Does Exercise Expel Excess Sodium From the Blood Stream?

You lose sodium when you sweat.
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Physical exertion makes you sweat, and sweat contains sodium. Sweating rates are variable, depending upon environmental factors, level of exertion and personal characteristics. The amount of sodium in sweat is also variable from one person to another, so the amount of sodium you excrete during exercise may or may not expel excess sodium.

Role of Sodium

    Sodium, a positively charged ion, is essential to a number of life-sustaining processes, according to the Linus Pauling Institute of the Oregon State University. Sodium and potassium are continually at work to maintain the appropriate sodium and potassium concentration gradients -- called cell membrane potential -- necessary to sustain life. The cell membrane potential primarily affects nerve impulse transmissions, muscle contraction and cardiac function. Blood volume and blood pressure are also influenced by sodium. The Food and Nutrition Board of the Institute of Medicine recommends 1.2 to 1.5 grams of sodium per day for adults.


    Excess sodium in your blood is a condition called hypernatremia. Normal blood sodium levels are between 135 and 145 milliequivalents per liter. Sweating during exercise can lead to an increased level of sodium in your blood due to fluid losses and greater sodium concentration. Unless fluids are replaced during exercise, instead of excreting excess sodium, you're in danger of developing hypernatremia. However, because each person has a different response to exercise, fluid replacement programs should be customized. You can determine your own sweat rate by weighing yourself before and after exercise, without consuming fluids during exercise. To prevent hypernatremia, fluid intake should not exceed sweat rate. Your blood sodium level can only be gauged by a blood test.


    Too little sodium in your blood is a condition called hyponatremia. Prolonged exercise through sports or work -- events lasting three to four hours or more -- can lead to hyponatremia when excessive amounts of water are consumed during exertion. This condition occurs because sweating excretes electrolytes, which includes sodium. Although sweat glands reabsorb sodium, all sodium is not reabsorbed. When fluids are replaced without replacing electrolytes, excess sodium is removed from your blood stream. If blood sodium falls below recommended levels, hyponatremia occurs.


    When threatened with low levels of sodium, your body conserves sodium by reducing excretions in sweat and urine, according to the Institute of Medicine. During exercise, fluids should be replaced and electrolytes should be kept in balance by consuming sports drinks and snacks to avoid a medical emergency such as hyponatremia or hyponatremia. Rather than using exercise as a means of reducing your blood sodium levels, Harvard Health Publications, in "Dynamic Duos," recommends dietary changes. Increasing your consumption of potassium-rich foods, such as fruits and vegetables, and decreasing your consumption of sodium by eliminating processed foods from your diet is the best way to reduce your blood sodium levels.

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