Iodine contents in conventional ultra-high temperature (UHT) processed cow milk: Changes over the year and regional differences. Implications for epidemiological studies on iodine nutritional status

Abstract

Background and objectivesUltra-high temperature (UHT) processed cow milk is the milk most commonly consumed in Southwest Europe. The study objectives were: 1) to describe the pattern followed by iodine concentration (IC) in conventional UHT milk over the year, and 2) to find out any differences in IC in this type of milk depending on its geographical origin. Material and methodsBricks of conventional UHT cow milk of commercial brands available in food stores in Vitoria-Gasteiz (Araba/Álava), Basque Country (Spain) were bought for 12 consecutive months, and their ICs were measured using high performance liquid chromatography (HPLC). ResultsMedian (P25-P75) IC in UHT milk (n = 489) was 190 (159–235) µg/L. IC in milk showed great changes over the year, reaching peak values between January and May (241 [201−272] µg/L), and minimal levels between July and November (162 [134–185] µg/L) (P < 0.0001). The IC of milk packed in Germany was significantly lower than that of milks packed in Spain and France, 119 (106–156) µg/L versus 189 (159–229) µg/L and 205 (176–243) µg/L respectively (p < 0.0001). ConclusionsConventional UHT cow milk is a very important nutritional source of iodine, but its IC is highly variable. Knowledge of the pattern followed by IC in milk over the year is of great interest for planning epidemiological studies on iodine nutritional status in schoolchildren and for interpretation of their results.