Is the current iodine content in edible salt appropriate for eliminating iodine deficiency in China.

OBJECTIVE: This study was designed to measure the urinary iodine excretion of volunteers who daily consumed iodized salt and to evaluate whether the current iodine content in salt is appropriate. A field trial study was then conducted to determine how the salt iodization content should be adjusted, either to prevent iodine deficiency or to avoid excess consumption. METHODS: A total of 1,099 volunteers from 399 households from urban and rural regions were selected. The levels of salt iodine and urinary iodine were measured prior to the field trial. All the households were randomly divided into four groups according to different salt iodine concentrations: group A, 6+/-2 mg/kg; group B, 15+/-2 mg/kg, group C, 24+/-2 mg/kg; and group D, 34+/-2 mg/kg. The urinary iodine levels of households were determined over five consecutive days, starting on the 27th day after the intervention. RESULTS: Before the intervention, the median urinary iodine excretions for urban and rural residents are 294 microg/L and 509 microg/L, respectively. By contrast, urinary iodine excretion in all groups significantly declined after the intervention. The median excretions of urinary iodine on the 28th day after the intervention for all groups were 97.2 microg/L, 199 microg/L, 249 microg/L and 331 microg/L for urban residents, and 101 microg/L, 193 microg/L, 246 microg/L and 308 microg/L for their rural counterparts, respectively. CONCLUSIONS: The trial exhibits a tendency of slightly excessive iodine intake among the households under the currently recommended standard.

[A field trial study on the influence of different salt iodine concentration on urinary iodine excrition among the target population].

OBJECTIVE: To evaluate the influence of different salt iodine concentration on urinary iodine excrition among the target population and to determine the appropriate level of salt iodization to the local people. METHODS: In the 31-day random control trial, 1099 subjects from 399 families were randomly distributed into four groups and were supplied with iodized-salt with different iodine concentration of (6 +/- 2)mg/kg, (15 +/- 2)mg/kg, (24 +/- 2)mg/kg and (34 +/- 2)mg/kg, respectively. The original family salt was retrieved, whose iodine content was determined in those subjects' families with single-blind method. Baseline survey was conducted including salt and urinary iodine of the subjects. From the 27th day after the intervention, the urinary samples of the subjects were continuously collected for 5 days and urinary iodine was tesed respectively. Meanwhile, daily meal investigation was conducted to evaluate the influences originated from food. RESULTS: The median of local water iodine content was 3.05 microg/L and the average salt iodine concentration was (36.4 +/- 5.4)mg/kg while 98.8% of the household consumed sufficient iodized-salt. The medians of baseline urinary iodine of the subjects were 293.6 microg/L in city, and 508.8 microg/L in the countryside. The urinary iodine medians of four groups in the day of 28th after intervention were 97.2 microg/L, 198.6 microg/L, 249.4 microg/L, and 330.7 microg/L respectively in the city group, while they were 100.5 microg/L, 193.0 microg/L, 246.3 microg/L and 308.3 microg/L seperately in the countryside group. There was no statistically significant differences among the medians of urine iodine in the 27th, 28th, 29th, 30th and 31st day after intervention (P > 0.05). CONCLUSIONS: The target areas were with iodine deficiency which possessed high coverage of qualified iodized-salt at household level. The average urinary iodine level of the subjects was slightly higher than the standard level, according to the baseline survey. The intervetion trail showed that the salt iodine concentration of 15-24 mg/kg was sufficient to the local people.