The Salt Switch That Is Quietly Affecting Your Health

Here is what changed when you upgraded your salt

Most people who switched to pink Himalayan, sea salt, or kosher salt made the swap for the right reasons. It tasted better. It felt like a more natural choice. Nobody told them that iodised table salt was doing something the premium alternatives are not.

Specifically:

• Why gourmet salts do not contain iodine and why that gap adds up
• What iodine actually does and how it connects to thyroid function
• Who is most at risk, including plant-based eaters and women planning a pregnancy
• What the guidance says and where home testing fits in

Small dietary shifts can have nutritional consequences that take a long time to surface. This is one of them.

Iodine disappeared from public conversation a long time ago. Salt iodisation programmes, rolled out across much of the world during the twentieth century, did their job well. Goitre became rare. Severe developmental complications linked to iodine deficiency during pregnancy became uncommon. The problem appeared solved, so people stopped thinking about it.

But a quiet shift has been happening in kitchens across the UK. Iodised table salt, once the default, has been steadily replaced by gourmet and natural alternatives. Pink Himalayan salt, sea salt, flaked salt, and kosher salt are now far more common in household cooking. They are perceived as more natural, more sophisticated, more health-conscious choices. What they are generally not is iodised.

At the same time, more people are eating plant-based diets, reducing dairy, and consuming more processed food where the iodine content cannot be relied upon. None of these changes happened overnight, and none of them announced themselves as a nutritional risk. But together they have created conditions where certain groups are once again not getting enough iodine, without any awareness that a gap exists.

The image problem with iodised salt

Iodised table salt has, to put it plainly, a branding problem. The WHO still regards it as one of the most effective and cost-efficient public health interventions available. UNICEF identifies it as the most widely used method for improving iodine intake globally. The evidence behind it is strong and decades old.

But compared to the culinary prestige of Himalayan pink, the artisan appeal of sea salt flakes, or the clean simplicity of kosher salt, iodised table salt feels ordinary. Outdated, even. When people reach for something they perceive as more natural or premium, they are not thinking about micronutrients. They are thinking about taste and identity.

The problem is compounded by processed and ultraprocessed food. A significant portion of daily salt intake now comes from manufactured products, and the iodisation of salt used in food production cannot be assumed. The WHO has explicitly called for coordination between policies aimed at reducing sodium intake and those promoting iodised salt, precisely because the two goals can work against each other if the iodine piece is not built in.

What iodine does and why the thyroid is involved

Iodine is an essential micronutrient. The body cannot make it and has no alternative source. It is needed specifically to synthesise two thyroid hormones, thyroxine and triiodothyronine, known as T4 and T3. These hormones regulate metabolism, growth, and a wide range of physiological processes. Without adequate iodine, the thyroid cannot produce them in sufficient quantities.

When iodine intake drops and thyroid hormone production is affected, the effects tend to be gradual and easy to attribute to other things. Fatigue, weight changes, difficulty concentrating, and feeling cold more often than usual are all consistent with reduced thyroid function. A goitre, which is an enlargement of the thyroid gland as it attempts to compensate, is a visible sign of deficiency but tends to appear at a more advanced stage.

The connection between what is on the kitchen shelf and how well the thyroid functions is not one most people would naturally make. But the mechanism is direct: less iodine in the diet means less raw material for thyroid hormone production, and that has downstream effects on how the body operates day to day.

Common salt types and iodine content

Plant-based diets and the gap that goes unmentioned

Iodine is naturally present in seafood, some dairy products, and eggs. For people who eat across all three categories regularly, getting enough is generally achievable. The difficulty arises when several of those sources are reduced or removed together, which is exactly what happens on a plant-based diet, particularly a fully vegan one.

A 2023 review published in the British Journal of Nutrition found that people following plant-based diets, and especially those eating fully vegan, may struggle to reach recommended iodine intake from food alone. The comparison that matters here is with vitamin B12. When people move to plant-based eating, B12 supplementation is now routinely flagged as necessary. Iodine rarely gets the same mention, despite the gap being just as real.

The solution is not complicated. Iodised salt, fortified foods, or a supplement that includes iodine can address it. But addressing something requires knowing it is there. Most people making the switch to plant-based eating are not being told to think about iodine at all.

Pregnancy: when getting this right matters most

Iodine requirements increase during pregnancy and breastfeeding. The body needs more to support increased thyroid hormone production, more iodine is lost through the kidneys, and iodine is actively transferred to the foetus and then to the infant through breast milk. The US National Institutes of Health sets a urinary concentration of 150 to 249 micrograms per litre as adequate for pregnant women, reflecting the higher threshold needed at this stage.

The evidence around severe deficiency during pregnancy is clear: it can affect foetal development and thyroid function. The picture around mild or moderate deficiency is more nuanced. There is plausible biological concern and some studies suggest associations with poorer outcomes, but controlled trials have not uniformly shown that supplementing mildly deficient pregnant women produces measurable improvements in infant neurodevelopment. The science remains cautious rather than conclusive.

What several scientific bodies have settled on, including the American Thyroid Association, is that a precautionary approach makes sense. Their guidance is that women planning to conceive, those who are pregnant, and those who are breastfeeding should receive 150 micrograms of iodine daily through prenatal or multivitamin supplements. The women most likely to be falling short include:

• Those who have switched from iodised table salt to gourmet or natural alternatives
• Women following plant-based or vegan diets without supplementing iodine
• Those whose main salt intake comes from processed or ultraprocessed foods
• Women who have reduced dairy intake without replacing it with other iodine sources

Because iodine deficiency affects thyroid hormone production directly, the thyroid is often where the effects become detectable first. TSH, thyroid-stimulating hormone, is the marker clinicians use to assess how well the thyroid is functioning. When iodine is low and the thyroid is under strain, TSH levels can shift as the body pushes the gland to compensate.

A TSH home test will not measure your iodine levels directly. What it tells you is whether your thyroid function currently sits within the normal range, which is a useful data point if you have changed your diet, switched salt types, or are planning a pregnancy. Berkeley Health's TSH rapid test kit is designed for home use with results in minutes from a simple finger-prick sample.

If your result sits outside the normal range, that is worth following up with your GP. You can find the test at berkeleyhealth.com.

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