TL;DR

• Iodine is a building block of thyroid hormones. In early pregnancy the baby relies entirely on its mother's thyroid hormone, so her iodine intake matters from the start.
• The US recommended intake rises from 150 mcg a day to 220 mcg in pregnancy and 290 mcg while breastfeeding. The WHO recommends 250 mcg for both.
• Two urban South African studies of pregnant women found median iodine levels at or just below the WHO's adequate range. "Borderline" is the honest summary, and researchers say nationally representative data are still needed.
• Severe deficiency clearly harms fetal development. For mild deficiency, trials of supplements haven't shown a benefit for child cognition, and too much iodine can disrupt the thyroid too.
• SAHPRA caps iodine at 150 mcg a day for adults in a health supplement, so food has to supply the rest.
• Our AM sachet provides 150 mcg of iodine as potassium iodide. It's designed to sit alongside iodised salt, dairy, fish and eggs, not replace them.

Why iodine matters in pregnancy

Your thyroid uses iodine to make thyroid hormones. Those hormones regulate metabolism, and they are needed for normal brain and skeletal development in a baby.

In the earliest weeks of pregnancy, the baby depends entirely on thyroid hormones supplied by its mother. As the baby's thyroid develops, it gradually begins producing its own hormones, but adequate maternal iodine remains important throughout pregnancy. A mother's thyroid hormone (T4) production rises by about 50% during pregnancy, which raises the amount of iodine she needs. That's also why guidelines cover women who are planning a pregnancy, not only women who are already pregnant.

How much you need

In the US, the recommended intake for adult women is 150 mcg a day. It rises to 220 mcg in pregnancy and 290 mcg while breastfeeding. The WHO recommends a slightly higher 250 mcg a day for both pregnancy and breastfeeding. The US upper limit for adults, including in pregnancy, is 1,100 mcg a day.

Exclusively breastfed babies depend on their mother's iodine intake. That's why the breastfeeding figure is higher still.

Too little, and too much

Severe iodine deficiency in pregnancy is clearly harmful. It can cause miscarriage, stillbirth, growth problems and irreversible damage to the baby's brain development, and it remains the most common preventable cause of intellectual disability worldwide.

Mild deficiency is a less clear picture. A pooled analysis of 6,180 mother and child pairs from three European birth cohorts found lower verbal IQ in children whose mothers had lower iodine status in the first trimester. That study was observational, so it shows an association, not proof of cause.

Randomised trials tell a different story. Two trials gave iodine supplements (150 or 200 mcg a day) from early pregnancy until delivery. Neither found an effect on the children's cognitive, language or motor scores at 1.5 to 2 years, and one found no benefit at age 5 or 6 either. A systematic review of supplementation trials in mildly to moderately iodine-deficient pregnant women reached the same conclusion for child neurodevelopment. NIH describes the evidence as inconclusive. So whether supplementing mild deficiency improves outcomes for children is still an open question.

Too much iodine is also a problem. High intakes can cause some of the same thyroid problems as too little, including goitre and an underactive thyroid. In a Spanish study, pregnant women taking iodine supplements of 200 mcg a day or more were more likely to have raised TSH than women taking less than 100 mcg. That study was cross-sectional, so it can't show the supplements caused it. People with autoimmune thyroid disease can also react to amounts that are safe for others.

Where South African women stand

South Africa has required table salt to be iodised since 1995, and this is credited with eliminating goitre as a public health problem. There are two limits worth knowing about. The rule covers table salt only. Iodising the salt used in food manufacturing is voluntary. And a salt reduction policy introduced in 2016 has led researchers to ask whether iodine intakes could fall.

Data on pregnant women are limited. In Johannesburg, a study of 562 pregnant women found a median urinary iodine of 144 µg/L. The WHO considers 150 to 249 µg/L adequate in pregnancy, so the authors described the women as possibly borderline iodine deficient. In the Free State, a study of 617 pregnant women attending antenatal clinics (430 urban, 187 rural) found an overall median of 155 µg/L, just inside the adequate range. The urban median was 150 µg/L, right on the WHO cut-off, which is why the authors called urban iodine status borderline adequate. In that study, 81% of urban and 70% of rural women said they used iodised household salt.

Neither study represents South Africa as a whole, and spot urine tests describe groups, not individuals. Both sets of researchers called for a national survey of pregnant women.

Getting iodine from food

Iodine in food is patchy.

• Greek yoghurt, plain, nonfat, ¾ cup: about 87 mcg
• Milk, nonfat, 1 cup: about 84 mcg (ranging from 38 to 160 across samples)
• Iodised table salt, ¼ teaspoon: about 78 mcg
• Egg, hard boiled, 1 large: about 31 mcg
• Cheddar, 28 g (1 oz): about 14 mcg

Sea salt and other specialty salts, including Himalayan salt, are usually not iodised, so swapping them in for iodised table salt removes a source. Seaweed varies enormously, from 16 to nearly 3,000 mcg per gram across commercial products, which makes kelp supplements unpredictable. Women who avoid dairy, fish and eggs, including vegans, are more likely to fall short.

What SAHPRA allows

SAHPRA's health supplement guideline (Annexure F) sets a maximum of 150 mcg of iodine a day for adults. This applies to products registered as health supplements. It's lower than the 220 to 250 mcg recommended in pregnancy, so a single health supplement can't provide the full amount. The rest is expected to come from food.

Where we use it

Our AM sachet provides 150 mcg of iodine as potassium iodide. We use potassium iodide because it provides a standardised, measurable source of iodine. A small study also found potassium iodide is almost completely absorbed.

Whether that's enough alongside your diet depends on what you eat. If you use iodised salt and eat dairy, fish or eggs most days, your food may already provide a good share of what's recommended. If you avoid iodised salt, dairy and seafood, your intake may be lower, and that's worth discussing with a doctor.

Needs stay high while breastfeeding, so iodine is one of the nutrients worth keeping covered after the birth too.

This article is for general educational purposes and isn't medical advice. Please speak to a doctor before taking extra iodine or kelp supplements, particularly if you have a thyroid condition, take thyroid medication, or have been told your thyroid or iodine levels are abnormal.

Sources

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