Iodine is required for thyroid hormone production and therefore is intricately involved in supporting a healthy metabolism throughout life. It is also essential for healthy brain development and growth in infants and children, particularly while in utero and for the first year of life.
At birth the brain is about one-third of its full size and there is rapid growth during the first year of life after which the growth rate significantly declines. Ensuring an adequate iodine intake to support this growth is crucial as a deficiency is estimated to be the leading cause of preventable reduced mental ability or lowering of IQ1
The NHMRC defines an adequate intake (AI) of iodine for infants aged 0-6 months as 90µg/day and from 7-12 months 110µg/day. A Recommended Daily Intake (RDI) is set for children aged 1-3 years at 90µg/day2.
Since infant feeding guidelines (3) recommend solids are introduced around 6 months, milk is the sole source of iodine for infants in those early months. Breastfeeding mothers need to ensure an adequate intake of iodine to fulfil their own requirements and to provide the necessary iodine for their infant.
The Estimated Average Requirement (EAR) for lactating mothers is 190µg/day based on meeting the adult female RDI of 100µg/day and replacing the estimated 90µg/day secreted in breast milk. The RDI during lactation is set at 270µg/day (2).
Iodine levels in infant formula
Where infants are not receiving breast milk, infant formulas should be used until 12 months (3). Therefore, the iodine content of Stage 1 formula (0-6 months) must be sufficient to provide 90µg/day for infants up to 6 months.
From 6-12 months, the iodine requirement for infants is increased, but some iodine may also now come from consumed food. Nevertheless breast milk or formula remains an important source of iodine.
A recent global review of iodine in breast milk suggested that a concentration of around 15µg/100mL during the first 6 months of lactation will achieve or exceed an infant’s iodine needs and prevent the neurological consequences of deficiency (4). However, levels in breast milk vary dramatically depending on iodine sufficiency in the food supply.
Areas known to be iodine deficient can have breast milk iodine concentrations of <5µg/100mL, while areas with iodine sufficiency are in the range 10-15µg/100mL and levels have been recorded as high as 15-18µg/100mL in some areas with plentiful iodine (5).
However, there are concerns that those higher levels may lead to excessive iodine intakes and this can lead to thyroid dysfunction and neurological problems in infants (6).
Iodine levels in infant formula vary significantly between brands and the legal requirements vary between countries. The International standard set by Codex is 2.5-14µg/100kJ of prepared formula. In Australia and New Zealand the Food Standards Code states an acceptable range of 1.2-10µg/100kJ (7).
The amount of iodine in Diamond pro+ 1 is 13.4µg/100mL or 4.8µg/100kJ. This is well within the range found in breast milk from mothers living in iodine sufficient areas and to Codex and Australia and New Zealand food standards codes. Consuming 670mL of formula correctly prepared according to on-pack instructions will meet the RDI of 90µg of iodine for this age group. The feeding guide recommends between 720-960mL up to 3 months of age and 900-1080mL from 3-6 months of age.
Diamond pro+ 2, formulated for infants 6-12 months, contains a higher level of iodine with 18.6µg/100mL or 6.9µg/100kJ. This is to ensure the higher requirement for iodine is met in this age group. Consuming 590mL of formula correctly prepared according to on-pack instructions will meet their RDI of 110µg of iodine. The feeding guide recommends between 720-1080mL from 6-9 months of age and 720-900mL from 6-12 months of age.
Diamond pro+ 3, formulated for toddlers, contains 14.4µg/100mL (shown on pack as 28.7µg per 200mL serve). The recommended serves per day is 1-2, providing 32-64% of the RDI for this age group. This sets them well on the way to meeting their iodine needs, supporting normal brain function and thyroid metabolism.