Sodium

Sodium is the main positively charged particle (ion) in the fluid outside your cells. EFSA, the EU’s food safety agency, lists its jobs. With potassium, it makes the electric charge that nerves and muscles use. It also helps set how much water your body holds, and it pulls sugars and amino acids into cells.

A 70-kg man holds roughly 85 to 96 g of sodium, and about 95% of it is outside cells.

Here is the part most people do not know: sodium is not the same as salt. And it is a nutrient most people eat too much of, not too little. Table salt is about 40% sodium and 60% chloride, says the American Heart Association, so 5 g of salt holds 2,000 mg of sodium.

WHO (the World Health Organization) put the global average in 2021 at 4,278 mg of sodium a day, more than double its advice. The FDA (the US Food and Drug Administration) puts the US average at about 3,400 mg.

Most of that sodium does not come from the salt shaker. More than 70% of the sodium Americans eat comes from packaged, prepared and restaurant food, the FDA says. Real deficiency from diet is rare, because the kidneys hold on to sodium when intake is low.

So this page is mostly about how much is enough and how much is too much. It also covers what the evidence says about cutting back, including the argument over whether eating very little could do harm.

Health benefits of sodium

• ★★★Lower blood pressureAcross 133 trials in adults, eating less sodium lowered the top number (by 4.26 mm Hg systolic). A separate review of 34 trials found a bigger drop with high blood pressure (5.39 mm Hg) than with normal pressure (2.42 mm Hg).
• ★★★Fewer IV fluids with a weaker rehydration drinkIn hospital children with acute diarrhea, a drink with less sodium and glucose made unplanned IV fluids less likely (0.59 times the odds). Both drinks contain sodium, so sodium alone was not tested.
• ★★Salt substitutes: lower blood pressure, fewer strokesA Cochrane review of 26 trials found salt substitutes probably lowered the top number (by 4.76 mm Hg systolic). In rural China, a substitute with 25% potassium chloride meant strokes were 0.86 times as frequent in people at risk.
• ★★Unclear effect on deaths and heart diseaseIn adults with prehypertension, sodium counseling went with 0.75 times the cardiovascular events 10 to 15 years later. A Cochrane review of eight trials found no clear drop in deaths.
• ★★Low sodium: no clear gain in heart failureIn 806 people with heart failure, advice to eat under 1500 mg of sodium a day brought intake down only to 1658 mg. That did not clearly cut hospital visits, emergency visits or deaths (15% against 17%), and a review of 17 trials agreed.

Foods high in sodium

Most whole foods are low in sodium. In our USDA-based ranking, only one food gives more than 20% of the Daily Value (the FDA’s label target, 2,300 mg) in a serving. That food is shrimp, with 805 mg in 3 oz (85 g), or 35%. Scallops follow with 333 mg (14%), then sardines (282 mg in a 92-g can) and olives (162 mg in five large olives).

Per 100 g, shrimp has 947 mg (41% of the Daily Value), then olives 735 mg, scallops 392 mg and sardines 307 mg. Per 100 kcal, shrimp (796 mg) and olives (634 mg) lead. The ranking below has the full list.

The ranking lists the foods in our database, which are mostly unprocessed. So it shows the sodium that is naturally in food, not where most sodium comes from. In a study of 450 US adults, 70.9% of sodium was added to food outside the home and 14.2% was in the food itself. Another 5.6% was added in home cooking and 4.9% at the table.

An older study of 62 regular salt users found 77% added in processing and 11.6% naturally in food. The NASEM report’s survey table puts yeast bread first (6.2% of intake), then pizza (5.9%), sandwiches (5.7%) and cold cuts and cured meats (5.4%).

How sodium works

Most of the biochemistry below comes from EFSA’s 2019 review and from physiology studies, not from trials of extra sodium in people. Four ideas cover it: sodium sits outside cells and moves water, the gut absorbs almost all of it, and the kidneys decide how much stays. Last, less sodium lowers blood pressure, and the body pushes back. After that comes what has been seen in people.

It moves water and carries signals

EFSA describes three jobs for sodium. It helps control the volume and spread of body water, and it lets cells take up dissolved substances (solutes). With potassium, it also makes the electrical charge across cell membranes.

A pump in the cell membrane (the Na+/K+ pump) pushes three sodium ions out for every two potassium ions it brings in. EFSA says this transport uses around 25% of the energy a person burns at rest.

It sits outside cells, and potassium sits inside

Fluid outside cells holds 135 to 145 mmol of sodium per liter and only 3.5 to 5.5 mmol of potassium, says EFSA. Inside cells the figures are about 15 and about 150. About 95% of the body’s sodium is outside cells, but a large share of that sits in bone, skin and muscle. Researchers have proposed that this pool works as a reserve.

In long balance studies, EFSA notes, body sodium also rose and fell in weekly and monthly cycles that did not follow intake. That makes short balance studies hard to read.

The gut absorbs almost all of it

In healthy people almost all dietary sodium is absorbed, even at very high intakes. EFSA reports that about 98.5% was absorbed in a series of balance studies in young adults eating 3.4 g of sodium a day. In men eating a very large amount, it was about 96%. In the small intestine, sodium enters cells through carriers (co-transporters) that bring sugars and other small molecules in with it, and water follows.

The kidneys decide how much stays

Sodium balance is controlled mainly by the kidneys. They filter a lot of sodium and take back more than 99% of it. EFSA says they excrete more when intake is high and save sodium when it is low.

When blood pressure or sodium in the kidney tubule falls, the kidney releases renin. That starts a chain that ends in aldosterone, the hormone that makes the last part of the tubule take back more sodium and lose potassium.

Sweat is the other route that varies. Its sodium ranges from 10 to 180 mmol per liter. That depends on factors such as sodium intake, sweat rate and how used to heat a person is.

Less sodium lowers blood pressure, and the body pushes back

In a study EFSA describes, eating 12.7 g of sodium a day instead of 1.2 g raised blood plasma volume by about 300 mL. Body weight did not change, which suggests water moved from the fluid between cells into the blood. The simple picture of “more salt, more water in the blood” is probably incomplete, though. EFSA notes that sodium can also be stored in skin, muscle and bone.

In trials, cutting sodium lowers blood pressure, and the body responds with a small rise in renin and aldosterone. Aldosterone rose 73.20 pmol/L in the He meta-analysis. Larger hormone rises and small rises in cholesterol and triglycerides appeared in the Cochrane review by Graudal and colleagues. The He review found no clear change in blood fats, so that point is still argued.

What has been seen in people

The clearest human finding is the blood pressure drop. Meta-analyses of randomized trials put it at about 4 mm Hg for the systolic number on average. Falls are bigger in people with hypertension, older adults and people with higher starting pressure.

For heart attacks, strokes and deaths the picture is thinner. A long follow-up of two trials in adults with prehypertension found fewer cardiovascular events. A large trial of a potassium-enriched salt substitute found fewer strokes and deaths, and trials in heart failure found no clear gain. All of these are among the study cards above.

How much sodium do you need?

In the US, the adequate intake for adults is 1,500 mg of sodium a day. In the EU, EFSA calls 2,000 mg a day safe and adequate. Both bodies say most people eat far more. The US advises cutting back above 2,300 mg a day, and WHO advises under 2,000 mg, which is 5 g of salt.

These numbers are not measured requirements. NASEM set the adequate intake from the lowest sodium levels tested in trials, where no deficiency symptoms were reported. It also used the best-designed balance study, in which 1,525 mg a day gave roughly neutral balance even with daily heat stress.

The 2,300 mg figure is a different kind of number, called a chronic disease risk reduction intake. It is the level above which cutting back is expected to lower the risk of chronic disease.

Apart from chronic disease, NASEM found too little evidence of harm from high sodium to set a tolerable upper intake level (a safe daily maximum). EFSA set none in its 2005 review because of insufficient data. EFSA also judged that its data could not give an average requirement.

Pregnancy and breastfeeding do not raise the target. NASEM’s adequate intake is 1,500 mg a day for both. EFSA says 2,000 mg is safe and adequate for pregnant and breastfeeding women, because the body’s own adaptations cover the extra sodium needed. For adults over 70, NASEM keeps the same 1,500 mg adequate intake and 2,300 mg risk-reduction level.

Children get lower numbers, scaled from the adult values by energy needs, shown in the table below. Hard exercise or heavy sweating in heat can raise needs. NASEM says sweat sodium varies widely, from 230 to 3,358 mg per liter, with an average of 1,012 mg per liter.

Almost everyone is above these numbers. The FDA puts average US intake at about 3,400 mg a day. NASEM found that median intake was above the 2,300 mg level in every adult group.

The FDA’s voluntary targets aim at food makers, not at you. Its 2021 final guidance for packaged and restaurant foods was designed to cut average intake by about 12%, from about 3,400 to 3,000 mg. Its August 2024 draft Phase II targets for 163 food categories would bring intake to about 2,750 mg, still above the 2,300 mg limit. Phase II was still a draft on the FDA page current as of November 2024.

Units trip people up. US labels list sodium, but EU labels list salt, calculated as sodium multiplied by 2.5. The EU Reference Intake is 6 g of salt, which equals 2,400 mg of sodium by that rule. WHO’s shortcut is that 1 g of salt holds 400 mg of sodium.

Sodium deficiency: signs and who is at risk

Real sodium deficiency from diet is rare. EFSA says sodium salts are in almost every food, and the body cuts its losses in urine, stool and sweat when intake is low. WHO calls deficiency extremely unlikely in healthy people. NASEM found no deficiency symptoms in the low-sodium groups of the trials it reviewed, which in eight trials went below 1,800 mg a day.

Low blood sodium, called hyponatremia, is a different problem: a serum (blood) sodium under 135 mmol/L. A European guideline calls it the most common disorder of fluid and electrolyte balance in clinical practice. It usually reflects water and hormone problems, not too little sodium in the diet. EFSA says it is seldom due to inappropriate sodium intake.

Symptoms progress from malaise, nausea, vomiting and headache to lethargy, impaired consciousness, seizures and coma. Severe symptoms are generally linked to levels under 120 mmol/L, when the brain swells.

Who is at risk? Endurance athletes who drink more than thirst calls for. A 2017 review says overdrinking and non-osmotic release of the hormone vasopressin are the most common causes of hyponatremia during exercise. The marathon and Ironman studies above fit that.

People taking thiazide diuretics (water pills) are another group. In a Swedish cohort of 159,080 adults, 0.80% of new thiazide users had profound hyponatremia (under 125 mEq/L) over two years. That compares with 0.46% of new users of calcium channel blockers. Among thiazide users aged 80 or older, it was 2.40%.

An older case-control study found the risk doubled with each 10 years of age and was higher in lighter people. The test is a blood measurement of serum sodium, where the usual range outside cells is 135 to 145 mmol/L. A low or high result needs a doctor’s reading, because treatment depends on the cause.

Forms of sodium: absorption and effects

Nearly all the sodium people eat is sodium chloride, which is table salt, plus smaller amounts from other sodium compounds in food and additives. Table salt, kosher salt and most sea salts are about 40% sodium by weight, says the American Heart Association (AHA). And 1 g of salt holds 400 mg of sodium, says WHO.

Sea salt and Himalayan pink salt keep trace minerals such as magnesium, potassium and calcium, which other foods also supply. Coarse crystals can hold less sodium per teaspoon, simply because fewer fit on the spoon. The AHA’s bottom line is that the sodium content of different salts is generally similar, and that total sodium intake is what matters.

The honest bottom line: we found one small randomized trial that compared a specialty salt with table salt. It found no difference in blood pressure. Iodine is the practical difference. WHO says all salt consumed should be iodized, and iodized salt is a major source of iodine in the US.

One analysis found that labeled iodized salt varied widely in iodine, so if you rely on salt for iodine, know which salt you use. We found no source that compared the iodine in sea salt or other specialty salts with table salt.

Sodium also comes from additives. The FDA names MSG, baking soda (sodium bicarbonate), sodium nitrite and sodium benzoate, and the AHA adds sodium citrate, phosphate and lactate. These add smaller amounts than salt itself. Replacing some salt with MSG lowers sodium in a recipe, since MSG holds about a third of the sodium of table salt.

In 2017 EFSA set a group acceptable daily intake of 30 mg per kg of body weight for glutamic acid and its salts. Earlier evaluations had left this “not specified”. EFSA estimated that intake from all dietary sources, including glutamate naturally in food, was above that figure for every group at the high end. Potassium-enriched salt substitutes are covered in the table and in the safety section below.

Form	Share of the mineral by weight	What studies show	Source
Table salt (sodium chloride), plain or iodized	About 40% sodium; 39.34 g per 100 g	The form behind most of the sodium in food. 1 g holds 400 mg of sodium. US iodized salt is labeled at 45 mg of iodine per kg, but 47 of 88 freshly opened containers held less than the FDA’s recommended range.	1, 2, 4, 5
Sea salt and kosher salt	About 40% for table salt, kosher salt and most sea salts	We found no trial. Sea salt keeps trace magnesium, potassium and calcium that other foods also supply, and coarse crystals hold less sodium per teaspoon.	1
Himalayan pink salt	Not stated	A crossover trial of 17 women with hypertension found no difference from table salt in blood pressure or urinary sodium. The AHA says sodium content is generally similar.	1, 3
Sodium bicarbonate (baking soda)	Not stated	Used as a leavening agent in baked goods. In 300 older adults with advanced kidney disease, up to 3 g a day did not improve physical function and caused more adverse events than placebo.	8, 9, 12
Monosodium glutamate (MSG)	About 12.28 g of sodium per 100 g, about a third of salt	Replacing part of the salt with MSG lowers sodium in a recipe. EFSA set a group ADI of 30 mg per kg of body weight in 2017. A systematic review found headache results inconsistent, with high-concentration studies not properly blinded.	5, 6, 7
Sodium citrate, phosphates, nitrite and other sodium additives	Not stated	The FDA names sodium nitrite and sodium benzoate, and the AHA names citrate, phosphate and lactate, among sodium-containing ingredients. NASEM adds that phosphates, lactate and diacetate are common in processed meats. We found no trial of these additives and blood pressure.	1, 9, 12
Potassium-enriched salt substitutes	SSaSS used 75% sodium chloride and 25% potassium chloride by mass	Across 26 trials, 3% to 77% of the sodium chloride was replaced. Salt substitutes lowered systolic pressure by 4.76 mm Hg and raised blood potassium by 0.12 mmol/L. SSaSS found fewer strokes and deaths.	10, 11

Here are the studies that compare or test forms, strongest evidence first, 4 in all.

Is sodium safe? Supplements, dose and interactions

Sodium from food is safe for most people at the amounts that meet needs, and the concern is long-term excess.

The US sets no tolerable upper intake level for sodium. NASEM found too little evidence of toxicity apart from chronic disease risk. It says the risk the old upper level covered is now captured by the 2,300 mg risk-reduction level. EFSA set none in 2005 either, while noting strong evidence that sodium raises blood pressure.

Very high, sudden intakes can cause high blood sodium (hypernatremia, over 145 mmol/L) and death, but only in extreme cases such as salt poisoning. NASEM adds that sodium eaten in a concentrated form might do harm that current evidence cannot put a number on.

EFSA’s 2005 review also concluded that sodium itself does not cause cancer. But high salt intake could raise susceptibility to carcinogens such as nitrosamines, and to infection with Helicobacter pylori, a stomach bacterium.

• Salt tablets and endurance sport. Most people do not need them. In the Ironman trial, tablets that added 3.6 g of sodium did not change blood sodium. NASEM says heavy sweaters in heat may need more than the adequate intake. If you do long events in heat, ask a sports doctor.
• Oral rehydration solutions. These pair sodium with glucose to treat dehydration from diarrhea. A Cochrane review found a lower-concentration version worked better in children. They are a treatment for illness, so follow the label or a doctor’s advice.
• Salt substitutes. Potassium chloride blends raised blood potassium by 0.12 mmol/L in a Cochrane review, but all trials excluded people in whom extra potassium is harmful. A 2024 review, whose authors include the SSaSS lead investigator, proposes these reasons to avoid them: advanced kidney disease, potassium supplements and potassium-sparing diuretics. A 2020 review lists possible hyperkalemia as the main risk, especially with conditions that impair potassium removal, such as chronic kidney disease. It says evidence on how often this happens is insufficient. Ask a doctor first if any of these apply.
• Medicines and conditions. Thiazide diuretics can lower blood sodium, mostly in older adults and women. People with heart failure or kidney disease should follow their care team’s sodium advice. Trials of sodium restriction in heart failure have not shown fewer deaths or hospital stays. In a small trial of people with kidney disease taking an ACE inhibitor, a low-sodium diet lowered protein in the urine. Some over-the-counter and prescription medicines also contain sodium, so check labels.
• Stomach cancer. Cohort studies link high salt intake to stomach cancer, but they cannot prove cause.

How to get less sodium

• Start with packaged and restaurant food. More than 70% of US sodium comes from processed, packaged and prepared foods. Bread, pizza, sandwiches and cold cuts lead the NASEM survey table. The FDA suggests buying fresh meat, poultry and seafood, and rinsing canned beans, tuna and vegetables, which removes some of the sodium.
• Read the label. In the US, 5% of the Daily Value or less per serving is low. And 20% or more is high. “Low sodium” means 140 mg or less per serving. EU rules allow “low sodium” for no more than 0.12 g of sodium per 100 g. Similar foods can differ a lot, so compare.
• Give your taste time, and consider a potassium salt substitute. The FDA says people usually do not notice cuts of about 10% and that taste adapts gradually. WHO suggests replacing table salt with lower-sodium salt substitutes that contain potassium, with the kidney and medicine cautions above.

Frequently asked questions about sodium

How much sodium is too much in a day?

Above 2,300 mg a day, the US National Academies and the Dietary Guidelines advise cutting back. WHO advises under 2,000 mg, which is 5 g of salt. The average American eats about 3,400 mg, the FDA says. The 2,300 mg limit is about 1 teaspoon of table salt, counting all sources and not just the shaker.

What is the difference between salt and sodium?

Salt is sodium chloride, which is about 40% sodium and 60% chloride by weight. That means 1 g of salt holds 400 mg of sodium and 5 g holds 2,000 mg. US labels list sodium, while EU labels list salt, calculated as sodium multiplied by 2.5.

Is sea salt healthier than table salt?

There is no evidence that it is. Table salt, kosher salt and most sea salts are about 40% sodium by weight. The AHA says total sodium intake is what matters, whatever the salt. Sea salt may carry trace magnesium, potassium and calcium, which other foods also supply. In a small crossover trial of 17 women with hypertension, Himalayan salt did not change blood pressure or urine sodium compared with table salt.

Can you eat too little sodium?

In healthy people it is rare, because the body holds on to sodium when intake is low. The low-sodium groups in the trials NASEM reviewed reported no deficiency symptoms, though evidence below 1,500 mg a day is limited. Some large cohort studies linked low estimated sodium intake to more heart events. The National Academies and the AHA say measurement problems and reverse causality may explain that J-shaped pattern, and the question is still debated. Low blood sodium is usually caused by water, drugs or illness, not by the diet.

Are potassium salt substitutes safe?

For most people they appear to be, but not for everyone. In SSaSS, with 20,995 people, serious adverse events put down to high blood potassium were not clearly higher (3.35 against 3.30 per 1000 person-years). But the trials excluded people for whom extra potassium is harmful. People with advanced kidney disease, or who take potassium supplements or potassium-sparing diuretics, should ask a doctor first.

Which foods are highest in sodium?

In our USDA-based ranking, shrimp leads per serving with 805 mg in 3 oz. Scallops (333 mg), sardines (282 mg per can) and olives (162 mg in five large olives) follow. Per 100 g, shrimp leads with 947 mg, ahead of olives with 735 mg. Shrimp is often treated with sodium-based additives during processing. Still, these foods are not where most sodium comes from: bread, pizza, sandwiches and cold cuts lead US intake in the National Academies’ survey table. More than 70% of sodium comes from packaged, prepared and restaurant food, the FDA says.

How quickly does cutting sodium lower blood pressure?

For many people, within a week. In a 2023 crossover trial of 213 adults, a low-sodium week lowered mean arterial pressure in 73.4% of people, against a high-sodium week. A meta-analysis found that trials shorter than 15 days showed less than half the effect per 50 mmol cut of longer trials. So the full effect takes longer to show.

Do I need salt tablets when I exercise?

Most people do not. In a trial of 413 Ironman triathletes, salt tablets did not change blood sodium. Low blood sodium in endurance events is mostly linked to drinking more than thirst calls for. In a Boston Marathon study, 13% of finishers tested had low blood sodium, and weight gain during the race was linked to it. Sweat sodium varies widely, so people who sweat heavily in heat may need more than the adequate intake and can ask a sports doctor.