Changes in iodine supply in adult Czech population after iodine deficit eradication and causes. Random study of adults in two regions in the Czech republic with in between period of 5 years

INTRODUCTION: By iodine, similar to many other elements that are important for human body, the daily intake has some limitations. Neither deficiency, nor surplus are required. In the second half of the nineties in the 20th century, iodine deficiency in Czech republic could have been eradicated to a great extent. However, changes in iodine supply in population still have to be monitored, looking for the causes in nutrition. AIM: To monitor the changes in ioduria in adult population and search for causes of these changes in dietary habits. METHODS: In 1999, 2000, 2004 and 2005, urinary iodine was determined in randomly selected population of 1139 adults aged 18 to 65, domiciled in the regions Jablonec nad Nisou or Pribram. The measurement of iodine was based on alcaline ashing of urine specimens preceding Sandell-Koldhoff reaction. The information about possible nutrition sources of iodine (seafood, milk, salt, eggs, mineral water) was found out through questionnaires and controlled interviews. RESULTS: During the respective 5 years, significant increase of the mean level of urinary iodine from 117 +/- 3.09 microg/l to 193 +/- 8.17 microg/l occured. In both regions, significant increased frequency of supernormal values of urinary iodine (over 300 microg/l) occured: from 0% to 13-18%. However, the changes in the region Jablonec nad Nisou were more positive than in the other one: decrease of below-normal urinary iodine concentration (50 to 99 microg/l) from 43% to 22% in the region Jablonec nad Nisou was found, while the number of below-normal urinary iodine concentration in the other region increased from 24% to 33% and the number of adults with optimum iodine concentration has also decreased (from 75% to 53%). Nutrition changes of possible influence on the urinary iodine concentration (seafood, milk, eggs, salt, mineral water with iodine) were observed and significant increase in consumption of eggs, mineral water with iodine and milk was found out. The consumption of mineral water with iodine has increased from 5% to 10% in Jablonec nad Nisou and from 15% to 26% in Pribram. Multi-factor analysis of four major nutrition sources of iodine (consumption of milk, seafood, eggs and salt) has proven the biggest influence of regular egg and milk consumption on urinary iodine concentration in adults.