Iodine content of New Zealand dairy products

Abstract

New Zealand provides a naturally low-iodine environment. Estimates of New Zealanders’ iodine intakes suggest that intakes have decreased steadily during the 1980s and 1990s. This evidence combined with the reported decrease in the use of iodophors in the dairy industry prompted a review of the iodine content of New Zealand dairy products. Sixteen main types of dairy product and one non-dairy alternative (soy drink) were examined in the survey. In general, up to five different brands with dominant market share were sampled for each type of dairy product in each of the two seasons (winter and spring). The mean values for almost all of the dairy products tested fell within a four-fold range (0.06–0.20 mg/kg). The sole exception was butter (all samples less than 0.04 mg/kg). Fresh milk products (standard and trim milk) sampled in winter (June 1997) had significantly higher iodine content than the products sampled in spring (October 1997). Also, for fresh milk products, samples from the south of the country had higher iodine content (significant for one of the two brands from this region) than samples from the north of the country; whereas samples from the north had significantly higher iodine contents than samples from the central region.