Beverage iodine levels in Germany

Abstract

Sales of iodized table salt (household use, bulk containers) have been flat in Germany since 1996/1997. Nevertheless, the amount of iodide excreted with the urine has been steadily increasing in the German population since 1993. We investigated the beverage iodine levels as possible source of the increased input of iodine into the food chain. No systematic studies on this topic have yet been carried out in Germany. A total of 510 samples were drawn from large grocery discounters who supply all German states with their products (35% fruit and vegetable juices, 35% beers, 10% pooled milk and yoghurt drinks, 10% mineral water, 10% soda). (1) Water-based beverage samples are prepared by solid-phase extraction and iodine concentration is determined by HPLC and electrochemical detection, (2) the samples of milk and milk products are prepared by trichloroacetic acid precipitation and centrifugation, and iodide concentration is determined by HPLC and electrochemical detection. Because the iodine concentrations in the beverage samples showed a left-skewed distribution, all expressed values are median values. Low iodine concentrations were observed in the water-based beverages: fruit and vegetable juices 2.92 μg I⁻/l, beers 2.91 μg I⁻/l, mineral waters 0.5 μg I⁻/l, sodas 0.5 μg I⁻/l. The median value measured in pooled milk and its derived products was 117 μg I⁻/l and 126 μg/l, respectively. As expected, the iodine was lower in summer milk than winter milk ($\tilde{x} = 108\,{\upmu {\text{g I}}}^{ - } /{\text{l}}$and $\tilde{x} = 1 3 4. 2\,{\upmu {\text{g I}}}^{ - } /{\text{l}},$ respectively). Although not statistically significant, beers from Northern Germany had higher concentrations of iodine than from Southern Germany ($\tilde{x} = 3. 6 {\text{ vs}}. 0. 5\,{\upmu {\text{g I}}}^{ - } /{\text{l}}$). In conclusion, based on our results, milk and milk products (117 μg I⁻/l and 126 μg/l, respectively) contribute significantly to the increased nutritional iodine supply of the German population.