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Walk down any drink aisle and "electrolyte water" is everywhere, promising better hydration than plain water for a dollar or two more. Most of it barely moves the needle. The electrolyte that actually helps your body hold onto fluid is sodium, and the drink that beats water hardest in lab testing isn't a flavored water at all. It's a plain rehydration solution, dosed specifically for sodium.
What "electrolyte water" promises versus what's in it
The pitch is consistent across brands: added electrolytes, better hydration, usually stamped on the label right next to a fruit flavor. What varies wildly is the dose. A splash of sea salt or a trace of potassium citrate technically qualifies as "electrolytes added," whether or not it's enough to change anything in your body.
Contrast that with oral rehydration solution (ORS), the formula the World Health Organization has used for decades to treat dehydration from diarrheal illness worldwide. ORS isn't flavored for the checkout aisle. It's dosed for one job: sodium, at a level high enough to measurably change how much fluid your body keeps.
Why sodium is the one that matters
Electrolytes aren't a hydration multiplier bolted onto water. Sodium's job is retention: it signals your kidneys to hold onto water rather than pass it straight through as urine. A 1996 trial (Shirreffs et al.) showed this directly: dehydrated men who drank more fluid than they'd sweated out still didn't retain it without enough sodium alongside it. The surplus was simply passed as urine.
The dose of sodium decides whether a drink beats water. The flavor never does.
Potassium plays a supporting role inside cells, but sodium is what drives the fluid-retention effect measured in hydration trials. Magnesium, common in mineral-water marketing, isn't part of that mechanism at all. It's a different mineral, doing a different job, in a different category of drink.
What's actually in the bottle
Composition isn't a mystery. The 2016 Beverage Hydration Index (BHI) trial (Maughan et al.) measured exactly what its 13 test drinks contained, sodium and potassium included, alongside how well each one hydrated. Converting the paper's own figures to a familiar label unit tells the story plainly:
| Drink | Sodium (mg/L) | Potassium (mg/L) |
|---|---|---|
| Oral rehydration solution | ~1,265 | ~780 |
| Skimmed milk | ~435 | ~1,565 |
| Full-fat milk | ~415 | ~1,600 |
| Orange juice | ~23 | ~1,290 |
| Plain water | 0 (benchmark) | 0 (benchmark) |
Oral rehydration solution carried roughly 55 times more sodium than orange juice in the same trial, and about three times more than either type of milk. That gap is not a coincidence. It's the entire reason ORS scored where it did.
Which drinks actually out-hydrate water
Composition on its own is just a label. What matters is whether it changes anything measurable, and the BHI trial checked that too, tracking urine output for four hours after each drink. Once the numbers are corrected for how much water each drink itself contains (milk and juice carry less water per liter than a glass of water), a clear, sodium-shaped pattern holds up:
| Drink | Hydration vs water |
|---|---|
| Oral rehydration solution | 1.50 |
| Skimmed milk | 1.44 |
| Full-fat milk | 1.32 |
| Water | 1.00 (benchmark) |
| Orange juice | ≈1.24 (not significant) |
Orange juice's edge shrinks once corrected and stops being statistically real. A mainstream sports drink, tested in the same trial, never beat water either, corrected or not. It carried plenty of marketing and not enough sodium.
How to read the label yourself
Our honest answer: check the sodium line on the nutrition panel, not the word "electrolyte" on the front. A drink built for real fluid loss, sweat, illness, or a long endurance session, needs a meaningfully high sodium dose. A drink built for the checkout aisle usually doesn't, and there's no rule that says it has to.
That's the same logic behind how Brim credits these drinks: a sports drink and coconut water both log close to water rather than above it (96% and 90%, Premium), because neither carried the sodium dose that moved the needle in testing. Real-world tracking should stay conservative wherever the label is doing the talking and the lab data isn't backing it up.
To compare what's actually in your own bottle against a published mineral panel, the Mineral Water Comparison tool breaks out sodium, calcium and magnesium side by side.
When you need none of it
For most days, the honest answer is none. You're not draining sodium through sweat if you spent the day at a desk, and ordinary meals, bread, cheese, soup, most anything processed, already carry more sodium than most people are short on.
The case for reaching past plain water gets real only when the loss is real too: heavy, visible sweat over a long session, vomiting or diarrhea, or a hard endurance effort well past a casual workout. Outside those, a normal day of meals and water has already covered it.
Key takeaways
Sodium, not flavor, is the electrolyte that actually helps your body hold onto fluid.
In the 2016 BHI trial, oral rehydration solution beat every other drink tested because of its sodium dose, not its label.
A mainstream sports drink never beat water in that trial, corrected or not. More sodium is what would have changed that.
Check the sodium line, not the marketing. Brim credits sports drinks and coconut water close to water, not above it (Premium).
Frequently asked
Is electrolyte water actually more hydrating than plain water?
Usually not by much. In the 2016 Beverage Hydration Index trial, a mainstream sports drink never beat water. The drink that clearly did, oral rehydration solution, worked because of a deliberately high sodium dose, not because it was labeled "electrolyte."
Which electrolyte matters most for hydration?
Sodium. It signals your kidneys to hold onto water instead of passing it straight through as urine. Potassium matters for other reasons, but the fluid-retention effect measured in hydration trials comes from sodium.
Do I need electrolyte water on a normal day?
No. Ordinary meals already supply plenty of sodium, and a desk day does not create the kind of fluid loss that would need replacing.
What is oral rehydration solution and why does it score so high?
ORS is a simple sodium-and-glucose formula that the World Health Organization has used for decades to treat dehydration from illness worldwide. It scored highest in the 2016 BHI trial because it is dosed specifically for sodium, not for taste.
How does Brim credit electrolyte and sports drinks?
Sports drinks and coconut water log at 96% and 90% of water (Premium), close to water rather than above it, matching the trial finding that a mainstream sports drink never out-hydrated plain water.
Keep reading
Sources
- 1.Maughan et al., "A randomized trial to assess the potential of different beverages to affect hydration status" (Beverage Hydration Index), Am. J. Clin. Nutr. (2016)
- 2.Shirreffs, Taylor, Leiper & Maughan, "Post-exercise rehydration in man: effects of volume consumed and drink sodium content," Medicine & Science in Sports & Exercise (1996)
