Food consumption data

As VKM was requested to evaluate scenarios of potential iodine exposure according to different levels of iodization of household salt and/or bread, the relevant food consumption data variables were iodine from all sources in the diet, the “background level”, household salt and salt in bread. The exposures to iodine were calculated using food consumption data from the national dietary surveys. Consumption data for the iodine exposure estimates were based on the national food consumption surveys listed below.

Norkost 3 was based on two 24-hour recalls by telephone at least one month apart. Food amounts were presented in household measures or estimated from photographs (Totland et al., 2012). The Norkost 3 study was carried out by the University of Oslo, Norwegian Food Safety Authority, Norwegian Directorate of Health and Norwegian Institute of Public Health in 2010/2011. A total of 1787 adults aged 18-70 years participated. The participation rate was 37%. No national dietary information among the older population (>70 years) exists in Norway.

VKM Report 2020: 05 109 Consumption data on bread from the Norwegian Mother and Child Cohort Study (MoBa) for pregnant women was considered. However, consumption data for bread in Norkost 3 were, considered to be more solid for the purpose of this benefit and risk assessment, as the consumption data in MoBa were based on a FFQ with relatively few questions related to bread consumption.

The exposures to iodine in 4-, 9- and 13-year-old children are calculated from the national food consumption survey Ungkost 3 (Hansen et al., 2017; Hansen et al., 2016). The Ungkost 3 study was carried out by the University of Oslo, Norwegian Food Safety Authority,

Norwegian Directorate of Health and Norwegian Institute of Public Health in 2015 for 4^th and 8^th graders (8-9-year-olds and 12-13-year-olds), and in 2016 for 4-year-old children. The dietary assessment tool was a 4 days validated web-based food diary. A total of 399 4-year-old, 636 9-year-old and 687 13-year-old children participated.

The iodine exposures in 1-year-old children were estimated from the national food

consumption survey Spedkost conducted in 2007 (Kristiansen et al., 2009), and the exposure in 2-year-olds were estimated from Småbarnskost 3, conducted in 2019 (Astrup et al., 2020).

These food consumption surveys were based on semi-quantitative FFQs. The caretaker was asked to have the last two weeks in mind when answering the questionnaire. In addition to predefined household units, food amounts were also estimated from photographs. A total of 1635 1-year-olds, and 1413 2-year-olds participated. The participation rate was 56%, and 47% respectively.

Figure 7.2-1 illustrates mean contribution to the total iodine intake from different food groups (not including food supplements) in adults, 13-year-olds and 2-year-olds in percentage of the total iodine intake for each age group (not including iodine containing supplements).

VKM Report 2020: 05 110 Figure 7.2-1 Contribution to the total mean iodine intake from the most significant food groups (not including supplements) in adults, 13-year-olds and 2-year-olds in % of the total mean iodine intake.

Consumption of total salt and household salt

Estimating salt (NaCl) intakes from dietary surveys has low validity due to a number of factors influencing the total salt intake. Processed foods may vary substantially in salt content. The same foods, e.g. cheese or bread, will differ in salt content depending on the producer. In addition, each producer will change recipes over time. Home cooked meals are prepared from a large variation of recipes, and both the recipes and the taste of the cook will influence how much salt was added. The individual amount of salt added to the food at the table varies depending on individual taste preferences. These variables are difficult to take into account in dietary surveys. Salt intake estimates from dietary surveys therefore

VKM Report 2020: 05 111 usually aim to cover salt added to processed foods, and standard amounts of salt added to home cooking. Use of household salt was not specifically asked for in the national dietary surveys.

The best method for measuring habitual salt intake is by measuring sodium from several 24-hour urine collections in the same person. The most recent sodium data from Norway are based on a single 24-hour urine collection in the seventh wave of the Tromsø study (Tromsø 7), carried out in 2015-16 (www.tromsostudy.com). The Tromsø Study is a population based longitudinal multi-purpose study focusing on lifestyle-related diseases and their risk factors (Jacobsen et al., 2012). All citizens aged 40 years and above (32 591) living in the

municipality of Tromsø in northern Norway were invited, and a total of 21 083 people participated. 24-hour urine was collected from 496 participants aged 40-69 years and analysed for sodium, potassium, creatinine and iodine (Meyer et al., 2019). The total daily intake of NaCl (g) was calculated by multiplying daily sodium excretion with a factor of 2.54.

Mean (SD) estimated daily salt intake was 10.4 (4.1) g in men and 7.6 (2.8) g in women.

There is a lack of knowledge about household salt use in the Norwegian population. Studies from England (Sanchez-Castillo et al., 1987), USA (Mattes and Donnelly, 1991), and

Denmark (Andersen et al., 2009) have shown that household salt consumption is in the order of 10% of the total salt consumption. However, in studies from Italy (Leclercq and Ferroluzzi, 1991) household salt comprised close to 40% of total salt consumption. In addition to differences between countries, there is large individual variation.

In our exposure estimates we have assumed that the intake of household salt constitutes 10% of the total salt intake based on the Tromsø 7 study. In this assessment, the estimated daily intake of NaCl from Tromsø 7 was for men and women independently fitted with a log-normal distribution. These distributions represented, to our knowledge, the best available charaterisation of daily salt intake for adult Norwegians. To transform these daily intakes into chronic intakes (i.e. long-term average intakes) used in the probabilistic exposure

assessment for each individual exposure, a mean of 365 randomly drawn daily salt intakes from the relevant distribution was calculated for each of the individuals used in the scenario calculations (see Appendix IV).

Data on salt consumption in Norwegian children or adolescents is, to our knowledge, lacking.

In a study by Whelton et al. (2012) it was concluded that sodium intake was highly correlated with total energy intake, due to its inclusion in a wide variety of foods and meals (Whelton et al., 2012). To estimate salt intake in children and adolescents for our scenario estimates, we therefore have assumed that sodium intake scale linearly with energy intake across age classes. Sodium intake was scaled by calculating overall mean energy intakes for adults (Norkost 3)/ mean energy intakes children (2-, 4-, 9- and 13-year-olds) (Småbarnskost 3 and Ungkost 3), independently for boys and girls. Household salt is assumed to be 10% of total salt also in children and adolescents. The daily energy intakes used are means from the national dietary surveys, and are for men and boys 10.7 MJ (adults), 8.6 MJ (13 years), 7.8 MJ (9 years) and 6.1 MJ (4 years), 5.6 MJ (2 years), and for

VKM Report 2020: 05 112 women and girls 9.0 MJ (adults), 7.4 MJ (13 years), 6.9 MJ (9 years), 5.5 MJ (4 years), and 5.3 MJ (2 years).

The salt estimates used for the scenario calculations for adults, children and adolescents are given in Table 7.2.1-1. Daily salt intake for adults is assumed to follow a log-normal

distribution (which means that the standard deviation of the log-normal distribution is the same for all groups within sexes). Parameters for the lognormal distributions of daily salt intake for adults are µfemales = log(7.1), σfemales = 0.381 and µmales = log(9.7), σmales=0.395.

The variation is assumed to represent variability between days. Reported below (7.2.1.-1) are the assumed long-term intakes of household salt (i.e. mean of 365 daily intakes, set to 10% of total salt intake). Note that for the scenario estimates, some variability in chronic salt intake is incorporated by sampling 365 ‘daily’ intakes of salt for each individual (see

Appendix IV).

One-year-olds consume less salt than adults, adolescents and children. The above assumption of a correlation between energy and salt intake was not presumed to be

applicable for 1-year-olds, and no data on household salt are presented for this age group.

Table 7.2.1-1 Assumed household salt intakes in adults, children and adolescents (g/day), based on approximations from Tromsø 7. These are long-term mean intake (i.e. the mean of a log-normal distribution = exp(µ + σ²/2)), see text for parameters.

Adults (g/day)

13 y (g/day)

9 y (g/day)

4 y (g/day)

2y (g/day)

Males 1.0 0.8 0.8 0.6 0.5

Females 0.8 0.6 0.6 0.5 0.5

Present iodine fortification of household salt in Norway is 5 mg/kg salt, with both iodized and non-iodized salt are available in the Norwegian market. We do not have data on the iodized vs iodized salt consumption, and we assumed that the current intake of salt is only non-iodized salt.

Consumption of bread

VKM is requested to evaluate different iodization levels in industrialised salt used in bread production. We have categorised ‘bread’ as all whole grain and fine bread, rolls and baguettes, rusks, focaccia, crispbreads and other yeast bakings usually eaten with breadspreads, pizza or pie bottoms, tortilla wraps, naan, potato wraps (‘lompe’), hot dog bread, and hamburger bun. It was assumed that all salt used for commercial bread production were iodized at the given levels. Not included in the category “bread” for the scenario estimates were sweet and salt biscuits, scones, taco shells, sweet yeast bakery wares, and cakes.

We do not have sales data regarding imported bread produce with iodized salt. If we assume that most of the imported bread is produced within Europe, the salt iodization levels could be as high as 75 mg iodine per kg salt. It should be noted that a noteworthy proportion of

VKM Report 2020: 05 113 bread products are imported, mostly as frozen breads, baguettes or rolls for home baking, or frozen doughs for in-store baking.

Imported bread with iodized salt is not included in our iodine exposure estimates neither in the estimates for current intake levels nor in the bread scenarios.

7.2.2.1 Salt content in bread

As bread consumption in Norway generally has been high, bread has been a significant contributor to the total salt intake in the Norwegian population. The Norwegian food industry and the health authorities collaborate to reduce salt in processed foods, including salt

reduction in bread. In this context, salt was monitored in 29 breads at the Norwegian market in 2016, and these are the most recent analysis available of salt in bread in Norway. The analysis includes bread and crispbreads, but not rolls or baguettes. The mean salt content in bread in these analyses, was 1.1 g salt per 100 g bread (NIFES, 2017) and unpublished analyses from 2018-2019. In the present assessment, 1.1 g salt per 100 g bread was used for all bread in the intake modelling of daily individual intakes of “salt in bread”.

Consumption of food supplements with iodine

The iodine content in regular food supplements used in Norkost 3 range from 25 to 150 µg per dose, but most iodine supplements contain 150 µg iodine per recommended daily dose.

In Norkost 3, 16% (n=145) of the women reported use of iodine supplements with a mean iodine contribution of 95 µg/day. Among women between 18-45 years of age, a total of 17%

(n=77) reported use of iodine supplements, with at mean iodine contribution of 96 µg/day.

Similarly, 11% (n=92) of the men reported use of iodine supplements with a mean iodine contribution of 117 µg/day. Iodine exposures including food supplement (users only) are presented in Appendix V.

In 13-year-olds in Ungkost 3, 4% of the girls (n=14) and 3% (n=9) of the boys reported to use iodine supplements. In 9-year-olds, 4% of the girls (n=13) and 2% (n=6) of the boys reported to use iodine supplements. In 4-year-olds, 4% of the girls (n=8) and 5% (n=12) of the boys reported to use iodine supplements. In Småbarnskost 3, 10% of the 2-year-olds reported to use iodine supplements with at mean iodine contribution of 96 µg/day. In Spedkost-07 there were no reported use of iodine supplements among the 1-year-old infants.

Kelp- and seaweed-based products and supplements may contain high concentrations of iodine.Duinker et al. at Institute of Marine Research has analysed 125 kelp and seaweed samples for iodine (personal communication Arne Duinker and (NIFES, 2016). The iodine content varies from 525 mg iodine per kg dry weight to 10094 mg iodine per kg dry weight.

(Gundersen and Olsen, 2018) collected 40 different dried kelp products from shops in Norway, and also from internet sites. The highest iodine content was measured in a kelp product with 5500 mg iodine per kg dry weight, while the lowest content was measured to 14 mg iodine per kg dry weight.

VKM Report 2020: 05 114 Consumption of kelp- and seaweed-based products and supplements may result in iodine intakes above UL. Vegetarians and vegans recruited to a study in the Oslo-area in 2014-2015 showed excessively high UIC (>1000 µg/L) in three individuals who used kelp-supplements (Brantsaeter et al., 2013). Thyrotoxicosis due to ingestion of kelp has been widely reported (Leung and Braverman, 2014).

Pregnant women participating in the Norwegian Mother and Child Cohort Study (MoBa) during years 1999-2008 provided information about dietary supplement use. The results showed that 10% of the women initiated iodine-supplement use prior to conception and

9% initiated iodine-supplement use in the first trimester (Abel et al., 2019). Overall, 32-37% of the women used iodine-containing supplements at some time during the first half of pregnancy (Abel et al., 2017a; Brantsaeter et al., 2013). The median amount of iodine intake from supplements (in iodine-supplement users) was 107 μg/day (Abel et al., 2017a;

Brantsaeter et al., 2013). Information about consumption of kelp or kelp supplements is not available in MoBa.

In a study among 804 pregnant women, 32.7% of the participants reported using iodine-containing supplements (Henjum et al., 2018a). In a study in 175 lactating women 29%

reported habitual iodine supplement use, whereas only 17.7% had actually consumed an iodine-containing supplement during the last 24-hours (Henjum et al., 2017). In a study in 403 women of childbearing age 9.4% reported habitual intake of an iodine-containing supplement (Henjum et al., 2018b). In this study, the median amount of iodine contributed by the supplements was 129 µg/day, the mean (SD) contribution was 106±60 µg/day, and the median adjusted increase in UIC associated with iodine supplement use was 70 µg/L.