Salt water: the wellness trend dividing health experts over kidney risk

Salt water: the wellness trend dividing health experts over kidney risk

A video by Mexican David Duarte has reignited the debate about drinking salt water. Duarte suggests starting with 5 grams of salt per litre of water, a concentration almost half that of hospital saline (9 grams per litre). According to him, this balances sodium and allows a drastic reduction in food intake — even to just one meal a week — by making the body more efficient. The proposal, which falls under Unani medicine (of Greco-Arabic origin), has sparked a storm of conflicting opinions.

The science behind salt in water

The main argument of supporters is that today's drinking water lacks electrolytes and that adding salt (preferably unrefined sea salt) restores a lost balance. They point out that sports isotonic drinks, such as Aquarius, contain similar concentrations. "Drinking water with lemon and salt has been done without problem," some argue. They even mention pioneers like French scientist René Quinton, who in the early 20th century showed that diluted seawater could be used as physiological saline, although in 1986 its use was banned in French healthcare.

But the numbers speak for themselves. Intravenous saline has an exact concentration of 0.9% (9 grams per litre) to maintain isotonicity with blood plasma. Exceeding that concentration — and seawater has about 40 grams per litre — causes cellular dehydration by osmosis. "Anyone who knew would rather die of thirst," warns an experienced health technician. "Drinking seawater is madness if you're not dehydrated; the kidney has to expend more water than you ingest to eliminate excess sodium, and in the long term it gets damaged."

Real testimonials: from euphoria to diarrhoea

Several users who have tried the method report notable improvements. Some combine it with a ketogenic diet or intermittent fasting and describe "more energy, appetite control, perfect digestion." An athlete claims that increasing his intake of flaked sea salt "has made me like a bull" in the gym. Another, with low blood sodium levels, assures that drinking diluted seawater (a quarter of a glass) has restored his mental clarity.

However, the other side is dominated by digestive discomfort. Someone experienced in the matter relates that, after years of pause, when resuming seawater he suffered "brutal diarrhoea" and had to stop; now he only uses flaked salt. Another confesses that in the first weeks he noticed weakness, headache and constipation. The most common adverse reaction is precisely osmotic diarrhoea: excess sodium draws water into the intestine.

The two currents: miracle or danger?

On one side are those who defend whole salt versus refined. They argue that supermarket salt is pure sodium chloride, often with additives, while unrefined sea salt or Himalayan salt contain bioavailable trace elements. "Refined salt is poison that raises blood pressure; whole salt is good," they summarise. They cite Spanish doctor Ángel Gracia and science communicator Josep Pamies as references.

At the other extreme, those who warn of the risk of hypertension and long-term kidney damage. The physiology of blood pressure is complex: the kidney finely regulates sodium, and forcing it with extra intake can precipitate stones or overload the system. A participant with technical knowledge explains that if the salt concentration in blood rises, the body retains fluid to dilute it, increasing pressure. "The problem is not salt itself, but excess in a context of a processed diet," they qualify.

What does the evidence say?

There are no large-scale clinical trials supporting the habitual intake of salt water in healthy people. The World Health Organization recommends limiting sodium to less than 5 grams per day (equivalent to 2 grams of sodium). Drinking a litre of water with 5 grams of salt already accounts for the full daily dose, without counting food. For those on ketogenic or very low-carbohydrate diets, electrolyte loss through urine may justify a moderate supplement, but there are no standardised protocols.

A striking case: a trinc of the ketogenic diet who has been taking 7 grams of salt per litre of water for almost a year had a blood test and all his lipid parameters came out perfect. But it is an anecdote, not a study. Prudence advises not to imitate recipes without medical supervision, especially if there is a history of hypertension, kidney or heart failure.

The fact that unsettles

Those who defend diluted seawater point out that René Quinton managed to cure thousands of malnourished children with his marine plasma in the early 20th century. But they omit that the technique was abandoned by conventional medicine when it was shown that, poorly dosed, it could be lethal. The French ban of 1986 was not a whim: the variability in the composition of seawater (depending on the area and season) made it impossible to guarantee sterility and exact concentration.

Today, the debate remains open. While some collect salt from ancient salt flats and drink it with lemon, others prescribe the classic advice to "add a little more salt to food and eat a banana." The tension between popular wisdom and established science is not resolved with a glass of salt water, however ancient the remedy may be.