12th IFDC 2017 special issue – Iodine, selenium and iron contents in Portuguese key foods as consumed

Iodine, selenium and iron are micronutrients essential for thyroid hormone synthesis causing their low plasma levels an additional risk of autoimmune thyroid diseases. A Portuguese TDS pilot study representative of diets in Portugal was carried out, since foods are the main natural sources of these micronutrients. Six hundred and twenty-four samples were collected based on local markets and later analysed in pools of ten meat samples, twenty-seven fish, nine chicken eggs and six cow dairy products. The iodine and selenium contents were determined using ICP-MS after alkaline (iodine) or acid digestion (selenium) and iron by ICP-OES after acid digestion. The highest content of three oligoelements was detected in fish. Meat had lower iodine content and the dairy products lower selenium and iron levels. Sardine presented significant different levels in summer and winter for iodine, and in summer and autumn for selenium, mackerel had diverse contents of iron in summer and autumn. The contribution of salmon and milk for iodine RNI was around 40%, for children and adults. Shrimp is also the food with more selenium, exceeding 1.5 times the % RNI for children and adults females, while iron maximum contribution was observed in meat for children and adult males.