New research suggests that pregnant or breastfeeding women could be putting the health of their babies at risk by switching to organic or long-life UHT milk.

University of Reading scientists found that milk certified as organic, as well as conventional long-life milk treated at ultra-high temperatures (UHT), was a third lower in iodine than conventionally-produced fresh milk. Researchers from Reading's Food Production and Quality division said the findings had potentially serious public health implications, as most iodine in our diet comes from milk products.

Iodine is particularly crucial for the brain development of babies, particularly in the early stages of pregnancy. Studies have found that iodine deficiency in mothers during these stages can lead to children with a lower IQ.

Iodine deficiency was once endemic in parts of the UK, with hundreds of thousands of people in the 1930s and 1940s suffering from goitre - an enlargement of the thyroid caused by a lack of iodine, which can lead to swollen glands and other health problems.

While some countries launched campaigns to add iodine to bread or salt, Britain solved its problem by accident with the enrichment of iodine in milk from supplements given to dairy cows. As post-war consumption of conventionally-produced milk increased, iodine deficiency was all but wiped out by the 1990s.

However, the researchers said that because organic cows predominantly ate a grass-based diet, they were not fed animal feed which boosted the iodine levels of their milk.

Professor Ian Givens, who led the research, said: "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 the situation is carefully monitored, we risk sleepwalking into a new health crisis in the 21st century."

Market round-up

Messrs Craig Wilson Ltd 16 prime heifers at Ayr on Tuesday to a top of £1316.70 per head and 231p per kg to average £1146.96 and 211.3p, while 7 prime bullocks peaked at £1276.50 and 206p to level at £1107.74 and 180.7p. Five prime bulls sold to £1035 and 195p to average £983.17 and 183.4p.

In the rough ring 64 beef cows averaged 136.5p and 144 dairy cows levelled at 107.7p. Nineteen bulls averaged 132.6p and 12 clean OTM cattle levelled at 159.5p.

The firm's weekly sale of dairy cattle was a poor show for quality with the top price for the four sold just £1220 for a second calved cow.