The amount of sodium lost in a day really depends on your activity level, environment and natural variations in sodium loss from person to person. Athletes in a hot climate, for example, can expect to lose far more sodium than a sedentary person in a cool region. Sodium losses also depend on your sodium intake. On average, daily sodium loss ranges from 1,500 to 6,000 mg depending on age, gender and circumstance.
Sodium Balance
In a healthy body, the kidneys regulate the amount of sodium in your body. Too much or too little sodium can cause health problems. So, if you eat more salt, the kidneys increase the excretion rate through urine. The Institute of Medicine of the National Academies suggests that the average adult person gets around 1.5 g -- or 1,500 mg -- of sodium per day to replace that which is lost through normal sweating. This doesn't take into account variations in lifestyle and environment, however.
Urine
Some medical centers perform a test known as the "24 hours sodium output measurement" to check for low sodium levels. A normal adult reading is between 100 and 260 mEq/24-hours, according to Vanderbilt University Medical Center. This works out at approximately 2,300 to 6,000 mg of sodium lost over the course of a whole day. Drinking too much water may lower the results as the salt levels become diluted in the body.
Athletes
Low sodium blood levels, or hyponatremia, frequently occurs in endurance athletes -- particularly when athletes drink water with no added electrolytes while training. Your sweat has between 2.25 and 3.4 g of salt in each liter, with as much as a liter lost per hour during vigorous exercise, according to Rice University's SportsMedWeb. That means that a four-hour race could remove between 9 and 14 g of salt, which includes sodium. In practice, however, your body will also regulate the amount of salt lost.
Considerations
Humid, hot conditions may increase your rate of sodium loss. For example, a 2008 report in the "Journal of Occupational Medicine and Toxicology" found that men exercising in warm summer-like conditions lost more sodium than those exercising in cooler conditions. They predict a loss of 4,800 to 6,000 mg of sodium during a standard work shift in hot conditions. Researchers also point out that people can become acclimatized to hotter conditions and lose less sodium over time.
References
- Institute of Medicine of the National Academies; Dietary Reference Intakes: Water, Potassium, Sodium, Chloride, and Sulfate; February 2004
- Vanderbilt University Medical Center; 24 Hour Urine Sodium Output Measurement; May 5, 2011
- Rice University; SportsMedWeb -- Salt and the Ultraendurance Athlete; 1997
- "Journal of Occupational Medicine and Toxicology"; Sweat Rate and Sodium Loss During Work in the Heat; Graham P. Bates, Veronica S. Miller; 2008
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