Iodine Content of Milk and Other Foods

Excess dietary iodine intake has been identified as an issue of public health concern. The recommended dietary allowance for iodine is 100-150 (μg for adults and 70-120 (μg per day for children. A 1978 Food & Drug Administration survey found that milk and dairy products contributed more than 50% of the total food iodine intake for most age groups. A wide variety of dairy and food products were analyzed for iodine content. Red breakfast cereals and red candy (that contain FD&C Red No. 3), dairy products, eggs, milk, marine fish, and iodized salt contained the most significant quantities of iodine. Iodide content of individual raw milk samples from approximately 2500 farms in New York State was measured. Approximately 62% of all farms had milk iodide levels less than 200 μg/L, 28% between 200 and 499 μg/L, 7% between 500 and 1000 μg/L and 3% had greater than 1000 μg/L. The iodine content of all types of retail milk averaged 394.1 μg/L, cheese and cheese products averaged 15.2 μg/100 g. Most of the iodine partitions into the whey during cheese processing. For dairy powders (including whey), the average iodine content was 471.8 μg/100 g. Use of these powders as ingredients in other dairy and non-dairy products can contribute to high iodine content of other food products. In particular, the iodine content of ice cream was extremely variable, ranging from 18 to 359 μg/100 g. Generally, ice creams and ice milks that contained high proportions of whey and non-fat milk powders had higher levels of iodine in the finished product. Addition of FD&C Red No. 3 to foods substantially increases their total iodine content. However, the measured free iodide content of four brands of red breakfast cereal was higher than would be expected. Food and Drug Administration specifications for certified lots of FD&C Red No. 3 allows up to 0.4% sodium iodide as a contaminant from manufacture. The four brands of red breakfast cereal averaged 6% of their total iodine as free iodide (366 μg/30 g serving). This may indicate that free iodide may be released from FD&C Red No. 3 during processing.