Prevalence of iodine deficiency disorders and urinary iodine excretion among primary children in Makina and Kilimani schools, Nairobi

Abstract

Children health around the world continues to be challenged by Iodine Deficiency Disorders (IDD) characterised by impaired development of the brain and mental function during pregnancy and early childhood. The control of IDD relies on universal salt iodation mainly in the form of potassium iodate (KIO). Despite iodination, IDD still account for much of the global divide in health among children in developing countries including Kenya. A survey on IDD prevalence in 1994 showed Kenya continues to resgister by high IDD prevalence of 15.5 %. As a result, iodate level was increased from 33.5mg to 168.5mg/Kg salt but since then no study has been carried out to determine the impact of this increased dosage on IDD among vulnerable groups. The main objective of this study was to investigate IDD prevalence among primary school going children by analysing urinary iodine excretion (UIE) levels in order to establish whether adequate amounts of iodine are reaching children in Makina and Kilimani primary schools. In addition, different brands of salts were analysed for iodine concentration using iodometric titration. The study also determined the effect of goitrogenic food consumption on UIE using a questionnaire. A total of 142 children participated in the study in May 2004. The study results show that the IDD prevalence was 3.5% which is below the WHO reference value of 5%. The median UIE of children was significantly different 2 = 6.88; df = 2; p = 0.032) between Kilimani (242.1 µg I2/L) and Makina (215.1 pg 12%L). UIE values were not related to age, sex and class in both schools. The overall median UIE for the study subjects was 229.1 µg I2/L which falls within the More than Optimum class according to WHO classification. On goitrogenic foods, cassava consumption significantly reduced the level of UIE (p < 0.05). Of the six salt brands analysed, the iodate levels ranged from 1.0 mg/kg to 288.0 mg/kg salt with only kensalt being within the WHO values (168.5 mg iodate/kg salt). When the six brands of salt were paired, there was a significant difference in: Kaysalt and Seasalt, Kensalt and Seasalt, and Mzuri with Refined (p < 0.05). In addition, the mean of the salt utilised at the household level had significantly different iodate levels compared with the market salts (p > 0.05). Of the goitrogenic foods analyzed, only cassava had effect on UIE levels. In conclusion, introduction of iodinated salt controlled IDD prevalence at 3.5% below the WHO reference value of 5% suggesting that the study population is iodine replete. However, this iodine sufficiency may be adversely affected by increased consumption of gitrogens, in particular cassava leading to hyperthyroidism. Though all salt brands contained iodate at different proportions, Sea salt in particular had low iodate levels below WHO recommended value putting consumers to the risk of developing hypothyroidism. Based on these findings, the study recommends periodic national evaluation of IDD control programme in order to ensure virtual elimination of IDD and sustainability of the programme in the country. It is also important that salt brands sold in the country are regularly monitored by Kenya Bureau of Standard (KBS) to avoid under and over iodination as revealed by the data on sea salt and refined salt respectively