Large Iodine Variability in Retail Cows' Milk in the U.S.: A Follow-Up Study among Different Retail Outlets

Area of Science:

• Nutritional Science
• Food Chemistry

Background:

• Previous studies revealed significant iodine content variability in retail milk across U.S. locations.
• The prior sampling design did not allow for location-specific difference detection.

Purpose of the Study:

• To assess iodine concentration in U.S. retail milk over time and across different geographic locations.
• To understand the extent of variability in iodine levels within and between locations.

Main Methods:

• Bimonthly collection of 2% fat milk samples from fourteen U.S. locations over one year.
• Duplicate sample analysis with quality control materials to ensure accuracy and precision.

Main Results:

• Overall mean iodine concentration was 82.5 (7.0) µg/240 mL, comparable to previous national findings.
• A wide range of iodine content (27.9-282 µg/240 mL) was observed among individual samples.
• Significant differences in mean iodine concentration were found between locations, with variations from -47 µg to +37 µg per serving compared to the national average.

Conclusions:

• Iodine levels in retail milk exhibit substantial geographic and temporal variability.
• Location-specific iodine concentrations can deviate significantly from the national average.
• Relying solely on national averages may lead to over- or underestimation of iodine intake from milk for certain populations.