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In this article, we describe:
- the major purposes of this specific nutrient in the human body,
- its experimentally confirmed health uses,
- conventional ways to estimate nutrient status,
- nutrient’s toxicities and deficiencies,
- experimentally confirmed and approved levels of the nutrient intake for different demographics,
- dietary sources of the nutrient.
Potassium, the most abundant intracellular cation, is an essential nutrient that is present in all body tissues and is required for normal cell function because of its role in maintaining intracellular fluid volume and transmembrane electrochemical gradients. Potassium has a strong relationship with sodium, the main regulator of extracellular fluid volume, including plasma volume. It is required for proper nerve transmission, muscle contraction, and kidney function.
About 90% of ingested potassium is absorbed and used to maintain its normal intracellular and extracellular concentrations. Potassium is excreted primarily in the urine, some is excreted in the stool, and a very small amount is lost in sweat. The kidneys control potassium excretion in response to changes in dietary intakes, and potassium excretion increases rapidly in healthy people after potassium consumption, unless body stores are depleted. The kidneys can adapt to variable potassium intakes in healthy individuals, but a minimum of 5 mmol (about 195 mg) potassium is excreted daily in urine. This, combined with other obligatory losses, suggests that potassium balance cannot be achieved with intakes less than about 400–800 mg/day.
Normal serum concentrations of potassium range from about 3.6 to 5.0 mmol/L and are regulated by a variety of mechanisms: diarrhea, vomiting. Kidney disease, use of certain medications, and other conditions can alter potassium excretion or cause transcellular potassium shifts resulting in hypokalemia (serum levels below 3.6 mmol/L) or hyperkalemia (serum levels above 5.0 mmol/L). Otherwise, in healthy individuals with normal kidney function, abnormally low or high blood levels of potassium are rare.
Assessing potassium status is not routinely done in clinical practice, and it is difficult to do because most potassium in the body is inside cells. Although blood potassium levels can provide some indication of potassium status, they often correlate poorly with tissue potassium stores. Other methods to measure potassium status include collecting balance data (measuring net potassium retention and loss); measuring the total amount of potassium or the total amount of exchangeable potassium in the body; and conducting tissue analyses (e.g., muscle biopsies), but all have limitations.
Insufficient potassium intakes can increase blood pressure, kidney stone risk, bone turnover, urinary calcium excretion, and salt sensitivity (meaning that changes in sodium intakes affect blood pressure to a greater than normal extent). Potassium inadequacy can occur with intakes that are below the AI but above the amount required to prevent hypokalemia. The following groups are more likely than others to have poor potassium status: people with inflammatory bowel diseases; people who use certain medications, including diuretics and laxatives; people with pica (persistent eating of non-nutritive substances, such as clay). Because of potassium’s wide-ranging roles in the body, low intakes can increase the risk of illness, examples include: hypertension and stroke; kidney stones; bone health; and blood glucose control and type 2 diabetes.
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In healthy people with normal kidney function, high dietary potassium intakes do not pose a health risk because the kidneys eliminate excess amounts in the urine. However, in people with impaired urinary potassium excretion, people with type 1 diabetes, congestive heart failure, adrenal insufficiency, or liver disease hyperkalemia can occur even with normal intake of potassium.
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Adequate Intakes (AIs) for Potassium*
|Birth to 6 months||400 mg||400 mg|
|7–12 months||860 mg||860 mg|
|1–3 years||2,000 mg||2,000 mg|
|4–8 years||2,300 mg||2,300 mg|
|9–13 years||2,500 mg||2,300 mg|
|14–18 years||3,000 mg||2,300 mg||2,600 mg||2,500 mg|
|19–50 years||3,400 mg||2,600 mg||2,900 mg||2,800 mg|
|51+ years||3,400 mg||2,600 mg|
*The AIs do not apply to individuals with impaired potassium excretion because of medical conditions (e.g., kidney disease) or the use of medications that impair potassium excretion.
Sources of Potassium
Many fruits and vegetables are excellent sources of potassium, as are some legumes (e.g., soybeans) and potatoes. Meats, poultry, fish, milk, yogurt, and nuts also contain potassium. Among starchy foods, whole-wheat flour and brown rice are much higher in potassium than their refined counterparts, white wheat flour and white rice.
Milk, coffee, tea, other nonalcoholic beverages, and potatoes are the top sources of potassium in the diets for adults, whereas milk, fruit juice, potatoes, and fruit are the top sources for children.
It is estimated that the body absorbs about 85%–90% of dietary potassium. The forms of potassium in fruits and vegetables include potassium phosphate, sulfate, citrate, and others, but not potassium chloride (the form used in salt substitutes and some dietary supplements).
Selected Food Sources of Potassium
|Dried apricots, ½ cup||1,101||23|
|Cooked lentils, 1 cup||731||16|
|Dried prunes, ½ cup||699||15|
|Mashed acorn squash, 1 cup||644||14|
|Raisins, ½ cup||618||13|
|Baked potato, flesh only, 1 medium||610||13|
|Canned kidney beans, 1 cup||607||17|
|Orange juice, 1 cup||496||11|
|Boiled soybeans, ½ cup||443||9|
|Banana, 1 medium||422||9|
|Milk, 1 cup||366||8|
|Raw spinach, 2 cups||334||7|
|Grilled chicken breast, boneless, 3 ounces||332||7|
|Yogurt, fruit variety, nonfat, 6 ounces||330||7|
|Cooked Atlantic salmon, farmed, 3 ounces||326||7|
|Top sirloin beef, grilled, 3 ounces||315||7|
|Molasses, 1 tablespoon||308||7|
|Raw tomato, 1 medium||292||6|
|Soymilk, 1 cup||287||6|
|Greek yogurt, plain, 6 ounces||240||5|
|Cooked chopped broccoli, ½ cup||229||5|
|Cantaloupe, cubed, ½ cup||214||5|
|Roasted turkey breast, 3 ounces||212||5|
|Cooked asparagus, ½ cup||202||4|
|Apple, with skin, 1 medium||195||4|
|Cashew nuts, 1 ounce||187||4|
|Brown rice, cooked, 1 cup||154||3|
|Canned in water light tuna, 3 ounces||153||3|
|Coffee, brewed, 1 cup||116||2|
|Iceberg lettuce, shredded, 1 cup||102||2|
|Peanut butter, 1 tablespoon||90||2|
|Black tea, brewed, 1 cup||88||2|
|Flaxseed, whole, 1 tablespoon||84||2|
|Whole-wheat bread, 1 slice||81||2|
|Egg, 1 large||69||1|
|White rice, cooked, 1 cup||54||1|
|White bread, 1 slice||37||1|
|Mozzarella cheese, 1½ ounces||36||1|
|Oil (olive, corn, canola, or soybean), 1 tablespoon||0||0|
- *DV = Daily Value.
- The DV for potassium is 4,700 mg for adults and children aged 4 and older.
- Foods providing 20% or more of the DV are considered to be high sources of a nutrient, but foods providing lower percentages of the DV also contribute to a healthful diet.
- Elson Haas. “Staying Healthy with Nutrition”
- U.S. Department of Health & Human Services: https://ods.od.nih.gov/factsheets/Potassium-HealthProfessional/