under the same broad category can be very different mixtures.

Dilution matters too. A packet containing 1,000 mg sodium mixed into 500 ml (17 US fl oz; 18 UK fl oz) of water gives 2,000 mg/L, while the same packet mixed into 1 litre (34 US fl oz; 35 UK fl oz) gives 1,000 mg/L. The total dose is identical, but the concentration is different. Comparing only the amount “per serving” while ignoring the water volume is therefore incomplete.

Three label questions are useful: how much sodium are you actually adding per day, how much potassium and magnesium are you receiving, and does the product contain sugar? Then comes the question the label cannot answer: why do you need that particular change?

A low-sodium mineral drink and a high-sodium solution are not interchangeable. At the same time, sodium content alone does not allow us to calculate the benefit, and similarity to ORS in one ingredient does not turn an ordinary product into a medical rehydration solution.

If the benefit is unproven, are electrolyte drinks harmful?

No. During this investigation, it was tempting to compare the “cost” of additional sodium with a few hundred millilitres of retained water and calculate a final balance. There is no reliable general coefficient that would make such arithmetic valid.

Blood-pressure responses to sodium vary between people and depend on baseline blood pressure, overall diet, and duration of exposure. Small studies of vascular function have sometimes found changes after a salty meal, while other experiments have not reproduced a simple picture of acute deterioration. These intermediate measures cannot support a claim that “one packet damages your blood vessels”.

But absence of proven harm does not create proven necessity. For a habit used every day, it is reasonable to want stronger justification than the ability of a product to alter urine output for several hours.

If a drink tastes good and helps someone consume an appropriate amount of fluid, that can be a practical benefit. If it replaces real losses or forms part of evidence-based treatment, the purpose is even clearer. These reasons should simply be named accurately rather than merged into the vague idea that “everyone needs better hydration”.

So, do you need electrolytes every day?

We began by drawing a boundary between exercise and no exercise. By the end of the investigation, that boundary looked secondary. What matters more is what is happening to the person: are they losing water and salts, are they eating normally, can they maintain blood pressure when standing, and is there an actual shortage that needs correction?

For a healthy adult in ordinary conditions, with a normal diet and no substantial fluid losses, convincing additional benefit from a daily electrolyte drink compared with adequate ordinary drinking has not been established. This is not proof that the effect is exactly zero in every individual. It is the boundary of what the experiments reviewed here allow us to claim.

What is reasonably well established?

Sodium and other components of a beverage can reduce urine output after a water load. The effect can remain visible not only in fasting experiments but also when normal meals are eaten. It is therefore incorrect to say that electrolyte drinks “do nothing”.

At the same time, BHI mainly measures a short-term difference in fluid excretion. A high index does not by itself demonstrate better well-being or better long-term health. Frequent urination after drinking a large amount of water also does not prove that minerals are being lost.

There are situations in which replacing water and electrolytes has a real benefit, especially fluid losses from diarrhoea. For some disorders of orthostatic regulation, there is experimental support for additional fluid and sodium, although long-term evidence and individual dose selection remain limited.

What remains uncertain, and why?

We do not know the persistent effect of an ordinary consumer dose added to a normal diet after one day or several days. Short studies cannot answer that question, while longer salt studies often use different doses and different populations.

Direct evidence is also insufficient for daily electrolyte drinks improving fatigue, concentration, or headache in healthy people. The contributions of taste, sugar, extra water intake, and expectation to subjective improvement have not been adequately separated.

Special hypotheses remain, such as possible benefit at the beginning of a major dietary change or in a not-yet-defined subgroup of people with orthostatic symptoms. These deserve testing, but a plausible mechanism does not turn them into established facts.

The most interesting next question

Who actually feels better from electrolytes if they receive the same amount of water, sugar is removed, and the control drink tastes similar?

A study like this could simultaneously measure well-being, tolerance of standing, urine output, and fluid balance over several days. It would separate the effect of the minerals from the other contents of the bottle and could help identify the people for whom the effect is genuinely useful.

At the beginning, we wanted to know whether the drink could retain water. The more interesting question now is whose existing problem that water retention actually solves. Without that distinction, we can measure millilitres with great precision and still not know why they should be retained.

References

The list below contains the primary studies, reviews, guidelines, and official scientific sources cited in this article, in order of appearance.

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2. Maughan RJ et al. (2019). Sucrose and Sodium but not Caffeine Content Influence the Retention of Beverages in Humans Under Euhydrated Conditions. International Journal of Sport Nutrition and Exercise Metabolism.
3. Millard-Stafford M et al. (2021). The Beverage Hydration Index: Influence of Electrolytes, Carbohydrate and Protein. Nutrients.
4. Bechke EE et al. (2022). Utility of an Isotonic Beverage on Hydration Status and Cardiovascular Alterations. Nutrients.
5. Clarke MM et al. (2019). A randomized trial to assess beverage hydration index in healthy older adults. American Journal of Clinical Nutrition.
6. Siow PC et al. (2017). Impact of Isotonic Beverage on the Hydration Status of Healthy Chinese Adults in Air-Conditioned Environment. Nutrients.
7. Tucker MA et al. (2015). Hydration Status over 24-H Is Not Affected by Ingested Beverage Composition. Journal of the American College of Nutrition.
8. Juraschek SP et al. (2020). Effects of Sodium Reduction on Energy Metabolism, Weight, Thirst, and Urine Volume: Results from the DASH-Sodium Trial. Hypertension.
9. Rakova N et al. (2017). Increased salt consumption induces body water conservation and decreases fluid intake. Journal of Clinical Investigation.
10. Kaptoge S et al.; STRIDES Trial Group (2026). Preventive interventions for vasovagal reactions in whole blood donors: a cluster-randomised, stepped-wedge, crossover trial of 73 sites involving 1.4 million donors in England. Lancet Haematology.
11. Randomized Trial to Assess the Safety and Tolerability of Daily Intake of an Allulose Amino Acid-Based Hydration Beverage in Men and Women. (2024). Nutrients.
12. EFSA Panel on Nutrition, Novel Foods and Food Allergens (2019). Dietary reference values for sodium. EFSA Journal.
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22. Raj SR et al. (2006). Sodium paradoxically reduces the gastropressor response in patients with orthostatic hypotension. Hypertension.
23. Phillips PA et al. (1984). Reduced thirst after water deprivation in healthy elderly men. New England Journal of Medicine.
24. Volkert D et al. (2022). ESPEN practical guideline: Clinical nutrition and hydration in geriatrics. Clinical Nutrition.
25. Rabast U et al. (1981). Loss of weight, sodium and water in obese persons consuming a high- or low-carbohydrate diet. Annals of Nutrition and Metabolism.
26. Thaler SM et al. (1998). “Beer potomania” in non-beer drinkers: effect of low dietary solute intake. American Journal of Kidney Diseases.
27. Dickinson KM et al. (2011). Endothelial function is impaired after a high-salt meal in healthy subjects. American Journal of Clinical Nutrition.
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How this article was prepared. We compared three partly overlapping branches of the investigation, checked the key primary publications, and recalculated several published quantities. We did not conduct our own experiment or reanalyse individual-level raw data, and no formal meta-analysis was performed. Product-composition figures refer to the stated formulations and may change. This article explains research and is not intended for self-treatment of sodium, potassium, or blood-pressure disorders.