Indicators of iodine status among adults. Dutch Nutrition Surveillance System

To evaluate the iodine status of Dutch adults we used three different iodine status indicators, namely urinary 24-hour iodide excretion (I/24 h), iodide/creatinine ratio in 24-hour urine samples (I/Cr) and 24-hour iodide excretion per kilogram body weight (I/kg). Additionally, the habitual daily iodine intake was calculated. Men had higher mean I/24 h and mean iodine intake than women. No differences between men and women were found for mean I/Cr and mean I/kg. Relatively high (greater than or equal to 18%) prevalences of low values for the different iodine status indicators were found, especially for I/24 h. The intraindividual variance for all three indicators was high. Risk assessment regarding iodine supply, based on urinary iodide excretion, depends on the indicator used, and therefore caution is called for when drawing conclusions. Our results do not argue against the usage of I/24 h as iodine status indicator. More research is needed to solve the question whether iodine requirement depends on such factors as body size, body composition and physical activity.