Prevention and control of iodine deficiency : studies on the efficacy of oral iodized oil

Iodized oil, either injected or given orally, is the major alternative to iodized salt for controlling iodine deficiency. Oral administration has considerable advantages despite its shorter duration of effect. Little information is available on factors which influence the effect of orally administered iodized oil. In this dissertation the efficacy of oral iodized oil is studied with regard to the type of oil used, the dosage technique, intestinal parasites, nutritional status, sex and the consumption of raw cassava. The studies were carried out among Malawian school children. All results are based on iodine concentrations in casual urine samples collected at regular intervals after oral dosing with iodized oil. A model has been developed to describe the urinary iodine excretion pattern over time based on the retention and rate of elimination of iodine for subjects with different characteristics. The estimated durations of effectiveness were 13.7, 9.9 and 55.2 weeks for a single dose of iodized oil A (ethyl esters of iodized fatty acids; 490 mg iodine in 1 mL), a split-dose of oil A (2 x 245 mg iodine in 0.5 mL), and a single dose of iodized oil B (triacylglycerols; 675 mg iodine in 1.25 mL), respectively. In general, the duration of effectiveness of iodized oil A was significantly increased in subjects treated for parasitic infestations. For Entamoeba histolytica it appears that the absorption of oral iodized oil A is greatly disturbed as the assessed duration of effectiveness was found to be only 2 weeks for the untreated subjects. Children with a relatively large subcutaneous fat mass retained more iodine than subjects with little subcutaneous fat. For goitrous subjects both the retention and elimination of iodine were increased. A reduction in midupper-arm. circumference during the study increased the duration of effect. Based on the cumulative frequency distributions, of individually assessed durations of effectiveness, oral dosing with iodized oil was less effective in girls than in boys, and in those who consumed raw cassava than those who did not.