Low Iodine Levels in Organic Milk Could Compromise Brain Development

Researchers at the University of Surrey (Guildford, United Kingdom) compared the iodine concentration of retail organic and conventional milk. Ninety-two samples of organic milk and 80 samples of conventional milk, purchased from retail outlets in sixteen areas in the United Kingdom, were analyzed for their iodine concentration. The results showed that organic milk has a 42.1% lower concentration of iodine than conventional milk.

The importance of the finding results from the fact that iodine is an essential component of thyroid hormones, crucial for brain development, with especially high significance in the womb and in early childhood. Mild-to-moderate iodine deficiency in pregnancy has been associated with poorer brain and neurological development of the baby in the womb, resulting in poorer outcomes for the child, including lower IQ and poorer school performance. The researchers stressed that the lower iodine concentration of organic milk has clear public-health implications, given the recent evidence of the reemergence of iodine deficiency in the UK population, particularly in young and pregnant women, and the increasing popularity of organic milk. The study was published in the July 2011 issue of the British Journal of Nutrition.

“As milk is the principal source of iodine in the UK diet, pregnant women and nursing mothers who choose organic milk should be aware that their iodine intake, and hence the brain development of their children, may be compromised,” said lead author professor of nutritional medicine Margaret Rayman, PhD. “They should therefore ensure that they have an adequate intake of iodine from other dietary sources, such as fish. That said, they should avoid kelp which can provide excessive amounts.”

Iodine is an essential trace element for life, the heaviest element commonly needed by living organisms. Its main role in animal biology is as a constituent of the thyroid hormones thyroxine (T4) and triiodothyronine (T3). Thyroid hormones play a basic role in biology, acting on gene transcription to regulate the basal metabolic rate. The total deficiency of thyroid hormones can reduce basal metabolic rate up to 50%, while in excessive production of thyroid hormones the basal metabolic rate can be increased by 100%. T4 acts largely as a precursor to T3, which is (with minor exceptions) the biologically active hormone.

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