1 Food Administration of Denmark Iodine deficiency disease elimination and universal salt iodisation The Danish Investigation of Iodine Intake and Thyroid

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Food Administration of Denmark

Iodine deficiency disease elimination and universal salt iodisation

The Danish Investigation of Iodine Intake and Thyroid Disorders

Lars Ovesen

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The Basic Questions

•What is the need and reference intake?

•What is the actual consumption?

•Which are the susceptible groups?

•What strategies are best to improve supply?

•What measures are best to prevent consumption of excess?

•Will fortification influence dietary habits?

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Iodine intake (μg/10 MJ)Frequency distribution from the Danish Dietary Survey 1995

0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 3600

5

10

15

20

25

g/10 MJ

%

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Aims:

In two areas in Denmark (Aalborg - west, and Copenhagen - east)

•Examine changes in the occurrence and distribution of clinical and subclinical thyroid disorders

•Examine changes in intake of sodium and iodine

in order to

•Estimate optimum levels of iodine fortification


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Study population

Invited: 9,274

Full participation: 4,649 (50.1%)

Short questionnaire: 2,485 (26.8%)

No response: 2,139 (23.1%)

Cohort Study

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Examinations performed:

Ultrasonography

Physical examination

Questionnaire (alcohol, smoking)

Blood biochemistry (TSH, free T4, free T3)

Spot urine (I)

Cohort study

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Iodineexcretion(g/L)

Enlargedthyroid(%)

Palpablegoitre(%)

Solitarynodules(%)

Multiplenodules(%)

Copenhagen(n = 2,419)

68 15.1 9.8 5.6 11.5

Aalborg(n = 2,174)

53 22.5 14.6 6.3 11.0

P < 0.001 <0.001 <0.001 0.33 0.69

Iodine excretion, and thyroid enlargement and pathology in areas with mild and moderate ID

Cohort study

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Strategies to improve supply

Policy instruments

•Nutrition information and educationAdvantage: No toxicity risk

Disadvantage: Dietary habits stable

•Recommendation of the use of supplementsAdvantage: Same dosage

Disadvantage: Less effective

•Food fortificationAdvantage: Effective towards target group

Disadvantage: All will be exposed

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How much iodine in a recommended diet (estimated 24 h iodine excretion)?

1 2 3

Copenhagen

75 (53-115) 93 (67-133) 114 (85-165)

Aalborg 48 (32-62) 63 (43-91) 70 (54-101)

1: <100 g of fish per week and <½ glass of milk per day

3: 200 g of fish per week and ½ litre of milk per day

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Distribution of iodine intake by fortification of salt

0 100 200 300 400 500 6000

5

10

15

20

25

30

All salt 5 ppmAll salt 12 ppmBreadsalt 40 ppm

No fortification

194 (74, 525)

104 (44, 257)154 (72, 317)212 (104, 473)

Total I intake (median (5, 95 CI))

g/10 MJ

%

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Principles for fortificationSelective vs. non-selective approach

Selective approach

Risk perception focused on avoidance of nutrient deficiencies

Non-selective approach

Risk perception focused on upper safe intake

•Only permissible if nutritionally justifiable, i.e., deficiency in a larger part of the population

•Fortification must effectively increase intake and remedy deficiency

•Mandatory vs. voluntary

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Iodine fortification in Denmark

•1920: Voluntary fortification of table salt

•1982: Iodine fortification prohibited

•06/1998: Voluntary fortification of all salt

All salt: 8 μg/g (market share: 75%)

Median (5-95 percentile): 50 (28-99) μg/day

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Implementation of a voluntary iodine fortification programme

•Political support – passage of statutory instruments and budgetary allocation

•Support from salt industry, and major professional and industrial bodies

•Communication to health professionals and the public

•Establishment of a monitoring and evaluation system

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Voluntary fortificationIodine fortification of household salt (% market share)

0%

10%20%

30%40%

50%60%

70%80%90%

100%

aug-98 okt-98 dec-98 feb-99

withoutwith

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Why did it fail?

•Technological concerns

•Costs

•Claims

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Consequences of fortification

07/2000: Mandatory fortification

Salt for household and bread: 13 μg/g

Median (5-95 percentile): 50 (23-142) μg/day


Low intake areasHigh intake areas

Hyperthyrodism Hypothyroidism

Shifts in hyper- and hypofunction of the thyroid with iodine intake


Types of hyperthyroidism in high and low intake areas

0%

20%

40%

60%

80%

100%

Denmark Iceland

OtherMNTGGD

100 g I/d 300 g I/d

Laurberg et alJ Intern Med 1991

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Measures to prevent excessive intakes

•Aim for the lowest effective dose

•Establish a system for monitoring intake and adverse effects

•Perform regular inspection of salt production facilities and analytical control of level of fortification

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Will fortification influence dietary habits?

A gradual decrease in average sodium intake corresponding to 5 gram of salt per person per day is desirableNordic Nutrient Recommendations, 1996

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Conclusions

•Improve data for upper and lower safe intake levels

•Improve data on intake, especially the tails of intake

•Establish a system which effectively can monitor effect and toxicity

•Involve all stakeholders in the “project”

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Documents

1 Food Administration of Denmark Iodine deficiency disease elimination and universal salt iodisation The Danish Investigation of Iodine Intake and Thyroid