Evidence explainerElectrolytes and sodium (salt tablets and electrolyte drinks)
Electrolyte Drinks vs Water: When the Extra Sodium Matters, and When It Does Not
Electrolyte powders are marketed for everyday hydration. The exercise evidence says drinking enough matters most, and drinks with electrolytes and carbs help only in certain conditions.
Key takeaways
- ACSM says drinks with electrolytes and carbohydrate can provide benefits over water alone during exercise under certain circumstances [1].
- In a 6-hour cycling study in the heat, matched volumes of water and dilute saline performed alike; drinking nothing cut exercise short by about 1.5 hours [2].
- ACSM's goal during exercise is to avoid losing more than 2% of body weight from water deficit [1].
- Most US and Canadian adults already exceed the 2,300 mg/day sodium risk-reduction level [3].
- Sweat rate can be estimated by weighing before and after exercise [1].
Safety at a glance
From our Electrolytes and sodium (salt tablets and electrolyte drinks) monograph. Published interactions and cautions only, each with its source.
Who should be careful
- Daily sodium intake. Most US and Canadian adults already eat more sodium than both the 1,500 mg/day Adequate Intake and the 2,300 mg/day Chronic Disease Risk Reduction Intake, above which reducing intake is advised.[1]
- Blood pressure. Reducing sodium has a greater effect in adults with hypertension; anyone managing blood pressure should discuss salt tablets with a clinician.[1]
- Drinking to a plan. ACSM recommends customized fluid plans because sweat rates and sweat electrolyte content vary widely; individual sweat rate can be estimated by weighing before and after exercise.[5]
- Before you start. Talk to your pharmacist or clinician before adding this supplement, especially if you take prescription medicines, are pregnant or breastfeeding, or have a chronic health condition.[1]
Full Electrolytes and sodium (salt tablets and electrolyte drinks) safety section
The evidence, graded
Pulled from our monograph evidence tables. Grades follow our evidence-grading policy.
- Grade DNo effect6-hour cycling in the heat: water vs saline vs no fluidWater and saline gave no significant differences in heart rate, body temperature, plasma sodium or perceived exertion; plasma sodium fell during both. With no fluid, participants stopped about 1.5 hours early.
- No effectNo effectBlood sodium and finishing time in an IronmanSodium tablets did not change post-race serum sodium, finishing time, weight change, rectal temperature or blood pressure compared with placebo or no supplement. Sodium was not needed to prevent hyponatremia in those who took none.
What the sports medicine guidance says
The ACSM position stand says the goal of drinking during exercise is to avoid excessive dehydration (more than 2% body-weight loss from water deficit) and excessive changes in electrolyte balance [1]. It adds that beverages containing electrolytes and carbohydrate can provide benefits over water alone under certain circumstances [1].
Because sweat rates and sweat electrolyte content vary widely, ACSM recommends customized fluid plans and suggests estimating sweat rate by weighing before and after exercise [1].
Water vs saline in a 6-hour ride
In a 1991 study, five men and three women cycled for 6 hours at 30 °C in three trials: water, dilute saline (25 mmol/L sodium) or no fluid [2]. With fluid matched to losses, water and saline gave no significant differences in heart rate, body temperature, blood sodium or perceived effort [2]. Without fluid, participants stopped about 1.5 hours early [2].
It is a tiny study, but it fits the larger picture: in a 413-athlete Ironman trial, extra sodium did not change blood sodium or finishing time [4].
Everyday hydration
Outside long or hot exercise, most people do not lack sodium. The adult Adequate Intake is 1,500 mg/day, and the National Academies advise reducing intakes above 2,300 mg/day; most US and Canadian population groups already consume more than both [3].
Adding a high-sodium electrolyte mix to every glass of water pushes that number higher, which matters most for people with high blood pressure [3]. For race-day salt, see salt tablets for endurance racing.
Quick answers
When are electrolyte drinks worth it?
ACSM says they can help over water in certain circumstances during exercise, and recommends a personal plan based on sweat rate [1]. Our sources do not support them for routine daily hydration [3].
Is drinking too much water dangerous?
ACSM aims to avoid both excessive dehydration (more than 2% body-weight loss) and excessive changes in electrolyte balance, using a plan matched to your sweat rate [1].
How much sodium do adults need?
The adult Adequate Intake is 1,500 mg/day; reducing intakes above 2,300 mg/day is advised [3].
Keep reading
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References
- [1]American College of Sports Medicine position stand. Exercise and fluid replacement. Med Sci Sports Exerc, 2007.
- [2]Fluid replacement during prolonged exercise: effects of water, saline, or no fluid. Med Sci Sports Exerc, 1991.
- [3]Dietary Reference Intakes for Sodium and Potassium: Report Highlights. National Academies of Sciences, Engineering, and Medicine, 2019.
- [4]Sodium supplementation is not required to maintain serum sodium concentrations during an Ironman triathlon. Br J Sports Med, 2006.