Salt

What it is

Table salt consists mainly of sodium chloride ¹.

Per 100 g, US iodised table salt averages 38.7 g sodium and 5080 µg iodine ².

In the body

The kidneys filter over 500 g of sodium a day and return almost all of it to the blood ³.

The Na⁺/K⁺-ATPase exports 3 Na⁺ and imports 2 K⁺ per ATP hydrolysed ⁴. It powers tubular sodium reabsorption and accounts for two-thirds or more of renal oxygen uptake ³. The proximal tubule reabsorbs 60–70% of filtered sodium (mainly NHE3), the thick ascending limb 25–30% (NKCC2, NHE3) and the distal nephron at most 5–10% (NCC, ENaC), which matches excretion to intake ³.

Renin, released when afferent arteriolar pressure or distal tubular sodium chloride falls, cleaves angiotensinogen to angiotensin I; angiotensin-converting enzyme then forms angiotensin II ¹.

Renin-angiotensin cascadePlasma, endothelial surface and renal tubule

Angiotensinogen
Renin (REN)Juxtaglomerular release; generating angiotensin I is its only known function
Angiotensin I
Angiotensin-converting enzyme (ACE)Zn2+, Cl-Lisinopril RamiprilatC-terminal domain removes the His-Leu dipeptide
Angiotensin II
Angiotensin-converting enzyme 2 (ACE2)Zn2+Carboxypeptidase; ACE inhibitors do not inhibit it
Angiotensin-(1-7)

Angiotensin II stimulates proximal sodium reabsorption, arteriolar constriction and aldosterone release; aldosterone stimulates distal sodium recovery in exchange for potassium ¹.

The sodium–iodide symporter (SLC5A5), driven by the Na⁺ gradient of the Na⁺/K⁺-ATPase, moves one I⁻ with two Na⁺ into thyroid cells ⁵.

What studies show

Eating less sodium lowers blood pressure ⁶.

In DASH-Sodium, 412 adults were fed a typical US or DASH diet at three sodium levels, 30 days each ⁶. From high to low sodium, systolic pressure fell by 6.7 mm Hg on the typical diet and 3.0 mm Hg on DASH ⁶.

In SSaSS, 600 rural Chinese villages (20,995 people with prior stroke, or aged 60 or more with poorly controlled blood pressure) were randomised to a 75% sodium chloride, 25% potassium chloride substitute or regular salt ⁷. Over a mean 4.74 years, stroke rates per 1000 person-years were 29.14 against 33.65, 4.51 fewer (rate ratio 0.86, 95% CI 0.77 to 0.96) ⁷. Per 1000 person-years, death rates were 39.28 against 44.61 (0.88, 0.82 to 0.95), and rates of serious adverse events attributed to hyperkalaemia 3.35 against 3.30 ⁷. Australia’s National Health and Medical Research Council funded the trial; a manufacturer donated the substitute in years 3–4 ⁷.

In a Cochrane review of six controlled studies, iodine status improved with iodised salt in most, and goitre tended to decrease ⁸.

References

Regulator
EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA), Turck D, Castenmiller J, de Henauw S, Hirsch-Ernst KI, Kearney J, et al. Dietary reference values for sodium EFSA Journal, 2019.
doi:10.2903/j.efsa.2019.5778 PubMed 32626425
Funding and finding
Funding
European Food Safety Authority, on request from the European Commission (question number EFSA-Q-2011-01224).
Finding
Sodium chloride is the main constituent of table salt; 1 g of sodium chloride provides 0.4 g of sodium and 0.6 g of chloride. In healthy people almost all dietary sodium is absorbed, along most of the small and large intestine; apical co-transporters couple sodium entry to the uptake of solutes, the basolateral Na+/K+-ATPase exchanges three intracellular Na+ for two extracellular K+, net sodium and water absorption occurs in the distal ileum and colon, and distal absorption responds to aldosterone. Renin is released from the juxtaglomerular apparatus in response to reduced afferent arteriolar pressure, increased sympathetic activity and decreased distal tubular NaCl; renin hydrolyses angiotensinogen to angiotensin I, which angiotensin-converting enzyme converts to angiotensin II; angiotensin II stimulates proximal sodium reabsorption, arteriolar constriction and adrenal aldosterone release; aldosterone stimulates sodium recovery in exchange for potassium in distal tubule, collecting ducts and distal colon. Genotypes with increased ENaC function cause volume expansion, hypertension and hypokalaemia (e.g. Liddle's syndrome). A sodium intake of 2.0 g/day is considered safe and adequate for adults, including pregnant and lactating women.
Textbook or database
Fukagawa NK, McKillop K, Pehrsson PR, Moshfegh A, Harnly J, Finley J. USDA's FoodData Central: what is it and why is it needed today? American Journal of Clinical Nutrition, 2022.
doi:10.1093/ajcn/nqab397 PubMed 34893796
Funding and finding
Funding
All authors are employed by the USDA Agricultural Research Service and have not received external support in the preparation of this manuscript.
Finding
FoodData Central is the USDA food-composition data system; Foundation Foods carry analytical values with sample metadata. Foundation Foods entry read on 2026-10-21: Salt, table, iodized (FDC 746775, 24 samples purchased from 2018), per 100 g: water 0.42 g, ash 99.0 g, sodium 38,700 mg (range 37,200 to 40,700), iodine 5,080 µg (3,410 to 7,430), calcium 50 mg (0 to 125), potassium 2 mg (0 to 53), energy 0 kcal; 1 teaspoon = 6.1 g.
Independent research
Palmer LG, Schnermann J. Integrated control of Na transport along the nephron Clinical Journal of the American Society of Nephrology, 2015.
doi:10.2215/CJN.12391213 PubMed 25098598
Funding and finding
Funding
L.G. Palmer: National Institutes of Health grant R01-DK27847. J. Schnermann: Intramural Research Program of the National Institute of Diabetes and Digestive and Kidney Diseases.
Finding
Review. More than 500 g of sodium is filtered daily; under most conditions the kidneys excrete more than 95% of ingested sodium. The proximal tubule reabsorbs 60-70% (apical NHE3 the main mechanism), the ascending loop of Henle, mostly the thick limb, 25-30% (NKCC2 and NHE3), and the distal convoluted tubule and collecting ducts no more than 5-10%, through thiazide-sensitive NCC (early DCT) and amiloride-sensitive ENaC (late DCT, connecting tubule, collecting duct); distal reabsorption is the regulated part. Two-thirds or more of renal oxygen uptake is spent on the Na,K-ATPase. With plausible tenfold changes in intake, fractional reabsorption varies between about 97% and 99.7%. Sodium depletion increases ENaC activity, an effect mimicked by aldosterone. Potassium loading lowers NCC phosphorylation and abundance and raises ENaC activity, shifting sodium reabsorption to segments where principal cells secrete K+ in exchange for Na+. Changes in body Na content and blood volume are the likely cause of the relation between Na intake and blood pressure.
Independent research
Gadsby DC. Ion channels versus ion pumps: the principal difference, in principle Nature Reviews Molecular Cell Biology, 2009.
doi:10.1038/nrm2668 PubMed 19339978
Funding and finding
Funding
NIH grants HL36783, HL49907 and DK51767.
Finding
Review. Each Na,K-ATPase pump exports 3 Na+ and imports 2 K+ for each ATP hydrolysed and can repeat this cycle up to a hundred times a second; the net charge movement generates a current of about 20 attoamperes per pump.
Independent research
Ravera S, Reyna-Neyra A, Ferrandino G, Amzel LM, Carrasco N. The sodium/iodide symporter (NIS): molecular physiology and preclinical and clinical applications Annual Review of Physiology, 2017.
doi:10.1146/annurev-physiol-022516-034125 PubMed 28192058
Funding and finding
Funding
National Institutes of Health grants DK-41544 (to N. Carrasco) and GM-114250 (to N. Carrasco and L.M. Amzel).
Finding
Review. NIS (SLC5A5) transports iodide into the thyroid electrogenically with a 2 Na+ : 1 I- stoichiometry, driven by the Na+ gradient generated by the Na+/K+-ATPase. Oxidised iodine is incorporated into thyroglobulin, the precursor of T3 and T4. A woman's iodide requirement rises from 150 to 250 µg/day in pregnancy and lactation.
Independent research
Sacks FM, Svetkey LP, Vollmer WM, Appel LJ, Bray GA, Harsha D, et al.; DASH-Sodium Collaborative Research Group. Effects on blood pressure of reduced dietary sodium and the Dietary Approaches to Stop Hypertension (DASH) diet New England Journal of Medicine, 2001.
doi:10.1056/NEJM200101043440101 PubMed 11136953
Funding and finding
Participants
412
Follow-up
three consecutive 30-day feeding periods
Funding
Supported by cooperative agreements and grants from the National Heart, Lung, and Blood Institute (U01-HL57173, U01-HL57114, U01-HL57190, U01-HL57139, K08 HL03857-01, U01-HL57156) and by the General Clinical Research Center Program of the National Center for Research Resources (M01-RR02635, M01-RR00722).
In-kind support
Food donated by the Almond Board of California, Beatrice Foods, Bestfoods, Cabot Creamery, C.B. Foods, Dannon, Diamond Crystal Specialty Foods, Elwood International, Hershey Foods, Hormel Foods, Kellogg, Lipton, McCormick, Nabisco U.S. Foods Group, Procter & Gamble, Quaker Oats and Sun-Maid Growers; food storage by Frost Cold Storage.
Finding
Parallel assignment to a typical US control diet or the DASH diet, with high, intermediate and low sodium (targets 150, 100 and 50 mmol/day) for 30 days each in random order; urinary sodium 142, 107 and 65 mmol/day. High to low sodium lowered systolic pressure by 6.7 mm Hg (95% CI 5.4 to 8.0) with the control diet and 3.0 mm Hg (1.7 to 4.3) with the DASH diet. The low-sodium DASH diet versus the high-sodium control diet gave systolic pressure 7.1 mm Hg lower without hypertension and 11.5 mm Hg lower with hypertension.
Independent research
Neal B, Wu Y, Feng X, Zhang R, Zhang Y, Shi J, et al. Effect of salt substitution on cardiovascular events and death New England Journal of Medicine, 2021.
doi:10.1056/NEJMoa2105675 PubMed 34459569
Funding and finding
Registration
NCT02092090
Participants
20,995
Follow-up
mean 4.74 years, median 5.12 years
Funding
Supported by research grants (APP1164206 and APP1049417) and an investigator grant (APP1197709, to Dr. Neal) from the National Health and Medical Research Council of Australia. The trial was sponsored by the George Institute for Global Health, where the analyses were performed; the first author wrote the first draft and all authors took the decision to submit. Registry lead sponsor: The George Institute; collaborators were universities and the Chinese Center for Disease Control and Prevention.
In-kind support
The salt substitute (75% sodium chloride, 25% potassium chloride) was purchased by the investigators from local manufacturers in each province for years 1, 2 and 5 and donated by Jiangsu Sinokone Technology for years 3 to 4.
Finding
Stroke 29.14 versus 33.65 events per 1000 person-years with salt substitute versus regular salt (rate ratio 0.86, 95% CI 0.77 to 0.96); fatal stroke 6.78 versus 8.79 (0.77, 0.65 to 0.91); haemorrhagic 4.37 versus 6.30 (0.69, 0.56 to 0.85); ischaemic 21.36 versus 22.90 (0.93, 0.82 to 1.05); major adverse cardiovascular events 49.09 versus 56.29 (0.87, 0.80 to 0.94); death 39.28 versus 44.61 (0.88, 0.82 to 0.95); serious adverse events attributed to hyperkalaemia 3.35 versus 3.30 (1.04, 0.80 to 1.37). Mean differences: 24-hour urinary sodium -350 mg, potassium +803 mg, systolic blood pressure -3.34 mm Hg. Exclusions: potassium-sparing diuretic, potassium supplement or known serious kidney disease in the household; no routine kidney function or serum potassium measurement; 22.8% used an ACE inhibitor or angiotensin-receptor blocker.
Independent research
Wu T, Liu GJ, Li P, Clar C. Iodised salt for preventing iodine deficiency disorders Cochrane Database of Systematic Reviews, 2002.
doi:10.1002/14651858.CD003204 PubMed 12137681
Funding and finding
Funding
Internal sources: Chinese Cochrane Centre, China. External sources: Australia Cochrane Centre, Australia. The acknowledgements thank the China Medical Board of New York for supporting the review.
Finding
Studies were too dissimilar and of insufficient quality for meta-analysis. Goitre tended to decrease with iodised salt, though not significantly in all studies; iodine status improved in most studies. The abstract states that no study observed adverse effects of iodised salt, but none assessed mortality, physical and mental development in children, symptoms of hypothyroidism or adverse effects. No conclusions could be drawn on physical and mental development in children or on mortality, and no study specifically investigated iodine-induced hyperthyroidism.
Industry-funded
O'Donnell M, Mente A, Rangarajan S, McQueen MJ, Wang X, Liu L, et al. Urinary sodium and potassium excretion, mortality, and cardiovascular events New England Journal of Medicine, 2014.
doi:10.1056/NEJMoa1311889 PubMed 25119607
Funding and finding
Participants
101,945
Follow-up
mean 3.7 years
Funding
Supported by the Population Health Research Institute, the Canadian Institutes of Health Research, the Heart and Stroke Foundation of Ontario and unrestricted grants from several pharmaceutical companies (major contributions from Boehringer Ingelheim, AstraZeneca, Sanofi-Aventis, Servier and GlaxoSmithKline; additional contributions from Novartis and King Pharma), and national or local organisations including the Unilever Health Institute (Brazil), the South Africa Sugar Association, AstraZeneca and Sanofi-Aventis (Turkey), and government, university and charitable bodies in other countries. The PURE-Salt substudy was funded by the Heart and Stroke Foundation of Ontario. The authors state that the funders had no role in design, conduct, data collection, analysis, interpretation, writing or the decision to submit.
Finding
Composite of death and major cardiovascular events in 3317 participants (3.3%). By estimated sodium excretion (Table 2): 462 of 10,810 (4.3%) below 3.00 g/day, 662 of 21,131 (3.1%) at 3.00 to 3.99 g/day, 1437 of 46,663 (3.1%) at 4.00 to 5.99 g/day, 391 of 12,324 (3.2%) at 6.00 to 6.99 g/day and 365 of 11,017 (3.3%) at 7.00 g/day or more. Versus estimated sodium excretion of 4.00 to 5.99 g/day: odds ratio 1.27 (95% CI 1.12 to 1.44) below 3.00 g/day and 1.15 (1.02 to 1.30) at 7.00 g/day or more. The high-sodium association was attenuated after adjustment for blood pressure; the low-sodium association was not. The authors state that reverse causation cannot be completely ruled out and that the findings do not show the effect of intentionally reducing sodium intake.
Expert consensus
World Health Organization. Guideline: sodium intake for adults and children World Health Organization, 2012.
PubMed 23658998
Funding and finding
Funding
WHO acknowledges financial support from the Ministry of Health, Labour and Welfare of the Government of Japan, the Korea Food and Drug Administration, the Korea Health Industry Development Institute and the International Kidney Evaluation Association Japan.
Finding
WHO recommends a reduction in sodium intake to reduce blood pressure and risk of cardiovascular disease, stroke and coronary heart disease in adults, and a reduction to less than 2 g/day sodium (5 g/day salt) in adults (strong recommendation); in children, a reduction to control blood pressure, with the adult maximum adjusted downward for energy requirements (strong recommendation).
Expert consensus
World Health Organization. Use of lower-sodium salt substitutes: WHO guideline World Health Organization, 2025.
PubMed 39946522
Funding and finding
Funding
WHO acknowledges financial support from Resolve to Save Lives and the Ministry of Health, Labour and Welfare of the Government of Japan for the guideline development work, and Qingdao University for hosting a guideline group meeting.
Finding
If choosing to use table salt, WHO suggests replacing regular table salt with lower-sodium salt substitutes that contain potassium (conditional recommendation), for adults in general populations, not pregnant women or children, and excluding individuals with kidney impairments or other conditions that might compromise potassium excretion. The recommendation applies to discretionary table salt, not to salt in manufactured or restaurant foods, and accompanies the strong recommendation to reduce sodium intake to less than 2 g/day.
Expert consensus
World Health Organization. Guideline: fortification of food-grade salt with iodine for the prevention and control of iodine deficiency disorders World Health Organization, 2014.
PubMed 25473709
Funding and finding
Funding
WHO thanks the Government of Luxembourg and the Bill & Melinda Gates Foundation for financial support; the Micronutrient Initiative supports the WHO Evidence and Programme Guidance Unit for the commissioning of systematic reviews.
Finding
All food-grade salt used in household and food processing should be fortified with iodine (strong recommendation); evidence quality moderate for goitre and cretinism, low for cognitive function. Suggested iodine addition ranges from 65 mg/kg salt at an intake of 3 g salt/day to 39 mg/kg at 5 g/day, 20 mg/kg at 10 g/day and 14 mg/kg at 14 g/day, based on 150 µg iodine/day, 30% losses before consumption and 92% bioavailability. Salt iodisation and reduction of salt to less than 5 g/day are compatible.
Independent research
Cook NR, Appel LJ, Whelton PK. Sodium intake and all-cause mortality over 20 years in the Trials of Hypertension Prevention Journal of the American College of Cardiology, 2016.
doi:10.1016/j.jacc.2016.07.745 PubMed 27712772
Funding and finding
Participants
2,974
Follow-up
median 24 years after the trials
Funding
TOHP I and II were supported by NHLBI cooperative agreements HL37849, HL37852, HL37853, HL37854, HL37872, HL37884, HL37899, HL37904, HL37906, HL37907 and HL37924. The TOHP Follow-up Study was supported by NHLBI grant HL57915 and American Heart Association award 14GRNT18440013. The NHLBI and AHA had no role in design, conduct, analysis, interpretation, manuscript preparation or the decision to submit.
Finding
272 deaths. Hazard ratio per 1000 mg/24 h of sodium 1.12 (95% CI 1.00 to 1.26), with no evidence of a J-shaped or nonlinear relation. Versus 3600 to <4800 mg/24 h: <2300 mg/24 h 0.75 (0.45 to 1.26; 23 deaths among 312 participants), 2300 to <3600 mg/24 h 0.95 (0.70 to 1.29), 4800 mg/24 h or more 1.07 (0.75 to 1.54). In the randomised comparison, 251 deaths; hazard ratio 0.85 (0.66 to 1.09) for sodium intervention.
Independent research
He FJ, Campbell NRC, Ma Y, MacGregor GA, Cogswell ME, Cook NR. Errors in estimating usual sodium intake by the Kawasaki formula alter its relationship with mortality: implications for public health International Journal of Epidemiology, 2018.
doi:10.1093/ije/dyy114 PubMed 30517688
Funding and finding
Participants
2,974
Follow-up
median 24 years
Funding
TOHP I and II were supported by NHLBI cooperative agreements HL37849, HL37852, HL37853, HL37854, HL37872, HL37884, HL37899, HL37904, HL37906, HL37907 and HL37924; the TOHP follow-up study by NHLBI grant HL57915 and American Heart Association award 14GRNT18440013. The funder had no role in design, conduct, analysis, interpretation, manuscript preparation or the decision to submit.
Finding
Measured sodium (mean of three to seven 24-hour urines) averaged 3769 ± 1282 mg/day. The Kawasaki estimate from the same urines overestimated intake by 1297 mg/day (95% CI 1267 to 1326), over-estimating low and under-estimating high intakes. 272 deaths: measured sodium showed a linear relation with mortality, whereas the averaged Kawasaki estimate appeared to show a J-shaped relation; single measurements flattened the relation.
Independent research
Brand A, Visser ME, Schoonees A, Naude CE. Replacing salt with low-sodium salt substitutes (LSSS) for cardiovascular health in adults, children and pregnant women Cochrane Database of Systematic Reviews, 2022.
doi:10.1002/14651858.CD015207 PubMed 35944931
Funding and finding
Participants
35,053
Funding
Internal sources: none provided. External sources: the World Health Organization provided funding to Stellenbosch University towards the cost of the review; the UK Foreign, Commonwealth and Development Office through the Research, Evidence and Development Initiative (READ-It, project 300342-104).
Finding
Adults, salt substitute versus regular salt: systolic blood pressure -4.76 mm Hg (95% CI -6.01 to -3.50; 21,414 participants, 20 trials) and diastolic -2.43 mm Hg (-3.50 to -1.36); non-fatal stroke 20 fewer per 100,000 person-years (40 fewer to 2 more; 3 trials); non-fatal acute coronary syndrome 150 fewer (250 to 30 fewer; 1 trial); cardiovascular mortality 180 fewer (310 fewer to 0; 3 trials); blood potassium +0.12 mmol/L (0.07 to 0.18); hyperkalaemia 4 more per 100,000 (47 fewer to 121 more). All 26 trials excluded participants in whom an increased potassium intake is known to be potentially harmful; the evidence in children is very uncertain and no trials in pregnant women were found.

Updated 2026-10-21