Iodine for babies and children: how much do they need?

by Dr Miriam Martinez-Biarge

Iodine is a vital nutrient at all ages.

Our thyroid gland takes iodine from the blood, combines it with the amino acid tyrosine and makes thyroid hormones: thyroxine (T4) and triiodothyronine (T3). Thyroid hormones control cardiac, muscle and digestive functions, body temperature, menstrual cycles, cholesterol levels and body weight.

Thyroid hormones also regulate bone growth and brain development, and that is why a normal thyroid function is essential during pregnancy and the first years of life: iodine deficiency or insufficient thyroid function (hypothyroidism) can cause poor growth and impaired intellectual function in babies and children. Iodine deficiency during pregnancy increases the risk of congenital anomalies and miscarriage.

The iodine content of land plant foods depends on the iodine present in the soil. This varies considerably by country, region and agricultural practices and is generally low in the UK and much of Europe. As a result, fruits, vegetables, grains, legumes and nuts usually provide relatively small amounts of iodine and are unlikely to meet requirements on their own. People following plant-based diets therefore need to ensure they have a reliable source of iodine through fortified foods, supplements or both.How much iodine do babies and children need?

The recommended daily intakes in the UK are: 70 micrograms (mcg) for 1-3 year old children, 100 mcg for 4-6 year olds, 110 mcg for 7-10 year olds and 130 / 140 mcg for 11-18 year old girls and boys respectively.  Pregnant and breastfeeding women should ensure an iodine intake of around 200 mcg per day from diet and/or supplements.

Where is iodine found?

Iodine is naturally abundant in the oceans. Sea vegetables and fish have the largest concentrations of iodine. Dairy products are one of the main sources of iodine in the UK’s diet, because cows’ feed is fortified with iodine and because of the use of iodine-containing disinfectants during milking. Unlike many other countries, iodised salt is rarely used in the UK and therefore cannot be considered as a source of iodine.

The iodine content of land plant foods depends on the iodine present in the soil. This varies considerably by country, region and agricultural practices and is generally low in the UK and much of Europe. As a result, fruits, vegetables, grains, legumes and nuts usually provide relatively small amounts of iodine and are unlikely to meet requirements on their own. People following plant-based diets therefore need to ensure they have a reliable source of iodine through fortified foods, supplements or both.

Babies under 1 year

During the first year iodine requirements are well covered with breastmilk or formula milk and babies do not need to take supplements. For breastfed babies, iodine intake depends on maternal iodine status, so breastfeeding mothers should ensure that their own iodine intake is adequate.

Children over 1 year

From one year of age, vegan children should obtain iodine regularly from fortified foods, supplements, or a combination of both. Many children’s multivitamins contain iodine, although the amount varies considerably between products. Families should check labels carefully. Some vegan-specific supplements, for example, The Vegan Society’s VEG 1 Baby and Toddler (for children 6 months-5 years) and VEG 1 tablets (for older children), are now available and provide the right amount of iodine alongside other nutrients of importance in plant-based diets, such as vitamin B12, vitamin D and selenium.

Many plant milks are now fortified with iodine, typically providing around 20–30 micrograms (mcg) per 100 ml, similar to the amount present in cow’s milk. A child drinking 250–300 ml of an iodine-fortified plant milk daily may obtain a substantial proportion of their iodine requirements from this source (60–75 mcg).

However, iodine fortification remains inconsistent between brands and many plant milks still contain little or no iodine. Families should therefore check labels carefully rather than assuming that a product contains iodine. Organic plant milks are generally not fortified with iodine.

It is also important not to assume that other plant-based dairy alternatives provide the same amount of iodine as fortified milk. Plant yoghurts are often not fortified with iodine, and most vegan cheeses contain little or no iodine. When assessing iodine intake, check the nutrition information for each product individually.

As a general guide, children up to 10 years of age who drink 250–300 ml of an iodine-fortified plant milk every day may not require an iodine supplement, whereas those who drink little or no fortified milk should consider one. Children over 10 years need two glasses of iodine-fortified milk a day to meet most of their requirements; if they don’t drink this amount, they should take a supplement.

What about sea vegetables?

Sea vegetables can contain significant amounts of iodine, but the iodine content varies enormously between species and even between batches of the same product. For this reason, seaweeds are not a reliable way to estimate iodine intake.

Small amounts of lower-iodine seaweeds such as nori can be enjoyed as part of a healthy diet and may be used in dishes such as sushi, rice balls or vegetable wraps. Occasional consumption of wakame, for example in miso soup or seaweed salads, is also unlikely to be a concern in older children.

However, some seaweeds, particularly kombu (kelp), arame and hijiki, can contain extremely high amounts of iodine and are not recommended for children or for pregnant and breastfeeding women because even occasional consumption may result in iodine intakes well above recommended levels and could affect thyroid function. In addition, hijiki may contain significant amounts of inorganic arsenic and is generally best avoided.

Because of the variability in iodine content, seaweeds should not be relied upon as the main source of iodine for vegan children. Babies and toddlers under 2 years of age are best offered alternative sources of iodine, such as breastmilk, formula, fortified foods or supplements where appropriate.

Families who consume seaweeds regularly, particularly as part of a cultural or traditional dietary pattern, may benefit from reviewing their overall iodine intake with a dietitian.