Electrolytes: who actually needs them

Day four or five of a cut, a lot of people stand up too quickly and see stars. The internet calls this detox. It is almost always sodium, water and a bit of low-carbohydrate physiology behaving exactly as expected.

Three minerals do most of the work here — sodium, potassium and magnesium — and understanding them is the difference between fixing a real problem for pennies and buying a subscription you did not need.

Why week one hits you

Two things happen at once when the plan starts. You cut out most processed food, which is where the large majority of the sodium in a typical diet comes from, so your intake falls off a cliff overnight without you having touched a salt shaker. And you burn through stored glycogen, which is held with water — as that water leaves, sodium leaves with it.

Add higher step counts and a training block, and you are losing more through sweat on top. The result is the classic first-week package: light-headedness on standing, a dull headache, flat sessions, and legs that feel like they belong to somebody less enthusiastic.

This is also why 3.5 litres of plain water can make things worse rather than better in that first week. Volume without any sodium at all is not the fix for a sodium shift.

The three that matter

Sodium is the one that causes the acute symptoms. Guidance for the general population is to keep intake below roughly 2,300 milligrams a day, and most people eating processed food are well above it — but a cut can push you the other way fast, and going too low has its own cost.

Potassium is the one almost nobody gets enough of. Adequate intake sits in the region of 2,600 to 3,400 milligrams a day depending on sex, and typical intakes fall short. It is not a supplement problem: potatoes, beans, lentils, yogurt, leafy greens, bananas and tomatoes will move it further than a capsule.

Magnesium is the one with the most claims attached and the least drama. Reference intakes sit around 310 to 420 milligrams a day, plenty of people run below that, and the food fixes are nuts, seeds, wholegrains, beans and dark greens. If you supplement it, note that the upper limit for supplemental magnesium is well below the food intake figure, and that the cheapest form on the shelf is also the one most likely to send you to the bathroom.

• Sodium: the acute one. A pinch of salt in water or on food usually fixes week-one light-headedness within a day
• Potassium: chronically low for most people, and fixed by potatoes, beans, yogurt and greens rather than by pills
• Magnesium: commonly short of the reference intake; nuts, seeds, wholegrains and dark greens are the first move
• Sweat losses are mostly sodium. Long sessions in heat are the situation that genuinely justifies a drink mix
• Very large volumes of plain water taken quickly, with very little sodium, is the combination to avoid

When a sachet is worth the money

There is a real case for an electrolyte drink, and it is narrower than the marketing suggests. Sessions running well past an hour, training in genuine heat, someone who sweats heavily and salts visibly, or a day where illness has cost you fluid and food. In those cases a mix does something a glass of water does not.

Outside them, the honest version is a quarter teaspoon of table salt stirred into a large glass of water, plus a potassium-rich food at two meals. It costs almost nothing, it works within hours, and it is the same active ingredient as the expensive box.

“Most electrolyte products are salt with a story. The salt is doing the work.”

A protocol for the first week

• Salt your food deliberately for the first seven to ten days rather than avoiding the shaker on principle
• If you feel light-headed on standing, take a large glass of water with a quarter teaspoon of salt and sit down for ten minutes
• Put a potassium-rich food in two meals a day — a potato, a portion of beans, a pot of yogurt or a large handful of greens
• Spread the 3.5 litres across the whole day rather than drinking a litre in one go
• Persistent dizziness, fainting, cramping or palpitations is a reason to stop and get checked, not a reason to buy a bigger tub

Who should not follow any of this

Adding sodium is not universally safe advice, and this is the point in the article to be blunt about it. If you have high blood pressure, kidney disease, heart failure, or you take diuretics, ACE inhibitors or other medication affecting fluid and electrolyte balance, do not add salt or potassium on the strength of a fitness article. Your targets are set by your clinician, and potassium in particular can be genuinely dangerous to raise without supervision in kidney disease.

The same applies to anyone whose symptoms are severe or persistent. Week-one wobble that resolves in a day is physiology. Ongoing dizziness is a reason to see somebody.