Urinary iodine excretion in mothers and their breast-fed children in relation to other childhood nutritional parameters

Objective: There is currently no coordinated policy on the epidemiology and control of iodine deficiency disorders (IDD) in many parts of Africa even where these disorders are endemic. Assessment of the urinary iodine excretion is believed to give the best index of the prevalence of IDD in the community. This study aimed to establish whether: (i) the breast-fed child of an iodine replete mother was protected from IDD and, (ii) infants at risk of IDD and in need of immediate iodine supplementation could easily be identified through simple screening methods. Design: Randomized, cross-sectional study. Setting: A tertiary care infant welfare clinic in Ibadan, South-western Nigeria, a geographical area recognised to be outside Nigeria's endemic goitre belt (goitre prevalence < 5.0%). Subjects: 68 healthy mother-child pairs. The children were all aged 9-18 months and breast-fed almost exclusively. Interventions: Nil. Methods: The relationships of anthropometric, iodine status (casual urinary iodine (I) and iodine/creatinine ratio (I/Cr)) and nutritional indices (weights, haematocrits) of the mothers with those of their breast-fed children were assessed, as well as how these parameters differed between the children classified on the basis of their mid-upper arm circumference, MUAC, as: (A) borderline malnourished, MUAC < 13.5 cm and, (B) well nourished, MUAC > 13.5 cm. Results: The maternal values for I and I/Cr were significantly (p < 0.001) greater than those of their breast-fed infants, although the respective mother-child pair values correlated positively (I, r 0.47; I/Cr, 0.21; both p < 0.05). There was thus a gradient in iodine status between the mother and her breast-fed infant that is unfavourable to the growing child; the latter may thus require iodine supplementation in spite of the fact that the mother is iodine replete. Among the children, those considered well nourished (Group B) had similar iodine status parameters as those considered poorly nourished (Group A) suggesting that malnutrition alone should not be the determinant of the prioritization (or otherwise) of iodine supplementation in a population with coexistent iodine deficiency and malnutrition. Mean values for (I) in all the children (9.9 microgram/dL) fell in the iodine deficiency range (< 10 microgram/dL), although all the mothers were iodine replete (mean urinary (I) 14.5 microgram/dL), despite the fact that all resided in a non iodine deficient area. Conclusion: The study suggests that: (i) the breast-fed child of an iodine replete mother resident in a non-iodine deficient area may be iodine deficient and in need of iodine supplementation; (ii) malnutrition, as defined by the simple community screening method of measuring the MUAC, will not accurately identify those infants in immediate need of iodine supplementation. These observations have important implications for planning IDD control programmes in Africa.