Sodium is a metallic element.  When it is combined with chloride to form sodium chloride, we refer to it as salt.  Sodium plays important roles in the regulation of blood volume, blood pressure, pH, nerve and muscle function.

Sodium is found in table salt and as a natural component of many foods, especially seafood and fermented soy products like soy sauce and miso.  It is used as a preservative and flavor enhancer in many processed, packaged and canned foods.

The minimum requirement for sodium is 500 mg per day.  The average North American intake is much higher than this, ten times higher or more.  Sodium deficiency manifests as generalized weakness.  Sodium excess is more of a concern and occurs much more commonly.  Excess sodium is thought to contribute to high blood pressure and premenstrual syndrome via water retention.  An appropriate adult intake for sodium is around 2000 mg – roughly the amount contained in one teaspoon of table salt.