Sodium and potassium are unlike other minerals, which are small amounts of inorganic material that participate in the body’s metabolic reactions. Rather, sodium and potassium are considered electrolytes, whose most important function is maintaining proper flow of water inside and outside of body cells. They are part of a delicate balancing mechanism that controls, among other things, blood pressure.

Athletes who lose excessive amounts of sodium through perspiration and people with high blood pressure or those at risk of high blood pressure need to be concerned about maintaining proper electrolyte balance.

FUNCTION

Sodium and potassium exist in and around cells as positively charged particles, known as ions. The water surrounding body cells contains thirty-one times as much sodium as potassium. Inside the cell, the ratio is reversed, with sixteen times as much potassium as sodium. Ions cannot exist in nature. They must be combined with another ion of equal but opposite charge. The most common negatively charged ion paired with both sodium and potassium is chloride. So the most common form of sodium found in nature is sodium chloride (common salt), Potassium also is most often found as potassium chloride.

Together, sodium and potassium provide the electrical potential necessary for cell membranes to be selective as to what they will or will not allow in or out of the cell. The flow of sodium potassium into and out of cells is self-regulated to maintain the proper concentrations of each ion inside the cell. As electrolytes flow across the cell membrane, they carry water with them.

Daily Requirements

It is generally accepted that people need about 1,000 mg of sodium a day, which works out to about 2.5 grams of salt, though most Americans actually eat almost twice as much. Our y potassium requirement is 2,000 to 6,000 mg.

Dietary Sources

We all know of sources of salt in our diet; they are the highly processed foods we like so much, foods such as bacon, canned and instant soup, bouillon, potato chips, pretzels and other snack foods, canned goods, and ham. Additional high-sodium foods are listed in the following table.

Because of the American penchant for salty foods, a typical diet can contain anywhere from 3,000 rng to 7,000 mg of sodium. Low-sodium diets usually provide from 500 to 2,000 mg of sodium. Clearly, as experts have noted, most of us would do well to reduce our salt intake because of the beneficial effect it would have on lowering our blood pressure. This is especially true for people who already have high blood pressure and who are taking medicines to control their pressure, but it also holds true for everyone else.

The fact that the body has a natural balance between sodium and potassium means that you should pay attention to the amount of potassium in your diet. A good way to look at it is that substituting foods with a high potassium content for high-sodium foods will help to reduce the amount of sodium in the fluid outside body cells, lowering blood pressure and improving overall health. Low-sodium diets also help your body to conserve calcium, an important consideration if you are taking extra calcium for osteoporosis.

Food Approximate Sodium Content (MG Per 3 OZ) Approximate Potassium Content (MG Per 3 OZ)

Apples (raw) 0.9 99
Bacon 919 3
Bananas 0.9 333
Beef (dried) 3,870 180
Beef (fresh ground) 42 405
Bread (while) 474 246
Bread (whole wheat) 456 95
Butter 888 21
Cabbage 13 93
Clams 909 180
Green beans (canned) 212 86
Green beans (fresh, cooked) 4 136
Grapefruit 0.9 122
Ham (cooked) 64 292
Margarine 888 21
Milk 45 130
Orange 0.9 180
Peas (fresh, cooked) 0.8 122
Potato 4 453
Raisins 24 687
Sardines (canned) 741 495
Squash 0.9 127
Tomatoes (canned) 117 424
Tomatoes (fresh) 3 366

Raw vegetables provide significant amounts of potassium but their canned versions have lots of added salt and should be avoided. Clams, sardines, and lima beans are rich in sodium but also relatively high in potassium. Some good high-potassium foods are bananas, raisins, potatoes, tomatoes, apples, and oranges. Some other good sources of potassium can be found in the previous table.

Deficiencies

While sodium deficiency can be associated with several diseases, it is found mainly in cases of overexertion, when sodium losses due to perspiration are excessive. Generally, a strenuous workout on the first hot day of the year is more likely to cause sodium depletion than continued exercise, even during hot weather. This is because the body is able to adjust its regulating mechanisms over time to protect itself from adverse conditions. Most people adapt to heat within a few days so that, even though exercise and perspiration may continue, less sodium is lost. Sodium chloride tablets (one or two 1 g tablets for the first few days) or a salt or sport electrolyte solution can be taken to prevent or relieve the condition.

Symptoms of sodium deficiency are muscle and stomach cramps, nausea, and fatigue. Occasionally, pregnant women on sodium-restricted diets develop symptoms of sodium deficiency.

Potassium deficiency usually develops for reasons other than a poor diet. Perhaps the most common reason for concern over potassium intake is the use of diuretic drugs that cause this electrolyte to be lost from the body through the urine. This phenomenon can be controlled to some extent by reducing the amount of sodium in the diet. Normally, the kidneys eliminate large amounts of sodium and some potassium along with water. If there is less sodium to be eliminated, more potassium will be retained.

Another common reason for potassium loss is prolonged diarrhea or vomiting. Fluids in the gut are potassium-rich, and prolonged losses of those fluids call for potassium replenishment. It is also possible, though unusual, to be potassium-deficient because of long-term intravenous therapy with fluids that are potassium-poor.

Symptoms of potassium deficiency include lethargy, poor reflexes, muscle cramps and spasms, weakness and, most important, abnormal heartbeat. If a person already has heart disease, potassium deficiency can make matters worse. Potassium deficiency can also make you more sensitive to digoxin, medicine used to treat heart failure and some abnormal heart rhythms. The symptoms of this problem would be the same as for a digitalis overdose: nausea, vomiting, loss of appetite, abnormal heart rhythms, and heart failure symptoms.

Toxicity

Most health authorities agree that excess sodium increases your risk of high blood pressure. Of course, high blood pressure increases your risk of kidney and heart disease. So while salt is not the sole cause of kidney or heart disease, it is one factor we can control. The practice of salting foods leads to a pattern of increasing the desire for salty foods. This is especially true when salt is added to children’s food. By sparing the salt shaker early in life, we can minimize the desire for salty foods later in life and minimize the potential for high blood pressure and kidney and heart disease.

Salt replacement products are designed lo replace the sodium ion while keeping the sally taste people like. The usual approach taken in formulating a salt replacement is to substitute potassium salts for sodium, but this can produce a metallic taste. Newer products take advantage of a wider variety of replacement ions and do not seek to totally eliminate sodium from the product. This yields a better-tasting salt replacement product.

Excess potassium could accumulate if you ate more than 18g a day, but this is highly unlikely. Potassium toxicity usually develops in people who take a potassium supplement (usually prescribed for people taking a diuretic drug) incorrectly. Potassium toxicity can also occur in people with kidney failure. Symptoms of potassium toxicity are similar to those of potassium deficiency: muscle weakness, pain, abnormal heartbeat, and even heart failure. Intravenous calcium (as calcium gluconate) or Kayexelate resin can be prescribed to fight potassium toxicity.

THERAPEUTIC USES

There is little reason for people to take either potassium or sodium, but they may be needed to counteract a deficiency symptom of either of these electrolytes or in situations where potassium or sodium replacement is medically necessary.

Availability

Salt tablets (I g each) may be purchased without a prescription. A great many potassium products are available by prescription. Some potassium replacement products can be purchased as food supplements, but neither sodium nor potassium supplements should be taken without your doctor’s knowledge. Potassium tablets have caused damage to the stomach or intestine. This risk can be minimized by taking a timed-release potassium product.