Organic milk could contain a third less iodine than normal milk , scientists claim - but the organic milk industry has issued a swift rebuttal ( file picture ) Pregnant women and breastfeeding mothers who drink organic milk may be putting their child ’ s health at risk , scientists claim . They say it contains a third less iodine than normal milk – which could affect infant brain growth and intelligence later in life . UHT longlife milk was also found to have similarly low levels of the mineral , academics from Reading University found . Because milk is the main source of iodine in the British diet – providing 40 per cent of the average daily intake – switching to organic may have a significant impact on health , they warn . The organic milk industry last night issued a swift rebuttal . Organic milk is often drunk for its supposed health benefits , with claims that it contains omega-3 fatty acids that are good for the heart . And in response to environmental and animal welfare concerns , the sector is growing . One in every 20 pints of milk bought is now organic and more than 300 million pints were sold in the UK last year , worth £160million . But researchers said that because organic farmers do not give their cows as many artificial supplements the milk lacks iodine , which is important for the healthy development of babies in the womb and in their first months of life . The mineral is thought to have a major impact on the formation of the brain , with repercussions for IQ and school success later in life . Study author Professor Ian Givens said the findings could have ‘ serious implications for public health ’ . He stressed that organic milk was not ‘ bad ’ for health , and said Britons could get the same amount of iodine as in a pint of normal milk by drinking an extra half-pint of the organic variety . But he warned that without careful monitoring , the country risks ‘ sleepwalking ’ into a new health crisis in the 21st century . Iodine deficiency was once endemic in parts of the UK , with thousands in the 1930s and 1940s suffering from the thyroid condition goitre . The latest findings , published in the journal Food Chemistry , were based on skimmed , semi-skimmed and full-fat milk purchased at four unnamed supermarkets . But the organic milk industry last night said the research – conducted in January last year – was out of date . Pregnant women and breastfeeding mothers who drink organic milk may be putting their child ’ s health at risk due to the smaller amount of iodine in the product . Iodine is essential for brain growth . OMSCo , which provides two-thirds of Britain ’ s organic milk , said procedures had been changed over the past 18 months to ensure more iodine is fed to dairy herds . Peter Melchett , of the Soil Association , also dismissed the findings , saying organic milk had ‘ scientifically proven ’ health benefits . Research in 2013 by experts in Bristol and Surrey found that children born to women deficient in iodine have a 60 per cent risk of lower IQ scores at the age of nine . Professor Jean Golding , one of the authors of that study , last night welcomed the new findings , saying : ‘ Milk is a major source of iodine , but it is important to know which sort of milk is most appropriate . ’
Milk is main source of iodine in Iodine diet , providing 40 % of daily intake . Academics say switching to organic milk could significantly impact health . UHT longlife milk was also found to have similarly low levels of the mineral .