Endocrine Abstracts

Background: Many studies in Norway have found inadequate iodine status in pregnant and lactating women, but no studies have been undertaken in a random, population-based sample. Globally, the main strategy to eliminate iodine deficiency is iodization of salt. However, this is not compulsory in Norway, where the current legislation only permits iodization up to 5 μg per gram of salt. To reach the Nordic Nutrition Recommendation (NNR) of 200 μg/day iodine, supplements are recommended to lactating women who do not cover their needs through food sources. In Norway, the main iodine sources in the diet are milk and lean seafood. A study in 130 lactating women in 2018 revealed that mild-to-moderate iodine deficiency was common in the inland area of Norway. Considering the importance of iodine for infant development, more information on iodine status in lactating women is needed.

Objective: This study aimed to evaluate iodine status and intake in a random sample of lactating women and their infants in the inland area of Norway.

Methods: From April 2020 to October 2021, 366 mother-infant pairs were recruited in a cross-sectional study through public health care centers. Urine samples from the mothers and children and breast milk samples were collected for analysis of iodine concentration. Data on habitual and recent iodine intake was collected using food frequency questionnaire (FFQ) and 2 x 24-h dietary recall (24HR), respectively.

Results: Urinary iodine concentration (UIC), breast milk iodine concentration (BMIC) and data from FFQ are pending analyses. Recent use of iodine-containing supplements was reported by 30.1 % of the women. Including supplements, the estimated 24 h median (IQR) iodine intake was 125 (70.8, 233.45) μg/day. Excluding supplements, the 24 h median (IQR) iodine intake was 100.1 (65.05, 161.5) μg/day. According to the 24 HR, the food sources that contributed the most to the iodine intake were milk and dairy products, carbonated mineral water from a specific water source in Larvik (Norway), lean fish, whey cheese and eggs. More than two-thirds of the 24HR (68.2 %) had an estimated iodine amount below the NNR recommendation for lactating women.

Conclusion: We found inadequate iodine intake in lactating women in the inland area of Norway. Milk, lean fish, eggs, and a specific type of carbonated mineral water were important iodine sources in the diet. The study indicates that a large proportion of lactating women in Norway may need iodine-containing supplements due to a low dietary iodine intake.