What is potassium?
Potassium, sodium and chloride comprise the electrolyte family of minerals. Called electrolytes because they conduct electricity when dissolved in water, these minerals work together closely. About 95% of the potassium in the body is stored within cells, while sodium and chloride are predominantly located outside the cell.
Potassium is especially important in regulating the activity of muscles and nerves. The frequency and degree to which our muscles contract, and the degree to which our nerves become excitable, both depend heavily on the presence of potassium in the right amount.
How it Functions
What is the function of potassium?
Muscle contraction and nerve transmission
Potassium plays an important role in muscle contraction and nerve transmission. Many of our muscle and nerve cells have specialized channels for moving potassium in and out of the cell. Sometimes potassium moves freely in and out, and sometimes a special energy-driven pump is required. When the movement of potassium is blocked, or when potassium is deficient in the diet, activity of both muscles and nerves can become compromised.
Other roles for potassium
Potassium is involved in the storage of carbohydrates for use by muscles as fuel. It is also important in maintaining the body’s proper electrolyte and acid-base (pH) balance. Potassium may also counteract the increased urinary calcium loss caused by the high-salt diets typical of most Americans, thus helping to prevent bones from thinning out at a fast rate.
What are deficiency symptoms for potassium?
Potassium occurs naturally in a wide variety of foods. As a result, dietary deficiency of potassium is uncommon. However, if you experience excessive fluid loss, through vomiting, diarrhea or sweating, or if you take certain medications (see section on Drug-Nutrient Interactions below), you may be at risk for potassium deficiency.
In addition, a diet that is high in sodium and low in potassium can negatively impact potassium status. While the typical American diet, which is high in sodium-containing processed foods and low in fruits and vegetables, contains about two times more sodium than potassium, many health experts recommend taking in at least five times more potassium than sodium.
The symptoms of potassium deficiency include muscle weakness, confusion, irritability, fatigue, and heart disturbances. Athletes with low potassium stores may tire more easily during exercise, as potassium deficiency causes a decrease in glycogen (the fuel used by exercising muscles) storage.
What are toxicity symptoms for potassium?
Elevated blood levels of potassium can be toxic, and may cause an irregular heartbeat or even heart attack. Under most circumstances, the body maintains blood levels of potassium within a tight range, so it is not usually possible to produce symptoms of toxicity through intake of potassium-containing foods and/or supplements.However, high intakes of potassium salts (potassium chloride and potassium bicarbonate) may cause nausea, vomiting, diarrhea, and/or ulcers.
In addition, the kidneys play an important role in eliminating excess potassium from the body, so if you suffer from kidney disease, you must severely limit your intake of potassium. To date, the National Academy of Sciences has not established a Tolerable Upper Intake Level (UL) for potassium.
Impact of Cooking, Storage and Processing
How do cooking, storage, or processing affect potassium?
Potassium losses from cooking of high-potassium foods can be significant. In the case of spinach for example, potassium levels have been shown to drop from 6.9 to 3.0 grams in 3 and 1/2 ounces of spinach after blanching for several minutes (a loss of about 56%).
Sometimes this passage of potassium out of foods can be nutritionally beneficial. For example, parsley tea often contains significant amounts of potassium because this mineral is leached out of the parsley leaves and into the hot tea water.
Factors that Affect Function
What factors might contribute to a deficiency of potassium?
In addition to poor dietary intake, overuse of muscles, as might occur in excessive physical activity, is a factor that can increase a person's need for potassium. Any events that draw excessive fluid out of the body - including excessive sweating, diarrhea, overuse of diuretics (including caffeine-containing beverages), poor water intake, or adherence to a ketogenic diet - can increase the need for potassium.
Since potassium functions in close cooperation with sodium, imbalanced intake of salt (sodium chloride) can also increase a person's need for potassium. Higher amounts of potassium are also needed by persons with high blood pressure.
What medications affect potassium?
The following medications may cause an increase in blood levels of potassium:
Angiotensin-converting enzyme (ACE) inhibitors, such as quinapril, ramipril, enalapril, captopril, are used to treat high blood pressure. These medications may increase potassium levels, especially when taken by individuals with kidney disease.
Potassium-sparing diuretics, including thiazide and loop diuretics, decrease the excretion of potassium in the urine, thereby causing blood levels of potassium to increase.
Non-steroidal anti-inflammatory medications, such as ibuprofen (Advil) and indomethacin, may cause an increase in blood levels of potassium by damaging the kidneys.
Heparin, an anticoagulant prescription medication used to prevent blood clots after surgery, may increase potassium levels.
Sulfonamide antibiotics may increase potassium levels, especially when taken by individuals with kidney disease.
The following medications may cause a decrease in blood levels of potassium:
Prolonged use of stimulant laxatives, such as those that contain senna, can cause excessive loss of potassium.
Cisplatin, a chemotherapy medication, may cause excessive loss of potassium.
Steroidal anti-inflammatory medications, including prednisone and cortisone, increase the loss of potassium in the urine.
Neomycin, an antibacterial drug, decreases blood levels of potassium by reducing the absorption of dietary potassium and/or increasing urinary excretion of potassium.
Theopylline and aminopylline, medications used in the treatment of asthma, may promote potassium deficiency.
Tobramycin, an antibiotic that is administered intravenously, can cause potassium depletion.
Diuretics, or “water pills”, flush fluid out of the body, and are often prescribed for the treatment of high blood pressure. While certain diuretics “spare” potassium, others decrease potassium levels. Because potassium can be helpful in maintaining normal blood pressure, these diuretics may make it even more difficult to treat high blood pressure.
How do other nutrients interact with potassium?
Through a mechanism known as the "sodium-potassium" pump, sodium and potassium work together closely to initiate muscle contraction and nerve transmission, and to maintain the body’s normal distribution of fluid. Most of the potassium in your body is stored inside of your cells, while most of the sodium in your body is stored in the fluid that surrounds your cells.
During muscle contraction and nerve transmission, potassium leaves the cell and sodium enters the cell via the "sodium-potassium pump." This transfer causes a change in electrical charge within the cell, which initiates the muscle contraction or the nerve impulse. Because sodium attracts water, once the muscle contraction or nerve impulse is initiated, the sodium is immediately pumped out of the cell to prevent water from entering the cell and causing the cell to swell or burst, and potassium is pumped back into the cell.
Potassium is known to decrease the excretion of calcium. As a result, increasing the amount of potassium-containing foods in your diet may be helpful in maintaining the density and strength of your bones.
What health conditions require special emphasis on potassium?
Potassium may play a role in the prevention and/or treatment of the following health conditions:
High blood pressure
Inflammatory bowel disease
Potassium depletion due to excessive fluid loss from diarrhea, vomiting, or sweating
Form in Dietary Supplements
What forms of potassium are found in dietary supplements?
Potassium is found in dietary supplements as potassium salts (potassium chloride and potassium bicarbonate) and potassium chelates (potassium citrate and potassium aspartate). It is also available in food-based supplements. In an attempt to prevent the health problems (see Toxicity Symptoms above) associated with high intakes of potassium salts, the United States Food and Drug Administration restricts the amount of potassium in non-food based supplements to 99 mg per serving.