Iodine 150 µg (potassium iodide)

The short version

What it does It gives the thyroid the raw material for its hormones. In a pregnant woman or on a vegan diet without iodised salt, the deficiency is real and avoidable — and during pregnancy it can cost the child’s brain development dearly.

What it does not do It does not “boost” the thyroid and does not help you lose weight. In excess it can unbalance it, in either direction. If you eat iodised salt, fish or dairy, you are probably not short of it.

What the studies say

Zimmermann and Delange’s European review recommends an intake of about 150 µg a day for women pregnant or planning a pregnancy, in most European countries. The American Thyroid Association notes that sufficient maternal intake is essential for thyroxine production, and that untreated insufficiency can cause irreversible brain damage in the foetus.

This is one of the rare supplements where overdosing is a genuine risk, not just waste: the French food safety agency logged seven reports, including two cases of congenital hypothyroidism, likely linked to supplements taken by the mother. Its advice is explicit — avoid simultaneous exposure to several iodine sources during pregnancy. And the window between deficiency and excess is narrower than for most nutrients.

Two situations justify this supplement: pregnancy or planning one, and a vegan diet without iodised salt. Outside those, a French diet generally covers the requirement — and adding more becomes a risk rather than a benefit.

How to take it

Relevant when planning a pregnancy, during pregnancy and breastfeeding, and on a vegan diet if you do not use iodised salt. TO BE RULED OUT if you have a treated thyroid, autoimmune thyroid disease, or already take an iodised prenatal supplement.

150 µg a day, one dose, and above all ONE SOURCE. Before adding any, check your other supplements: many prenatals and multivitamins already contain it, and stacking is precisely what the agency is pointing at.

There is nothing to feel. If your thyroid is being followed, it is the TSH test that talks, and your doctor who reads it. Palpitations, jitteriness or unexplained weight change after starting: stop and see a doctor.

What is inside

Potassium iodide, the form used in salt iodisation and in the recommendations. The useful dose is counted in micrograms, not milligrams — a factor of a thousand, and it is the most dangerous mistake in this aisle.

Look for a dose stated in µg of IODINE, at 150 µg. A single, isolated source rather than a complex where iodine hides among twenty ingredients: it is the only way to control your total intake.

Seaweed, kelp and spirulina sold as iodine sources: their content varies unacceptably between batches, to the point where the European review explicitly recommends avoiding them. And any stacking of iodine sources during pregnancy.

Cautions

• Known or treated thyroid disease: medical advice mandatory
• Autoimmune thyroiditis
• Stacking with an already iodised prenatal supplement