You may know that the recommended maximum intake of sodium is 2,300 mg daily, or the equivalent of 1 tsp. of table salt. People with increased risk factors for high blood pressure and heart disease are advised to limit sodium to 1,500 mg daily. In fact, the American Heart Association advises adapting the 1,500 mg maximum across the board. At the same time, the reality is that your body needs sodium to function properly, and the right balance between fluid and sodium is crucial to good health.
Sodium Function
Regulating the balance of fluid -- including blood volume -- in your body is one of the primary roles of sodium. However, sodium also plays a vital role in healthy nerve function, muscle contraction and regulating blood pressure. Sodium also helps you absorb chloride, which enables your body to properly digest and absorb nutrients. In addition, roughly 20 to 40 percent of the calories you burn at rest are used to maintain the right balance of sodium and potassium in and around cell membranes to ensure proper nerve impulse transmission, heart function and muscle contraction, according to Linus Pauling Institute.
Symptoms
When sodium levels are depleted, symptoms may include nausea, fatigue, muscle weakness or cramps, irritability, loss of appetite, headache, confusion or lethargy, according to MayoClinic.com. The medical term for an abnormally low sodium level is hyponatremia. Technically, hyponatremia is diagnosed when blood serum levels of sodium fall below 136 mmol/leter. In severe cases, fainting, seizures, coma, swelling of the brain and brain damage may occur. Acute hyponatremia, if not treated promptly, can be fatal.
Causes
A low intake of sodium is not generally the cause of sodium deficiency. Hyponatremia may occur when you lose excess fluids, consume too much fluid or retain too much fluid. Because you lose sodium during exercise, consuming more water than you need during endurance activities such as marathons can cause an imbalance of fluid and sodium in your body, for example. Hormonal changes due to conditions such as Addison's disease or an underactive thyroid can also lead to low sodium levels. Some pain and antidepressant medications may also cause sodium levels to drop, either as a result of more frequent urination or increased sweating. Additionally, severe vomiting or diarrhea, as well as dehydration in general, may be the culprit. Conditions such as kidney disease, cirrhosis and congestive heart failure that cause you to retain water may also lead to an unhealthy ratio of sodium to fluid.
Considerations
Even individuals on a low-salt diet are unlikely to experience depleted sodium levels based on intake alone. If you have risk factors for hyponatremia, talk with your doctor about monitoring and regulating your balance of fluids and sodium. If you experience symptoms of hyponatremia during prolonged exercise, seek immediate medical attention. For activities lasting longer than an hour, a sports drink that contains electrolytes may help you maintain adequate sodium levels.
References
- MayoClinic.com; Healthy Diet: End the Guesswork With These Nutrition Guidelines: Sodium; February 2011
- American Heart Association; American Heart Association Supports Lower Sodium Limits for Most Americans; March 2009
- MayoClinic.com; Hyponatremia Causes; July 2009
- Linus Pauling Institute: Sodium (Chloride)
- Linus Pauling Institute: Glossary: Membrane Potential
- MayoClinic.com; Hyponatremia Symptoms; July 2009
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