Organic milk claims usually aim to correlate organic farming's lower-input practices with health benefits. But in the United Kingdom, iodine supplements provided to conventional dairy cow diets translated into an "accidental public health triumph," curing decades of human iodine deficiency without adding the chemical to salt or bread as is done in many countries.
Due to the lack of iodine elsewhere in diets of those in the United Kingdom, researchers at the University of Reading are calling notice to their recent article, published in Food Chemistry, which determined that organic and ultra-high temperature (UHT) pasteurized milk had low enough iodine concentrations to cause concern for pregnant women and their unborn children. The US Institute of Medicine and World Health Organization both agree pregnant women should increase iodine during their gestation and lactation, between 47 and 93%. According to the article, milk provides 40% of iodine in the UK diet. 70% of teenage girls across the UK are iodine-deficient, as are 44% of children and adults in Europe, the article states.
The studies was conducted with milk bought during winter. Researchers found that organic milk had only a two-thirds of the iodine found in conventional milk, as did UHT milk (32.2 and 30% less, respectively). The study notes that a previous study showed organic milk had a lower concentration of iodine in the summer, as well.
The recent research stemmed from two short studies. The first pitted two samples each of pasteurized conventional and organic milk against each other in the categories of whole, semi-skimmed, and skimmed, totaling 22 samples. A second study broadened the categories to five types; organic semi-skimmed, branded organic semi-skimmed, UHT semi-skimmed, and conventional whole milk bought from four markets over three weeks, totaling 60 samples.
The researchers found no difference in fat, protein, or lactose between conventional and organic milk.