The introduction of complementary foods poses a serious risk for deteriorating iodine status. Thus, iodine fortification of complementary foods is recommended to ensure sufficient intake.The objetives of this study were to assess iodine status of peri-urban complementary-fed South African infants and to test the efficacy of small-quantity lipid-based nutrient supplements (SQ-LNS) in maintaining adequate iodine status.
Infants aged six months (n=750) were assigned to one of two SQ-LNS/day, both fortified with 45µg iodine, or a control group not receiving SQ-LNS. Urinary iodine concentrations (UIC) were measured at baseline (n=386) and at 12 months (n=262).
The geometric mean (95%CI) UIC at baseline was 333.8 (310.5,358.9)µg/L and decreased to 214.9 (189.2,242.6)µg/L at 12 months. Non-breastfed infants had lower UIC (159.6 [65.9,397.5]µg/L) and higher odds for being iodine deficient (UIC<100µg/L) than infants who continued to be breastfed (373.2 [202.6,522.9]µg/L) at 12 months. Infants receiving SQ-LNS had higher UIC (P=0.025) and lower odds for having a UIC<100µg/L at 12 months than controls, adjusting for maternal baseline UIC, age, sex and continued breastfeeding. In sub-group analysis, the effect of SQ-LNS for higher UIC at 12 months was only apparent in non-breastfed infants (P=0.039). These effects were no longer significant after adjusting for infant baseline UIC, reducing the sample size to n=124.
Only in non-breastfed infants iodine intake decreased from six to 12 months. In those, the provision of 45 µg iodine per day as SQ-LNS resulted in higher UIC at 12 months, but was not efficacious in counteracting an overall decline in iodine status.