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Potassium

Potassium

Other name(s):

KCl, potassium chloride

General description

Potassium is a highly reactive, metallic element normally found in nature as a "salt," such as potassium chloride or potassium nitrate. It plays a critical role in generating nerve signals that are required for skeletal smooth muscle and heart muscle contractions. It helps sustain normal blood pressure. Potassium is also important for maintaining electrolyte and pH balance (the acidity of the blood and other bodily fluids).

Most potassium in our body is found in muscle and lean tissue cells. Potassium is available in most foods and is readily absorbed by the body.

Potassium salts are water soluble, and potassium is found in solution as a positively charged particle (cation). Potassium is the major cation inside living cells.

Potassium is needed to maintain the electrochemical potential across cell membranes. This potential is crucial in conducting nerve signals, which then lead to skeletal muscle contraction, hormone release, and smooth muscle and heart contraction.

Potassium levels are regulated in the kidneys by a hormone called aldosterone.

Medically valid uses

Adequate levels of potassium have been shown to reduce hypertension (high blood pressure).

A diet rich in fruits, vegetables, and high-potassium, low-fat dairy products has been shown to decrease blood pressure and decrease calcium excretion. However, supplements of potassium are not generally recommended due to the potential for serious toxic effects, including cardiac arrest.

Unsubstantiated claims

Please note that this section reports on claims that have NOT yet been substantiated through scientific studies.

Research in animals indicates that potassium may play a role in preventing strokes and may also protect the kidney from damage that occurs in hypertension. The effects in humans are not known.

Recommended intake

There is no Recommended Dietary Allowance (RDA) or Dietary Recommended Intake (DRI) for potassium. The normal dietary intake of potassium is approximately 1,000 to 2,000 mg per day for adults, with no increased intake recommended during pregnancy and breastfeeding.

Potassium may be taken in liquid or tablet form.

Photo of a variety of fruit

Potassium is widely available in foods because it is a major component of living cells. Particularly good sources include fruits and vegetables (such as bananas, citrus fruits, and tomatoes), milk and yogurt, and fresh meats. The following table lists the potassium content of some of the better food sources.

Food

Potassium content

Tomato paste ( cup)

1,221 mg

Avocado (1 medium)

1,097 mg

Potato, baked w/ skin (1 potato)

844 mg

Navy beans (1 cup, boiled)

669 mg

Prunes, dried (10 prunes)

626 mg

Dates, dried (10 dates)

541 mg

Cantaloupe, raw (1 cup pieces)

494 mg

Honeydew, raw (1 cup pieces)

461 mg

Banana, raw (1 medium)

451 mg

Milk, skim (8 fl oz)

406 mg

Milk, whole (8 fl oz)

370 mg

Yogurt (6 oz)

350 mg

Apricots, raw (3 medium)

313 mg

Nectarine, raw (1 medium)

288 mg

Tomato, raw (1 tomato)

273 mg

Orange, raw (1 medium)

250 mg

Strawberries, raw (1 cup)

247 mg

Pear, raw (1 medium)

208 mg

Peach, raw (1 medium)

171 mg

Although potassium is lost during cooking, adding potassium chloride to cooking water may prevent the potassium from leaching out into the cooking water. Minimal amounts of water should be used when cooking vegetables. Steaming foods will also help retain potassium levels.

Muscle weakness, lethargy, and cardiac arrhythmias (irregular heartbeats) can result from low potassium (hypokalemia). Low potassium concentration in the blood makes it difficult for the nerves to fire signals, thereby inhibiting muscle contraction. Other signs of hypokalemia include nausea, bone fragility, adrenal hypertrophy (enlarged adrenal gland), decreased growth rate, weight loss, and irrational behavior.

Deficiency does not occur under normal circumstances, due to the wide availability of potassium in foods. However, prolonged vomiting and diarrhea, diuretic use, laxative and steroid abuse, anorexia, chronic starvation, and disturbances in hormonal regulation can cause a deficiency.

People using certain diuretics (water pills) may be prescribed a potassium supplement by their physician. However, a health care professional should carefully supervise any patient taking more than 300 mg of potassium supplements per day.

Increased potassium leads to decreased calcium excretion (usually a desirable effect).

Side effects, toxicity, and interactions

Hyperkalemia (high potassium concentration in the blood) is dangerous. The effects of too much potassium are similar to the effects of low levels, and include muscle weakness, cardiac arrhythmias and cardiac arrest. Cells have difficulty responding to nerve impulses with too much potassium, thus affecting muscle contractions.

Hyperkalemia can result from malfunctioning kidneys, severe hormonal imbalances, and excessive supplement use.

Crushing injuries that cause cell damage and red blood cell hemolysis can release excess potassium into the bloodstream, potentially causing hyperkalemia, as well. Strenuous exercise can lead to a rise in blood potassium levels, but is not usually dangerous.

Hyperkalemia (high potassium concentration in the blood) can cause cardiac arrest. Potassium supplements are generally not recommended unless specifically advised by a physician.

Women who are pregnant or breastfeeding should consult a physician before taking any mineral supplements.

Certain diuretics (water pills) can deplete potassium in the blood. Note: Potassium-sparing diuretics are available and should not be taken with potassium supplements. If you are taking a diuretic, consult your physician before taking any potassium supplements.

Additional information

People may use potassium chloride as a salt replacement when trying to lower their blood pressure. Usually this does not lead to hyperkalemia because the bitter taste of potassium chloride tends to limit how much people use. Talk to your doctor, however, before trying this strategy. Research suggests that the ratio of sodium to potassium may be as important as the presence of sodium in lowering blood pressure. Low potassium levels may play a bigger role in hypertension than high levels of sodium.

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