Plasma or serum sodium concentration

What acts on it

1. Serum sodium correlated only partly or poorly with the isolated body-composition ratios, including exchangeable sodium/body weight.

   Total exchangeable body sodium → Plasma or serum sodium concentration source_derived_draftungraded
   Experimental context and source evidence

   evidence_span

   {"source_cache": "artifacts/sodium-research/13575523.fulltext.txt", "locator": "Exact primary full-text span; zero-based, end-exclusive Unicode character offsets", "file_sha256": "ee58d9f6c640fec095876c15e7ddf6fe8bf539cb972c74841db02d2640eebbe2", "start_char": 54337, "end_char": 56036, "text_sha256": "29b3a155f7b33a8b86aa9e30182063d71f5af3c60910a237794c1310094a4c39"}

   experimental_model

   Simultaneous isotope-dilution and serum measurements, including serial observations

   exposure

   Observed variation in body composition

   limitations

   Historical observational regression; serum-water sodium and exchangeable pools are not interchangeable with current clinical plasma measurements or all body sodium. Not an individual correction calculator.

   nutrient_topic

   Sodium research collection; topical membership is not evidence of a direct dietary effect. · Sodium

   organism

   Human patients with chronic illnesses

   plain_language

   A low blood sodium result does not, by itself, identify a dietary sodium shortage.

   primary_references

   [sodium-p13575523] Interrelations between serum sodium concentration, serum osmolarity and total exchangeable sodium, total exchangeable potassium and total body water. (1958). https://pubmed.ncbi.nlm.nih.gov/13575523/ DOI: 10.1172/jci103712

   tissue_or_cell_type

   Whole-body water and exchangeable cations

   Sodium: gradients, nutrient transport, fluid regulation and loss states (2026-09-17) · lines 278–289

   AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Simultaneous isotope-dilution and serum measurements, including serial observations · source_derived_draft · unverified_draft

   ### sodium-body-sodium-marker-limit Serum sodium correlated only partly or poorly with the isolated body-composition ratios, including exchangeable sodium/body weight. Condition category: normal nutrient_topic: Sodium research collection; topical membership is not evidence of a direct dietary effect. plain_language: A low blood sodium result does not, by itself, identify a dietary sodium shortage. organism: Human patients with chronic illnesses tissue_or_cell_type: Whole-body water and exchangeable cations experimental_model: Simultaneous isotope-dilution and serum measurements, including serial observations limitations: Historical observational regression; serum-water sodium and exchangeable pools are not interchangeable with current clinical plasma measurements or all body sodium. Not an individual correction calculator. exposure: Observed variation in body composition evidence_span: {"source_cache": "artifacts/sodium-research/13575523.fulltext.txt", "locator": "Exact primary full-text span; zero-based, end-exclusive Unicode character offsets", "file_sha256": "ee58d9f6c640fec095876c15e7ddf6fe8bf539cb972c74841db02d2640eebbe2", "start_char": 54337, "end_char": 56036, "text_sha256": "29b3a155f7b33a8b86aa9e30182063d71f5af3c60910a237794c1310094a4c39"} [sodium-p13575523] Interrelations between serum sodium concentration, serum osmolarity and total exchangeable sodium, total exchangeable potassium and total body water. (1958). https://pubmed.ncbi.nlm.nih.gov/13575523/ DOI: 10.1172/jci103712

   Complete structured claim and evidence

2. Serum-water sodium correlated strongly with (exchangeable sodium + exchangeable potassium)/total body water in the studied patients.

   Exchangeable sodium plus potassium divided by total body water → Plasma or serum sodium concentration source_derived_draftungraded
   Experimental context and source evidence

   evidence_span

   {"source_cache": "artifacts/sodium-research/13575523.fulltext.txt", "locator": "Exact primary full-text span; zero-based, end-exclusive Unicode character offsets", "file_sha256": "ee58d9f6c640fec095876c15e7ddf6fe8bf539cb972c74841db02d2640eebbe2", "start_char": 54337, "end_char": 56036, "text_sha256": "29b3a155f7b33a8b86aa9e30182063d71f5af3c60910a237794c1310094a4c39"}

   experimental_model

   Simultaneous isotope-dilution and serum measurements, including serial observations

   exposure

   Observed variation in body composition

   limitations

   Historical observational regression; serum-water sodium and exchangeable pools are not interchangeable with current clinical plasma measurements or all body sodium. Not an individual correction calculator.

   nutrient_topic

   Sodium research collection; topical membership is not evidence of a direct dietary effect. · Sodium

   organism

   Human patients with chronic illnesses

   plain_language

   Blood sodium reflects a relationship between body cations and water, rather than a simple count of how much sodium was eaten.

   primary_references

   [sodium-p13575523] Interrelations between serum sodium concentration, serum osmolarity and total exchangeable sodium, total exchangeable potassium and total body water. (1958). https://pubmed.ncbi.nlm.nih.gov/13575523/ DOI: 10.1172/jci103712

   tissue_or_cell_type

   Whole-body water and exchangeable cations

   Sodium: gradients, nutrient transport, fluid regulation and loss states (2026-09-17) · lines 265–276

   AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Simultaneous isotope-dilution and serum measurements, including serial observations · source_derived_draft · unverified_draft

   ### sodium-body-water-ratio Serum-water sodium correlated strongly with (exchangeable sodium + exchangeable potassium)/total body water in the studied patients. Condition category: normal nutrient_topic: Sodium research collection; topical membership is not evidence of a direct dietary effect. plain_language: Blood sodium reflects a relationship between body cations and water, rather than a simple count of how much sodium was eaten. organism: Human patients with chronic illnesses tissue_or_cell_type: Whole-body water and exchangeable cations experimental_model: Simultaneous isotope-dilution and serum measurements, including serial observations limitations: Historical observational regression; serum-water sodium and exchangeable pools are not interchangeable with current clinical plasma measurements or all body sodium. Not an individual correction calculator. exposure: Observed variation in body composition evidence_span: {"source_cache": "artifacts/sodium-research/13575523.fulltext.txt", "locator": "Exact primary full-text span; zero-based, end-exclusive Unicode character offsets", "file_sha256": "ee58d9f6c640fec095876c15e7ddf6fe8bf539cb972c74841db02d2640eebbe2", "start_char": 54337, "end_char": 56036, "text_sha256": "29b3a155f7b33a8b86aa9e30182063d71f5af3c60910a237794c1310094a4c39"} [sodium-p13575523] Interrelations between serum sodium concentration, serum osmolarity and total exchangeable sodium, total exchangeable potassium and total body water. (1958). https://pubmed.ncbi.nlm.nih.gov/13575523/ DOI: 10.1172/jci103712

   Complete structured claim and evidence

3. Intestinal NHE3-null mice developed hyponatremia.

   Mouse sodium/hydrogen exchanger NHE3 / Slc9a3 → Plasma or serum sodium concentration source_derived_draftungraded
   Experimental context and source evidence

   availability_state

   machinery_impairment Imported condition classification; unverified.

   evidence_span

   {"source_cache": "artifacts/sodium-research/32227118.abstract.txt", "locator": "Exact primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "0a9c8f006f6b0b8ff35bd7e67c529c9c72e0cf3d3fd29cd46ec8c23942129b39", "start_char": 0, "end_char": 1643, "text_sha256": "0a9c8f006f6b0b8ff35bd7e67c529c9c72e0cf3d3fd29cd46ec8c23942129b39"}

   experimental_model

   Inducible intestinal epithelial Slc9a3 deletion

   exposure

   Tamoxifen-induced NHE3 loss

   limitations

   Genetic machinery failure, not isolated low sodium intake. Gut loss differs from proximal-tubule-specific deletion.

   nutrient_topic

   Sodium research collection; topical membership is not evidence of a direct dietary effect. · Sodium

   organism

   Mouse

   plain_language

   A gut transport defect can affect the measured blood sodium.

   primary_references

   [sodium-p32227118] An inducible intestinal epithelial cell-specific NHE3 knockout mouse model mimicking congenital sodium diarrhea. (2020). https://pubmed.ncbi.nlm.nih.gov/32227118/ DOI: 10.1042/cs20200065

   tissue_or_cell_type

   Intestine with systemic electrolyte measurements

   trigger_kind

   machinery_impairment Imported condition classification; unverified.

   Sodium: gradients, nutrient transport, fluid regulation and loss states (2026-09-17) · lines 850–861

   AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Inducible intestinal epithelial Slc9a3 deletion · source_derived_draft · unverified_draft

   ### sodium-gut-sodium Intestinal NHE3-null mice developed hyponatremia. Condition category: machinery_impairment nutrient_topic: Sodium research collection; topical membership is not evidence of a direct dietary effect. plain_language: A gut transport defect can affect the measured blood sodium. organism: Mouse tissue_or_cell_type: Intestine with systemic electrolyte measurements experimental_model: Inducible intestinal epithelial Slc9a3 deletion limitations: Genetic machinery failure, not isolated low sodium intake. Gut loss differs from proximal-tubule-specific deletion. exposure: Tamoxifen-induced NHE3 loss evidence_span: {"source_cache": "artifacts/sodium-research/32227118.abstract.txt", "locator": "Exact primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "0a9c8f006f6b0b8ff35bd7e67c529c9c72e0cf3d3fd29cd46ec8c23942129b39", "start_char": 0, "end_char": 1643, "text_sha256": "0a9c8f006f6b0b8ff35bd7e67c529c9c72e0cf3d3fd29cd46ec8c23942129b39"} [sodium-p32227118] An inducible intestinal epithelial cell-specific NHE3 knockout mouse model mimicking congenital sodium diarrhea. (2020). https://pubmed.ncbi.nlm.nih.gov/32227118/ DOI: 10.1042/cs20200065

   Complete structured claim and evidence

4. Weight gain during the marathon was independently associated with hyponatremia, odds ratio 4.2 (95% CI 2.2–8.2).

   Weight gain during endurance exercise → Plasma or serum sodium concentration source_derived_draftungraded
   Experimental context and source evidence

   availability_state

   biomarker_context Imported condition classification; unverified.

   evidence_span

   {"source_cache": "artifacts/sodium-research/15829535.abstract.txt", "locator": "Exact primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "9bf7f638ff3cfcad3d43536a75ffedf40a2ef726f783922f3169c9252c12a8e5", "start_char": 0, "end_char": 1893, "text_sha256": "9bf7f638ff3cfcad3d43536a75ffedf40a2ef726f783922f3169c9252c12a8e5"}

   experimental_model

   Prospective marathon cohort with prerace/postrace weights and blood sampling

   exposure

   2002 Boston Marathon; 488 usable finish-line blood samples

   limitations

   Observational associations and sampling limitations; fluid composition was not independently associated. Not a treatment protocol or pure dietary-depletion study.

   nutrient_topic

   Sodium research collection; topical membership is not evidence of a direct dietary effect. · Sodium

   organism

   Human runners

   plain_language

   A low sodium concentration can accompany gaining water rather than simply losing salt.

   primary_references

   [sodium-p15829535] Hyponatremia among runners in the Boston Marathon. (2005). https://pubmed.ncbi.nlm.nih.gov/15829535/ DOI: 10.1056/nejmoa043901

   tissue_or_cell_type

   Systemic water/sodium balance

   trigger_kind

   biomarker_context Imported condition classification; unverified.

   Sodium: gradients, nutrient transport, fluid regulation and loss states (2026-09-17) · lines 1006–1017

   AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Prospective marathon cohort with prerace/postrace weights and blood sampling · source_derived_draft · unverified_draft

   ### sodium-marathon-weight Weight gain during the marathon was independently associated with hyponatremia, odds ratio 4.2 (95% CI 2.2–8.2). Condition category: biomarker_context nutrient_topic: Sodium research collection; topical membership is not evidence of a direct dietary effect. plain_language: A low sodium concentration can accompany gaining water rather than simply losing salt. organism: Human runners tissue_or_cell_type: Systemic water/sodium balance experimental_model: Prospective marathon cohort with prerace/postrace weights and blood sampling limitations: Observational associations and sampling limitations; fluid composition was not independently associated. Not a treatment protocol or pure dietary-depletion study. exposure: 2002 Boston Marathon; 488 usable finish-line blood samples evidence_span: {"source_cache": "artifacts/sodium-research/15829535.abstract.txt", "locator": "Exact primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "9bf7f638ff3cfcad3d43536a75ffedf40a2ef726f783922f3169c9252c12a8e5", "start_char": 0, "end_char": 1893, "text_sha256": "9bf7f638ff3cfcad3d43536a75ffedf40a2ef726f783922f3169c9252c12a8e5"} [sodium-p15829535] Hyponatremia among runners in the Boston Marathon. (2005). https://pubmed.ncbi.nlm.nih.gov/15829535/ DOI: 10.1056/nejmoa043901

   Complete structured claim and evidence

5. Hyponatremia below 130 mmol/L occurred in 29/142 versus 16/150 participants receiving reduced-osmolarity versus standard ORS; affected participants were symptom-free.

   Oral rehydration solutions (formulation specified per study) → Plasma or serum sodium concentration source_derived_draftungraded
   Experimental context and source evidence

   availability_state

   biomarker_context Imported condition classification; unverified.

   evidence_span

   {"source_cache": "artifacts/sodium-research/10440307.abstract.txt", "locator": "Exact primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "cd7239d3f0a151f53930364ba35b974cd938a67bc4282e4b67a02e24f68e9969", "start_char": 0, "end_char": 2141, "text_sha256": "cd7239d3f0a151f53930364ba35b974cd938a67bc4282e4b67a02e24f68e9969"}

   experimental_model

   Randomized double-blind comparison in 300 adults with severe cholera

   exposure

   Reduced-osmolarity versus then-standard WHO oral rehydration solution

   limitations

   Historical formulation comparison; not a current formulation recommendation. Both sodium and other solution properties changed; no isolated sodium effect.

   nutrient_topic

   Sodium research collection; topical membership is not evidence of a direct dietary effect. · Sodium

   organism

   Human

   plain_language

   Replacing fluid is not just replacing water: solution composition affected blood sodium.

   primary_references

   [sodium-p10440307] Efficacy and safety of oral rehydration solution with reduced osmolarity in adults with cholera: a randomised double-blind clinical trial. CHOICE study group. (1999). https://pubmed.ncbi.nlm.nih.gov/10440307/ DOI: 10.1016/s0140-6736(98)09332-5

   tissue_or_cell_type

   Intestinal fluid loss and serum sodium

   trigger_kind

   biomarker_context Imported condition classification; unverified.

   Sodium: gradients, nutrient transport, fluid regulation and loss states (2026-09-17) · lines 1045–1056

   AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Randomized double-blind comparison in 300 adults with severe cholera · source_derived_draft · unverified_draft

   ### sodium-ors-sodium Hyponatremia below 130 mmol/L occurred in 29/142 versus 16/150 participants receiving reduced-osmolarity versus standard ORS; affected participants were symptom-free. Condition category: biomarker_context nutrient_topic: Sodium research collection; topical membership is not evidence of a direct dietary effect. plain_language: Replacing fluid is not just replacing water: solution composition affected blood sodium. organism: Human tissue_or_cell_type: Intestinal fluid loss and serum sodium experimental_model: Randomized double-blind comparison in 300 adults with severe cholera limitations: Historical formulation comparison; not a current formulation recommendation. Both sodium and other solution properties changed; no isolated sodium effect. exposure: Reduced-osmolarity versus then-standard WHO oral rehydration solution evidence_span: {"source_cache": "artifacts/sodium-research/10440307.abstract.txt", "locator": "Exact primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "cd7239d3f0a151f53930364ba35b974cd938a67bc4282e4b67a02e24f68e9969", "start_char": 0, "end_char": 2141, "text_sha256": "cd7239d3f0a151f53930364ba35b974cd938a67bc4282e4b67a02e24f68e9969"} [sodium-p10440307] Efficacy and safety of oral rehydration solution with reduced osmolarity in adults with cholera: a randomised double-blind clinical trial. CHOICE study group. (1999). https://pubmed.ncbi.nlm.nih.gov/10440307/ DOI: 10.1016/s0140-6736(98)09332-5

   Complete structured claim and evidence

6. Supplemented preterm infants had fewer recorded serum sodium values below 135 mmol/L.

   Sodium → Plasma or serum sodium concentration source_derived_draftungraded
   Experimental context and source evidence

   availability_state

   nutrient_deficiency Imported condition classification; unverified.

   evidence_span

   {"source_cache": "artifacts/sodium-research/25406227.abstract.txt", "locator": "Exact primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "a3c6cd28e4896dc8cdaeaacb7d524c55098b87dd5bf9d028ce49ba544832e339", "start_char": 0, "end_char": 1645, "text_sha256": "a3c6cd28e4896dc8cdaeaacb7d524c55098b87dd5bf9d028ce49ba544832e339"}

   experimental_model

   Randomized masked trial in 53 infants born before 32 weeks

   exposure

   4 mEq/kg/day supplemental sodium versus placebo, days 7–35

   limitations

   Study regimen, not a dosing recommendation. Small neonatal trial; improved weight gain is not proof that every blood sodium measurement diagnoses total-body depletion.

   nutrient_topic

   Sodium research collection; topical membership is not evidence of a direct dietary effect. · Sodium

   organism

   Human preterm infants

   plain_language

   Very premature infants can need a different sodium provision than older children or adults.

   primary_references

   [sodium-p25406227] Impact of Early Sodium Supplementation on Hyponatremia and Growth in Premature Infants: A Randomized Controlled Trial. (2016). https://pubmed.ncbi.nlm.nih.gov/25406227/ DOI: 10.1177/0148607114558303

   tissue_or_cell_type

   Whole-body growth and serum sodium

   trigger_kind

   nutrient_deficiency Imported condition classification; unverified.

   Sodium: gradients, nutrient transport, fluid regulation and loss states (2026-09-17) · lines 967–978

   AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Randomized masked trial in 53 infants born before 32 weeks · source_derived_draft · unverified_draft

   ### sodium-preterm-sodium Supplemented preterm infants had fewer recorded serum sodium values below 135 mmol/L. Condition category: nutrient_deficiency nutrient_topic: Sodium research collection; topical membership is not evidence of a direct dietary effect. plain_language: Very premature infants can need a different sodium provision than older children or adults. organism: Human preterm infants tissue_or_cell_type: Whole-body growth and serum sodium experimental_model: Randomized masked trial in 53 infants born before 32 weeks limitations: Study regimen, not a dosing recommendation. Small neonatal trial; improved weight gain is not proof that every blood sodium measurement diagnoses total-body depletion. exposure: 4 mEq/kg/day supplemental sodium versus placebo, days 7–35 evidence_span: {"source_cache": "artifacts/sodium-research/25406227.abstract.txt", "locator": "Exact primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "a3c6cd28e4896dc8cdaeaacb7d524c55098b87dd5bf9d028ce49ba544832e339", "start_char": 0, "end_char": 1645, "text_sha256": "a3c6cd28e4896dc8cdaeaacb7d524c55098b87dd5bf9d028ce49ba544832e339"} [sodium-p25406227] Impact of Early Sodium Supplementation on Hyponatremia and Growth in Premature Infants: A Randomized Controlled Trial. (2016). https://pubmed.ncbi.nlm.nih.gov/25406227/ DOI: 10.1177/0148607114558303

   Complete structured claim and evidence

7. Kidney-specific NHE3 deletion did not change the measured baseline plasma sodium, pH or bicarbonate.

   Mouse sodium/hydrogen exchanger NHE3 / Slc9a3 → Plasma or serum sodium concentration source_derived_draftungraded
   Experimental context and source evidence

   availability_state

   machinery_impairment Imported condition classification; unverified.

   evidence_span

   {"source_cache": "artifacts/sodium-research/30571224.abstract.txt", "locator": "Exact primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "14f3ce82ae25bafc1d5d935be05b3a8d68420b6d8a36fdbbc5d7e89aba77bc33", "start_char": 0, "end_char": 1779, "text_sha256": "14f3ce82ae25bafc1d5d935be05b3a8d68420b6d8a36fdbbc5d7e89aba77bc33"}

   experimental_model

   Proximal-tubule-specific Slc9a3 knockout and controlled renal perfusion changes

   exposure

   Genetic deletion; increased perfusion pressure; saline and dietary salt challenges

   limitations

   Unlike intestinal deletion, the kidney-specific model retained measured baseline plasma sodium, pH and bicarbonate. Tissue context, not a contradiction.

   nutrient_topic

   Sodium research collection; topical membership is not evidence of a direct dietary effect. · Sodium

   organism

   Mouse

   plain_language

   Changed sodium handling need not produce a changed blood sodium value.

   primary_references

   [sodium-p30571224] Proximal Tubule-Specific Deletion of the NHE3 (Na+/H+ Exchanger 3) Promotes the Pressure-Natriuresis Response and Lowers Blood Pressure in Mice. (2018). https://pubmed.ncbi.nlm.nih.gov/30571224/ DOI: 10.1161/hypertensionaha.118.10884

   tissue_or_cell_type

   Kidney proximal tubule

   trigger_kind

   machinery_impairment Imported condition classification; unverified.

   Sodium: gradients, nutrient transport, fluid regulation and loss states (2026-09-17) · lines 915–926

   AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Proximal-tubule-specific Slc9a3 knockout and controlled renal perfusion changes · source_derived_draft · unverified_draft

   ### sodium-renal-nhe3-marker Kidney-specific NHE3 deletion did not change the measured baseline plasma sodium, pH or bicarbonate. Condition category: machinery_impairment nutrient_topic: Sodium research collection; topical membership is not evidence of a direct dietary effect. plain_language: Changed sodium handling need not produce a changed blood sodium value. organism: Mouse tissue_or_cell_type: Kidney proximal tubule experimental_model: Proximal-tubule-specific Slc9a3 knockout and controlled renal perfusion changes limitations: Unlike intestinal deletion, the kidney-specific model retained measured baseline plasma sodium, pH and bicarbonate. Tissue context, not a contradiction. exposure: Genetic deletion; increased perfusion pressure; saline and dietary salt challenges evidence_span: {"source_cache": "artifacts/sodium-research/30571224.abstract.txt", "locator": "Exact primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "14f3ce82ae25bafc1d5d935be05b3a8d68420b6d8a36fdbbc5d7e89aba77bc33", "start_char": 0, "end_char": 1779, "text_sha256": "14f3ce82ae25bafc1d5d935be05b3a8d68420b6d8a36fdbbc5d7e89aba77bc33"} [sodium-p30571224] Proximal Tubule-Specific Deletion of the NHE3 (Na+/H+ Exchanger 3) Promotes the Pressure-Natriuresis Response and Lowers Blood Pressure in Mice. (2018). https://pubmed.ncbi.nlm.nih.gov/30571224/ DOI: 10.1161/hypertensionaha.118.10884

   Complete structured claim and evidence