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Sodium / Electrolyte Sodium

Evidence Level
Moderate
4 Clinical Trials
3 Documented Benefits
3/5 Evidence Score

Sodium is the main positively charged mineral in the fluid outside cells and is essential for fluid balance, nerve signaling and muscle contraction. Most people eat more than enough: US adults average about 3,400 mg a day, above the 2,300 mg level at which the National Academies advise cutting back to lower blood pressure and heart risk. Sodium as a supplement matters mainly when large amounts are lost in sweat. In controlled rehydration studies, drinks containing sodium were retained better than low-sodium drinks after exercise, and in one randomized trial, salt capsules taken during a half-ironman triathlon shortened race time. Low blood sodium during long endurance events is caused mainly by drinking too much fluid, not by a lack of sodium, so sodium does not replace drinking to thirst.

Studied Dose Adult Adequate Intake 1,500 mg/day; cut back if above 2,300 mg/day. Rehydration studies used drinks with about 40 to 60 mmol/L sodium; a half-ironman trial gave salt capsules with 113 mmol (about 2,600 mg) sodium before and during the race.
Active Compound Sodium, usually as sodium chloride (salt), sodium citrate or sodium bicarbonate in electrolyte products.
Deficiency information View details

Sodium deficiency from low dietary intake is rare: US adults average about 3,400 mg a day, above the 2,300 mg level the National Academies set for chronic disease risk reduction (no upper limit was set). Low blood sodium (hyponatremia) is usually caused by excess water intake, kidney problems or other medical conditions rather than low salt intake. In endurance athletes, it comes mainly from drinking more fluid than is lost.

Common symptoms

  • Headache, nausea, vomiting
  • Confusion, lethargy, or altered mental status
  • Muscle cramps or weakness
  • Restlessness or irritability
  • Loss of appetite
  • Severe acute hyponatremia: seizures, coma, brain swelling
  • Endurance athletes: exercise-associated hyponatremia from drinking too much fluid during long events

At-risk groups

  • Endurance athletes who drink large volumes of plain water during long events (marathons, ultra-events)
  • People with SIADH (syndrome of inappropriate ADH secretion)
  • People with congestive heart failure, cirrhosis, or nephrotic syndrome
  • People taking thiazide diuretics, SSRIs, antipsychotics, or NSAIDs
  • Older adults (impaired water excretion, polypharmacy)
  • People with severe vomiting or diarrhea who replace fluids with plain water
  • People with adrenal insufficiency
  • People with primary polydipsia or extreme low-sodium diets combined with high water intake
When to see a doctor: Sudden confusion, severe headache or seizures in someone who has been drinking large amounts of water, especially during endurance exercise, needs emergency medical care. Most US adults eat more sodium than recommended and benefit from eating less, not more; the National Academies advise cutting back if intake is above 2,300 mg a day.
Explore related deficiencies →
Sources: National Academies: Dietary Reference Intakes for Sodium and Potassium (2019), summary · FDA: Sodium in Your Diet · Hew-Butler et al. 2017, Exercise-Associated Hyponatremia: 2017 Update

Benefits

Fluid retention and rehydration after exercise

In controlled studies of men dehydrated by about 2% of body weight through exercise, drinks containing sodium (40 to 61 mmol/L) reduced urine output and restored fluid balance better than low-sodium or sodium-free drinks. Drinking more than was lost in sweat only helped when the drink's sodium content was high enough.

Supported by Trial 1, Trial 2

Electrolyte replacement in long endurance events

For ultramarathon racing, a sports nutrition position stand says sodium may be needed at more than 575 mg per liter of fluid, above most commercial products, with needs rising in hot or humid conditions. Low blood sodium in such events comes mainly from drinking too much; in a 161 km race, low supplement sodium intake played little role.

Supported by Trial 4, Trial 1

Endurance race performance

In a randomized trial in 26 experienced triathletes, salt capsules taken before and during a half-ironman shortened total race time versus placebo, kept blood sodium higher and tended to limit body weight loss; strength and jump losses were unchanged. In another study, better rehydration with sodium did not improve exercise capacity 4 hours later.

Supported by Trial 3, Trial 2

Mechanism of action

1

Osmolality and fluid volume

Sodium is the main regulator of extracellular fluid volume, including blood plasma volume. Changes in blood sodium concentration and osmolality trigger thirst and antidiuretic hormone, which together keep body water in balance.

2

The sodium-potassium pump

The sodium-potassium ATPase pump keeps sodium high outside cells and potassium high inside. This gradient is required for nerve transmission, muscle contraction and kidney function.

3

Hormonal control by the kidneys

The kidneys adjust sodium excretion over a wide range of intakes, mainly under the control of aldosterone, which increases sodium reabsorption when intake is low.

Clinical trials

1
Drink volume and sodium content in post-exercise rehydration
PubMed

Controlled crossover study of four drink volumes (50% to 200% of sweat loss) with a low-sodium (23 mmol/L) or higher-sodium (61 mmol/L) drink after exercise dehydration (Shirreffs et al. 1996, Med Sci Sports Exerc).

12 healthy men dehydrated by about 2% of body mass.

Both drink volume and sodium content affected rehydration. Drinking more than the sweat loss restored fluid balance only with the higher-sodium drink; with the low-sodium drink, the extra fluid was mostly lost as urine.

2
Sodium concentration, rehydration and later exercise capacity
PubMed

Randomized crossover study of four otherwise identical drinks with 1, 31, 40 or 50 mmol/L sodium chloride, drunk at 150% of sweat loss after exercise in the heat (Merson et al. 2008, Eur J Appl Physiol).

8 healthy men dehydrated by about 2% of body mass.

The 40 and 50 mmol/L drinks reduced urine output compared with the sodium-free drink, giving more effective rehydration, but time to exhaustion in a cycling test 4 hours later did not differ between drinks.

3
Salt capsules during a half-ironman triathlon
PubMed

Randomized controlled trial of salt capsules (113 mmol sodium) or placebo capsules taken before and during a real half-ironman race (Del Coso et al. 2016, Scand J Med Sci Sports).

26 experienced triathletes matched for age, body size and training.

Total race time was shorter with salt (P = 0.04), post-race blood sodium and chloride were higher, and body mass loss tended to be smaller (P = 0.09). Sweat loss, sweat sodium, and post-race losses in strength and jump height did not differ.

4
Sodium supplements and low blood sodium in a 161 km race
PubMed

Observational study of drinking habits, sodium supplement use, body weight and post-race blood sodium in the Western States Endurance Run (Hoffman et al. 2015, Med Sci Sports Exerc).

Finishers of a 161 km ultramarathon; 6.6% developed low blood sodium.

Sodium supplement intake did not differ between runners who developed low blood sodium and those who did not; overhydration was the main feature of those affected, so avoiding overdrinking was the key preventive step.

Side effects and drug interactions

Common Potential side effects

High sodium intake raises blood pressure; in a controlled feeding trial, cutting sodium lowered blood pressure in people with and without hypertension.
Taking large amounts of sodium without enough water can raise blood sodium too far (hypernatremia), causing confusion and, rarely, seizures.
Fluid retention and swelling can occur with high sodium intake in susceptible people.

Important Drug interactions

Lithium: changes in sodium intake change lithium levels; a sudden drop in sodium intake can raise lithium toward toxic levels.
Blood-pressure medicines: high sodium intake can blunt their effect.
Diuretics: thiazide and loop diuretics increase sodium loss; discuss electrolyte intake with a doctor.
ACE inhibitors: their blood-pressure lowering is greater on a lower-sodium diet.

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Frequently asked questions about Sodium / Electrolyte Sodium

How much sodium do I need?

The Adequate Intake for adults is 1,500 mg a day, and the National Academies advise cutting back if you eat more than 2,300 mg a day. US adults average about 3,400 mg. Heavy sweaters and endurance athletes lose more and may need extra during long events.

What is sodium used for in supplements?

Sodium is the key electrolyte in sports and rehydration products. In controlled studies, drinks containing sodium were retained better than low-sodium drinks after sweating, helping restore fluid balance.

Do I need extra sodium during exercise?

For long events, especially in heat, sports nutrition guidance advises replacing sodium lost in sweat. For short workouts and everyday activity, a normal diet usually provides plenty. Drinking too much fluid, not too little sodium, is the main cause of low blood sodium in endurance events.

Is sodium bad for blood pressure?

Eating less sodium lowers blood pressure in people with and without hypertension. Sodium is still essential, and one large observational study linked both very low and very high intakes with higher cardiovascular risk.

What is Sodium / Electrolyte Sodium?

Sodium is the main positively charged mineral in the fluid outside cells and is essential for fluid balance, nerve signaling and muscle contraction. Most people eat more than enough: US adults average about 3,400 mg a day, above the 2,300 mg level at which the National Academies advise cutting back to lower blood press…

What is Sodium / Electrolyte Sodium used for?

Sodium / Electrolyte Sodium is researched primarily for Athletic Performance and Hydration. In controlled studies of men dehydrated by about 2% of body weight through exercise, drinks containing sodium (40 to 61 mmol/L) reduced urine output and restored fluid balance better than low-sodium or sodium-free drinks.

What are the signs of Sodium / Electrolyte Sodium deficiency?

Sodium deficiency from low dietary intake is rare: US adults average about 3,400 mg a day, above the 2,300 mg level the National Academies set for chronic disease risk reduction (no upper limit was set).

What is the recommended dosage of Sodium / Electrolyte Sodium?

The clinically studied dose is Adult Adequate Intake 1,500 mg/day; cut back if above 2,300 mg/day. Rehydration studies used drinks with about 40 to 60 mmol/L sodium; a half-ironman trial gave salt capsules with 113 mmol (about 2,600 mg) sodium before and during the race. Always follow the product label and check with a healthcare provider for personal advice.

Is Sodium / Electrolyte Sodium safe, and does it have side effects?

For most healthy adults, Sodium / Electrolyte Sodium is well tolerated at studied doses. Reported effects can include: High sodium intake raises blood pressure; in a controlled feeding trial, cutting sodium lowered blood pressure in people with and without hypertension. It may also interact with some medications. Sodium / Electrolyte Sodium is not right for everyone, so check with a healthcare provider first if you are pregnant or breastfeeding, have a medical condition, or take prescription medication.

Does Sodium / Electrolyte Sodium interact with any medications?

Possible interactions include: Lithium: changes in sodium intake change lithium levels; a sudden drop in sodium intake can raise lithium toward toxic levels. Blood-pressure medicines: high sodium intake can blunt their effect. If you take prescription medication, check with a pharmacist or doctor before using it.

How strong is the scientific evidence for Sodium / Electrolyte Sodium?

NutraSmarts rates the evidence for Sodium / Electrolyte Sodium as Moderate (3 out of 5). It is backed by 4 clinical trials and 12 cited references summarized on this page. A higher rating reflects more, larger, and better-designed human studies.

References(12 citations)

Evidence ratings on NutraSmarts are based on the totality of human clinical research, with emphasis on randomized controlled trials, meta-analyses, and systematic reviews. The references below directly support claims made throughout this page.

  1. Sacks FM, Svetkey LP, Vollmer WM, Appel LJ, Bray GA, Harsha D, Obarzanek E, Conlin PR, Miller ER 3rd, Simons-Morton DG, Karanja N, Lin PH. Effects on blood pressure of reduced dietary sodium and the Dietary Approaches to Stop Hypertension (DASH) diet. DASH-Sodium Collaborative Research Group. N Engl J Med. 2001;344(1):3-10. doi: 10.1056/NEJM200101043440101.PubMedUsed to support: Controlled feeding trial in 412 adults: lowering sodium from high to intermediate to low levels lowered systolic blood pressure stepwise, with and without the DASH diet; the DASH diet with low sodium was 7.1 mmHg lower than the control diet with high sodium in people without hypertension and 11.5 mmHg lower in those with hypertension.
  2. He FJ, Li J, Macgregor GA. Effect of longer term modest salt reduction on blood pressure: Cochrane systematic review and meta-analysis of randomised trials. BMJ. 2013;346:f1325. doi: 10.1136/bmj.f1325.PubMedUsed to support: Meta-analysis of 34 trials (3,230 participants): a modest salt reduction of about 4.4 g/day for at least 4 weeks lowered blood pressure by 4.18/2.06 mmHg on average (5.39/2.82 in people with hypertension), with small rises in renin, aldosterone and noradrenaline and no significant change in blood lipids.
  3. O'Donnell M, Mente A, Rangarajan S, McQueen MJ, Wang X, Liu L, Yan H, Lee SF, Mony P, Devanath A, Rosengren A, Lopez-Jaramillo P, Diaz R, Avezum A, Lanas F, Yusoff K, Iqbal R, Ilow R, Mohammadifard N, Gulec S, Yusufali AH, Kruger L, Yusuf R, Chifamba J, Kabali C, Dagenais G, Lear SA, Teo K, Yusuf S. Urinary sodium and potassium excretion, mortality, and cardiovascular events. N Engl J Med. 2014;371(7):612-23. doi: 10.1056/NEJMoa1311889.PubMedUsed to support: Observational cohort of 101,945 people in 17 countries (intake estimated from a morning urine sample): compared with estimated sodium excretion of 4 to 6 g a day, both higher (7 g or more) and lower (below 3 g) levels were associated with higher risk of death and cardiovascular events. Observational, with intake estimated from a single urine sample.
  4. Hew-Butler T, Loi V, Pani A, Rosner MH. Exercise-Associated Hyponatremia: 2017 Update. Front Med (Lausanne). 2017;4:21. doi: 10.3389/fmed.2017.00021.PubMedUsed to support: Review: overdrinking beyond thirst and non-osmotic vasopressin release are the most common causes of exercise-associated hyponatremia, with volume and sodium depletion playing a role in a subset of athletes.
  5. Hoffman MD, Stuempfle KJ. Sodium Supplementation and Exercise-Associated Hyponatremia during Prolonged Exercise. Med Sci Sports Exerc. 2015;47(9):1781-7. doi: 10.1249/MSS.0000000000000599.PubMedUsed to support: Observational study of 161 km ultramarathon finishers: 6.6% had low blood sodium; sodium supplement intake did not differ between those with and without it, and overhydration was its primary feature.
  6. Tiller NB, Roberts JD, Beasley L, Chapman S, Pinto JM, Smith L, Wiffin M, Russell M, Sparks SA, Duckworth L, O'Hara J, Sutton L, Antonio J, Willoughby DS, Tarpey MD, Smith-Ryan AE, Ormsbee MJ, Astorino TA, Kreider RB, McGinnis GR, Stout JR, Smith JW, Arent SM, Campbell BI, Bannock L. International Society of Sports Nutrition Position Stand: nutritional considerations for single-stage ultra-marathon training and racing. J Int Soc Sports Nutr. 2019;16(1):50. doi: 10.1186/s12970-019-0312-9.PubMedUsed to support: ISSN position stand on single-stage ultra-marathon nutrition: fluid of 450 to 750 mL per hour during racing, and electrolytes (mainly sodium) possibly at more than 575 mg per liter, above most commercial products, to reduce hyponatremia risk; needs rise in hot or humid conditions.
  7. Shirreffs SM, Taylor AJ, Leiper JB, Maughan RJ. Post-exercise rehydration in man: effects of volume consumed and drink sodium content. Med Sci Sports Exerc. 1996;28(10):1260-71. doi: 10.1097/00005768-199610000-00009.PubMedUsed to support: Crossover study in 12 men dehydrated by about 2% of body mass: rehydration depended on both drink volume and sodium content; drinking more than the sweat loss only restored fluid balance when the drink's sodium was high enough (61 versus 23 mmol/L).
  8. Merson SJ, Maughan RJ, Shirreffs SM. Rehydration with drinks differing in sodium concentration and recovery from moderate exercise-induced hypohydration in man. Eur J Appl Physiol. 2008;103(5):585-94. doi: 10.1007/s00421-008-0748-0.PubMedUsed to support: Crossover study in 8 men: drinks with 40 or 50 mmol/L sodium chloride reduced urine output versus a sodium-free drink, improving rehydration, but exercise capacity 4 hours later did not differ.
  9. Maughan RJ, Owen JH, Shirreffs SM, Leiper JB. Post-exercise rehydration in man: effects of electrolyte addition to ingested fluids. Eur J Appl Physiol Occup Physiol. 1994;69(3):209-15. doi: 10.1007/BF01094790.PubMedUsed to support: Crossover study in 8 men: drinks containing sodium chloride, potassium chloride or both were retained better than a glucose-only drink after exercise dehydration, leaving a smaller fluid deficit the next morning.
  10. Del Coso J, González-Millán C, Salinero JJ, Abián-Vicén J, Areces F, Lledó M, Lara B, Gallo-Salazar C, Ruiz-Vicente D. Effects of oral salt supplementation on physical performance during a half-ironman: A randomized controlled trial. Scand J Med Sci Sports. 2016;26(2):156-64. doi: 10.1111/sms.12427.PubMedUsed to support: Randomized controlled trial in 26 triathletes: salt capsules (113 mmol sodium) before and during a half-ironman shortened total race time (P = 0.04), kept serum sodium and chloride higher and tended to reduce body mass loss, without changing sweat loss or post-race strength and jump losses.
  11. National Academies of Sciences, Engineering, and Medicine. Dietary Reference Intakes for Sodium and Potassium. Summary. The National Academies Press. 2019;Washington, DC. doi: 10.17226/25353.SourceUsed to support: Not PubMed-indexed (official National Academies report). Sets the sodium Adequate Intake for adults at 1,500 mg/day and a Chronic Disease Risk Reduction Intake of 2,300 mg/day (reduce intake if above it), and found insufficient evidence of toxicity risk to set a Tolerable Upper Intake Level for sodium.
  12. U.S. Food and Drug Administration. Sodium in Your Diet. U.S. Food and Drug Administration. 2024;Online consumer page. https://www.fda.gov/food/nutrition-education-resources-materials/sodium-your-diet.SourceUsed to support: Not PubMed-indexed (official FDA page). Americans eat on average about 3,400 mg of sodium per day, and the Dietary Guidelines for Americans recommend adults limit sodium to less than 2,300 mg per day.