The salt aisle dilemma
Walk into any grocery store and you'll find a shelf full of salt options. Regular table salt. Sea salt. Pink Himalayan. Kosher. The differences seem obvious until you flip over a table salt container and scan the ingredient list. Beyond sodium chloride, you'll see something called sodium ferrocyanide or E535. Then silicon dioxide, also known as E551. These names sound industrial and unfamiliar, which is exactly why many people reach for sea salt instead.
But does the presence of these additives actually make table salt unsafe? Or is it more about personal preference for less-processed foods? Let's look at what the research shows.
What are these additives, anyway?
Table salt is mined from underground deposits and processed to remove minerals and moisture. This processed, fine grain is susceptible to clumping in humid environments. To prevent caking, manufacturers add anti-caking agents. The three most common are sodium ferrocyanide (E535), silicon dioxide (E551), and calcium silicate (E552).
Sodium ferrocyanide sounds like something from a chemistry lab, and it is. It's a complex salt containing iron and cyanide ions. The cyanide part is what catches people's attention. After all, cyanide is a poison. But what matters is the dose: a substance can be toxic at high doses and safe at low ones.
Silicon dioxide is better known as sand. You'll find it in some supplements, anti-caking formulations, and processed foods. The EFSA (European Food Safety Authority) re-evaluated it in recent years and concluded that it's generally recognized as safe at current use levels.1
What does the safety research show?
The European Food Safety Authority conducted a comprehensive re-evaluation of sodium ferrocyanide in 2018. They set an Acceptable Daily Intake (ADI) of 0.03 milligrams per kilogram of body weight per day.2 For a 70-kilogram adult, that translates to about 2.1 milligrams per day.
If you're using a typical amount of table salt in your diet, roughly 5-10 grams per day depending on your sodium intake, you're consuming a tiny fraction of that limit. The ferrocyanide content in table salt is typically around 0.0001% to 0.001%, meaning you'd ingest far less than the safety threshold from the salt in your food.
One in vitro study showed that potassium ferrocyanide could cause genetic damage at very high concentrations in a lab setting.3 But in vitro studies (which use cells in dishes, not whole organisms) don't translate directly to what happens when you consume salt with food. The researchers themselves noted that the concentrations they tested were not relevant to dietary exposure. A finding in a lab setting doesn't automatically mean health risk from eating.
The bottom line from regulatory agencies like the EFSA and FDA: these anti-caking agents are safe at the levels found in table salt.
So why do people choose sea salt instead?
If anti-caking agents are safe, why has sea salt become the default for people trying to eat cleaner? There are a few reasons, and they're not all about safety.
First, there's the processing question. Sea salt is made by evaporating seawater, requiring less chemical processing than mined table salt. For people who prefer foods that are less industrially processed, sea salt aligns with that philosophy. This is a valid preference, but it's distinct from a safety concern.
Second, there's the mineral content. Sea salt contains small amounts of magnesium, calcium, potassium, and trace minerals.4 These sound beneficial, but the quantities are so small that they don't meaningfully contribute to your daily mineral intake. The marketing often suggests you're getting significant minerals from sea salt, but the reality is much less dramatic. [inference]
Third, there's taste. Many people genuinely prefer the flavor of sea salt, which can vary depending on its source. Maldon sea salt, for example, is prized by chefs for its briny taste and texture.
But sea salt has its own issues
Here's where the picture gets more complicated. If you're choosing sea salt because it sounds purer or cleaner, you should know that seawater doesn't come out of the ocean in pristine condition.
Research in recent years has identified microplastics in sea salt samples. A 2018 study published in Environmental Science & Technology tested various salt types and found microplastics in sea salt, pink Himalayan salt, and rock salt, though at varying concentrations.5 This is a genuine concern that doesn't get as much attention as anti-caking agents, partly because it's newer research and partly because anti-caking agents are easier to debate.
Additionally, sea salt is typically not iodized. Iodine is added to table salt specifically because iodine deficiency is a public health issue, particularly in pregnancy and early childhood. It's linked to thyroid function and developmental health. If you use sea salt regularly, you might need to get iodine from other sources like seaweed, fish, or dairy.
Brands like Celtic Sea Salt, Redmond Real Salt, and Maldon are marketed as more natural or less processed, and they do offer a different product than standard table salt. But they still have tradeoffs: higher cost, lack of iodine, and their own potential exposure to microplastics if sourced from seawater.
The honest comparison
Neither table salt nor sea salt is perfect. Table salt with anti-caking agents is safe according to regulatory bodies and peer-reviewed research. The additives are present in tiny amounts and well below levels that would cause harm. The real advantage is that iodized table salt helps prevent iodine deficiency, which matters for health.
Sea salt is less processed, which appeals to people who prefer minimally refined foods. It may have a different flavor profile that you prefer. The downside is the lack of iodine, the presence of microplastics (though this also appears in table salt and other sources), and the trace minerals are nutritionally negligible.
The choice between them isn't about one being toxic and the other being clean. It's about weighing priorities: processing preferences, flavor, iodine intake, and cost.
What to do about salt
If you currently use table salt and it hasn't been a concern for you, there's no safety reason to switch. The anti-caking agents are well-regulated and present in safe amounts.
If you prefer sea salt for taste or personal values around processing, that's a fine choice, provided you make sure you're getting adequate iodine. You can do this by eating iodized sea salt, adding iodized table salt to some meals, consuming seaweed, or eating other iodine-containing foods.
If you're looking for a middle ground, kosher salt is another option: large crystals, minimal additives, and a less processed profile than table salt. It's not iodized, so you'd need to address that elsewhere if needed.
The bigger picture with salt is intake, not type. The health focus should be on total sodium consumption across your diet, since sodium intake has clearer links to blood pressure and cardiovascular health than the specific additive profile of your salt. Whether your salt comes from processed table salt, sea salt, or anything in between matters far less than whether you're eating too much of it overall.
This is one of those cases where the fear narrative gets ahead of the science. The additives in table salt are not hidden dangers. They're disclosed on the label, regulated by food safety agencies, and present in amounts well below what would cause harm. If you prefer sea salt for taste or philosophical reasons about processing, go ahead. But you don't have to choose it for safety reasons.