Iodine intake among children and adolescents in Norway: Estimates from the national dietary survey Ungkost 3 (2015-2016)

National monitoring of iodine, sodium, and vitamin D status in toddlers and women of childbearing age - results and lessons learned from a pilot study in Norway

Background

Norway is lacking a population-based national monitoring program for iodine, sodium, and vitamin D status.

Objective

The aim of this study was to pilot-test a study design for collecting biological samples from a country-representative sample of 2-year-old children and their mothers and to report results for iodine, salt, and vitamin D at baseline, before initiation of salt iodization in Norway.

Design

In a cross-sectional study, we recruited 2-year-old children and their mothers during the routine 2-year check-up through 38 randomly selected health clinics in 2021. Spot urine samples were analyzed for iodine, creatinine, and sodium, and dried blood spots from the mothers were analyzed for thyroglobulin (Tg) and 25-hydroxyvitamin D (25(OH)D).

Results

We aimed at including 400 mother-child pairs but recruited only 55 pairs. Major challenges were closed health clinics due to the COVID-19 pandemic, lack of motivation of the health personnel to prioritize recruiting, missing information about non-participation, and high workload for participants. The median urinary iodine concentration (UIC) was 123 (95% CI: 76, 228) µg/L in the toddlers and 83 (95% CI: 72, 99) µg/L in the mothers. The median urinary sodium concentration (UNaC) was 62 (95% CI: 37, 91) mmol/L in the toddlers and 93 (95% CI: 77, 107) mmol/L in the mothers. Of the mothers, 18% had levels of 25(OH)D <50 nmol/L (suboptimal status).

Discussion and conclusion

Lessons learned from the pilot study will be used to design a national monitoring program for toddlers and women of childbearing age in Norway. The results indicate that 2-year-old children and women of childbearing age in Norway may have inadequate iodine intakes at the group level, while for vitamin D, most of the mothers had adequate status.

Iodine concentration in tap water, mineral water, and coffee

Background

Sufficient iodine intake is important for thyroid function and, particularly, among women of reproductive age. Water is a universal component of the diet and could be an important source of iodine. Iodine concentration in drinking water varies geographically. It is therefore of nutritional interest to explore the variation and the contribution of iodine from water and beverages.

Objective

To analyze the iodine concentrations in tap water, mineral waters, and coffee from different regions of Norway.

Design

Samples of tap water were obtained from different regions of Norway. Six brands of mineral water and several samples of coffee brews were sampled. The iodine concentration was determined by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS).

Results

Iodine concentration in tap water varied from below Limit of Quantification to 0.8 μg/100 mL. Five out of six brands of mineral water had low concentrations of iodine, and one brand had a concentration of 38 μg/100 mL. Iodine concentrations in black coffee brews were similar to the tap water. Adding milk or plant-based milk alternatives increased the iodine concentration.

Discussion

Overall, iodine concentrations in tap water were generally low; however, variations were observed both for inland and coastal regions. A trend was seen for higher iodine concentrations in coastal region compared with inland region. For the average habitual iodine intake in Norway, tap water may not contribute significantly. One brand of mineral water could have considerable impact on iodine intake. Coffee does not contribute substantially more to iodine intake than tap water, unless the brew is added with milk or plant-based milk alternatives that contain iodine.

Conclusion

This study adds new information about iodine dietary sources in Norway. While tap water and black coffee have limited impact due to generally low concentrations, one mineral water brand may contribute significantly to iodine intake.

Comparison of dietary intake measured by a web-based FFQ and repeated 24-hour dietary recalls: the Hordaland Health Study

All dietary assessment methods inevitably introduce measurement errors, which should ideally be considered during data analysis and interpretation. Methodological studies should be conducted to address how well a given assessment method captures dietary intake and to highlight the extent and direction of the measurement error. Within a subgroup of the Hordaland Health Study (HUSK3), we examined the relative validity of a web-based food frequency questionnaire (WebFFQ) by comparing its estimates of mean daily intake of nutrients and foods with estimated mean daily intakes from repeated administrations of 24-hour dietary recall interviews (24-HDRs). Men and women born between 1950 and 1951 were recruited from HUSK3. The participants (n = 67) completed a WebFFQ and three non-consecutive 24-HDRs over the course of a year. Relative validity was assessed using Spearman's rank correlation, crosstab analysis and Bland-Altman plots. Linear regression models were used to compute the calibration coefficients. The estimated correlation coefficients were acceptable or strong for all nutrients and foods except iodine (r_s = 0⋅19). The highest correlation coefficient was found for juice (r_s = 0⋅71), whereas the lowest correlation coefficient was found for iodine (r_s = 0⋅19). Cross-classification by quartiles categorised more than 72 % of the participants into the same or adjacent quartiles using the two methods. Few data points fell outside the limits of agreement in the Bland-Altman plots. Calibration coefficients ranged from 0⋅10 (wholegrain) to 0⋅81 (alcohol). Our findings suggest that the WebFFQ has reasonable ranking abilities for all the included nutrients and foods, except for iodine.

Assessment of iodine fortification of salt in the Danish population

PURPOSE

We assessed the effect of the current iodine fortification level (20 µg/g household salt and salt included in bread and bakery products) on inadequate and excessive intake in the general Danish population. Intake models with/without the contribution from food supplements and effects of excluding specific food groups were evaluated.

METHOD

Data from the Danish National Survey of Dietary Habits and Physical Activity in 2011-13 (N = 3946, aged 4-75 years) stratified by age-group and sex were used to estimate habitual dietary iodine intakes, and compared with established dietary reference values.

RESULTS

The proportion with an estimated inadequate iodine intake was ≤ 3% for males and ≤ 5% for females, except for 15-17-year-old girls, where the probable prevalence of an inadequate intake was 11%. Including the contribution from food supplements gave similar results (10%). High intakes (as defined by 95th percentile) from food sources generally did not exceed the tolerable upper intake level (UL). However, for the youngest age-groups (4-6-year-old boys/girls and 7-10-year-old boys), the 95th percentiles exceeded the UL with 11%, 4% and 7%, respectively, when food supplements were included in the estimates. Especially exclusion of dairy products and bread led to an inadequate intake for both boys and girls.

CONCLUSION

The current fortification level may provide an inadequate iodine intake for some females and on the other hand lead to excessive intakes in the youngest age-groups. The study shows the importance of choosing iodine-rich alternatives when excluding major sources of iodine in the Danish diet.

OUP accepted manuscript

Context

Adequate iodine intake is essential throughout life. Key dietary sources are iodized salt and animal products, but dietary patterns in Europe are changing, for example toward lower salt intake and a more plant-based diet.

Objective

To review iodine intake (not status) in European populations (adults, children, and pregnant women) to identify at-risk groups and dietary sources.

Data sources

PubMed, Embase, and Cochrane databases, as well as European national nutrition surveys were searched for data on had iodine intake (from dietary assessment) and sources of iodine, collected after 2006.

Data selection

In total, 57 studies were included, comprising 22 national surveys and 35 sub-national studies. Iodine intake data were available from national surveys of children aged <10 years (n = 11), 11–17 years (n = 12), and adults (n = 15), but data from pregnancy were only available from sub-national studies.

Results

Iodine intake data are lacking—only 17 of 45 (38%) European countries had iodine-intake data from national surveys. Iodine intake reported from national surveys was below recommendations for: (1) children aged <10 years in 2 surveys (18%), (2) boys and girls aged 11–17 years in 6 (50%) and 8 (68%) surveys, respectively, and (3) adult men and women in 7 (47%) and 12 (80%) surveys, respectively. In pregnant women, intake was below recommendations except where women were taking iodine-containing supplements. Just 32% of national surveys (n = 7) included iodized salt when estimating iodine intake. Milk, dairy products, fish, and eggs were important contributors to intake in many countries, suggesting limited sources in plant-based diets.

Conclusion

Results are limited by the challenges of dietary assessment for measuring iodine intake. Future national surveys should include iodine intake. Policy makers should consider dietary sources alongside any iodized salt policies when considering methods for improving population iodine intake.

Systematic Review Registration

PROSPERO 2017 CRD42017075422.

Lack of nutritional knowledge among Norwegian medical students concerning vegetarian diets

Aim

Vegetarian diets are increasingly popular, particularly among young women. However, exclusion of animal products from the diet increases the risk of micronutrient deficiencies, which is particularly unfortunate during pregnancy and childhood. A person needs a substantial amount of nutritional knowledge to achieve a nutritionally complete vegetarian diet. We have tested nutritional knowledge among well-educated young vegetarians and omnivores.

Subjects and methods

In October 2018, medical students at the University of Bergen, Norway (N = 880), were invited to take an anonymous survey to test their nutritional knowledge concerning micronutrients in vegetarian diets.

Results

The responses from the students (n = 394, 45%) were categorized according to diet: former or current vegetarians (24%) versus always omnivores (76%). Forty-five percent of the vegetarians and 28% of the omnivores did not consider it necessary to take supplements while following a vegetarian diet. Sixty-one percent of vegetarians and 38% of omnivores considered it possible to have a well-balanced vegan diet. Plant foods were wrongly considered to be a dietary source of vitamin B12 by 33% and of iodine by 20% of the students.

Conclusion

Nutritional knowledge concerning vegetarian diets was not optimal among Norwegian medical students, even if they had ever followed a vegetarian diet. As vegetarian diets are popular among the younger generation and pose a risk of micronutrient deficiencies, this is a public health concern. Nutrition education should be improved in the population. A more extensive integration of nutritional training in the medical curriculum must be implemented so doctors can give adequate nutritional guidance.

Mesopelagic Species and Their Potential Contribution to Food and Feed Security-A Case Study from Norway

The projected increase in global population will demand a major increase in global food production. There is a need for more biomass from the ocean as future food and feed, preferentially from lower trophic levels. In this study, we estimated the mesopelagic biomass in three Norwegian fjords. We analyzed the nutrient composition in six of the most abundant mesopelagic species and evaluated their potential contribution to food and feed security. The six species make up a large part of the mesopelagic biomass in deep Norwegian fjords. Several of the analyzed mesopelagic species, especially the fish species Benthosema glaciale and Maurolicus muelleri, were nutrient dense, containing a high level of vitamin A1, calcium, selenium, iodine, eicopentaenoic acid (EPA), docosahexaenoic acid (DHA) and cetoleic acid. We were able to show that mesopelagic species, whose genus or family are found to be widespread and numerous around the globe, are nutrient dense sources of micronutrients and marine-based ingredients and may contribute significantly to global food and feed security.