Sodium helps nerve impulse function and muscle contraction. It also helps the body regulate body fluids and affects blood pressure. 

How Much: Adequate intake (AI) is 1,500 milligrams (mg) for adults. 

Too Much: Tolerable upper limit (UL) = 2,300 mg.

Too Little: Sodium deficiency is rare except for those who work or exercise in a hot climate. Symptoms for these individuals include, headache, nausea, dizziness, fatigue, muscle cramps and fainting.

Foods: Salt, soy sauce, processed meats, canned soups, monosodium glutamate (MSG) and fast food.

Interactions: Corticosteroids, diuretics, NSAIDS, opiates and tricyclic antidepressants.

Research Notes: One study found women who consumed a high-salt diet (9 grams [g] daily) lost 33 percent more calcium and 23 percent more of a bone protein than those on a low-salt diet (2 g per day).