A paper published in the journal Food Chemistry has analysed the levels of iodine in British supermarket milk, reporting lower levels in milk labelled as organic compared with conventional milk. The authors suggest that this may increase the risk of iodine deficiencies in at-risk groups such as pregnant women.
Catherine Collins, Spokesperson for The British Dietetic Association, said:
“This is an interesting piece of research that confirms the lower iodine content of pasteurised organic and UHT-treated milks compared to pasteurised conventional milks produced during winter months. These results add to existing data on summer milks, which has also shown a lower level of iodine in organic milks.
“Iodine is important as it’s an absolutely essential component of thyroxine, the ‘master’ hormone that controls all metabolic processes and in particular our metabolic rate. Thyroxine cannot be made without sufficient iodine.
“Iodine is found in small amounts in plant foods, although the majority of UK dietary iodine comes from milk, seafood and seaweed. ‘One-a-day’ multivitamin and mineral supplements usually provide 100% of daily iodine requirements per tablet.
“Milk contributes 40% of our dietary iodine intake, so variations in the levels found in milk can have significant impact on dietary iodine intake. Research shows that organic milk provides a third less iodine than conventionally farmed milks.
This [...] suggests that if you choose organic milk you would need to consume 30% more to reach the same iodine content of non-organic milk.”