Potassium: benefits, foods rich in it and blood pressure

What potassium does

Potassium is an essential mineral the body uses as an electrolyte: a particle with an electrical charge, indispensable for the body's "electrical" functions. It is the main cation inside cells — sodium dominates outside — and much of its work depends on that split. Its basic jobs are three. First, keeping the balance of fluids inside and outside the cell, which affects hydration and pressure. Second, allowing nerves to generate and transmit their electrical signals. And third, making muscle contraction possible, from the biceps to the heart, which is nothing more than a muscle that beats thanks, in part, to potassium. To this is added its role in acid-base balance and, above all, in the regulation of blood pressure, where it acts as a counterweight to sodium.

Potassium and blood pressure: the balance with sodium

If potassium deserves a prominent place in any nutrition guide, it is for its effect on blood pressure, and to understand it you have to talk about its dance partner: sodium. These two minerals work in opposite directions. Sodium (which arrives mainly with salt and ultra-processed foods) makes the body retain fluid and raises pressure; potassium helps eliminate the excess sodium in the urine and relaxes the walls of the blood vessels, lowering it. The problem with the modern diet is that this balance is broken: we eat too much sodium and far too little potassium, exactly the opposite of what blood pressure needs. That is why raising dietary potassium while reducing salt is one of the best-supported nutritional levers for caring for blood pressure, and the basis of patterns like the DASH diet.

The symptoms of deficiency

Unlike other minerals, a significant potassium shortfall (hypokalaemia) rarely comes from eating little alone: there are almost always losses involved. The most common causes are vomiting, diarrhoea, very heavy sweating and the use of diuretics. When potassium drops, the symptoms affect mainly the muscles and the heart:

• Muscle weakness and fatigue.
• Muscle cramps.
• General tiredness and lack of energy.
• Constipation (the gut is muscle too).
• In severe cases, heart rhythm disturbances (arrhythmias).

Where potassium is (and the banana myth)

The banana is the symbol of potassium, but the myth needs qualifying: it provides a reasonable amount, but is far from the richest source. The true champions are potatoes and sweet potatoes with skin, legumes (lentils, beans, chickpeas), spinach and other dark leafy greens, avocado, tomato — especially concentrate or in sauce — squash, nuts and dried fruit such as apricots and raisins. Fish, yoghurt and citrus also contribute. In other words: potassium is in almost everything plant-based and lightly processed, and the challenge for most is not finding exotic sources, but eating enough fruit, vegetables and legumes. A practical detail: potassium dissolves into water, so boiling vegetables and throwing away the water carries part of it off; steaming, baking or roasting keeps far more.

Who is most at risk of deficiency

Because potassium deficiency comes mainly from losses, the risk groups differ from those of other minerals. At greater risk are those who take diuretics (very common for blood pressure and the heart), which increase potassium elimination; people with prolonged vomiting or diarrhoea, who lose potassium through the digestive tract; endurance athletes or anyone who sweats a lot in hot environments, though this loss is usually replaced by diet; and those with certain digestive diseases or eating disorders. To this is added, at a milder level, the large majority of the population who simply do not eat enough fruit and vegetables and fall below the recommended potassium, without reaching a clinical deficiency but losing its benefit on blood pressure.

The important warning: kidneys, heart and medications

Here is the part that sets potassium apart from almost any other nutrition advice, and that no responsible guide can omit. The "eat more potassium" message is good for the healthy general population, but NOT for everyone. In a person with healthy kidneys, the body eliminates surplus potassium without a problem. But when the kidney does not work well — chronic kidney disease — potassium builds up in the blood and can cause hyperkalaemia, a dangerous state capable of causing serious arrhythmias. The risk rises with certain very common blood-pressure and heart medications (ACE inhibitors, ARBs, potassium-sparing diuretics) and with salt substitutes, which are usually potassium chloride. For these people, increasing potassium on their own can be outright dangerous.

When (and how) to increase potassium

For most healthy people, the conclusion is simple and reassuring: no supplements or calculations are needed, just eat more plants. Several portions of fruit, vegetables and legumes a day, spread out, cover potassium amply and, along the way, raise fibre and lower pressure twice over (more potassium, fewer ultra-processed foods). Baking or steaming instead of boiling and draining helps keep it. Potassium supplements, on the other hand, are not a self-service product: in high doses they can affect the heart, so their use is reserved for specific medical situations and under supervision. And for those with kidney disease or on the medications mentioned, the strategy is the opposite and must be individualised with the doctor. The general rule, once again: food first, and potassium in a pill only when indicated.

Potassium is a good example of why knowing your real diet is worth more than fixating on a single star food, and here Renzy helps you without keeping counts by hand. By photographing your meals you see at a glance how much fruit, vegetables, legumes and potato enter your week — the potassium sources — and along the way you spot whether your pattern is heavy on ultra-processed foods, the main source of the sodium that unbalances the scale. With that data you can move the two levers that care for blood pressure: more plants, less processed. Because with potassium, more than almost any other mineral, the answer is on the plate and not in the bottle — and, if you have any kidney or heart problem, always alongside your doctor.