When sodium is lost alone, water flows into the cells, causing cellular swelling and symptoms of water intoxication. These may include anorexia, fatigue, apathy, and muscle twitching. With low sodium, there is also usually poor carbohydrate metabolism.

When we lose sodium through sweat, the best treatment is not just replacement with salt tablets but by drinking salt solution prepared by adding about one-fifth teaspoon (1 gram) of salt to a quart of water; this will replenish us with a concentration similar to that in perspiration. Most salt tablets contain 1 gram of salt. One tablet can be taken with a quart of water, or two or three tablets with two or three quarts of water to replace greater fluid losses. It is ideal to add some potassium as well, about 500 mg. per quart.

Requirements: There is no specific RDA for sodium because almost everyone consumes more than needed. The Senate Select Committee on Nutrition and Human Needs suggests about 5 grams of salt, which provides about 2 grams of sodium, per day. We really need only about 0.5 gram to maintain the body's salt concentration and probably 1-2 grams to be safe, unless we perspire a great deal or are active exercisers.

Most people consume excess sodium. The average American diet contains about 3-6 grams of sodium, or about 7-15 grams of salt, per day. There are tribes that cook their food in seawater and consume huge amounts of salt, up to 40 grams per day. These people have a higher incidence of hypertension.

Another way to evaluate salt intake is to break down how it comes into the diet. The average diet derives about 3-4 grams of naturally occurring salt in food, 4-5 grams from eating processed foods, and another 3-4 grams from salt added in cooking or at the table. That adds up to about 10-13 grams of sodium chloride, or approximately 4-5 grams of sodium, per day, twice the suggested level. Higher sodium intake has evolved in the last century or two as a result of habit, taste, and social customs. It is probably most helpful to limit sodium to 1-3 grams per day and to obtain at least as much potassium as sodium, although the ideal potassium intake is double that of sodium. These precautions reduce the risk of sodium- sensitive hypertension and other effects of excess sodium. Potassium chloride as a salt substitute may be one helpful way to maintain this sodium-potassium balance. Eating more fresh fruits and vegetables is a good safeguard against problems with high blood pressure or diseases of the cardiovascular system.