Study Raises Concerns About Iodine Levels in Organic and Long-Life Milk During Pregnancy

Milk Shelves at Whole FoodsIs organic better? According to a new study from scientists at the University of Reading published online in the journal Food Chemistry, milk certified as organic and conventional long-life milk treated at ultra-high temperatures (UHT) contains one-third less iodine than conventionally-produced fresh milk. Iodine deficiency during pregnancy has been linked to poorer cognitive ability in children. Because milk is a main source of iodine in the United Kingdom, drinking organic milk during pregnancy or breastfeeding could put the health of babies at risk.

Iodine is a chemical element required for synthesizing thyroid hormones, which contain the element. Iodine is particularly crucial for the brain development of babies, particularly in the early stages of pregnancy. Previous studies have found that iodine deficiency in mothers during pregnancy and breastfeeding can result in children with lower IQs.

Iodine deficiency was once endemic in parts of the UK. For example, during the 1930s and 1940s, hundreds of thousands  of citizens suffered from goiter, an enlargement of the thyroid caused by a lack of iodine.

Explains Catherine Collins of the British Dietetic Association:

“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. Low levels of thyroxine are associated with a lower metabolic rate and weight gain, so it’s essential for us to have sufficient dietary iodine to maintain metabolic rate at its optimum level.”

While some countries launched campaigns to add iodine to bread or salt, Britain solved the problem with the enrichment of iodine in milk from supplements given to dairy cows. Iodine deficiency was thus effectively eliminated by the 1990s.

As the trend towards organic food increases, however, more consumers are purchasing organic milk, which contains lower levels of the essential element. Says Professor Ian Givens of the University of Reading who led the current study:

“People are increasingly buying organic and UHT milk for perceived health benefits or convenience. But our research shows that this trend could have serious implications for public health.

“Iodine deficiency ought to be a health problem from the past. But unless this situation is carefully monitored, we risk sleepwalking into a new health crisis in the 21st century.

“Organic and UHT milk is not bad for you, and drinking all types of milk has numerous health benefits. But to get the same amount of iodine as in a pint of conventional pasteurised milk, you would need to drink around an extra half-pint of organic or UHT milk.”

The current study found that organic winter milk is 32.2% lower in iodine than conventional milk and UHT milk is 30% lower in iodine than pasteurized milk. However, the fat content of milk did not influence iodine content, meaning that skimmed milk contains as much iodine as full-fat or semi-skimmed milk.

Further xplains Collins:

“The research shows that organic milk provides a third less iodine than conventionally farmed milks, which may be due to differences in the iodine content of winter feeds or different practices in cleaning cow teats prior to milking.”

Up to 70% of teenage girls across the UK are currently iodine deficient, probably as a result of a decline in milk consumption. Because milk contributes 40% dietary iodine intake, variations in the levels found in milk can have significant impact on dietary iodine intake.

Adds Dr. Sarah Bath, Medical Research Council Population Health Scientist Fellow at the University of Surrey:

“While there are limitations in this study, the lower iodine concentration in organic milk may have implications for risk of iodine deficiency, as milk and dairy products are the principal source of iodine in the UK diet.

“However, the study has no measures of iodine status in an individual, so we cannot conclude that those who consume organic milk have a lower iodine status, as that depends on the quantity of organic milk consumed and intake of other iodine-rich foods (such as fish).”

The researchers of the study recommend that individuals who insist on buying organic milk should drink an extra half pint a day to obtain the recommended daily iodine dose or take a multivitamin that contains iodine.


Concerns Over Organic Milk in Pregnancy:
Effect of milk type and processing on iodine concentration of organic and conventional winter milk at retail: Implications for nutrition:
Organic and Long-Life Milk ‘Risk to Children’s IQ’ – New Study:
Organic Milk ‘Is Less Healthy Than Regular Milk and Could Harm Child IQ’:
Women Urged to Avoid Organic Milk During Pregnancy Over Health Risks to the Unborn Baby:

Image Credits

Milk Shelves at Whole Foods:

Parmesan Cheese Crisps

Parmesan Cheese Crisps Recipe

Letter J Preschool Activities

Preschool Homeschool Curriculum: Letter J Lesson Plan