Introduction
Iodine is a micronutrient essential for the synthesis of thyroid
hormones. An optimal iodine intake is necessary to avoid thyroid
abnormalities.1 Worldwide, iodine deficiency is still widespread,
although iodization of salt has clearly improved iodine status in
many countries.2 In all countries where an iodine fortification
program has been implemented, systematic monitoring should be
carried out to ensure that the fortification level is optimal.
In some countries, only household salt is iodized; in some
countries, all salt; and in other countries, salt for specific products
(e.g. bread salt) is iodized.3 Likewise, the fortification level and the
market share of iodized salt differ from country to country.3 The
effectiveness of a fortification program depends on these parameters.
To be successful, a fortification program should take into
account not only its effect on the median iodine intake in a population,
but also its effectiveness in reaching all groups of a
Abbreviations: C1a, cross-sectional study before fortification; C1b, follow-up
study of C1a; DanThyr, the Danish investigation of iodine intake and thyroid diseases;
IQR, interquartile range (range between 25 and 75 percentile); FFQ, food
frequency questionnaire.