Science

— The three minerals

What's actually in every stick.

Electrolytes are not optional. They regulate fluid balance, muscle contraction, nerve signalling and blood pressure. Miss one and the whole system wobbles. Here's exactly what you get — per single-serve stick, and what each mineral is quietly doing for you.

Element · Na⁺

Sodium — the primary driver.

Most commercial sports drinks cut sodium to make the label look safer. The result: you pee out your water before you rehydrate. 1000 mg is the dose sports-nutrition literature consistently points to for meaningful fluid retention during moderate-to-heavy output.

It's also the dose a normal, sweating human — gardening, commuting, sitting in an overheated meeting room — needs to actually hold on to the water they drink.

What enough sodium feels like: sharper endurance, steadier blood pressure under load, fewer afternoon headaches, less of that flat, washed-out feeling after a big workout or a hot day outside.

Element · K⁺

Potassium — the counter-balance.

Sodium alone isn't enough. Potassium partners with it to regulate cellular fluid, muscle contraction, and blood pressure. Most people in Northern Europe are under-consuming — especially anyone who skips the fruit-and-veg half of their plate more often than they'd admit.

300 mg per stick tops you up without overdoing it, and without the bitter metallic note most cheap potassium sources bring with them.

What enough potassium feels like: stronger, cleaner muscle contractions, fewer 3 AM calf cramps, a steadier heartbeat at threshold, and the kind of long-term blood-pressure benefit your GP keeps telling you to eat more vegetables for.

Element · Mg²⁺

Magnesium — the steady hand.

The third electrolyte most blends forget. Magnesium is involved in over 300 enzymatic reactions in your body. 80 mg is a meaningful top-up without the laxative effect bigger doses bring.

We use magnesium citrate for real bioavailability — not the cheap magnesium oxide that passes through you without ever getting absorbed.

What enough magnesium feels like: deeper sleep, faster recovery between sessions, less soreness the day after, steadier energy through the afternoon — and a noticeably calmer nervous system under stress.

— When to drink it

One stick. Any of these moments.

Repleo is designed to be flexible. You don't need a protocol — you need clean hydration at the moments that actually matter. Here's what our customers already do.

First thing
Wake up rehydrated
One stick in 400 ml of cold water on waking. You've lost fluid and minerals overnight — this replaces both before coffee does its thing.
2 PM slump
Beat the office wall
That heavy, foggy feeling an hour after lunch is almost never about food — it's mild dehydration plus the minerals your morning coffee flushed out. One stick, 15 minutes, and you're back in the room.
Pre / mid session
Hold the ratio
Long ride, long run, hot day, heavy lift? Sip one stick across the session. Matches typical sweat-sodium output for most adults in the 55–85 kg range.
Wind-down
Refill and recover
After the gym, a hot sauna, a long flight, or simply a heavy day. Replaces what was lost — and the magnesium helps you sleep a bit deeper too.

— How we compare

More of what works. Less of what doesn't.

The category is crowded with under-dosed minerals dressed up in fluorescent sugar. We benchmarked Repleo against the three things you're most likely already reaching for — and went the other way on almost every metric that matters.

Averages compiled May 2026 across leading SKUs in each category, per single serving, using publicly available nutrition labels and pharmacy product data.

Sodium per serving · mg

Higher is better for fluid retention during exertion, heat and long work days.

Repleo

1000

Pharmacy rehydration salts Sold for stomach bugs

520

Generic hydration powders Supermarket & gym shelf

340

Electrolyte tabs Effervescent dissolvable tablets

300

Typical sports drink Ready-to-drink bottles

200

Figures are category averages, not individual products. Most pharmacy rehydration salts also add 3–5 g of sugar per serving to drive absorption during illness — useful in that context, much less so for a regular glass of water on your desk.

— The research

What the peer-reviewed literature says.

Our ratios are not opinions. They're informed by published sports-nutrition and hydration research. Some primary sources — cherry-picked for readability.

Sodium · Salt myth

Why healthy eaters often need more sodium, not less

How the 1970s salt guidelines were built for processed-food diets — and the PURE study in NEJM showing optimal intake is actually 3–6 g/day.

NEJM · JAMA · Lancet

Dosing · Competitors

Why most electrolyte products are under-dosed

You lose 500–2000 mg of sodium per hour of exercise. The shelves are full of 200–400 mg products. The maths doesn't work.

ACSM · EFSA · Sports Med

Cognition · Brain fog

Brain fog is dehydration, not tiredness

A 1.59% drop in body water — a level you wouldn't even call thirst — measurably impairs focus, mood and memory in healthy adults.

BJN · BMC · Lancet

Fasting · Low-carb

The fasting & low-carb electrolyte trap

Why keto and fasting accelerate sodium loss — and why most "zero-sugar" electrolyte products still hide maltodextrin on the label.

Keto · Fasting · Maltodextrin

Sugar · Absorption

The science of zero-sugar electrolytes

Sodium-glucose co-transport was discovered in cholera patients. In a healthy gut, sugar isn't required for absorption — and it slows gastric emptying.

Glucose · Gastric emptying

Foundations · Primer

What electrolytes actually are (and what they do)

Sodium, potassium, magnesium — the three minerals that keep water in your body and every cell firing. A clean, no-jargon primer.

Na · K · Mg

— Common questions

The science, demystified.

Isn't 1000 mg of sodium a lot?

It's a lot compared to most hydration drinks — which is the problem with most hydration drinks. The daily reference intake is ~2300 mg, and sweat-sodium losses in warm climates can exceed 700 mg/hr.

For non-athletes or low-sodium-diet individuals, one stick a day pairs well with a normal diet. Athletes may use one to three.

Why no sugar? Don't electrolytes need glucose to be absorbed?

This is the single most repeated myth in the hydration category — and it's built on a misreading of 1970s research.

The original sodium-glucose co-transport studies were done on subjects with cholera-induced diarrhoea. In that very specific, very unwell gut, glucose genuinely helps pull sodium (and therefore water) across the intestinal wall.

In a healthy gut, sodium absorbs perfectly well on its own via multiple independent transporters. Worse, added sugar slows gastric emptying, meaning your drink sits in your stomach longer before it can rehydrate you at all.

Is Stevia safe? Why use it?

Yes. Stevia is EFSA-approved, zero-calorie, non-glycaemic and has 40+ years of safety data. We use it sparingly — just enough to round the mineral edge without pretending to be a soft drink.

Can I have more than one stick per day?

Yes — up to 3 per day is well within the safety envelope for healthy adults. If you're on blood-pressure medication, have kidney disease, or are following a low-sodium medical protocol, check with your clinician first.

Is Repleo suitable for kids?

The formulation is adult-targeted. For children, we recommend halving the dose (mix one stick into 800 ml) and consulting a paediatric professional if it's routine usage rather than occasional.

Why is it made in Denmark specifically?

Small-batch production, tight regulatory oversight, short supply chains, and access to Scandinavian mineral sourcing. It lets us keep quality high and explain exactly what's in every sachet.