KOSHER SALT

When I was a child, in the 1990s, there was only one kind of salt; we called it “salt.” It came in a blue cylindrical container—you probably know the one—and we dumped it into pasta water and decanted it into shakers. I didn’t know that any other kind existed, and the women who taught me to cook didn’t seem to, either: Joy of Cooking, Mastering the Art of French Cooking, and Moosewood Cookbook all call, simply, for “salt” in their recipes.

But about a decade ago, I started buying coarse kosher salt instead of the fine, uniform, iodized table salt I’d grown up with. I do not remember why. As my friends grew up and started building their own pantries, many of them also made kosher salt their default. These days, The New York Times calls explicitly for kosher salt in nearly all of its recipes, as does Bon Appétit. Two of the most influential cookbooks of the past decade, The Food Lab, by J. Kenji López-Alt, and Salt, Fat, Acid, Heat, by Samin Nosrat, both devote paragraphs to the benefits of kosher over table salt. It is now “the lingua franca of restaurant kitchens”—as Mark Bitterman, who has written four books about cooking with salt, put it—and a cheffy shibboleth in home kitchens, too. You can find Diamond Crystal, the coolest brand, in the background of the famously verisimilitudinous restaurant show The Bear, and on cooking influencers’ beautiful countertops; in 2023, when Trader Joe’s started carrying it, chef Reddit exploded in enthusiastic all caps.

Pretty much everyone eats salt, every day, and it’s different now. Yet even kosher salt’s most fervent converts may not entirely understand how it’s different.

Kosher salt, like all salt, is NaCl—sodium ions electrostatically bound with chloride ions and arranged in a crystal formation. Unlike certain specialty salts, it doesn’t have unique properties by virtue of its provenance; it’s not collected from the coast of France or mined from a mountain in Pakistan. Kosher salt is just big salt.

It’s also more expensive than table salt. You might assume that this is because it has been manufactured according to a stringent set of religious rules. But much iodized table salt is kosher—that is, prepared in adherence with Jewish dietary law—and what we call “kosher salt” isn’t categorically kosher: If you’re feeling pedantic, the right term would be “koshering salt,” because its oversize, craggy crystals are best for drawing the blood out of animals during kosher slaughter.

America’s great salt swap began in the 1980s, when farmers’-market culture and the health-food movement helped American chefs acquaint themselves with specialty ingredients, Bitterman told me: Himalayan pink salt; “bad-ass, real good” fleur de sel from France.

But by and large, chefs settled on kosher as their go-to. They did this for a reason so unbelievably basic that I laughed out loud when I first heard it: Kosher salt is easier to pick up. “Table salt is too hard to pinch,” Adam Ragusea, a food YouTuber, told me. “I mean, just try it. Anyone who’s reading, just try it. Just pick it up … It’s a pain in the ass, and it’s messy.”

Kosher salt is simply better for the way chefs tend to season their food, which is frequently, and without measuring, by eye and by feel. No one wants to be fiddling with a teaspoon on the line at a busy restaurant during the dinner rush. “You can really feel it sort of touching your fingers, and leaving your fingers,” Chris Morocco, the food director at Bon Appétit and Epicurious, told me, whereas finer salt “has a tendency to want to slip away.”

Kosher salt’s migration to home kitchens started in the late ’90s, when the Food Network became a cultural force. Its big crystals suddenly had an added benefit: They look great being pinched out of a saltcellar and flung around on television, or at least better than table salt does being juddered out of a shaker. (Ina Garten, one of the network’s early celebrities, has described Diamond Crystal kosher salt as “always perfect.”) As television turned chefs into celebrities, their fans began trying to emulate them at home.

At the same time, recipes, like the rest of media, were moving online, and their tone was changing. Older cookbooks, Morocco told me, assumed a lot of knowledge on the part of their readers: “Recipe language was very terse. They were not really holding your hand too much.” Online, recipe writers had unlimited space, a broader potential audience, and a business imperative to build a relationship with their readers. So their guidance became chattier and more descriptive, designed for a home cook who was eager to learn—and who could hold recipe developers more immediately accountable, yelling about bland soup or bad bakes in the comments section.

“Salt to taste,” which had for decades been a standard instruction in most savory recipes, gave way to specific measurements. But different salts have different densities, meaning a teaspoon of one brand can be recipe-ruiningly saltier than that of another. So recipe developers needed to be able to recommend a standard salt. Being chefs, they already liked kosher. In 2011, Bon Appétit, which was then becoming a major resource for Millennials teaching themselves how to cook, adopted Diamond Crystal as its house salt.

This is all a little funny. Restaurant chefs started using kosher precisely because it was easy to use without measuring—now home cooks are measuring it out by the teaspoon. And a movement that espoused seeking the ideal ingredients for every dish resulted in widespread adoption of a one-size-fits-all salt.

In doing so, modern cooking has inadvertently all but abandoned one of the most significant public-health advances in history. A few years ago, a 6-year-old girl showed up at a medical clinic in Providence, Rhode Island, her neck so swollen that it looked like she’d swallowed a grapefruit whole. After a series of tests, doctors figured it out: She was iodine-deficient. Her thyroid—the butterfly-shaped gland that is responsible for just about everything the body does, and which requires iodine to function—had swelled in an attempt to capture any microgram of iodine it could from her bloodstream.

For centuries, thyroid dysfunction was endemic; millions of people around the world suffered from slow heartbeats, weakness, muscle fatigue, sluggish metabolism, and brain fog. When, in 1924, American manufacturers introduced artificially iodized salts, it was a miracle, right there on the shelf in the grocery store. Within a few years, the thyroids of the developed world were working again.

Recently, however, doctors have started reporting more cases of iodine-deficient hypothyroidism—and our salt preferences may be at least partially to blame. Kosher salt, as you have probably guessed, does not contain iodine. Neither do most ultraprocessed foods, the main vehicle by which most people in this not-exactly-sodium-deficient country take in salt.

Iodine deficiency can be serious, but is eminently treatable. (Pregnant women should be particularly attentive to their iodine levels, the UCLA endocrinologist Angela Leung told me, because deficiency can result in birth defects.) The 21st-century rise in hypothyroidism might therefore be less a cause for alarm than a chance to rethink our contemporary salt orthodoxy. Kosher’s dominance, to hear Bitterman tell it, “doesn’t come out of magic or merit—it’s cookbook writers and chef culture, a weird confluence of circumstances brainwashing everyone at the same time.” What’s great for chefs may not be great for home cooks. Kosher salt isn’t inherently better, and in some cases may be worse.

I’ve now spent hours on the phone with salt connoisseurs—at one point, Bitterman earnestly described a certain type as “luscious” and “warm”—and have come around to the view that we should all be more open to using different salts for different purposes, in the same way that well-outfitted cooks might keep different types of olive oil on hand. Flaky fleur de sel is great for finishing dishes; flavored salt is perfect on popcorn. And for everyday cooking, iodized table salt is just as good as kosher—preferable, even, if you’re worried about your iodine levels. Sure, all the recipes now call for kosher salt, but a solution exists: Ignore the instructions and season intuitively. Like a real chef would.