Prevalence of Iodine Deficiency Disorders and Urinary Iodine Excretion among Primary School Children in Makina and Kilimani in Nairobi, Kenya

Objective: This study was design to determine the prevalence of IDD by measuring urinary iodine excretion among primary school age children, to assess the effect of goitrogen on urinary iodine absorption and assess the impact of salt iodization program.

Methods: A questionnaire was given to all students participating in the study to be filled out by their families regarding whether or not they used iodized salt in the preparation of food in their homes, whether they consumed cassava, kale cabbage and sorghum including the frequency of consumptions and to bring two table spoonful of salt they use at home. The iodine in urine was determined using sadell kolthoff method while iodate in salt was analysed using iodometric titration.                                                                                                                                                                                                                                                          

Results: Of the 142 respondents who participated in the study, the overall prevalence of IDD in the study population was 3.5% (excreting less than 99 µg I₂/l) which is below the WHO value of less than 5% implying sufficient iodine in the study population. In Makina, it was 5.4% with a median urinary iodine excretion (UIE) of 215.1µgI₂/l ±57.8 while Kilimani had a prevalence of 2.4% and a median UIE of 242.2 µg I₂/l. ±67.7. In addition, 18.4% of the study subjects excrete optimum UIE (100-199 µg I₂/l) while 78.1% excrete above 200 µg I₂/l. On the consumption of salt, 82.3% reported that the salt was iodated and 63.9% knew why salt is iodated while 17.7% reported that the salt was not iodated while 36.1% did not know the reason for salt iodation. All the samples (home salt) (range 8.1-341.93 mg iodate/kg salt were analysed and had a mean of 134.88 mg iodate/kg salt (± 61.8). However, there was no significant difference between the iodate levels in the salt samples from the households of the two schools  (Makina and Kilimani having a mean of 145.1 mg iodate per Kg salt and 135 mg iodate per Kg salt respectively) (t = -0.932;p > 0.05). Analysis of the six salt brands (53  salt samples) obtained by direct purchase indicated that the brands Kay salt, Kensalt, sea salt, refined, mzuri and unknown had a mean of 159.67, 165.89, 2.02, 191.45, 150.55 and 176.58 mg iodate/Kg salt respectively.  Only Kensalt was within the recommended iodate levels of 168.5 mg/kg salts. When iodate levels in the direct purchase salt brands and home salt were paired, there were significant differences (p < 0.05).  On the association between UIE and consumption of goitrogenic foods, there was significantly increased levels of urinary iodine in non-consumers of cassava relative to the consumers (p = 0.032).

Conclusion: IDD prevalence in Nairobi is 3.5%, which is below the WHO value of less than 5% suggesting that the study community is iodine sufficient. Universal salt iodation is effective in controlling IDD among school children in the study population in Kenya. Many brands of salt sold in the Kenya have less and others high iodate levels than the Kenya Government recommended levels of 168.5 mg/kg salt. Consumption of kale (sukuma wiki), cabbage and sorghum has no effect on urinary iodine excretion except cassava since it affects iodine absorption that could put consumers at risk of hypothyroidism. Effective monitoring and surveillance by Kenya Bureau of standards should be encouraged to guard against consumption of salt preparations that do not meet the required standards. Health Education programs in schools should be conducted across Kenya to guard against IDD.