Hypertension and Salt-Restrictive Diet Promotes Low Urinary Iodine Concentration in High-Risk Pregnant Women: Results from a Cross-Sectional Study Conducted After Salt Iodination Reduction in Brazil

Iodine Intake and its Interindividual Variability in Brazilian Pregnant Women: EMDI Brazil Study

Data on pregnant women's iodine intake are limited in Brazil. The aim of the study was to evaluate the contribution of foods, food groups, and food subgroups to the Brazilian pregnant women's iodine intake, and identify which food items explain the interindividual variability of their intake. A cross-sectional study with food consumption data of 2247 pregnant women from 24-h recalls was developed. Food items were classified according to the FAO/WHO GIFT classification, and their contribution to iodine intake and interindividual variability was assessed by the proportion of means method and linear regression, respectively. The mean usual iodine intake was 163.1 mcg (95% CI: 162.9-163.2). The food groups "spices and condiments," "cereals and their products," and "milk and milk products"; and the food subgroups "herbs and spices," "wheat and wheat-based products," "milk: fresh and processed," "dough-based sweets," and "eggs: fresh and processed" contributed to at least 80% of the iodine intake. Of these, only the food subgroups "milk," "dough-based sweets," and "eggs" did not explain the higher proportion (> 80%) of the interindividual variability. The contribution of "salt," "white French bread," "fluid whole milk," and "rice" to the iodine intake and its interindividual variability is highlighted. This study confirms the importance of "salt" as a dietary source of iodine and that few food groups and subgroups explained the difference in the iodine intake among pregnant women. Despite that, Brazilian staple foods, such as "rice," "beans," "eggs," "milk," and "bread" were identified as important for iodine intake and could be included in nutritional guidelines targeted to Brazilian pregnant women.

HPLC Analysis of the Urinary Iodine Concentration in Pregnant Women

Iodine is an essential component for fetal neurodevelopment and maternal thyroid function. Urine iodine is the most widely used indicator of iodine status. In this study, a novel validated ion-pair HPLC-UV method was developed to measure iodine concentration in clinical samples. A sodium thiosulfate solution was added to the urine sample to convert the total free iodine to iodide. Chromatographic separation was achieved in a Pursuit XRs C8 column. The mobile phase consisted of acetonitrile and a water phase containing 18-crown-6-ether, octylamine and sodium dihydrogen phosphate. Validation parameters, such as accuracy, precision, limits of detection and quantification, linearity and stability, were determined. Urinary samples from pregnant women were used to complete the validation and confirm the method's applicability. In the studied population of 93 pregnant women, the median UIC was lower in the group without iodine supplementation (117 µg/L, confidence interval (%CI): 95; 138) than in the supplement group (133 µg/L, %CI: 109; 157). In conclusion, the newly established ion-pair HPLC-UV method was adequately precise, accurate and fulfilled validation the criteria for analyzing compounds in biological fluids. The method is less complicated and expensive than other frequently used assays and permits the identification of the iodine-deficient subjects.

Effect of iodine supplementation in pregnancy on neurocognitive development on offspring in iodine deficiency areas: a systematic review

Objective

To investigate the effect of iodine supplementation during gestation on the neurocognitive development of children in areas where iodine deficiency is common.

Methods

Based on the PRISMA methodology, we conducted the search for articles in the PubMed, LILACS and Scopus databases, between March and April 2020, without limitation of dates. We used descriptors in English, Portuguese, and Spanish, without filters. Four clinical trials and four cohort articles were included in the review.

Results

The maximum supplementation was 300 μg of potassium iodide per day. The Bayley scale and Children's Communication Checklist-Short were used to assess neurodevelopment in children. There was no significant improvement in the children's mental development index and behavioural development index in the supplemented group; however, the psychomotor development index (PDI) showed improvement in the poorer gross motor skills. We found differences in the response time to sound in the supplemented group living in mild deficiency areas.

Conclusion

Daily supplementation with iodine can improve poor psychomotor development of children living in mild to moderate iodine deficiency areas. Thus, it is necessary to perform further studies to assess the effect of supplementation on neurodevelopment before, during and after gestation in mild to moderate iodine deficiency areas.