By Sebastian Madlangbayan, founder of Cleonse: the world's cleanest 3-ingredient organic electrolyte.
French grey sea salt — sel gris — is unrefined salt hand-raked from clay-bottomed evaporation ponds on France's Atlantic coast, mostly around Guérande in Brittany. It's grey because it touches the clay. It holds about 13% residual moisture and 85+ trace minerals. The honest part: those minerals are present in very small amounts.
I use it in Cleonse. It's one of three ingredients. So I have an obvious incentive to oversell it, which is exactly why I want to write the skeptical version of this article rather than the marketing version.
How it's actually made
The Guérande marshes sit on the southern edge of Brittany, and the method hasn't fundamentally changed in about a thousand years.
Seawater is let in on the high tide and moved through a series of channels called étiers into progressively shallower and saltier basins. By the time it reaches the final crystallisation ponds — the oeillets, ten to forty centimetres deep — the brine is concentrated enough that sun and wind pull salt crystals out of it. There are roughly 7,000 of these ponds in the Guérande complex.
The people who run them are called paludiers. They manage water levels by hand, pond by pond, day by day, because the salinity has to stay in a narrow band or the crystals don't form correctly. When the salt is ready, the paludier drags it toward the pond edge with a long-handled wooden tool — a las or cimauge — and piles it to drain.
Harvest runs roughly June through September. No heat is applied. No solvent, no wash, no bleach, no anti-caking agent. The salt goes from the pan to the pile to the bag.
Since 2012, "Sel de Guérande" has held European Protected Geographical Indication (PGI/IGP) status, which ties the name to the place and the method. Some producers also carry Nature & Progrès certification on top of that.
Why it's grey and why it's damp
Two questions I get constantly.
The grey comes from contact with the pond floor. Fleur de sel — the expensive stuff — is the thin crust that forms on the surface of the brine on still, dry afternoons and is skimmed off before it ever sinks. Sel gris is the salt that settles to the bottom and is raked up off the clay. It picks up fine clay particles, plus algae and plankton residue from the marsh. That's the colour.
The damp is because it's never kiln-dried. Sel gris typically carries around 13% residual moisture. That's why it clumps in the bag, why it dissolves a bit differently than table salt, and why a gram of it contains slightly less sodium chloride than a gram of bone-dry refined salt.
Both of those are consequences of not processing it. They're not features someone engineered.
What "refined" actually means
This is the comparison that matters, and it's usually described vaguely, so here's the concrete version.
Industrial table salt is typically produced by solution mining — pumping water underground to dissolve a salt deposit, then bringing the brine up and evaporating it mechanically in vacuum pans. The brine is chemically treated to precipitate out calcium and magnesium compounds before crystallisation. The result is around 99.9% sodium chloride.
Then things get added back:
- An anti-caking agent so it pours in humidity — commonly sodium ferrocyanide, calcium silicate, or silicon dioxide.
- Iodine, usually as potassium iodide, because iodised salt was one of the most successful public-health interventions of the 20th century.
- Sometimes dextrose, in tiny amounts, to stabilise the iodine.
So refined table salt is not a worse product in every respect. Iodisation genuinely prevented an enormous amount of disease. But it is a manufactured product: stripped to near-pure sodium chloride, then re-dosed.
Sel gris is the opposite process. Nothing taken out, nothing put back.
Now the part most brands skip
Here's the claim you see everywhere, including on my own product: 85+ trace minerals.
That number is real in the sense that if you run unrefined sea salt through a sensitive enough instrument, you will detect a long list of elements. It is not real in the sense that most people read it — as "this salt is a meaningful source of minerals."
Two things you should know.
First, the quantities are tiny. The best public data on this comes from specialty salt analyses. A 2020 study in Foods analysed pink salt sold in Australia and found that while it did contain calcium, iron, magnesium and potassium, one teaspoon (5 g) "did not make a clinically significant contribution to nutrient intake." To get a meaningful amount, you'd need over 30 grams of salt a day — which the authors calculated would blow past sodium guidelines by roughly 592%. Grey sea salt is a different salt from a different place, but the arithmetic is the same arithmetic: trace minerals are, by definition, present in trace amounts, and salt is a food you eat by the gram, not the tablespoon.
Second, "84 minerals" or "85 minerals" is a count of detected elements, not a count of nutrients. Of the elements typically listed, roughly fifteen have confirmed biological roles in humans and about seven more are possibly essential. The rest are not recognised nutrients. Some of them — trace arsenic, lead, mercury — are things you'd list as contaminants in any other context, present at parts-per-million to parts-per-billion levels. A high element count is not automatically a good thing.
So if a brand tells you their salt's trace minerals will fix your cramps, replace a supplement, or transform your hydration, they are ahead of the evidence. Including if that brand is me.
So why do I still use it?
Because the honest argument for unrefined salt was never the mineral count. It's this:
Nothing was removed and nothing was added.
That's it. That's the whole pitch. No wash, no vacuum pan, no chemical precipitation step, no anti-caking agent, no flow agent, no dextrose carrier. The thing in the packet is the thing that came out of the marsh, dried by sun and wind, raked by hand.
I built Cleonse around a three-ingredient constraint — organic lemon or strawberry powder, organic cane sugar, French grey sea salt — and the point of that constraint is that every line on the panel is a food, not a processing aid. Refined salt with an anti-caking agent would technically still read "salt" on the label. It would also quietly break the rule.
The trace minerals are a consequence of that choice, not the reason for it. They come along because nothing stripped them out. If they do something for you at these doses, great. I'm not going to build a claim on it.
What's actually doing the work: sodium
Here's the electrolyte that matters, and it isn't subtle.
One 30 g Cleonse stick delivers 500 mg of sodium — in 16 oz (473 ml) of water. That is a real, measurable dose of the electrolyte you lose in the largest quantity in sweat, and it's the number I'd want you to judge the product on.
Sweat sodium concentration varies enormously between people — roughly 200 mg/L at the low end to over 2,300 mg/L for very salty sweaters. Sodium is what you're replacing. Chloride comes along with it. Everything else in unrefined salt is measured in milligrams and micrograms.
If someone in this category is advertising trace minerals louder than they advertise sodium, check the sodium number.
Refined table salt vs French grey sea salt
| Refined table salt | French grey sea salt (sel gris) | |
|---|---|---|
| Source | Solution-mined brine or washed sea salt | Atlantic seawater, coastal marshes (Guérande, Île de Ré, Noirmoutier) |
| Method | Mechanical vacuum evaporation, chemically treated brine | Solar and wind evaporation, hand-raked |
| Purity | ~99.9% sodium chloride | Unrefined; retains residual minerals and moisture |
| Moisture | Bone dry | ~13% residual |
| Colour | White | Grey (clay, algae, plankton) |
| Anti-caking agent | Usually yes | No |
| Added iodine | Usually yes | No |
| Trace minerals | Largely removed in refining | Present — in trace amounts |
| Sodium per gram | Slightly higher (drier, purer) | Slightly lower (moisture + minerals) |
| Honest advantage | Iodine; cheap; consistent | Nothing removed, nothing added |
Three caveats I'd want you to hear
I'd rather you get these from me than from a comment section.
1. Grey sea salt is not iodised. If unrefined salt is your only salt and you don't eat much dairy, seafood, or eggs, iodine is worth thinking about. This is a genuine advantage of table salt and I'm not going to pretend otherwise. Cleonse is a drink mix, not your salt shaker, so it's unlikely to be your primary source either way — but it's the right caveat to name.
2. Sea salt is not immune to the ocean. Studies sampling commercial salt brands worldwide have found microplastics in the large majority of them, sea salt included. "Unrefined" means less processing, not a guarantee of zero contamination. Anyone selling you sea salt as perfectly pure is skipping this.
3. It isn't a supplement. If you're low on magnesium or potassium, salt is not the fix — not grey salt, not pink salt, not any salt. Dosed magnesium and potassium come from products that put dosed magnesium and potassium on the panel, and Cleonse doesn't. That's a real trade-off in my formula, and I've written about it in our Re-Lyte comparison.
The short version
French grey sea salt is a genuinely different product from refined table salt: hand-harvested, unprocessed, nothing stripped, nothing added. That's a sourcing story, and it's a true one.
The 85+ trace minerals are real and they are small. They're evidence of minimal processing, not a dose of anything. The sodium — 500 mg per stick — is what does the work.
If you want a fuller breakdown of what belongs on a clean label and what doesn't, start with what is the cleanest electrolyte.
Try The World's Cleanest Electrolyte™
Three ingredients. 500mg sodium. Nothing artificial. Free shipping and a 30-day guarantee.
Shop CleonseFrequently asked questions
What is French grey sea salt? French grey sea salt, or sel gris, is unrefined sea salt harvested by hand from clay-bottomed solar evaporation ponds on France's Atlantic coast, most famously around Guérande in Brittany. It gets its grey colour from contact with the clay pond floor and retains around 13% moisture because it is never kiln-dried. It contains no anti-caking agents and no added iodine.
Is French grey sea salt healthier than table salt? Not in the way it's usually marketed. Both are predominantly sodium chloride, and the trace minerals in grey sea salt are present in amounts too small to meaningfully affect nutrient intake. The defensible difference is processing: grey sea salt has nothing removed and nothing added, while refined table salt is stripped to about 99.9% sodium chloride and then dosed with an anti-caking agent and iodine.
Do the 85+ trace minerals in sea salt actually do anything? At the amounts you'd get from a drink mix, almost certainly not much. A 2020 analysis of pink salt found that a teaspoon contained minerals but made no clinically significant contribution to nutrient intake, and reaching a meaningful dose would require over 30 grams of salt a day. Treat the trace mineral count as evidence of minimal processing, not as a nutritional claim.
How much sodium is in a Cleonse stick? Each 30 g stick delivers 500 mg of sodium, mixed into 16 oz (473 ml) of water. Sodium is the headline electrolyte in the product and the number worth judging it on.
Why is grey sea salt damp and clumpy? Because it retains roughly 13% residual moisture from the salt marsh and has no anti-caking agent added. Refined salt pours freely because it has been mechanically dried to near-zero moisture and dosed with a flow agent such as silicon dioxide or sodium ferrocyanide.
Does French grey sea salt contain iodine? Not added iodine. Unrefined sea salt contains naturally occurring iodine only at trace levels, far below the amount in iodised table salt. If unrefined salt is your only salt, it's worth making sure iodine is coming from somewhere else in your diet.
Keep reading
- Sea salt vs table salt: does it matter for electrolytes?
- How to read an electrolyte label (without getting fooled)
- Cleonse facts: the full ingredient and nutrition breakdown
Cleonse: three ingredients — organic lemon or strawberry powder, organic cane sugar, French grey sea salt. 500 mg sodium and 85+ trace minerals per 30 g stick, mixed into 16 oz of water. No stevia, no artificial sweeteners, no dyes, no gums, no fillers. $33 for 10 sticks, $66 for 30, $110 for 60, free shipping, 30-day guarantee. See the product.
Related: What is the cleanest electrolyte · Cleonse vs Redmond Re-Lyte · The 3-ingredient electrolyte drink
Editor's note and sources
I founded Cleonse, which uses French grey sea salt as one of its three ingredients. The 85+ trace mineral figure is our own sourcing claim and is not independently verified here — and, as the article argues at length, it should not drive your buying decision. Salt composition varies by harvest, producer and season. Figures were checked against public sources in July 2026.
- Sel gris — harvesting method, moisture content, relation to fleur de sel: https://en.wikipedia.org/wiki/Sel_gris
- Guérande salt marshes, paludiers, oeillets, PGI status since 2012 (Taste France): https://www.tastefrance.com/us/magazine/french-pantry/salt-guerande-salt-marshes-taste-sea
- Fayet-Moore F. et al., "An Analysis of the Mineral Composition of Pink Salt Available in Australia," Foods 2020: https://www.mdpi.com/2304-8158/9/10/1490
- Science-Based Medicine on specialty salt mineral claims and element counts: https://sciencebasedmedicine.org/pink-himalayan-sea-salt-an-update/
- Kim J-S. et al., "Global Pattern of Microplastics in Commercial Food-Grade Salts," Environmental Science & Technology 2018: https://pubs.acs.org/doi/10.1021/acs.est.8b04180
- Greenpeace summary: over 90% of sampled global salt brands contained microplastics: https://www.greenpeace.org/international/press-release/18975/over-90-of-sampled-salt-brands-globally-found-to-contain-microplastics/
- Sweat sodium concentration ranges, Precision Fuel & Hydration: https://www.precisionhydration.com/performance-advice/hydration/how-to-estimate-sweat-salt-loss/
Nothing here is medical advice. Cleonse supports hydration; it does not diagnose, treat, or prevent any condition.