This page summarises which reference intakes apply in the EU for potassium and for magnesium, in which foods both occur, and which four claims the European Commission has authorised for each of them individually.
Anyone wanting to understand why nutrition texts constantly talk about electrolytes must first know how the body divides up its water. In a person of 70 kilograms, around 42 litres of water are involved. About 28 litres of it are inside the cells, the remaining 14 litres outside — distributed across the interstitial space and about three litres of blood plasma.
Both compartments contain the same quantity of dissolved particles, but entirely different ones. Inside the cell the potassium concentration is about 140 millimoles per litre, outside only 4 to 5. For sodium it is the reverse: around 140 millimoles per litre outside, about 12 inside. Magnesium follows a pattern of its own — most of it is bound, and only fractions are measurable in free form.
This gradient does not arise by itself. It is produced by transport proteins in the cell membrane and held permanently against diffusion pressure. As soon as a cell's energy supply fails, the concentrations equalise.
Cell membranes let water pass, but dissolved ions only through channels and pumps. If the particle concentration rises on one side, water moves there until the pressure is balanced. This principle is called osmosis, and it explains why salt balance and water balance are not considered separately in physiology.
Tonicity describes the effect a solution has on cell volume. An isotonic solution leaves the cell unchanged, a hypotonic one causes it to swell, and a hypertonic one draws water out of it. Infusion solutions and beverages are classified by exactly this property.
In quantitative terms, potassium is the most important positively charged particle inside body cells. An adult carries about 130 to 140 grams of it, stored overwhelmingly in skeletal muscle. Because only one to two percent circulates outside the cells, a serum value reflects the total amount in the body only to a limited extent.
After every electrical signal, a muscle or nerve cell must return to its initial state before it can react again. This return happens because potassium channels open and potassium ions follow their concentration gradient out of the cell. The inside thereby becomes negative again. The sodium-potassium ATPase then brings the potassium back, consuming ATP.
The speed of this process determines how quickly a fibre can be excited in succession. In cardiac muscle the time span is particularly finely tuned, because there every excitation is embedded in a fixed sequence.
| Food | Condition | Potassium per 100 g |
|---|---|---|
| Apricots | dried | 1,370 mg |
| White beans | dried | 1,300 mg |
| Avocado | raw | 485 mg |
| Spinach | raw | 550 mg |
| Potatoes | cooked | 410 mg |
| Banana | raw | 360 mg |
Guide values from common nutrition tables. Variety, cultivation, storage and preparation lead to deviations. Reference figure for potassium: 2,000 mg per day under Annex XIII of Regulation (EU) No 1169/2011.
“Potassium contributes to normal muscle function”
Under Regulation (EU) No 432/2012
“Potassium contributes to normal functioning of the nervous system”
Under Regulation (EU) No 432/2012
Of the roughly 24 to 26 grams of magnesium in an adult body, around 60 percent is deposited in bone mineral, just under 30 percent is in muscle, and the rest is distributed across liver, nervous tissue and other organs. Less than one percent of the total is in blood serum.
Free ATP is not a usable substrate for most enzymes. Only when a magnesium ion attaches to the phosphate groups does the complex arise that kinases, ATPases and polymerases actually process. Magnesium therefore stands indirectly behind every reaction that releases chemical energy from ATP — from muscle contraction to the work of ion pumps.
A second, well-described site of action lies at the pore of certain calcium channels. Magnesium ions can attach there and dampen the influx of calcium. Since incoming calcium in the muscle fibre triggers the signal to shorten, the ratio of the two ions influences how a fibre alternates between tension and relaxation.
| Food | Condition | Magnesium per 100 g |
|---|---|---|
| Pumpkin seeds | dried | 400 mg |
| Sunflower seeds | dried | 330 mg |
| Almonds | raw | 270 mg |
| Rolled oats | Wholegrain | 140 mg |
| Wholegrain bread | baked | 60 mg |
| Spinach | raw | 60 mg |
Guide values from common nutrition tables. Extraction rate, harvest and preparation lead to deviations. Reference figure for magnesium: 375 mg per day under Annex XIII of Regulation (EU) No 1169/2011.
“Magnesium contributes to normal muscle function”
Under Regulation (EU) No 432/2012
“Magnesium contributes to electrolyte balance”
Under Regulation (EU) No 432/2012
Potassium and magnesium often appear in the same sentence in nutrition texts. Legally that is imprecise: Regulation (EU) No 432/2012 lists each claim separately and ties it to exactly one mineral. A joint formulation for two minerals is not provided for under these rules. That is why the four claims stand here side by side, individually.
Potassium contributes to normal muscle function. Magnesium also contributes to normal muscle function. Both claims are authorised separately and apply only to the mineral named in each case.
Potassium contributes to normal functioning of the nervous system.
Magnesium contributes to electrolyte balance.
Under Regulation (EU) No 432/2012
Both minerals are absorbed through the intestine and largely excreted again via the kidneys. Each day the kidney filters many times the amount present in the blood and recovers by far the greatest part of it in the tubules. How much ends up in the urine depends on intake, on fluid balance and on hormonal signals.
A portion also leaves the body through sweat, where sodium and chloride dominate by volume; potassium and magnesium are present at markedly lower concentrations. During prolonged physical exertion in warm conditions, however, these losses add up.
There are some well-documented interactions regarding absorption in the intestine:
Both figures come from Annex XIII of Regulation (EU) No 1169/2011 and serve the labelling of foods. They are reference figures for the percentages on the packaging, not individual recommendations. The values differ because the body contains many times more potassium than magnesium and turns over correspondingly larger amounts.
As a rule, yes. The analysis on the back label lists the dissolved constituents in milligrams per litre, usually including potassium, magnesium, calcium, sodium, chloride, sulfate and bicarbonate. The spread between individual sources is large: for magnesium it ranges from a few milligrams to three-digit values per litre.
These are different compounds of the same mineral. They differ in the proportion of elemental magnesium per gram of substance and in their solubility. Which form may be used in a product is governed by the list of permitted mineral sources in the annex to the relevant EU rules. The authorised wording of the health claim always refers to magnesium as a mineral, not to a particular compound.
Yes, mainly through leaching. Both minerals are water-soluble and partly pass into the liquid when cooked in plenty of water. This effect is strongest for potassium. Short cooking times, little water, steaming, or reusing the cooking water in soups and sauces keep more of it in the finished dish.
No. The guide is an editorial text and stays with reference intakes from EU labelling, content values of foods and the wording of the authorised claims. A quantity recommendation tailored to an individual belongs in the hands of a medical practice or a nutrition professional.
The digital guide continues the tables on this page in extended form, adds a glossary of terms from water and salt balance, and gives the sources of the four claims in the Official Journal of the European Union.
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