Sodium Intake Calculator (Beta)

The calculator assumes a base sweat rate of 1.00 L/h [Learn More].

• Sweat rate can vary greatly between individuals due to genetic factors, body weight, surface area of the skin, heat acclimation, and metabolic efficiency [Link, Link].
• Despite individual variability, we know that sweat rates during exercise typically range between 0.5 and 2.0 L/h [Link], and that it is pretty common to see sweat rates of 1 L/h [Link].
• For instance, one study found an average whole-body sweat rate of 1.21 L/h across a wide range of sports and environmental conditions. Controlling for participants’ weight revealed a whole-body sweat rate of about 15.3 ml/kg/h [Link].

Sweat sodium concentration increases linearly as sweat rate increases [Learn More].

• The faster you sweat, the fewer electrolytes your sweat glands are able to reabsorb before your sweat evaporates. [Link, Link]. This can result in significantly greater sweat sodium concentration. 
• One study found that as exercise intensity increased from 50% to 90% HR_max, sweat rate increased by 328% and sweat sodium concentration increased by 311% [Link].
• To initiate this effect, an average-sized individual (1.8 m2 body surface area) must sweat at a rate of 0.3 L/h or more [Link]. While this threshold varies by person, it is quite low—so you can assume that the faster you sweat, the saltier your sweat will be.

The calculator assumes a base sweat sodium concentration of 830 mg/L [Learn More].

• Sweat sodium concentration can differ greatly between individuals and exercise environments due to variations in heat acclimation and sweat rate [Link].
• Biological sex, ambient temperature, and the type of exercise performed may have small effects on sweat sodium concentration, but other variables such as humidity, age, race/ethnicity, hydration status, dietary sodium intake, and aerobic fitness do not appear to affect sweat sodium concentration [Link, Link].
• Despite individual variability, normal sweat sodium concentrations across a range of sports and environmental conditions appear to fall between 590 and 1,070 mg/L. The science-backed average is about 830 mg/L [Link].

People with high blood pressure (hypertensives) tend to be salt-sensitive due to underlying metabolic issues [Learn More]. For these people, it oftentimes makes sense to limit sodium intake while they work on improving their metabolic health. There are many other common causes of high blood pressure to consider as well. One thing is super clear, though: hypertensives tend to see great results with higher potassium intakes. This is likely not only due to adequate potassium, but also because eating potassium-rich foods often means ditching processed foods for whole foods.

A significant human adaptation, which sets us apart from all other primates, is our greater ability to conserve water [Link]. Even though we sweat more than any other organism on a size-matched basis (besides horses), we’ve adapted to consume roughly half as much water as our closest primate relatives.

Despite this, bad advice persists: “Drink 8 glasses of water per day!” Let’s settle the debate: barring medical or unique factors that may blunt one’s thirst mechanism, drinking to thirst is sufficient to maintain fluid balance, and drinking beyond it puts you at risk of diluting blood sodium levels [Learn More].

Dehydration can decrease sweat rate [Learn More].

• The less hydrated you are, the less you'll sweat. Dehydration raises the threshold body temp to start sweating AND decreases sweat rate at a given core body temperature [Link].
• A 1985 study in the Journal of Applied Physiology analyzed 9 men exercising under different hydration conditions. While somewhat dehydrated men (1–3% net water loss) had a 5 to 15% lower sweat rate, severely dehydrated men (5–7% water loss) had a 50% lower sweat rate [Link].

Dehydration’s effect on sweat sodium concentration is currently unclear [Learn More].

• Sweat sodium concentration has increased, decreased, and been unaffected in association with dehydration [Link]. Further research is needed.

Dietary sodium intake may affect sweat sodium concentration [Learn More].

• Some studies of sustained higher salt intakes show a bump in sweat sodium concentration, but others do not [Link, Link]. The explanation for this inconsistency may be that transient fluctuations in sodium intake (for less than 3 days) produce different results than prolonged changes (over days or weeks), but more research is needed to provide conclusive results [Link].
• The takeaway is that sweat sodium concentration varies with habitual (but not acute) sodium intake. If you consume an extra gram of sodium on a super sweaty day, your sweat glands probably won’t notice—but your energy levels will thank you.

Dietary sodium intake does not affect sweat rate [Learn More].

• We have not found any study—of any duration—which shows a connection between sweat rate and sodium intake [Link].

It makes sense why high sodium intakes are conflated with poor health outcomes. The Standard American Diet (SAD) is notoriously high in processed foods, which contribute more than 70% of U.S. adults’ sodium intake [Link]. But when folks make the healthy decision to replace processed foods with whole foods (particularly when combined with other healthy decisions like exercise) they often end up sodium deficient.

Better aerobic fitness increases sweat rate [Learn More].

• Aerobic training unlocks adaptations that increase sweat rate. In one study [Link], endurance-trained men and women had 123% and 144% higher sweat rates than sedentary controls, respectively. Another paper found that older folks had similar sweat rates to younger folks when matched for aerobic capacity [Link]. Fitness keeps your sweat glands functioning.

Better aerobic fitness has no direct effect on sweat sodium concentration [Learn More].

• Aerobic fitness (measured as relative VO_2max), does not seem to affect sweat sodium concentration [Link].

Biological sex does not directly influence sweat rate in a significant way [Learn More].

• Females tend to sweat at a lower rate than males, but this is mostly due to lower cooling demands. On average, females have lower cooling requirements than males due to their typically lower body mass and surface area [Link].
• Other potential contributors to lower female sweat rates—which need corroboration—are much less significant. However, they include [Link]:
  • Mechanisms that minimize fluid loss
  • Sex hormones that have been shown to promote fluid retention
  • A greater reliance on convective heat loss (basically, heat lost to the wind) compared with evaporative heat loss (heat lost by sweating)
  • Lower sweat output stimulated by exercise compared with males.

Biological sex does not directly influence sweat sodium concentration [Link].

• Males show significantly higher sweat sodium concentrations than females, but this is likely due to differences in body mass [Link, Link, Link]. Greater body mass increases sweat rate, and the faster we sweat, the saltier our sweat is [Link, Link, Link].

Wear reasonably breathable, cool clothing to reduce sweat rate [Learn More].

• Warm and impermeable winter clothing can increase sweat rate. One analysis conducted at -4°F showed that cutting cold weather clothes’ warmth factor in half reduced subjects’ sweat rates by a factor of 5 [Link]. When tinkering with your layers, try to stay reasonably warm while minimizing perspiration. Read this article to learn more about winter hydration.

Both cold weather and high altitude present unique hydration challenges [Learn more].

In cold temperatures, you:

• Sweat more due to higher metabolic demands (from bulky clothing or higher work rates) [Link, Link]
• Lose more fluids and electrolytes through urine [Link]
• Lose more water through respiration [Link]
• Don’t get as thirsty [Link]

And at high altitudes, you ALSO:

• Sweat more due to higher metabolic demands from less oxygen intake [Link]
• Lose more fluids and electrolytes through urine [Link]
• Don’t get as thirsty, though this issue wears off in a few days [Link]
• Should be mindful of Acute Mountain Sickness—and possibly restrict fluid and electrolyte intake to prevent swelling after 1 week of altitude exposure [Link]

Pregnant and nursing women may consider bumping up their sodium intakes a gram or two to replace what’s going to their children [Learn more].

• Salt restriction during pregnancy is often encouraged to help women avoid pre-eclampsia, despite uncertain conclusions around whether sodium restriction actually helps. More concerning is the link between low-salt diets and slowed fetal growth, lower birth weight, and other complications [Link].
• Sodium remains vital postpartum as well. Some research on exclusively breast-fed infants suggests that inadequate electrolyte content adversely affects a child’s health down the road [Link]. Furthermore, a good chunk of animal literature suggests that sodium supplementation increases lactation in mammals [Link], and anecdotally we’ve heard similar stories from salty mamas in our community.

Hyperhidrosis, postural orthostatic tachycardia syndrome (POTS), and Addison’s disease all have the potential to contribute to sodium imbalance or deficiency, and typically require increased sodium intakes to manage symptoms. If you or a loved one has one of these conditions, consult a trusted medical professional to determine how much of a sodium shortfall may need to be made up.