Sources and Content of Iodine in California Milk and Dairy Products

In recent years, milk and milk products have been implicated as a major contributor to dietary iodine. The possible sources of iodine in milk are supplemental iodine in dairy feeds, iodophor-containing sanitizers used at the dairy farm and/or the processing plant, iodophor-containing teat dips used to control the spread of mastitis among dairy cows, and iodine-containing medications used by veterinarians. A five-year program to determine the California raw milk iodine concentration and identify the sources of adventitious iodine has resulted in the California dairy industry deciding late in 1980 to reduce iodine supplementation of dairy feeds. This resulted in a decrease in milk iodine concentration in samples received in 1981 to 256 ± 234 μg/kg compared to 1980, when the concentration was 474 ± 304 μg/kg. The industry has set up a program to monitor the raw milk iodine concentration at the producer level, thus ensuring that the concentration will continue to decline.