Iodine

Iodine is the only element whose entire role in the body comes down to one thing: it is the raw material for thyroid hormones. T4 contains four iodine atoms and T3 contains three — and without them, nothing gets made.

And because thyroid hormones regulate the metabolic rate of every cell in the body, and above all brain development in the fetus and the infant, iodine deficiency is the world’s leading cause of preventable cognitive impairment.

And Israel has a unique problem here worth knowing about: in many countries, table salt is iodized as a public health policy. Israel has no mandatory iodization, and at the same time a large share of drinking water is desalinated water — and desalination removes its natural iodine. A national survey in Israel found high rates of iodine deficiency, including among pregnant women.

Dosage and sources

Benefits (Pros)

1. Producing thyroid hormones

This is its only, decisive role. Thyroid hormones regulate metabolic rate, body temperature, heart rate, mood and digestive function. Iodine deficiency causes hypothyroidism and goiter — the gland swells in an attempt to capture more iodine from the blood.

2. Fetal brain development — the most critical of all

In the first trimester of pregnancy, the fetus depends entirely on the mother’s thyroid hormones. Maternal iodine deficiency during this period damages brain development irreversibly. In severe cases the result is cretinism; in milder cases — a measurable drop in IQ and cognitive function, with no outward sign. This is why most health organizations recommend an iodine supplement for pregnant and breastfeeding women.

3. Cognitive function in children

Studies in iodine-poor populations have shown measurable improvement in children’s cognitive function after supplementation — one of the strongest findings in public health nutrition.

4. Breast tissue health

Breast tissue concentrates iodine using the same transporter (NIS) as the thyroid. There are research hypotheses about a link between iodine status and breast tissue health, but the evidence is preliminary and does not justify supplementing for this reason.

Downsides and Side Effects (Cons)

1. Kelp — the most common danger

Seaweed supplements and kelp powders are the most common source of iodine poisoning. The iodine content of kelp varies by orders of magnitude between products and even between batches, and a single product can supply dozens of times the daily intake — far above the UL. Cases of iodine-induced hyperthyroidism and hypothyroidism have been described. Anyone who wants to add iodine needs a supplement with a defined dose (potassium iodide), not seaweed.

2. The Wolff-Chaikoff effect — excess that causes the same problem

Too much iodine temporarily suppresses thyroid hormone production. In a healthy person the gland “escapes” the suppression within days; in someone with Hashimoto’s, Graves’ disease or another thyroid disease, this mechanism may fail and cause prolonged hypothyroidism. Excess iodine is almost as dangerous to a diseased thyroid as deficiency.

3. Worsening autoimmune disease

Iodine supplementation in a population that isn’t deficient has been linked in several studies to an increase in autoimmune thyroiditis. Anyone with positive TPO antibodies should consult a professional before supplementing.

4. Goitrogens — a caveat in proportion

Cruciferous vegetables (cabbage, broccoli, cauliflower) and soy contain compounds that interfere with iodine uptake. The effect is significant only in combination with existing iodine deficiency and very large intake of the raw vegetables. For someone with normal iodine intake, this is not a practical consideration.

5. Allergy — a clarification

“Iodine allergy” does not exist as an entity. Allergy to iodine-containing contrast media or to seafood is unrelated to dietary iodine, and is no reason to avoid iodized salt.

Summary

Iodine does one thing — it makes thyroid hormones — but that one thing sets the metabolic rate of every cell in the body and the brain development of the fetus. In Israel, the combination of non-iodized salt and desalinated drinking water creates an unusual situation for a developed country, so it is worth thinking about iodine actively: iodized salt, sea fish, dairy products and eggs. For pregnant and breastfeeding women — consult about a supplement; this is the period in which the gap cannot be fixed after the fact. And never through kelp, whose dose is unpredictable and dangerous.