Low urinary selenium levels are associated with iodine deficiency in Brazilian schoolchildren and adolescents.

BACKGROUND: Selenium (Se) and iodine (Io) are important micronutrients for the proper functioning of the thyroid gland, as they are crucial for the synthesis and activation of the thyroid hormones (TH) triiodothyronine (T3) and thyroxine (T4). OBJECTIVE: To evaluate the Se and Io nutritional status among schoolchildren. METHODOLOGY: Cross-sectional, descriptive and analytical study conducted in 982 schoolchildren aged 6-14 years from public schools in the state of Bahia, Brazil. Sociodemographic and anthropometric variables, as well as urinary Se (USC) and Io concentrations (UIC) using the inductively coupled plasma mass spectrometry (ICP-MS) method and thyroid-stimulating hormone (TSH) from filter paper blood collection, were evaluated. RESULTS: The median USC and UIC were 38.7 and 210.0 (IQR: 26.8-52.9 and 129.3-334.1 µg/L, respectively). The prevalence of iodine deficiency and excessive UIC were observed in 17.1% and 30.9% of schoolchildren, respectively. Concomitant low USC and IoD was found in 3.9% of schoolchildren. There was a positive correlation between USC and UIC (r = 0.60; p = 0.00). The median TSH was 0.95 (IQR: 0.69-1.30 µUI/L). CONCLUSIONS: This study demonstrates that USC is a good biomarker for assessing Se status, meantime more studies are needed to establish cutoff USC in child population. Despite adequate median intake, a subgroup of schoolchildren had IoD and low USC. The correlation between UIC and USC point at the importance of two micronutrients, raising the question whether measuring Se should be included in monitoring programs that address the prevention of nutritional disturbances.

Association of Salt Iodization and Urine Iodine Concentration in Schoolchildren from Public Schools in Northeast of Brazil.

Iodine deficiency (ID) is recognized as a leading risk factor for child development. Universal salt iodization (USI) is an effective and well-established intervention strategy for the prevention of iodine deficiency disorders (IDD). To evaluate the levels of iodine in household salt samples and the urinary iodine concentration (UIC) in schoolchildren aged 6 to 14 years in public schools in Bahia, Brazil. A cross-sectional study was conducted with 1231 students (6 to 14 years old) from 17 public schools in Bahia. The iodine concentration was evaluated in salt and UIC samples. The adapted Sandell-Kolthoff reaction was used to determine urinary iodine levels. A spectrophotometer (UV-Vis) was used to examine the reduction of ceric ammonium sulfate. A standard iodine solution using a potassium iodate was used to extrapolate the iodine concentrations. The total of 665 salt samples had a median iodine concentration of 24 mg/kg (25th-75th percentile 17.0 to 28.5 mg/kg). The largest proportion (79.6%) of salt samples had iodine concentration in the recommended range, 17.6% of the samples presented iodine at a salt concentration below the established level (<15 mg/kg) and a small proportion was above it (2.8%). The general mean urinary iodine concentration (MUIC) was 217.53 ± 28.30 µg/L and median was 205.50 µg/L. The students evaluated and the salt samples analyzed showed satisfactory results, as recommended by Brazilian legislation and nutritional recommendations of the World Health Organization (WHO).

Assessing Cassava Flour Consumption Impact on Iodine Nutritional Status in Schoolchildren from Public Schools in Brazil.

Cassava (Manihot esculenta Crantz) is an important food source in many developing countries. This root contains cyanoglucosides, which can aggravate iodine deficiency disorders (IDDs). To analyze the impact of cassava flour consumption (CFC) on urinary iodine concentration (UIC) among schoolchildren from public schools in Bahia, Brazil. Cross-sectional study was conducted on 1231 schoolchildren (ages 6-14 years old). Anthropometric parameters, household food insecurity, UIC, and CFC were evaluated. CFC prevalence was 90.8%. The mean UIC indicated adequate iodine nutrition in group A (CFC positive) and group B (CFC negative) (203.29 ± 81.08 µg/L versus 225.98 ± 76.59 µg/L, respectively). We found that daily cassava flour intake did not significantly raise the risk of iodine deficiency (ID) (odds ratio [OR] = 1.43 [confidence interval (CI) 0.72-2.82]; p = 0.29), nor did it significantly protect against excessive iodine intake (EII) (OR = 0.70[CI 0.39-1.26]; p = 0.24). The prevalence of iodine deficiency (ID) (12.6% versus 8.9%) and EII (9.6% versus 15%) did not significantly differ between both groups. The results of this study suggest that the cyanides present in cassava flour have very little influence on iodine metabolism, which is probably justified by cassava processing methods.

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.

During pregnancy, the demand for daily iodine increases by 50-70% which occurs to reach around 250 µg/day. Limited information is available on the association of high-risk pregnancy (HRP) with urinary iodine concentration (UIC) and variables such as socioeconomic factors. To analyze iodine nutritional status and socioeconomic, demographic and anthropometric characteristics among women with HRP screened at the main referral public health center at Bahia, Brazil, a cross-sectional study was conducted in 241 women with HRP (15-46 years old) in Salvador, Bahia, Brazil. The median UIC (MUIC) was 119 µg/L (25-75th, 58.7-200.4 µg/L), indicating mild iodine deficiency. Low UIC (< 150 µg/L) was detected in 61.8% (n = 149) - 18.3% between 100 and 150 µg/L, 24.5% between 50 and 100 µg/L, and 19.1% with UIC < 50 µg/L. Overall, 53% (n = 128) of our population adhered to a low-salt diet, and 32.5% (n = 77) had hypertension. Among the 73% of hypertensive women adhering to a salt-restricted diet, there was a 112% increased risk of iodine deficiency observed (OR = 2.127; 95% confidence interval [1.178-3.829]; p = 0.011). Adhering to a salt-restricted diet was associated with iodine deficiency (OR = 1.82; 95% confidence interval [1.073-3.088], p = 0,026). Hypertension and salt restriction diet significantly increased susceptibility for iodine deficiency in HRP. Therefore, low-salt diet when prescribed to pregnant women (PW) might be carefully followed by iodine nutritional status assessment or universal preconception iodine supplementation.