Potassium: Reference and Dietary Sources

Abstract

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.

Introduction

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*

AgeMaleFemalePregnancyLactation
Birth to 6 months400 mg400 mg
7–12 months860 mg860 mg
1–3 years2,000 mg2,000 mg
4–8 years2,300 mg2,300 mg
9–13 years2,500 mg2,300 mg
14–18 years3,000 mg2,300 mg2,600 mg2,500 mg
19–50 years3,400 mg2,600 mg2,900 mg2,800 mg
51+ years3,400 mg2,600 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 

FoodMilligrams
(mg) per
serving
Percent
DV*
Dried apricots, ½ cup1,10123
Cooked lentils, 1 cup73116
Dried prunes, ½ cup69915
Mashed acorn squash, 1 cup64414
Raisins, ½ cup61813
Baked potato, flesh only, 1 medium61013
Canned kidney beans, 1 cup60717
Orange juice, 1 cup49611
Boiled soybeans, ½ cup4439
Banana, 1 medium4229
Milk, 1 cup3668
Raw spinach, 2 cups3347
Grilled chicken breast, boneless, 3 ounces3327
Yogurt, fruit variety, nonfat, 6 ounces3307
Cooked Atlantic salmon, farmed, 3 ounces3267
Top sirloin beef, grilled, 3 ounces3157
Molasses, 1 tablespoon3087
Raw tomato, 1 medium2926
Soymilk, 1 cup2876
Greek yogurt, plain, 6 ounces2405
Cooked chopped broccoli, ½ cup2295
Cantaloupe, cubed, ½ cup2145
Roasted turkey breast, 3 ounces2125
Cooked asparagus, ½ cup2024
Apple, with skin, 1 medium1954
Cashew nuts, 1 ounce1874
Brown rice, cooked, 1 cup1543
Canned in water light tuna, 3 ounces1533
Coffee, brewed, 1 cup1162
Iceberg lettuce, shredded, 1 cup1022
Peanut butter, 1 tablespoon902
Black tea, brewed, 1 cup882
Flaxseed, whole, 1 tablespoon842
Whole-wheat bread, 1 slice812
Egg, 1 large691
White rice, cooked, 1 cup541
White bread, 1 slice371
Mozzarella cheese, 1½ ounces361
Oil (olive, corn, canola, or soybean), 1 tablespoon00
  • *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.

References

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