In the 1980s, a team measured the salt passing through the bodies of 10,079 people in 52 places around the world. At one end were the Yanomami of the Brazilian rainforest, who passed about 0.2 millimoles of sodium a day in their urine. At the other end was north China, at 242. More than a thousand times as much salt, in the same species.
Both groups were drinking water. Only one of them was eating much salt.
"Drink more water" is the advice you have heard a thousand times. It is incomplete advice: half of it. The other half is the thing water follows around your body, and the thing that has been treated as a villain for most of a century: salt. It has had worse press than sugar, which takes some doing.
What sodium does
Your body runs on electricity, and salt is the wiring.
Sodium sits mostly outside your cells. Potassium sits mostly inside. Between them, in the wall of every cell, a tiny protein machine pushes sodium out and pulls potassium in, again and again, without rest. The difference it keeps up is what lets a nerve fire, a muscle contract, and a heart keep its beat.
That machine is the sodium–potassium pump. It was found in 1957 by Jens Christian Skou, a Danish physiologist working on the nerves of crabs in Aarhus, and forty years later it won him the Nobel Prize in Chemistry. In a nerve cell, the pump can account for up to three-quarters of the cell's energy. Your brain spends much of its fuel on keeping salt where it belongs. Your head is, in a sense, a very expensive salt cellar.
Salt is two minerals, not one. Table salt is sodium chloride, and the chloride half has a job of its own. The cells lining your stomach release hydrogen and chloride separately, and the two meet to make hydrochloric acid: your stomach acid. Acid Reflux: Why It Keeps Coming Back, and What Settles It has what that acid does. It starts breaking down protein, frees B12 and minerals from food, and kills many of the bacteria swallowed with every meal. The salt on your plate ends up working in your stomach.
Water follows sodium. Think You’re Hydrated? Why Your Body Might Be Thirsty for More has how your kidneys filter about 180 litres a day and use salt to decide how much water to keep. Drink water without the salt to hold it, and much of it goes straight through.
Where the salt fear came from
For decades, salt was public enemy number one. Cut it, and blood pressure falls. That part is real. What to Drink Instead of Plain Water, linked below, has the 34 controlled tests with 3,230 people where eating less salt brought blood pressure down, more so in people whose pressure was already high.
The low-salt diet has a famous starting point. In 1939, at Duke University, Walter Kempner, a German refugee, began treating patients with malignant high blood pressure, many with failing kidneys and no drug that could help them. He put them on nothing but white rice, sugar, fruit and fruit juice: about 2,000 calories, 20 grams of protein and about 150 milligrams of sodium a day. They improved fast. The diet that started the salt fear was also a sugar diet with almost no protein, and it was built for people who were gravely ill, not for a healthy dinner table. Nobody now recommends the rest of that menu.
The Intersalt measurements told a more complicated story. Sodium in the urine went with blood pressure in individuals, and four places with very little salt had low blood pressure that barely rose with age. But across the other 48 places, salt went with how fast blood pressure climbed over the years, not with how high it was, or how common high blood pressure was.
The biggest measurement came later. In PURE, the urine of 101,945 people in 17 countries was tested, and they were followed for nearly four years. The average person passed about 4.9 grams of sodium a day. Compared with people at 4 to 6 grams a day, those above 7 had a higher risk of death or a major heart event, and the link was strongest in people with high blood pressure. And people below 3 grams also had a higher risk.
People also differ. When 378 people with normal blood pressure and 198 with high blood pressure had their salt and fluid drawn down, the response varied widely. More of those with high blood pressure turned out to be salt-sensitive, and salt-sensitive people tended to be older.
So the risk rose at both ends. The middle, where the average person in PURE ate, did best. Salt is not poison, and it is not harmless in any amount either. Like water, it has a sensible range. So does almost everything worth eating.
And most of the salt was never in the shaker. In 62 adults who salted their own food, 77% of their sodium came from processing, 11.6% was in the food itself, and only 6.2% came from the table and 5.1% from cooking. Cut the processed food, and most of the salt goes with it. The shaker on a plate of real food is a small share.
Who needs more salt
Some people run short, and they are easy to spot.
Low-carb and carnivore eaters. When carbohydrate drops, insulin drops, and the kidneys let go of more salt, with potassium and magnesium following. What a Diet That Supports Your Health Looks Like has why the first days bring headaches, tiredness and irritability, and what fixes them. Hint: it lives in the salt cellar.
Heavy sweaters. Sweat is salty for a reason. Heat Survival Guide: How to Stay Cool and Safe in Hot Weather has why salt matters as much as water on a hot, sweaty day.
People who are ill. Diarrhoea and vomiting take salt and water out together, which is why the rehydration drink that saves lives in cholera is salt and a little sugar in clean water.
People on some medicines. Water tablets and some other drugs push salt and potassium out through the kidneys. If that is you, ask whoever prescribes them before changing how much salt you eat.
Older people. Low blood sodium in later life is often mild and thought to cause no symptoms. Among 122 patients with an average age of 72 who had it, 21.3% came into hospital after a fall, against 5.3% of matched patients. Their walking was less steady and their attention slower, and both improved once the sodium was put right.
One craving worth a check. A strong, lasting craving for salt, together with dizziness when you stand up, can be a sign of Addison's disease, where the adrenal glands make too little of the hormones that hold on to salt. Low aldosterone can make people crave salty food and drop their blood pressure. That pair is worth having looked at.
The cramp that brine stops
Cramps are usually blamed on missing minerals. One test suggests something stranger.
A team dehydrated a group of men, then set off a cramp in a small muscle of the foot with an electrical current. After a sip of plain water, the cramp lasted about 134 seconds. After the same small sip of pickle juice, about 85: almost fifty seconds shorter. Fifty seconds is a long time to stand on one leg, swearing. Their blood salts barely changed. The brine had not had time to reach the blood.
So the team suspect the relief came from the mouth and throat, not the bloodstream: a sharp, salty, sour taste setting off a reflex that tells the cramping muscle to stand down. It would be the same trick thirst plays, deciding before the water arrives.
For cramps at night, the story is different again. The Quiet Signals of Mineral Deficiency, linked below, has why magnesium tablets barely beat a dummy pill for night cramps, and why a daily calf stretch is the better bet.
Histamine is another suspect, and it comes from food. It builds up in aged cheese, cured meats, fermented foods, wine, and fish that has not been kept cold, and some people break it down poorly. Histamine makes smooth muscle contract, the kind that lines the gut, which is why stomach cramps are among the symptoms put down to it, along with muscle twitching, headaches and flushing. The evidence that histamine in food causes these symptoms is still thin and contradictory. So the test is personal: if cramps follow those foods, leave them out for a while and see whether the cramps go with them.
Potassium, the other half
Sodium has a partner, and it gets far less attention.
In PURE, people who passed more potassium had a lower risk than those who passed less. In Intersalt, more potassium went with lower blood pressure in individuals. Salt and potassium work as a pair: sodium out, potassium in.
The usual advice is a banana. A banana has potassium, and it comes with a load of sugar. A steak does not. Meat and fish carry potassium too, along with protein and none of the sugar: beef, salmon and chicken. A plate built on them brings both halves of the pair to the table, and The Quiet Signals of Mineral Deficiency, linked below, has who runs low on potassium and why it is usually lost, not missing from the diet. James DiNicolantonio and Siim Land's takes sodium, potassium and magnesium together.
Too much water
Water can be overdone, and plain water is the way to do it.
7 Fun and Tasty Ways to Stay Hydrated Without the Boredom has the 2002 Boston Marathon, where 13% of the runners tested at the finish had too little sodium in their blood. The ones most at risk had gained weight during the race, from drinking more than they sweated out. Healthy kidneys can clear up to about a litre an hour, and water beyond that dilutes the blood.
You do not need a marathon to overdo it a little. If you are drinking all day and your urine is always as clear as the water going in, you are giving your kidneys extra work, not extra health.
What to do
Use good salt, always. Plain unrefined sea salt or rock salt, with nothing added, such as . Ordinary table salt often carries an anti-caking agent such as calcium silicate, and iodised table salt can carry a stabiliser such as dextrose, which is a sugar. The trace minerals in unrefined salt are small. What you gain is salt without the extras. Where it comes from matters too. When 39 brands of salt were tested, sea salts carried anywhere from none to 1,674 particles of microplastic per kilo, with one outlier far above that, lake salt 28 to 462, and rock salt none to 148. Sea salt from Asian waters ran highest. Rock salt, or sea salt from cleaner water, is the safer pick. Then salt your food to taste, and know that your taste will move with you. Why Processed Food Is Hard to Leave — and When It Gets Easier has the young adults who cut their salt for five months: by the end, the same crackers tasted saltier to them, and the amount of salt they liked in soup and crackers had fallen. The group eating as usual had not moved.
One thing to know when you switch: unrefined salt carries virtually no iodine. The Quiet Signals of Mineral Deficiency, linked below, has why iodine matters, and where to get it instead: sea fish, shellfish, eggs and milk.
Drink salted bone broth. A mug of it is water with salt in it, plus the gelatine from the bones. What to Drink Instead of Plain Water, linked below, has why it stays in the body better than water alone. When there is no time to make it, stir into hot water.
Add a pinch of good salt to water on the days that need it: heavy sweat, illness, the first weeks of low-carb eating.
Aim for pale yellow, not clear. The colour of your urine is the simplest check you have.
Filter your water if you want to, and know what it takes out. Reverse osmosis removes most contaminants, and most of the minerals with them, which makes the salt on your plate matter more.
Know what coffee really costs. Best Coffee Alternatives: What's Really in Each Cup has why coffee counts as fluid for an everyday drinker, and what it costs instead: your sleep.
If you have high blood pressure, or heart or kidney disease, salt carefully and check first. Those are the people the low-salt advice was really written for. Babies are the other clear exception: the NHS advises adding no salt to a baby's food or cooking water, because it is not good for their kidneys.
Worth your salt
The word "salary" comes from the Latin salarium, "to do with salt". The popular story that Roman soldiers were paid in salt is, as far as anyone can tell, baseless. The link between the word and the mineral is real; the payday was not. Being worth your salt is still a compliment. "Salad" is salted too: the word comes from the Latin herba salata, a salted herb.
What is true is that salt was valuable for a reason. In 1930, Gandhi walked 387 kilometres over 24 days to the sea at Dandi to make salt in defiance of the British salt monopoly, and millions followed him. Your nerves, your muscles and your heart run on it. Water without it is only half of what your body asks for.
Drink when you are thirsty, aim for pale yellow, and put the salt shaker back on the table.
Tonight, salt your dinner properly with good salt, and drink a glass of water with it.
Wondering which drinks hold water best? What to Drink Instead of Plain Water — and What the Popular Alternatives Do to Your Body — the 13-drink test, why salt helps water stay in the body, and the drinks that cost more than they give.
Want to know which mineral signs are real? The Quiet Signals of Mineral Deficiency — seven minerals, the signs that hold up, the ones that are folklore, and which tests can be trusted.
Know someone who drinks all day and still gets cramps and headaches? Send them this, and pass the salt.
Disclaimer: This article is general information. For advice about your own health, talk to a qualified health professional. If you have high blood pressure, heart or kidney disease, or take medicine that affects your fluid or salt, check before adding salt to your water or food.
Affiliate Disclosure: This article contains affiliate links. As an Amazon Associate, All For Life earns from qualifying purchases, at no extra cost to you. We only link to products we would recommend without the commission.
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