What is the general understanding of dietary iodine and the adequacy of iodine concentration in household iodized salt in rural and urban Jalisco, Mexico?
INTRODUCTION: Mexico began the iodization of salt in 1960, which dramatically reduced the incidence of goiter, but in the last year the incidence of goiter tripled in the state of Jalisco.
PURPOSE: Assess iodine knowledge of the people and concentration of iodine in salt samples in rural and urban localities of Jalisco, Mexico to explain the rise in goiter incidence.
METHODS: IRB approval was granted for this cross-sectional study. A convenience sample of 50 individuals, men and women older than 18, were selected from a rural and urban locality of Jalisco. The 100 individuals that completed a survey answered questions about demographics, medical history, iodine knowledge, and iodine dietary sources. A total of 130 salt samples were collected for potassium iodate (KIO3) analysis, 50 from each locality, and 30 were newly purchased samples. KIO3 concentration was measured by titration method, using a kit supplied by Boiteccsa Laboratorios in Sonora, Mexico. SPSS was used to conduct ANOVA, T-tests, and Coefficient Correlation statistical analyses.
RESULTS: Surprisingly, 32% of the rural salt, 22% of urban, and 11% of fresh salt samples had no iodine. Only 24% of rural salt samples contained adequate levels (15-40 mg/kg) and only 38% of urban samples. Only 8% of newly purchased salt had the correct amount of iodine as indicated on the label, 48% had less iodine, and 33% had excess potassium iodate (>40 mg/kg). Sadly, 88.1% of rural and 81.6% of urban residents did not know that pregnant women have higher iodine needs, and only 53% of rural and 56% of urban residents know that a lack of iodine can cause goiter. In addition, 78% of urban and 48% of rural residents used non-iodized sea salt. Education levels varied between rural and urban areas; however, education did not determine iodine knowledge (p value ≥ 0.5).
CONCLUSIONS: Even though Mexico mandates the iodization of salt, most of the salt samples did not meet the recommended potassium iodate concentration. Increased consumption of non-iodized sea salt and great variation in KIO3 concentrations in salt may explain the recent increase in goiter incidence. Iodizing sea salt might be an acceptable solution.
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Knowledge of dietary iodine and KIO3 concentration in household iodized salt in rural and urban Jalisco, Mexico
Research advisor: Amy Olson, PhD, RDN, LD