Iodine content in fish and other food products from East Africa analyzed by ICP-MS

The purpose of this study was to measure the iodine content in sea water fish, fresh water fish, and different foods of plant origin commonly consumed in East Africa in order to evaluate dietary iodine sources for the population in the selected areas. Fish, and food items of cereals, vegetables, legumes, salt, and tea, were obtained from local market sampling areas in Ethiopia, Tanzania, and Burundi. In Ethiopia, water samples were also collected. The biological samples were dried, homogenized, and analyzed for iodine content by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) using tellurium as an internal standard. Quality control was carried out by analysis of four standard reference materials (SRM) with certified iodine concentrations. The results of the collected samples showed that the iodine concentration in fillet of salt water fish was 5 to 10 times higher than those of fresh water fish, with highest value of 920 microgram I/kg wet weight for change. The lowest iodine concentration in fillet was found in barbus from Lake Awasa with only 5-8 microgram I/kg wet weight. The iodine concentration in skin was higher than in fillets and the iodine concentration in fillets seemed to increase with fish size. The samples of plant origin were, in general, low in iodine. Highest values were found in red teff from Ethiopia with 64 microgram I/kg, while all samples from Mwanza in Tanzania, except spinach, contained iodine below the limit of detection of the method. As an iodine source, fresh water fish do contribute some to the iodine intake and might be of importance, especially since other foods contain small amounts of the element. In addition, the contribution of iodine from the surface water sampled in Ethiopia can be of importance. However, only sea water fish in the diet can be regarded as a really good iodine source.