Potassium in food: sources, cooking and common myths

Potassium is involved in cell function, nerve transmission and muscle contraction, including the heart's. The body keeps its blood concentration within a narrow range, and the kidneys eliminate any excess.

The European Food Safety Authority (EFSA) proposes an adequate intake of 3,500 mg per day for adults, including during pregnancy, and 4,000 mg during breastfeeding. This is a population-level reference, not a target to hit down to the milligram, nor an invitation to take a supplement. Other authorities use different values depending on their methods.

These references don't apply to people who poorly eliminate potassium because of a disease or medication. The right amount then depends on kidney function, blood potassium level, treatments, and whether dialysis is involved.

Values from the US NIH table (servings converted), for illustration only.

Content varies with the serving size, variety, ripeness and processing. Weight for weight, a dried fruit is more concentrated than a fresh one. Juice provides potassium but less fiber than the whole fruit. Spreading sources across meals (a starchy food or legume, vegetables, a fruit, a dairy product) is generally enough: there's no need for a daily banana.

Potassium is water-soluble. Cooking in a large volume of water lets some of it leach into the liquid, more so when the food is cut small and cooking lasts longer. Steaming, oven cooking, or a short cooking time preserve more of it.

For someone with no medical restriction, this isn't a reason to change habits: choose the cooking method based on taste and the recipe. For someone prescribed a potassium restriction, the approach changes. The NIDDK, the US institute for kidney disease, advises for example cutting potatoes into small cubes or grating them, then boiling them in a large volume of water. A 2024 study on double-cooking potatoes confirms that cooking time and protocol influence the reduction achieved.

Draining a can of fruit or vegetables removes some of the potassium that has leached into the liquid, without making the food low in potassium. Also check the ingredient list: potassium chloride sometimes replaces salt in soups, tomato sauces or "reduced salt" products. A low-sodium product isn't necessarily suitable for someone who needs to limit potassium.

Salt substitutes based on potassium chloride contain, according to the NIH, 440 to 2,800 mg of potassium per teaspoon. Herbs, spices, garlic or a squeeze of lemon can season a dish without that risk.

Hypokalemia rarely comes from a shortfall on the plate. It more often results from diarrhea or vomiting, laxative overuse, certain diuretics, or very heavy sweating. Frequent, substantial licorice consumption can also lower potassium and raise blood pressure, as noted by Anses (the French food safety agency) in a toxicovigilance report: see our article on licorice, blood pressure and interactions.

Cramps or fatigue aren't enough to draw a conclusion: only a blood test can confirm it. For supplements and the risk of hyperkalemia, see also the article potassium supplements.

"Bananas are the best source of potassium" It's a convenient source, not a benchmark. Dried apricots, lentils, potatoes, dairy and fish provide as much or more per serving.

"The more potassium you eat, the better" In a healthy person, dietary potassium rarely causes problems, since the kidneys eliminate the excess. Kidney disease or certain medications change that rule, and a supplement or salt substitute concentrates the risk of error.

"Boiling removes all the potassium" No. The effect depends on the food, how it's cut, the volume of water, the cooking time, and whether the water is discarded. It's a reduction technique for certain situations, not a way to get a potassium-free food.