Chloride

How much you need

The official Adequate Intake for adults, per day:

These are Adequate Intakes, set in 2005 to match the sodium Adequate Intakes of the time molecule for molecule, because almost all chloride in the diet comes with sodium, as salt — 2.3 g of chloride is the amount in 3.8 g of salt. The lower values after 50 followed the lower sodium values then set for older adults; sodium's were raised in 2019, but chloride's were not revisited.

People aged 18 fall in the official 14–18 group — 2.3 g a day, including in pregnancy and when breastfeeding. Its upper limit is the same as for adults, 3.6 g. Pregnancy and breastfeeding change what you need — confirm yours with your midwife, obstetrician or doctor.

Upper limit

The upper limit is the most chloride a day that is unlikely to cause harm, not a target. It was set to match, molecule for molecule, the 2005 upper limit for sodium, which was based on the rise in blood pressure as salt intake increases; that sodium limit has since been replaced, as "Too much" below explains.

What it does

Chloride, paired with sodium, is the main osmotically active negative ion in the fluid outside cells, and is important in maintaining fluid and electrolyte balance ^[1]. It is also a component of gastric juice, as hydrochloric acid ^[1]. Sodium and chloride are absorbed mainly in the small intestine — about 98% across a wide range of intakes — and most is excreted in the urine ^[1].

Forms

Almost all chloride in the diet comes with sodium, as sodium chloride — salt ^[1]. Where potassium is added to processed foods, and in potassium supplements, it usually comes as potassium chloride, and salt substitutes are potassium chloride too ^[1].

Where it comes from

Almost all chloride comes from salt, and most salt is added to food before it reaches the table ^[1]. An estimated 77% of the salt eaten is added in processing, 6% while eating and 5% in cooking, while about 12% occurs naturally in food and less than 1% comes from tap water ^[1]. Foods high in salt added in processing include luncheon meats and hot dogs, canned vegetables, processed cheese and potato chips, and most breads, baked goods and breakfast cereals contain some; so do condiments such as soy sauce, ketchup and bouillon cubes ^[1].

The source gives no per-serving food table, so this page has no top-five list or chart; the paragraph above is what it says about where chloride comes from.

In the United States

The report did not estimate chloride intake on its own: almost all chloride comes with sodium, so its intake follows sodium's ^[1]. In the 1988–1994 national survey, median sodium intake from food, not counting salt added at the table, ranged by age from 3.1 to 4.7 g a day for men and 2.3 to 3.1 g for women — the amount in 7.8 to 11.8 g of salt for men and 5.8 to 7.8 g for women ^[1].

Who is most likely to run low

• People losing fluid through heavy vomiting or diarrhea ^[1]
• People taking diuretics, which increase chloride loss in urine; low blood chloride has been seen with their use ^[1]
• People with cystic fibrosis, whose sweat is very high in sodium and chloride, especially when they exercise ^[1]
• People with Bartter syndrome or kidney tubule disorders, which cause chloride loss ^[1]

What deficiency looks like

Severe chloride depletion causes low blood chloride and a condition called hypochloremic metabolic alkalosis, seen in people who vomit heavily and so lose hydrochloric acid ^[1]. Most of what is known comes from infants who were fed formulas mistakenly made with too little chloride: they had growth failure, lethargy, irritability, poor appetite, gastrointestinal symptoms and weakness, and nine to ten years later their growth and thinking had recovered, though some had language deficits ^[1]. Deficiency is otherwise rare, because foods that contain sodium also provide chloride ^[1].

What the evidence supports, and what it doesn't

Established. Chloride is essential: it maintains fluid and electrolyte balance and forms the hydrochloric acid in stomach juice ^[1]. Infants fed formula lacking chloride failed to grow normally ^[1].

Not supported by trials. There were too few dose-response data to set an average requirement for chloride, so its Adequate Intakes were not derived from studies of chloride but matched to sodium's ^[1].

Mixed. Chloride's own part in blood pressure is unclear: in some studies, sodium given without chloride, as sodium bicarbonate, did not raise blood pressure as much as sodium chloride did ^[1].

Too much

The chloride upper limit of 3.6 g a day was set to match the 2005 sodium upper limit of 2.3 g, which rested on the rise in blood pressure as salt intake increases ^[1]. Older people, African Americans, and people with high blood pressure, diabetes or chronic kidney disease are especially sensitive to that effect ^[1]. In 2019 the National Academies replaced the sodium upper limit with a Chronic Disease Risk Reduction Intake of 2,300 mg; that review covered sodium and potassium only, and its summary tables still give chloride's 2005 values, including the 3.6 g upper limit ^[2].

Medicines that interact

Diuretics increase the loss of chloride in urine, and low blood chloride has been seen with their use ^[1]. If you take a diuretic, ask your doctor or pharmacist whether you need to watch your salt or electrolyte intake.