Abstract
Sufficient I intake is important for the synthesis of thyroid hormones, which play an important role in normal growth and development. Our aim was to estimate habitual I intake for the Dutch population and the risk of inadequate or excessive intakes. Further, we aimed to provide an insight into the dietary sources of I and the association with socio-demographic factors. Data from the Dutch National Food Consumption Survey 2007-2010 (n 3819; 7-69 years), and from the Dutch food and supplement composition tables were used to estimate habitual I intake with a calculation model. Contribution of food groups to I intake were computed and multiple linear regression was used to examine associations of intakes with socio-demographic factors. A total of ≤2 % of the population had an intake below the estimated average requirement or above the upper level. The main sources of I were bread containing iodised salt (39 %), dairy products (14 %) and non-alcoholic drinks (6 %). I intake (natural sources only, excluding iodised salt and supplements) was positively associated with (parental) education, which could at least partly be attributed to a higher consumption of dairy products. Among children, the consumption of bread, often containing iodised bakery salt, was positively associated with parental education. The I intake of the Dutch population (7-69 years) seems adequate, although it has decreased since the period before 2008. With the current effort to reduce salt intake and changing dietary patterns (i.e. less bread, more organic foods) it is important to keep a close track on the I status, important sources and potential risk groups.
Highlights
Sufficient I intake is important for the synthesis of thyroid hormones, which play an important role in normal growth and development
For all these food groups, the addition of iodised salt was on a voluntary basis; there is a covenant between the Ministry of Health and the bakery sector to use iodised bread salt for bread (because of a court decision (Box 1) organic bread is excluded from this covenant, iodised bread salt may voluntary be added to organic bread)
The observed I intake from natural sources was estimated for several population characteristics (age, sex, BMI, income of the head of the household, education, season, region) using Proc SurveyMeans (SAS 9.2)
Summary
Sufficient I intake is important for the synthesis of thyroid hormones, which play an important role in normal growth and development. I intake (natural sources only, excluding iodised salt and supplements) was positively associated with (parental) education, which could at least partly be attributed to a higher consumption of dairy products. With the current effort to reduce salt intake and changing dietary patterns (i.e. less bread, more organic foods) it is important to keep a close track on the I status, important sources and potential risk groups. Besides harmful effects of too low I intakes, excessive intakes cause biochemical changes such as elevated thyroxin and decreased thyroid stimulating hormone concentrations It is, uncertain if clinical health effects would appear because of chronic exposure to these biochemical changes[2]. With the change of the I policy, Abbreviations: DNFCS, Dutch National Food Consumption Survey; EAR, estimated average requirement; SPADE, Statistical Program to Assess Dietary Exposure; UL, tolerable upper intake level. Because of the covenant between the Ministry of Health and the bakery sector, almost all bread contains iodised bakery salt[5]
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