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Celtic Sea Salt vs. Table Salt: Moisture, Sodium, Iodine and Additives Compared

By · Reviewed · 15 sources

Celtic Sea Salt Vs. Table Salt

One is gray, damp and crunchy. The other is white, dry and pours like sand. Yet both are sodium chloride, and once they dissolve in food, Celtic sea salt and table salt taste the same.1 “Celtic sea salt” usually means Celtic Sea Salt, a brand founded in 1976,2 and the biggest practical gap isn’t flavor at all: iodized table salt is an important source of iodine,3 and the gray salt has none added. Which one you grab comes down to whether the salt goes on top of the food or into it.

Side by side

Celtic sea salt (gray salt)Table salt
What it isSea salt from evaporation pans; “Celtic Sea Salt” is a brand nameFine-grained sodium chloride
How it’s madeIn Guérande, France, gray salt crystallizes on the clay bottom of salt pans and is gathered by hand4Mined from salt deposits and processed to a fine texture (AHA);5 tiny, uniform crystals from rapid vacuum evaporation (ATK)1
Where it comes fromThe brand’s pages we read don’t say where Light Grey Celtic is harvested6Many countries; 2024 world production about 280 million tonnes, led by China and the United States7
ColorGray, from fine clay particles (Guérande)White
MoistureUp to 12% for Guérande gray salt;4 the brand says brine stays in its salt6Dry; anticaking agents help it pour1
IngredientsAdditives prohibited in Guérande salt4Morton iodized: salt, calcium silicate (anticaking agent), dextrose, potassium iodide8
Weight per teaspoon6.0 g, from the Light Grey Celtic label (1.5 g per ¼ teaspoon)9About 6 g (ATK);10 Morton’s label: 1.5 g per ¼ teaspoon8
Sodium per teaspoonAbout 1,920 mg, from the label (480 mg per ¼ teaspoon)92,325 mg (Tufts);11 about 2,300 mg (FDA);12 2,400 mg (AHA)5
IodineNone added; the brand reports about 0.2 ppm naturally present6Iodized salt in the US: 45 mcg per gram;3 plain salt: none added
FlavorSalty, with a damp crunch when eaten wholeClean and salty
PriceNo dated, sourced retail comparison foundNo dated, sourced retail comparison found

The Celtic weight and sodium figures are the brand’s own label, not an independent measurement. The three table-salt sodium figures come from three sources and differ slightly, so we show all three.

How each is made

Gray salt. The best-documented gray salt comes from Guérande, a protected salt-making area on France’s Atlantic coast that spans two départements, Loire-Atlantique and Morbihan. Its official specification says gray salt forms as crystals on the clay bottom of the final pans, and the harvester, the paludier, gathers it by hand from the brine. The salt drains for several hours, isn’t washed, and can’t contain additives. The gray comes from insoluble matter, which the specification describes as fine particles of clay.4 And it’s not a tiny operation. The local intercommunal authority gives 16,000 tonnes of gray salt and 700 tonnes of fleur de sel a year from the Guérande salt marshes, on an undated page.13

Celtic Sea Salt is a brand of this style of salt. The company says its founder, Dr. Jacques Delangre, coined the word “Celtic.” Its FAQ names Spanish sites for two other products, but on the pages we read, it gives no harvest site for Light Grey Celtic.6 So “Celtic” on a label tells you the brand. It doesn’t tell you the salt is from Brittany or Guérande.

Table salt. The American Heart Association describes table salt as mined from salt deposits and processed to a fine texture that’s easy to mix.5 America’s Test Kitchen says its tiny, uniform crystals come from rapid vacuum evaporation and mentions the usual anticaking agents.1 Salt is an industrial commodity on a huge scale. The US Geological Survey puts 2024 world production at about 280 million tonnes, led by China (55 million) and the United States (40 million).7

What’s in each, besides salt

Sodium chloride. The Codex Alimentarius standard requires food-grade salt to be at least 97% sodium chloride on a dry basis, whether it comes from the sea, rock deposits or brine.14 The AHA says table salt and most sea salts are about 40% sodium.5

Sodium per spoon. Light Grey Celtic’s label gives 480 mg of sodium in 1.5 g, about 32% by our math.9 That’s lower than the roughly 40% the AHA gives for most salts. The label doesn’t explain the gap. Moisture could be part of it, since the brand says brine stays in its salt,6 but we found no analysis that confirms it. Either way, it’s not a low-sodium salt. The FDA’s Daily Value for sodium is less than 2,300 mg a day, about a teaspoon of table salt.12

Iodine. This is the biggest practical difference. US iodized salt contains 45 mcg of iodine per gram, and iodization in the US is voluntary.3 Under US rules, iodized salt has to say “This salt supplies iodide, a necessary nutrient,” and salt without it has to say it doesn’t.15 Celtic Sea Salt says it adds no iodine and that a natural trace of about 0.2 ppm is present,6 which by our math is about 0.2 mcg per gram. The NIH Office of Dietary Supplements notes that specialty salts like sea salt usually aren’t iodized. If your kitchen has switched entirely to gray salt, you’ve given up that iodine. See iodized vs. non-iodized salt.

Additives. Read the label. Morton’s iodized table salt lists salt, calcium silicate (an anticaking agent), dextrose and potassium iodide.8 Under US rules, salt with an anticaking agent can be labeled “free flowing.”15 Guérande salt can’t contain additives.4

Minerals. Celtic Sea Salt says its salt contains more than 70 trace minerals and elements.2 The AHA says sea salt may carry trace minerals like magnesium, potassium and calcium, and that for heart health, total sodium is what matters most.5 We found no independent analysis of Celtic Sea Salt’s minerals.

Flavor

America’s Test Kitchen found that sea salts vary in color but only slightly in flavor, and that they taste no different from table salt once mixed into food. People often blame iodine for a bitter edge in table salt, but ATK’s tasters couldn’t tell iodized and noniodized salt apart.1 If gray salt tastes brinier at all, you’ll notice it most when the crystals are eaten whole on top of food. We found no measurement of that, though.

In the kitchen

  • On top of food, gray salt’s damp crystals stay whole and crunchy on steak, roast vegetables, tomatoes and salads. ATK recommends sea salts as finishing salts.1
  • In the pot, in pasta water, soups, braises and brines, the difference disappears once the salt dissolves.1 A finishing salt’s crystals are wasted there.
  • In baking, fine table salt spreads evenly through a dough or batter and measures predictably by volume. Damp gray crystals can clump, and the brand suggests drying them gently over low heat if they’re too damp to grind.6

Can one stand in for the other?

Yes. A teaspoon of Light Grey Celtic and a teaspoon of table salt weigh the same, going by the labels and ATK’s weighings, so a straight swap by volume puts the same weight of salt in the dish.9108 By sodium, they differ. The figures below reuse the conversions on our Celtic salt substitute page.

SwapMatch by weightMatch by sodiumTreatment
Table salt for 1 teaspoon Light Grey Celtic1 teaspoon (6.0 g ÷ 6.0 g)About ⅘ teaspoon (1,920 mg ÷ 2,325 mg)Computed91011
Light Grey Celtic for 1 teaspoon table salt1 teaspoonAbout 1¼ teaspoons (2,325 mg ÷ 1,920 mg)Computed91011
Table salt for gray salt as a finishing saltNot a good match: fine grains give no crunchMethod

How these were worked out. The Celtic figures are the brand’s label. The table-salt sodium figure is Tufts’ general number for a teaspoon of table salt, not a specific brand.11 In practice, start with the weight match and season to taste. For finishing, use another coarse sea salt like fleur de sel or Maldon; see the Celtic salt substitute page.

Converting to kosher salt. If your recipe is written for table salt and you want to use kosher salt, the sources disagree on the conversion. See kosher salt vs. table salt.

What isn’t known

  • We found no independent analysis of Celtic Sea Salt’s weight, sodium, minerals or moisture. The figures here are the brand’s.
  • The brand’s pages we read don’t say where Light Grey Celtic is harvested.
  • You’ll often read that only about 20 metric tons of this salt come out of France each year. We found no source for it, and the Guérande figure above, though undated, is far larger.13
  • We found no dated, sourced price comparison.

Footnotes

  1. Salt Types and Measurements, America’s Test Kitchen. americastestkitchen.com · Publication ↩ ↩2 ↩3 ↩4 ↩5 ↩6 ↩7

  2. About Celtic Sea Salt, Celtic Sea Salt (Selina Naturally). celticseasalt.com · Merchant ↩ ↩2

  3. Iodine: Fact Sheet for Health Professionals, NIH Office of Dietary Supplements. ods.od.nih.gov · Regulator ↩ ↩2 ↩3

  4. Cahier des charges de l’IGP Sel de Guérande / Fleur de sel de Guérande, French Ministry of Agriculture, 2025. info.agriculture.gouv.fr · Regulator ↩ ↩2 ↩3 ↩4 ↩5

  5. Sodium Sources: Where Does All That Sodium Come From?, American Heart Association, 2025. heart.org · Reference work ↩ ↩2 ↩3 ↩4 ↩5

  6. FAQs, Celtic Sea Salt (Selina Naturally). celticseasalt.com · Merchant ↩ ↩2 ↩3 ↩4 ↩5 ↩6 ↩7

  7. Wallace P. Bolen, Salt, Mineral Commodity Summaries 2025, U.S. Geological Survey. pubs.usgs.gov · Regulator ↩ ↩2

  8. Morton Iodized Table Salt, product page, Morton Salt. mortonsalt.com · Merchant ↩ ↩2 ↩3 ↩4

  9. Light Grey Celtic, product page, Celtic Sea Salt (Selina Naturally). celticseasalt.com · Merchant ↩ ↩2 ↩3 ↩4 ↩5 ↩6

  10. Kate Shannon Levine, The Best Kosher Salt, America’s Test Kitchen, 2019. americastestkitchen.com · Publication ↩ ↩2 ↩3 ↩4

  11. Tufts Health & Nutrition Letter, kosher salt Q&A, 2019. nutritionletter.tufts.edu · Publication ↩ ↩2 ↩3 ↩4

  12. Sodium in Your Diet, U.S. Food and Drug Administration. fda.gov · Regulator ↩ ↩2

  13. Récolte du sel dans les marais salants de Guérande, Cap Atlantique (La Baule-Guérande Agglo), undated. cap-atlantique.fr · Reference work ↩ ↩2

  14. Standard for Food Grade Salt, CXS 150-1985 (rev. 2012), Codex Alimentarius. services.bis.gov.in · Standard ↩

  15. 21 CFR 100.155, Salt and iodized salt, Electronic Code of Federal Regulations. ecfr.gov · Regulator ↩ ↩2