Background: Iodine concentrations in Chilean schoolchildren are the highest in South America. This may be related to excessive sodium intake, which is associated with hypertension. However, iodine decreases blood pressure (BP), which would be a cardiovascular protective factor.
Objective and hypotheses: The objective of this study is to evaluate the effects of iodine on BP and cardiovascular risk factors, despite salt intake.
Method: Cross-sectional study. Seventy schoolchildren in Santiago, Chile were recruited (54.3% female, median age 13 (12.116.1)). Anthropometry, BP, and pubertal stages were evaluated, and a salt questionnaire was applied; salt intake was ad libitum. Samples were obtained of ultra-sensitive C reactive protein (hsCRP), glucose, triglycerides, LDL, creatinine, microalbuminuria, TSH, fT4, aldosterone and plasma renin activity (ARP). Iodine, creatinine, and sodium were measured in 24-h urinary samples and urinary iodine/urinary sodium ratio was calculated. Pearson correlation was performed for continuous variables; MannWhitney test for independent samples.
Results: Urinary iodine (medium; (interquartile range)) was 298.5 ug/l (168.5416.8). 65.7% presented iodine levels above requirements. A negative correlation was observed between urinary iodine and age (r=−0.4; P=0.001), systolic BP (r=−0.3; P=0.01), even when corrected for sodium excretion (r=−0.32; P=0.01). No statistically significant correlation was observed between urinary iodine and hsCRP (P=0.13), glycemia (P=0.3), cholesterol (P=0.93), triglycerides (P=0.76), LDL (P=0.34), TSH (P=0.98), aldosterone (P=0.59), ARP (P=0.19), neither with diastolic BP (P=0.09).
Conclusion: Schoolchildren in Santiago have much higher urinary iodine than recommended by the WHO (adequate iodine nutrition between 100199 ug/l). It decreases with age. Higher levels of urinary iodine corrected for urinary sodium excretion correlated with lower systolic BP, which could represent a cardiovascular protective factor.
Funding: This work was supported by Fondecyt 1130427 and 1150437, CORFO 13CTI-21526-P1, IMII P09/016-F (ICM), School of Medicine, Catholic University of Chile 2013 Chilean Grants.
01 Oct 2015 - 03 Oct 2015