Iodine excretion in school children in Copenhagen.

INTRODUCTION: Studies of dietary habits show a high iodine intake in children in Denmark. Iodine excretion in children has not previously been assessed. Iodine excretion in adults is below the recommended threshold, and it is therefore being discussed to increase the fortification level. The main objective of this study was to assess iodine excretion in children living in Copenhagen to establish whether a moderate increase in iodine fortification would lead to excess iodine intake in this group. METHODS: Children in first and fifth grade were recruited through schools in Copenhagen. In total, 244 children de-ivered a urine sample. Urine samples were analysed for iodine and creatinine, and the results were expressed as urinary iodine concentration (UIC) and as estimated 24-h iodine excretion. Iodine excretion in children was also compared with that of adults living in the same area, investigated in a prior study. RESULTS: The median UIC was within the recommended level; 145 (range: 116-201) µg/l for boys and 128 (range: 87-184) µg/l for girls, and was lower in fifth grade students than in first grade students. Estimated 24-h iodine excretion was higher in boys than in girls, but did not differ according to grade. The UIC was higher in children than in adults from the same area. CONCLUSIONS: The iodine excretion among schoolchildren in Copenhagen, an area with a relatively high iodine content in tap water, was within the recommended range as assessed by the UIC. An increased iodine fortification will not have negative consequences for this group. FUNDING: The Ministry of Food, Agriculture and Fisheries. TRIAL REGISTRATION: not relevant.

Greenlandic Inuit show genetic signatures of diet and climate adaptation.

The indigenous people of Greenland, the Inuit, have lived for a long time in the extreme conditions of the Arctic, including low annual temperatures, and with a specialized diet rich in protein and fatty acids, particularly omega-3 polyunsaturated fatty acids (PUFAs). A scan of Inuit genomes for signatures of adaptation revealed signals at several loci, with the strongest signal located in a cluster of fatty acid desaturases that determine PUFA levels. The selected alleles are associated with multiple metabolic and anthropometric phenotypes and have large effect sizes for weight and height, with the effect on height replicated in Europeans. By analyzing membrane lipids, we found that the selected alleles modulate fatty acid composition, which may affect the regulation of growth hormones. Thus, the Inuit have genetic and physiological adaptations to a diet rich in PUFAs.

Iodine excretion has decreased in Denmark between 2004 and 2010--the importance of iodine content in milk.

Fortification with the essential trace element iodine is widespread worldwide. In the present study, results on iodine excretion and intake of iodine-rich foods from a cross-sectional study carried out in 2004-5, 4 to 5 years after the implementation of mandatory iodine fortification, were compared with data in a study carried out in 2008-10. The 2008-10 study was a follow-up of a cross-sectional study carried out before iodine fortification was implemented. Participants in the cross-sectional studies were randomly selected. Both studies were carried out in the cities of Aalborg and Copenhagen in Denmark. The median urinary iodine concentration decreased in women from 97 µg/l (n 2862) to 78 µg/l (n 2041) (P< 0.001). The decrease persisted after adjustment for age, city and education, and if expressed as estimated 24 h iodine excretion. The prevalence of users of iodine containing dietary supplements increased from 29.4 to 37.3 % (P< 0.001). The total fluid intake increased in women (P< 0.001), but the intake of other iodine-rich foods did not change. The median urinary iodine concentration did not change in men (114 µg/l (n 708) and 107 µg/l (n 424), respectively), while the total fluid intake decreased (P= 0.001). Iodine content was measured in milk sampled in 2000-1 and in 2013. The iodine content was lower in 2013 (12 (sd 3) µg/100 g) compared with that in 2000-1 (16 (sd 6) µg/100 g) (P< 0.001). In conclusion, iodine excretion in women has decreased below the recommended level. The reason might probably, at least partly, be a decreased content of iodine in milk.

Thyroid nodules in an 11-year DanThyr follow-up study.

CONTEXT: Limited longitudinal data are available on changes in the thyroid gland structure in a population and how this is influenced by iodine fortification (IF). OBJECTIVE: Our objective was to clarify how IF influenced thyroid gland structure in 2 regions with different iodine intake at baseline (Copenhagen, mild iodine deficiency [ID]; Aalborg, moderate ID). DESIGN AND SETTING: We conducted a longitudinal population-based study (DanThyr) where participants were examined before (1997) and after (2008) the Danish mandatory IF of salt (2000). PARTICIPANTS: We examined 2465 adults, and ultrasonography was performed by the same sonographers using the same equipment, after controlling performances. MAIN OUTCOME MEASURE: Change in thyroid gland structure was evaluated. RESULTS: The follow-up period saw an increased prevalence of multinodularity (9.8%-13.8 %, P < .001), especially in the previously moderate ID region of Aalborg (9.1%-15.4%, P < .001), whereas no change in prevalence was seen for solitary nodules (5.6%-5.1%, P = .34). In individual participants, changes in thyroid structure and disappearance of thyroid nodules during the 11 years was common with an overall normalization rate of 21.2 (95% confidence interval [CI] = 17.9-24.9) per 1000 person-years. Solitary nodules had a significantly higher normalization rate than multiple nodules (normalization rate ratio 0.47 [95% CI = 0.32-0.67]). A regional difference (Aalborg vs Copenhagen) was seen between normalization rates of multiple nodules (normalization rate ratio 0.29 [95% CI = 0.12-0.64]), but not for solitary nodules (normalization rate ratio 0.81 [95% CI = 0.53-1.21]). CONCLUSIONS: Changes in the thyroid gland structure with both appearance and disappearance of thyroid nodules are common after an iodization program.

Iodine fortification may influence the age-related change in thyroid volume: a longitudinal population-based study (DanThyr).

OBJECTIVE: To assess the individuals' thyroid volume changes after the mandatory nationwide iodine fortification (IF) program in two Danish areas with different iodine intake at baseline (Copenhagen, mild iodine deficiency (ID) and Aalborg, moderate ID). DESIGN: A longitudinal population-based study (DanThyr). METHODS: We examined 2465 adults before (1997) and after (2008) the Danish IF of salt (2000). Ultrasonography was carried out by the same sonographers using the same equipment, after controlling performances. Participants treated for thyroid disease were excluded from analyses. RESULTS: Overall, median thyroid volume had increased in Copenhagen (11.8-12.2 ml, P=0.001) and decreased in Aalborg, although not significantly (13.3-13.1 ml, P=0.07) during the 11 years of follow-up. In both regions, there was an age-related trend in individual changes in thyroid volume from baseline to follow-up; thyroid volume increased in women <40 years of age and decreased in women >40 years of age. IN A MULTIVARIATE REGRESSION MODEL, HIGHER AGE AT ENTRY WAS A PREDICTOR (P0.05) FOR THYROID VOLUME DECREASE 20% DURING THE FOLLOW-UP PERIOD (WOMEN AGED 4045 YEARS: odds ratio (OR) 4.3 (95% CI, 2.2-8.2); women aged 60-65 years: 5.8 (2.9-11.6)) and individuals of higher age were also less likely to have an increase in thyroid volume (women aged 40-45 years: OR 0.2 (0.1-0.3); women aged 60-65: OR 0.3 (0.2-0.4)). CONCLUSIONS: Age-dependent differences in thyroid volume and enlargement had leveled out after the Danish iodization program. Thus, the previously observed increase in thyroid volume with age may have been caused by ID.

Mandatory iodine fortification of bread and salt increases iodine excretion in adults in Denmark - a 11-year follow-up study.

BACKGROUND & AIMS: Iodine fortification is widespread. Systematic monitoring of iodine fortification programs should be carried out to secure an optimal fortification level. Our aim was to investigate the effectiveness of the Danish iodine fortification program by comparing iodine excretion at baseline and at 11-year follow-up, and to study determinants for any change in iodine intake including dietary habits, education, life style factors and health parameters. METHODS: A follow-up study based on the Danish DanThyr cohort examined in 1997-1998 just before iodine fortification was introduced, and reexamined in 2008-2010. In total, 2465 (59.1%) adult participants were reexamined. RESULTS: Median (IQR) iodine concentration in urine had increased by 19 (-25-68) µg/L to 83 (47-133) µg/L. Estimated 24-h iodine excretion had increased by 36 (-21-95) µg/24-h to 134 (93-206), and calculated total iodine intake (diet plus supplements) had increased by 16 (-18-48) µg/day. Iodine excretion had increased significantly in all age and gender groups, but was still below the recommended amount at follow-up. The increase in iodine excretion was positively associated with changes in milk intake, with changes in the use of iodine supplements, and with bread intake at follow-up. Salt intake, education, self-rated health, smoking, alcohol intake and physical activity were not associated with the increase in iodine excretion. CONCLUSIONS: The strategy to combat iodine deficiency in Denmark seems to be working because the fortification led to increased urinary iodine excretion in (almost) all participants. However, the level of iodine fortification of salt is too low.

Serum selenium is low in newly diagnosed Graves' disease: a population-based study.

CONTEXT: Selenium deficiency may play an important role in the initiation and progression of autoimmune thyroid disease. OBJECTIVE: To compare serum selenium (s-Se) values in patients with newly diagnosed autoimmune thyroid disease and controls from the Danish population. DESIGN AND SETTINGS: S-Se was measured in triplicate by a fluorimetric method. PARTICIPANTS: Patients with newly diagnosed Graves' disease (GD) (n = 97) or autoimmune overt hypothyroidism (AIH) (n = 96), euthyroid subjects with high serum levels of thyroid peroxidase antibody (TPO-Ab) (TPO-Ab > 1500 U/ml, n = 92) and random controls (n = 830). MAIN OUTCOME MEASURE: Differences in s-Se values. RESULTS: S-Se was lower in patients with GD than in controls (mean (SD), GD: 89·9 µg/l (18·4); controls: 98·8 µg/l (19·7), P < 0·01). This was confirmed in a multivariate logistic regression model adjusting for age, sex, mineral supplements, smoking, geographical region and time of sampling (P < 0·01). In a linear model, s-Se was similar in patients with AIH (mean (SD): 98·4 µg/l (24·9)) and in controls (P = 0·86). In the multivariate model however, s-Se was marginally lower in patients with AIH compared to controls (P = 0·04). There was no significant difference in s-Se between euthyroid participants with high TPO-Ab and random controls (linear: P = 0·97; multivariate: P = 0·27). CONCLUSION: Patients with newly diagnosed GD and AIH had significantly lower s-Se compared with random controls. Our observation supports the postulated link between inadequate selenium supply and overt autoimmune thyroid disease, especially GD.

Predictors of change in serum TSH after iodine fortification: an 11-year follow-up to the DanThyr study.

CONTEXT: Few data are available on the effect of iodine fortification on thyroid function development in a population. OBJECTIVE: Our objective was to evaluate changes in thyroid function after iodine fortification in a population and to identify predictors for changes in serum TSH. DESIGN AND SETTING: A longitudinal population-based study of the DanThyr C1 cohort examined at baseline (1997-1998) and reexamined 11 yr later (2008-2010). The mandatory program for iodization of salt was initiated in 2000. PARTICIPANTS: A total of 2203 individuals, with no previous thyroid disease, living in two areas with different levels of iodine intake, with measurement of TSH and participation in follow-up examination were included in the analysis. MAIN OUTCOME MEASURE: Change in serum TSH was evaluated. RESULTS: During the 11-yr follow-up, mean TSH increased significantly from 1.27 mU/liter [95% confidence interval (CI) = 1.23-1.30] to 1.38 mU/liter (CI = 1.34-1.43) (P < 0.001). The most pronounced increase was observed in the area with the highest iodine intake [1.30 mU/liter (CI = 1.25-1.35) to 1.49 mU/liter (CI = 1.43-1.55), P < 0.001], whereas the increase was not significant in the low-iodine-intake area [1.24 (CI = 1.19-1.29) to 1.28 (CI = 1.23-1.34), P = 0.06)]. Change in TSH was positively associated with the presence of thyroid peroxidase antibody at baseline (P < 0.001) and negatively associated with baseline thyroid enlargement (P < 0.001) and multiple nodules (P < 0.001). CONCLUSIONS: Even small differences in the level of iodine intake between otherwise comparable populations are associated with considerable differences in TSH change at the 11-yr follow-up. Multinodular goiter predicted a less pronounced TSH increase during follow-up, which may be explained by iodine-dependent activity of autonomous nodules.

Mobilization of metals during treatment of contaminated soils by modified Fenton's reagent using different chelating agents.

Changes in pH and redox conditions and the application of chelating agents when applying in situ chemical oxidation (ISCO) for remediation of contaminated sites can cause mobilization of metals to the groundwater above threshold limit values. The mechanisms causing the mobilization are not fully understood and have only been investigated in few studies. The present work investigated the mobilization of 9 metals from two very different contaminated soils in bench and pilot tests during treatment with modified Fenton's reagent (MFR) and found significant mobilization of Cu and Pb to the water in mg/l levels. Also Fe, As, Mn, Ni, Zn, Mg, and Ca mobilization was observed. These findings were confirmed in a pilot test where concentrations of Cu and Pb up to 52.2 and 33.7 mg/l were observed, respectively. Overall, the chelating agents tested (EDTA, citrate and pyrophosphate) did not seem to increase mobilization of metals compared to treatment with only hydrogen peroxide and iron. The results strongly indicate that the mobilization is caused by hydrogen peroxide and reactive species including oxidants and reductants formed with MFR. Based on these results, the use of chelating agents for ISCO will not cause an increase in metal mobilization.

[Iodine fortification of salt and thyroid disease in Denmark]. / Dansk jodberigelse af salt og forekomst af thyroideasygdom.

Until 2000 Denmark was iodine deficient with moderate deficiency in the western part and mild deficiency in the eastern part. The occurrence of goitre and autonomous hyperthyroidism was high, and pregnancy was associated with a reduction in thyroid function. After cautious mandatory iodization of household salt and salt used for bread production, the iodine intake in Denmark is now low normal. The DanThyr monitoring has shown a transient increase in hyperthyroidism followed by a decrease, and goitre is becoming less common. Hypothyroidism has become more common, and this has to be followed.

Lifestyle and genetic determinants of folate and vitamin B12 levels in a general adult population.

Danish legislation regarding food fortification has been very restrictive resulting in few fortified food items on the Danish market. Folate and vitamin B12 deficiency is thought to be common due to inadequate intakes but little is known about the actual prevalence of low serum folate and vitamin B12 in the general population. The aim of the present study was to evaluate the folate and vitamin B12 status of Danish adults and to investigate associations between vitamin status and distinct lifestyle and genetic factors. The study included a random sample of 6784 individuals aged 30-60 years. Information on lifestyle factors was obtained by questionnaires and blood samples were analysed for serum folate and vitamin B12 concentrations and several genetic polymorphisms. The overall prevalence of low serum folate ( < 6.8 nmol/l) was 31.4 %. Low serum folate was more common among men than women and the prevalence was lower with increasing age. Low serum folate was associated with smoking, low alcohol intake, high coffee intake, unhealthy diet, and the TT genotype of the methylenetetrahydrofolate reductase (MTHFR)-C677T polymorphism. The overall prevalence of low serum vitamin B12 ( < 148 pmol/l) was 4.7 %. Low serum vitamin B12 was significantly associated with female sex, high coffee intake, low folate status, and the TT genotype of the MTHFR-C677T polymorphism. In conclusion, low serum folate was present in almost a third of the adult population in the present study and was associated with several lifestyle factors whereas low serum concentrations of vitamin B12 were less common and only found to be associated with a few lifestyle factors.

Serum selenium and selenoprotein P status in adult Danes - 8-year followup.

Selenium is an essential micronutrient important to human health. The main objective of this study is to describe serum selenium and selenoprotein P status in two samples of the Danish population. In addition, the influence of various factors potentially associated with selenium status was investigated. Blood samples from a total of 817 randomly selected subjects from two cities in Denmark were analyzed. Half of the samples were collected in 1997-1998 and the other half in 2004-2005. Samples from women aged 18-22, 40-45 and 60-65 years, and men aged 60-65 years were selected for this study. All subjects had filled in a food frequency questionnaire (FFQ) and a questionnaire with information about smoking habits, alcohol consumption and exercise habits. Mean serum selenium level was 98.7+/-19.8microg/L and median selenoprotein P level was 2.72 (2.18-3.49)mg/L. Serum selenium and selenoprotein P increased with age, and selenoprotein P was higher in men than in women. Serum selenium levels decreased by 5% on average from 1997-98 to 2004-05 (P<0.001), whereas selenoprotein P level increased (P<0.001). The intake of fish correlated weakly with serum selenium level (r=0.14, P<0.001) but not with selenoprotein P level. Smoking status, alcohol intake, exercise habits, BMI and medicine use did not influence selenium status. It is concluded that selenium status in this Danish population is at an acceptable level. No major groups with regard to age, sex or lifestyle factors could be identified as being in risk for selenium deficiency.

Association of iodine fortification with incident use of antithyroid medication--a Danish Nationwide Study.

CONTEXT: Iodine-induced hyperthyroidism has been reported in the early phases of almost all iodine fortification programs, depending on prior iodine intake in the population, the amount of fortification, and the rate of change. OBJECTIVE: The aim of the study was to monitor the effect of the Danish iodine fortification program on incidence of hyperthyroidism as measured by the incident use of antithyroid medication. DESIGN: We conducted a register study. Using the unique identification number of all Danes, we linked data from the Register of Medicinal Product Statistics and the Civil Registration register on an individual level. All dispensing of antithyroid medication from 1995 to 2007 was studied. The place of residency was used to divide patients into mildly and moderately iodine-deficient groups. MAIN OUTCOME MEASURE: We measured the incident use of antithyroid medication. RESULTS: In the region with moderate iodine deficiency, the number of incident users of antithyroid medication increased 46% in the first 4 yr of iodine fortification. The use increased the most among the youngest age group (younger than 40 yr) and the oldest age group (older than 75 yr). In the mildly iodine-deficient region, the number of incident users increased only 18%, and only in the youngest age groups (below 40 and 40-59 yr). After 4 yr of fortification, the incidence rates started to fall and reached baseline, for most groups, 6 yr after onset of fortification. CONCLUSIONS: This study shows that iodine fortification induced a temporary, modest increase in the incidence of hyperthyroidism as measured by use of antithyroid medication. A new steady state has not yet evolved.

Iodine intake before and after mandatory iodization in Denmark: results from the Danish Investigation of Iodine Intake and Thyroid Diseases (DanThyr) study.

Iodine deficiency is still common in some European countries. In Denmark an iodine fortification programme was introduced in 1998 and a monitoring programme was established prior to iodization. This study reports the change in urinary iodine excretion caused by fortification and investigates determinants of iodine intake after fortification. Iodine excretion in casual urine samples was assessed in 4649 subjects in 1997-8 and in 3570 comparable subjects in 2004-5 in women 18-22, 25-30, 40-45 and 60-65 years of age and in men 60-65 years of age living in Aalborg (western part of Denmark) or Copenhagen (eastern part of Denmark). These areas had moderate and mild iodine deficiency, respectively, before iodine fortification. All subjects filled in a FFQ and a questionnaire regarding lifestyle factors. Iodine excretion, expressed as the estimated 24 h urinary iodine excretion and as urinary iodine concentration, increased significantly in all age and sex groups. However, the iodine intake was still below the recommended in the youngest age groups in both cities and in women 40-45 years of age living in Aalborg. Intake of milk and salt had strong significant direct associations with iodine excretion (P < 0.001). It is concluded that although the median iodine intake in the whole study population is at the recommended level, some groups still have an intake below the recommended. It is important to have a moderate milk intake to obtain a sufficient iodine intake in Denmark.

Changes in iodine excretion in 50-69-y-old denizens of an Arctic society in transition and iodine excretion as a biomarker of the frequency of consumption of traditional Inuit foods.

BACKGROUND: Iodine intake in Greenland has been hypothesized to exceed 10 times the recommended amount. The transition from a traditional Arctic society may change the iodine intake, but no field studies have been performed. OBJECTIVE: We aimed to ascertain iodine intakes, factors affecting iodine intake in circumpolar populations, and the usefulness of urinary iodine excretion as a biomarker for validation of Inuit food-frequency questionnaires. DESIGN: Data were collected in a cohort study of 4 Greenland population groups: Inuit living in the capital city, the major town, and settlements in East Greenland and non-Inuit. Supplement use and lifestyle factors were evaluated with questionnaires, and dietary habits were ascertained with a food-frequency questionnaire. Iodine was measured in spot urine samples. RESULTS: One percent of the population of Greenland was invited, and the participation rate was 95%. Less than 5% of Inuit but 55% of non-Inuit had urinary iodine excretion < 50 microg/24 h. Median urinary iodine excretion declined with the degree of decrease in the traditional lifestyle: it was 198, 195, 147, and 58 microg/24 h among Inuit in settlements, town, and city and in non-Inuit, respectively (P < 0.001). Participants were divided into diet groups calculated from Inuit food frequency. Iodine excretion decreased with increasing intake of imported foods (P < 0.001). In regression models, type of diet and the subject's lifestyle, sex, weight, ethnicity, and intake of iodine-containing supplements affected urinary iodine excretion. CONCLUSIONS: Circumpolar non-Inuit are at risk of iodine deficiency. Departure from the traditional Inuit diet lowers iodine intake, which should be monitored in Arctic societies. Urinary iodine excretion may be a useful biomarker of traditional Inuit food frequency.

Gastrointestinal dysfunction in a community sample of subjects with symptoms of irritable bowel syndrome.

BACKGROUND/AIM: Irritable bowel syndrome (IBS) affects about 15-20% of the population of the Western countries. Traditionally, IBS has been an exclusion diagnosis, but recently definitions have emerged from population-based research. The aim of this population-based study was to evaluate any association between gastrointestinal pathophysiology and IBS in subjects with symptoms of IBS compared to subjects with no abdominal complaints. METHODS: From a random sample of 2,656 participants, subjects with IBS (32) together with subjects without abdominal complaints (26), were invited for further evaluation. IBS was defined as more than weekly experience of abdominal pain and distension, and in addition either borborygmia or altering stool consistency. The diagnostic work-up consisted of gastroscopy, manometry and 23-hour pH and pressure recordings of the oesophagus, lactose tolerance test, barium enema, measurement of colonic transit time, and rectoscopy. RESULTS: Compared to the group without abdominal complaints significantly more subjects with IBS had spasms of the colon (OR = 10.2 (1.2-87.3)), and abnormal contractions of the oesophagus at manometry (OR = 9.1 (1.1-78.2)). Furthermore, there was a non-significant tendency towards spasms at 23-hour pH and pressure recordings (OR = 3.58 (0.4-35.2)), and more discomfort at lactose tolerance test (OR = 5.8 (0.6-51.3)) in persons with IBS compared to subjects without abdominal complaints. CONCLUSION: The results of this population-based study indicate that signs of gastrointestinal dysmotility and hyperperception are more prevalent in subjects with IBS than in subjects without abdominal complaints.

Relations between various measures of iodine intake and thyroid volume, thyroid nodularity, and serum thyroglobulin.

BACKGROUND: Iodine intake can be measured in various ways, and each method may have advantages and disadvantages. OBJECTIVE: We sought to investigate the potential associations of various measures of iodine intake with thyroid volume, prevalence of thyroid nodules, and serum thyroglobulin. We also sought to identify, if possible, groups at risk of thyroid disease because of their food choices. DESIGN: This cohort study included 4649 randomly selected subjects with mild-to-moderate iodine deficiency; the subjects lived in 2 cities in Denmark. Iodine intake was estimated by using a food-frequency questionnaire and by measuring iodine excretion in spot urine samples. Thyroid volume and nodularity were measured with ultrasonography. RESULTS: In multiple linear regression models, significant inverse relations were found between thyroid volume and estimated 24-h iodine excretion, iodine intake from diet plus supplements, iodine intake from diet/kg body wt, and milk intake (P = 0.001 for all), but not urinary iodine excretion measured as a concentration (P = 0.40). All measures of iodine intake were significantly related to serum thyroglobulin concentration (P

Large differences in incidences of overt hyper- and hypothyroidism associated with a small difference in iodine intake: a prospective comparative register-based population survey.

Around 3-4 billion people in the world are covered by iodine supplementation programs to prevent developmental brain damage and other iodine deficiency (ID) disorders. Mild ID is associated with more hyperthyroidism and less hypothyroidism in the population than a high iodine intake. Knowledge of the iodine intake levels where the shifts in incidences occur is important for planning of iodine supplementation programs. A computer-based register linked to thyroid diagnostic laboratories was used to continuously identify all new cases of overt hyper- and hypothyroidism in two population cohorts with moderate and mild ID, respectively (Aalborg, n = 310,124; urinary iodine, 45 micro g/liter; and Copenhagen, n = 225,707; urinary iodine, 61 micro g/liter). The investigation was initiated before iodization of salt in Denmark and was part of the monitoring program. In 1997-1998, the incidence rate of overt hyperthyroidism was high in the area with the lowest iodine intake (92.9/100,000 per year) compared with the area with only mild ID (65.4/100,000 per year). Standardized rate ratio was 1.49, and 95% confidence interval was 1.22-1.81. The opposite relationship was present for overt hypothyroidism (moderate ID, 26.5/100,000 per year; mild ID, 40.1/100,000 per year; standardized rate ratio, 0.73; 95% confidence interval, 0.55-0.97). The different incidence rates were confirmed during each of the two following years. The results of this prospective investigation of the incidence of overt hyper- and hypothyroidism suggest that iodine supplementation of a population may increase the incidence of overt hypothyroidism, even if the population is moderately iodine-deficient. In such a population, the increase in risk of hypothyroidism should be weighed against the risk of ID disorders such as hyperthyroidism due to multinodular toxic goiter. The optimal level of iodine intake to prevent thyroid disease may be a relatively narrow range around the recommended daily iodine intake of 150 micro g.

Use of dietary supplements in Denmark is associated with health and former smoking.

OBJECTIVES: To describe the use of dietary supplements in a group of Danish adults and to investigate the differences between users and non-users with respect to age, gender, health and lifestyle factors. DESIGN: Cross-sectional study in two Danish cities. SETTING: The Danish Investigation on Iodine Intake and Thyroid Diseases, 1997-1998. SUBJECTS: Participants were 3707 women (selected age groups between 18 and 65 years) and 942 men (60-65 years). Participation rate was 50%. Supplement data were collected in a personal interview. Data on education, smoking, alcohol intake, physical activity, use of medication and self-perceived health were derived from a self-administered questionnaire. Multiple logistic regression was used for the statistical analysis. RESULTS: Participants were asked about all kinds of supplements, ranging from products containing vitamins and minerals, to fish oils and products of herbal origin. On average 59% reported use of some kind of dietary supplement. Most common were combined multivitamin/mineral products (48%) followed by single vitamin C products (10%). Twelve per cent used three or more different supplements. Supplement use was strongly associated with age and gender, being highest among elderly women (78%). Ex-smokers were more likely to use supplements than subjects who had never smoked (odds ratio (OR) 1.36, 95% confidence interval (CI) 1.09-1.76). Supplement use was more likely among subjects who had many days of illness 95% CI 1.12-1.66) and among users of medication 95% CI 1.04-1.42). Subjects who perceived their health as poor were more likely to use supplements other than just a multivitamin/mineral tablet 95% CI 1.31-3.77). CONCLUSIONS: Use of dietary supplements was related to age, gender and smoking, but also to poor self-perceived health status and absence from work. This indicates that a group of people use supplements as a form of self-medication.