Determining median urinary iodine concentration that indicates adequate iodine intake at population level.
OBJECTIVE
Urinary iodine concentration is the prime indicator of nutritional iodine status and is used to evaluate population-based iodine supplementation. In 1994, WHO, UNICEF and ICCIDD recommended median urinary iodine concentrations for populations of 100- 200 micro g/l, assuming the 100 micro g/l threshold would limit concentrations <50 micro g/l to </=20% of people. Some scientists felt this proportion was unacceptably high and wanted to increase the threshold above 100 micro g/l. The study was carried out to determine the frequency distribution of urinary iodine in iodine-replete populations (schoolchildren and adults) and the proportion of concentrations <50 micro g/l.


METHODS
A questionnaire on frequency distribution of urinary iodine in iodine-replete populations was circulated to 29 scientific groups.


RESULTS
Nineteen groups reported data from 48 populations with median urinary iodine concentrations >100 micro g/l. The total population was 55 892, including 35 661 (64%) schoolchildren. Median urinary iodine concentrations were 111-540 (median 201) micro g/l for all populations, 100-199 micro g/l in 23 (48%) populations and >/=200 micro g/l in 25 (52%). The frequencies of values <50 micro g/l were 0-20.8 (mean 4.8%) overall and 7.2% and 2.5% in populations with medians of 100-199 micro g/l and >200 micro g/l, respectively. The frequency reached 20% only in two places where iodine had been supplemented for <2 years.


CONCLUSIONS
The frequency of urinary iodine concentrations <50 micro g/l in populations with median urinary iodine concentrations >/=100 micro g/l has been overestimated. The threshold of 100 micro g/l does not need to be increased. In populations, median urinary iodine concentrations of 100-200 micro g/l indicate adequate iodine intake and optimal iodine nutrition.
Delange
François
F
International Council for Control of Iodine Deficiency Disorders, Brussels, Belgium. fdelange@ulb.ac.be
de Benoist
Bruno
B
Burgi
Hans
H
D000328:Adult; D002648:Child; D003677:Deficiency Diseases / Q000453:epidemiology / Q000652:urine*; D005260:Female; D014943:Global Health; D006801:Humans; D007455:Iodine / Q000008:administration & dosage / Q000172:deficiency / Q000652:urine*; D008297:Male; D009752:Nutritional Status; D011159:Population Surveillance; D012016:Reference Values; D011795:Surveys and Questionnaires
D007455:Iodine