Potassium: Health Benefits, Deficiency and Toxicity
Potassium is a mineral found in cells of all living organisms, including those of plants, animals and humans. This mineral is an essential part of electrical and cellular functions within the body’s tissues and organs and plays an important role in metabolism. The heart, kidneys, digestive system, muscles and nerves all rely on potassium to function properly.
Potassium found in the blood and other body fluids is, along with calcium, chloride, magnesium, phosphorus, sodium and sulfur, commonly known as electrolyte. Electrolytes keep bodily fluid levels in balance and help maintain the integrity of the cells. In addition, they generate electrical impulses that enable cells to communicate with each other.
Each of the electrolytes has a specific role in the body with potassium being the major positive ion within the cells. The potassium concentration is balanced against that of another positively charged ion – sodium. The balance between these two electrolytes helps maintain the electric charge of the cell membrane that allows for communication between the nerves and the muscles. Potassium also plays a key part in the process of moving nutrients into cells and waste products out of cells.
Certain health conditions and lifestyle factors can alter the levels of potassium outside the cells. This can result in changing the activity of nerves and muscles, particularly the heart muscle. Low levels cause increased activity, while higher levels cause decreased activity. Thus, abnormally low or high potassium levels can lead to heart-rhythm disturbances or respiratory failure.
Most people’s diets do not provide adequate quantities of potassium. Recommended dietary allowances (RDAs) for potassium expressed in grams per day are shown in the table below. Tolerable upper intake levels for potassium have not been established.
|Age (both genders)||RDA (grams per day)|
|14 years and older||4.7|
However, athletes may require higher intakes because they tend to lose potassium from muscle during exercise and to lesser extent also through increased perspiration.
Health Effects of Potassium
In addition to maintaining the integrity of the cells mentioned earlier, potassium has many other roles in the body. These include helping to metabolize carbohydrates and synthesise proteins, building muscles and allowing them to contract, maintaining stable acid-base balance in the blood, controlling the electrical activity of the heart and ensuring normal body growth.
Maintaining adequate levels of potassium in the body helps prevent bone loss, kidney stones, high blood pressure, keep heart rate in check and lower the risk of stroke.
Potassium deficiency, known as hypokalemia, is a rare condition and typically occurs because of excessive losses of potassium from the body rather than from inadequate potassium intake. Hypokalemia appears to be the most common source of electrolyte imbalance.
The major cause of low potassium is the use of diuretics. Prolonged use of laxatives and steroid medications may also lead to potassium deficiency. In addition, diarrhea, vomiting and severe dehydration often cause a rapid loss of potassium. Other conditions associated with potassium deficiency include eating disorders, low-calorie diets, kidney disorders, alcoholism, diabetic acidosis and colon polyps.
Symptoms of low potassium usually include fatigue, appetite loss, nausea, muscle cramps and muscle weakness, and irregular heartbeats or decreased heart rate. The most severe cases of hypokalemia can be fatal.
The steroid hormone aldosterone controls potassium levels. As a result, excessive amounts of potassium are normally excreted from the body so that it does not cause any harm. However, when kidney problems or other illness cause excess potassium to build up, then a condition known as hyperkalemia occurs. Overuse of potassium supplements or consuming energy-fitness drinks when a person becomes dehydrated can also lead to potassium toxicity. Other possible causes of high potassium include:
- Abnormal breakdown of body proteins
- Adrenal gland failure (Addison’s disease)
- Destruction of red blood cells following severe burns or injury
- Muscle breakdown resulting from exercise, heat or medications
- Severe infection
- Use of certain hypertensives, such as ACE inhibitors
Hyperkalemia can cause heart problems and in its most severe form it can be deadly.
Symptoms of high potassium. Hyperkalemia often does not have any symptoms. However, when symptoms do occur, they include nausea, muscle fatigue and weakness, paralysis, abnormal heart rhythms and slow, weak or absent pulse.
Dietary Sources of Potassium
Boiling dramatically reduces potassium levels of most foods by 50-75%. Therefore, the best source of potassium is fresh foods of all types, especially certain fruits and vegetables. Good sources of potassium include:
- Fruits: apricots, avocado, bananas, cantaloupe, dates, grapefruit, oranges, prunes, raisins and watermelon
- Vegetables: broccoli, carrots, lettuce (especially dark green), parsnip, potatoes (especially sweet potato), spinach, Swiss chard and winter squash (e.g., butternut, acorn)
- Legumes: white beans, lentils and peas
- Bran/bran products
- Nuts and seeds (e.g., pistachios)
- Dairy products: milk and yogurt
- Fish: cod, flounder, halibut, salmon, sardines and tuna
- Fresh meat: pork and poultry
However, patients diagnosed with kidney failure, heart failure or adrenal gland failure and those who take antihypertensives (e.g., ACE inhibitors) should not increase their intake of potassium.