Health experts are issuing new warnings about the consumption of organic milk by pregnant or breastfeeding women.

University of Reading scientists have found that milk certified as “organic” or “UHT” — meaning it has been treated at ultra-high temperatures — has lower levels of iodine than conventionally-produced fresh milk. As a result, pregnant or breastfeeding women who drink it could be putting the health of their babies at risk for brain abnormalities, Medical Xpress reports.

Iodine is crucial for the brain development of babies, particularly in the early stages of pregnancy. Studies have shown iodine deficiency in mothers during these stages can lead to children with a lower IQ. Most iodine in our diet comes from milk products.

“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,” said Ian Givens, a professor at University of Reading, who led the research. ""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.”

The study, published online in the journal Food Chemistry, noted that organic and UHT milk is not bad for you, and many studies have suggested proteins, fats, and vitamins in the beverage confer health benefits.

"But to get the same amount of iodine as in a pint of conventional pasteurized milk, you would need to drink around an extra half-pint of organic or UHT milk," Givens said.