Electrolytes: Really Effective? What Studies Show

The question has no single answer, because it covers three unrelated situations. In acute diarrhea, the oral rehydration solution with sodium and glucose is a reference treatment that has reduced childhood mortality in many countries. In prolonged effort in heat, sodium has documented utility on certain criteria. In daily life or for a one-hour session, water does exactly the same job, and a sports drink does not surpass it.

A mineral that carries an electrical charge once dissolved in water: sodium, potassium, chloride, magnesium, calcium. They regulate the distribution of water between body compartments, nerve transmission, and muscle contraction. Sodium is by far the most important for hydration, because it is what retains water in the blood and what is lost in quantity in sweat.

That they are a treatment for diarrhea, in the form of an oral rehydration solution with sodium and glucose. That in prolonged effort in heat, sodium has documented utility, particularly on susceptibility to cramps, but that the first rule is to drink to your thirst because excess water is the real danger. That for an ordinary session, water is sufficient and a sports drink does not do better. And that sugar-free tablets provide sodium while forgoing the mechanism that makes the reference formula effective.

No, and it's measurable. In the trial that established the hydration index of beverages, 72 men drank one liter each of 13 different beverages, then their urine production was monitored for four hours. The sports drink did not retain more water than plain water. The only beverages that did better were oral rehydration solution, whole milk, and skim milk, with an index of approximately 1.5 versus 1.0 for water.

Because they provide significant amounts of sodium and nutrients that slow gastric emptying and reduce diuresis. A classic sports drink contains significantly less sodium than a rehydration solution, which explains why it behaves like water in this trial. The lesson is simple: it's not the presence of electrolytes that matters, it's their dose.

For a session of about one hour, under normal conditions, water is sufficient and sodium losses are largely compensated by food intake during the rest of the day. The question of electrolytes becomes relevant for prolonged efforts, in heat, in people who sweat heavily, or when multiple sessions occur in succession during the day.

According to thirst, for the majority of practitioners. This is the recommendation of the international consensus on exercise-associated hyponatremia, motivated by the fact that severe cases almost always occur in people who drank beyond their losses by following volume guidelines. Rare exceptions concern very specific contexts supervised by professionals.

Excess water kills more surely than dehydration. In a Boston Marathon cohort, 13% of the 488 runners analyzed at the finish line had hyponatremia, and 0.6% at a critical level. The main associated factor was weight gain during the race, that is, drinking more than was lost. Consuming more than three liters and drinking at every mile were among the associated behaviors.

Not in the available data. In the Boston study, the composition of beverages consumed was not associated with the risk of hyponatremia, unlike the quantity. In other words, drinking too much of an electrolyte drink is still drinking too much. The international consensus on exercise-associated hyponatremia recommends drinking according to thirst rather than following a fixed schedule. Electrolytes do not replace this rule; at best, they complement it.

Nausea, vomiting, headache, confusion, swelling of hands and feet, and in severe cases convulsions or loss of consciousness, in someone who drank heavily during prolonged exercise. These signs resemble those of dehydration, which sometimes leads to drinking more and worsening the situation. Faced with this presentation after a long race, it is a medical emergency.

Two crossover trials provide a clear signal, in small numbers. In ten men dehydrated by 2% through downhill running at 35 degrees, drinking spring water made muscles more susceptible to electrically-induced cramps, while an oral rehydration solution had the opposite effect. The same result was found when the beverage was consumed during exercise. Blood sodium and chloride decreased with water alone and were maintained with the solution.

In a specific context, yes: after significant dehydration from sweating, drinking only water dilutes remaining sodium, and this dilution appears to increase susceptibility to cramps in these trials. This is not an argument against water in general; it is an argument for also replacing sodium when you have sweated heavily.

This varies enormously from one person to another and, in the same person, depending on intensity, heat, acclimatization and training. This is the central conclusion of the reference review on the subject: there is no universal figure, and replacement recommendations must be individualized. Two people doing the same session can lose very different amounts of sodium.

Sweat tests exist, but the review examining them emphasizes that non-standardized methods and field conditions often produce inconsistent results. A more accessible benchmark is weight loss during exercise, which reflects water loss. For sodium, white stains on clothing and eye irritation are crude indicators of salty sweat, without measurement value.

Most often, a few hundred milligrams of sodium per tablet, potassium, sometimes magnesium and calcium, a flavoring and a sweetener, with little or no sugar. This last point deserves attention: it is both their sales argument and what distances them from the formula whose effectiveness is best demonstrated.

Because the reference oral rehydration solution combines sodium with glucose, and this combination is not decorative: glucose and sodium are absorbed together by the intestine, and glucose accelerates the absorption of sodium and water. This is the physiological basis of the solution recommended by the World Health Organization. A tablet without sugar provides sodium, but deprives itself of the mechanism that makes the original formula effective.

No, it has a specific use: providing sodium during prolonged exercise or in high heat, when you sweat heavily and drink heavily. In this context, replacing sodium rather than drinking only water makes sense, as shown by cramp trials. Outside this context, in an ordinary day, it adds sodium to a diet that already generally contains too much.

Nothing supports this for a healthy person eating normally. Common diet provides sodium in excess rather than deficiency, and potassium comes from fruits and vegetables. A daily tablet outside of exercise therefore mainly adds sodium where it is not lacking. People with high blood pressure or under treatment should be particularly careful about this additional intake.

We did not identify any trial demonstrating that an electrolyte tablet reduces hangover symptoms. Alcohol has a diuretic effect and rehydration is reasonable, but nothing shows that an electrolyte drink performs better than water in this context. Marketing use on this ground goes beyond the data.

This is the only context where electrolytes are part of treatment, and you should use a pharmaceutical oral rehydration solution, not a sports tablet. A Cochrane review of hospitalized children with diarrhea shows that the reduced osmolarity formula reduces the need for intravenous therapy, stool volume and vomiting compared to the standard formula. In infants, elderly people or in case of signs of dehydration, consult a healthcare provider.