Iodine

What iodine does in the body

Iodine is a trace mineral your body cannot make itself. The thyroid, a small gland in the neck, uses iodine to build the hormones T3 and T4. Iodine contributes to the normal production of thyroid hormones and to normal thyroid function. It also contributes to normal cognitive function, normal functioning of the nervous system, normal energy-yielding metabolism and the maintenance of normal skin.

In the UK, cows' milk, dairy and white fish supply most of the iodine people get. Iodine in plant foods follows the soil, so levels vary from field to field. Swap dairy for a plant drink that is not fortified with iodine and your intake can fall without you noticing. Iodine is one of the trace elements in our Minerals range, needed in micrograms rather than milligrams.

The forms differ mainly in dosing accuracy

Most tablets and capsules use potassium iodide or potassium iodate. Both deliver iodine well. Iodate is a little more stable on the shelf, which is why some brands prefer it. The useful part is that the amount is fixed per tablet, usually 150 mcg, sometimes 100 mcg or 225 mcg, so you know what you take each day.

Kelp, sea moss and other seaweed products work differently. Their iodine content depends on the harvest and the species, so one capsule can supply several hundred micrograms and the next batch more again. Liquid drops sit in between: they let you dose in small steps, handy if you want less than a full tablet, but you have to count drops carefully.

How we choose the iodine we stock

We look at three things: the form, the amount per serving and the combinations that make sense. For iodine we prefer forms with a fixed, declared dose, potassium iodide or potassium iodate, because 150 mcg on the label should mean 150 mcg in the capsule. We do stock seaweed products, and we say plainly that their content varies more. We do not present high-strength iodine solutions as a daily supplement, because those doses sit far above what a normal diet needs. Every product passes our compliance team, we test ourselves, and independent labs spot-check batches. Read how we select our brands.

Who a supplement genuinely suits

Topping up makes most sense when your diet is low in iodine. That usually means:

• no fish and no dairy, for example on a plant-based diet
• no iodised salt, which is uncommon in British kitchens
• plant drinks that are not fortified with iodine

If that describes you, a modest fixed dose is the practical route, and you will find more options among our products for a vegan diet. If you eat fish, eggs or dairy most days, you are probably already covered.

Selenium is often bought alongside iodine. It carries its own approved claim for normal thyroid function, which is a separate claim, not evidence that the two work better as a pair. If that interests you, browse the selenium range and decide per nutrient.

Be honest with yourself about what to expect. Iodine is not a supplement you feel working from one day to the next. Its value is quiet: it fills a gap in the diet so a normal process can keep running normally. More is also not better here. The NHS advises that 0.5 mg or less a day from supplements is unlikely to cause harm, and standard products stay well below that.