Just Electrolyte

The science

The science,
all the way down

Hydration is simpler than the supplement aisle makes it look, and deeper than a label can hold. Five threads run through everything we make. Skim the chunks, check the figures, and follow any thread as deep as you want to go.

01 · The hook

Why water isn’t enough

Drinking more isn’t always drinking smarter — your body defends concentration, not volume.

Water is a solvent. What it does depends on what’s already dissolved in your blood.

Your body defends concentration, not volume.

Too much, too fast dilutes the sodium you’re trying to hold.

Line chart showing blood sodium falling as water intake climbs, crossing the 135 mmol/L hyponatremia threshold into a shaded danger zone.
Fig. 1 — Blood sodium falls as water volume climbs; past 135 mmol/L is the named condition.
Key figures
135 mmol/Lthe blood-sodium line below which is hyponatremia
5–51 %low blood sodium across screened endurance events
0electrolytes plain water puts back

In this thread

Hyponatremia: when hydration goes too farYou can drink too much water. The named condition, told carefully. Dehydration vs. depletionTwo different problems with two different fixes. Fluid balance 101Osmosis, and why sodium is the master variable.

02 · The credibility

The glucose that moves salt

The most important sugar in hydration isn’t there for taste.

Diagram of the SGLT1 cotransporter: two sodium ions and one glucose molecule crossing the gut wall together, with water following.
Fig. 2 — SGLT1 carries two sodium ions per glucose across the gut wall. Water follows.

Sodium needs a ride across the gut wall. Glucose is the ride.

SGLT1 carries two sodium for every glucose. Water follows.

It’s why Quick Rehydrate has a little dextrose, and nothing more.

Key figures
2:1sodium ions SGLT1 carries per glucose
~4 g/Ldextrose we use — the functional dose
1978the Lancet called it the advance of the century

In this thread

Sodium-glucose cotransportThe discovery that moves water. Oral rehydration therapyThe salt-and-sugar solution that saved millions. Why dextrose, not sugarSame molecule family, different job.

03 · The spine

Why we left everything else out

Most of what’s in the bottle isn’t electrolyte.

Color, sweetener, acid, flavor — there to make a drink feel like something.

None of it does a job for your body.

One test per ingredient: does it work, or is it out?

An ingredient list with most lines struck through — dyes, added sugar, citric acid, flavors, sweeteners, preservatives — leaving only sodium, potassium, magnesium, calcium, and dextrose.
Fig. 3 — The test every ingredient has to pass: does it do a job, or not?
Key figures
5ingredients that earned their place: 4 minerals + dextrose
0dyes, sweeteners, or added flavors
1test every ingredient had to pass

In this thread

What “just” meansThe thesis. If you read one, read this. Why no dyesColor does one job, with an evidence trail. Why no added sugarSweetener and color travel together; we carry neither.

04 · The athlete

What your sweat is actually losing

Your sweat isn’t the same as anyone else’s.

A distribution curve of sweat sodium across people, ranging about 10 to 90 mmol/L, with the high tail above 60 marked as the roughly one-in-five salty sweaters.
Fig. 4 — Sweat sodium across people; the accent tail above ~60 mmol/L is the salty sweaters.

Sodium loss varies almost ten-fold between people.

Roughly one in five are “salty sweaters.”

Generic guidance fails the people who sweat hardest.

Key figures
~9×range in sweat sodium between people
~1 in 5endurance athletes who are “salty sweaters”
10–90 mmol/Lthe span, low end to high

In this thread

The salty sweaterWhy sweat sodium varies, and how to tell if you’re high. Sweat-rate mathA weigh-in / weigh-out protocol for your own number. Dosing for enduranceTurning losses into a per-hour plan.

05 · The trust

What’s not on the label

The most important part of an electrolyte never makes the front of the box.

Mineral salts can carry trace heavy metals from the ground they come from.

There’s no US limit specific to supplement heavy metals.

The only honest answer is testing — and showing it.

A Supplement Facts panel with a faint second panel behind it labeled 'what isn't listed' — the contaminants a label doesn't show.
Fig. 5 — The panel, and the part of the story a panel never prints.
Key figures
47 %of protein powders over a contaminant threshold (2024 study)
0US federal caps specific to supplement heavy metals
4metals the standard test screens: As, Cd, Pb, Hg

In this thread

Heavy metals in supplementsA documented problem, fairly stated. How testing actually worksICP-MS and the Certificate of Analysis. Our testing standardPublished once a first batch is tested and cleared.soon

The whole map

Every article, two ways in

The threads above are the front doors. Behind them is a growing library — foundations, mechanism and formula, the case for subtraction, purity and safety, and the practical use cases. Start with one of these, or browse the whole thing filtered by what you came for or how deep you want to go.

If you read one What “just” means The mechanism Sodium-glucose cotransport For athletes The salty sweater
Browse every article Or read the FAQ

Read the label, then decide

The shop lists every number these articles cite again, per format.

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