Bioavailability of Iodine in Cow's Milk in Swiss Adults

Study Overview
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Brief Summary
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Iodine deficiency remains a global problem impairing health and development in affected populations. Although there has been remarkable global progress against iodine deficiency, mild and moderate iodine deficiency remain common globally, including European countries. Besides salt, milk and dairy products are important iodine sources in many industrialized countries, with varying contributions depending on the milk iodine concentration and the amount of milk and dairy consumed. Iodine absorption in humans depends on the iodine species and possibly on the iodine status of the person. Very little data is available on iodine absorption or bioavailability from different dietary sources including milk. Inorganic iodide is thought to be absorbed almost completely (>90%). In contrast, only about two-thirds of some forms of organically-bound iodine are absorbed. The absorption of iodine from milk has not been quantified in humans. In this balance study, the investigators want to quantify the absorption of iodine in cow's milk in male and female adults and compare with the bioavailability from an iodine water solution (potassium iodide). The results of this study will inform on the bioavailability rate of iodine from cow's milk. Knowing the actual iodine bioavailability from milk is critical because milk and dairy products are major iodine sources in many industrialized countries. The primary objective of this randomized, cross-over design study is to assess iodine bioavailability (measured using excretion in urine) from whole cow's milk delivering an iodine level of about 600 µg/L and compare them with a control iodine solution. The investigators will test three drinks within one subject: 1) a milk with an intrinsic iodine concentration of about 600 µg/L; 2) a milk with a naturally low iodine concentration and an added amount of potassium iodide (extrinsic iodine in milk matrix) to reach a level of about 600 µg/L (adapted to the intrinsic concentration in 1)); and 3) control iodine solution (extrinsic iodine in water matrix) with the same iodine concentration.

Official Title
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Bioavailability of Iodine in Cow's Milk in Swiss Adults

Conditions
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Iodine Bioavailability

Intervention / Treatment
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* Dietary Supplement: extrinsic iodine in milk
* Dietary Supplement: intrinsic iodine in milk
* Dietary Supplement: water iodine solution


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Aged between 18 and 45 years BMI 19-25 kg/m2 Current use of iodized salt at home Signed informed consent Exclusion Criteria: Inadequate iodine status (defined as UIC <70 µg/L or >300 µg/L and assessed during screening from 5 urine spot samples) Exposure to iodine-containing X-ray/ computed tomography contrast agent Use of iodine-containing disinfectants (betadine) History of thyroid disease (according to the participants own statement) Any metabolic, gastrointestinal or chronic disease such as diabetes, hepatitis, hypertension, or cancer (according to the participants own statement) Chronic use of medications (except for contraceptives) Use of iodine containing supplements within 1 month prior to study start Pregnancy (according to the participants own statement but confirmed by a pregnancy test with the first urine spot sample from screening) Breast feeding Vegan diet Drug abuse Extensive alcohol intake, defined as more than 3 (men) or 2 (women) standard drinks per day (i.e. 3dl beer, 1dl wine, 3-4cl liquor), with less than 2 days per week without alcohol consumption

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 45 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Other: bioavailability iodine milk (extrinsic)<br>300 ml whole cow's milk delivering ≈ 200 µg iodine (extrinsic iodine in milk, low protein-bound fraction) | Dietary Supplement: extrinsic iodine in milk<br>* 300 ml whole cow's milk delivering ≈ 200 µg iodine (extrinsic iodine, low protein-bound fraction) The whole cow's milk will be produced in an experimental barn feeding supplementary iodine to reach a final iodine concentration of ≈ 50 µg/L. The iodine content of the extrinsically labelled milk will be adjusted to the required concentration (same as intrinsic iodine milk) by adding iodine in form of potassium iodide.<br>|
| Other: bioavailability iodine milk (intrinsic)<br>300 ml whole cow's milk delivering ≈ 200 µg iodine (intrinsic iodine in milk, high protein-bound fraction) | Dietary Supplement: intrinsic iodine in milk<br>* 300 ml whole cow's milk delivering ≈ 200 µg iodine (intrinsic iodine, high protein-bound fraction) The whole cow's milk will be produced in an experimental barn feeding supplementary iodine to reach a final iodine concentration of ≈ 600 µg/L. This concentration will define final supplemental iodine given to the participants (adapting the total portion size).<br>|
| Other: bioavailability water iodine solution<br>300 ml water iodine solution delivering ≈ 200 µg iodine (water iodine solution) | Dietary Supplement: water iodine solution<br>* 300 ml water delivering ≈ 200 µg iodine (control)<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Iodine concentration in urine | measured by Sandell-Kolthoff method, mikrograms per liter To calculate iodine absorption, excretion and retention. | Days 1, 2, 3, 8, 9, 10, 15, 16 and 17 | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| TSH | thyroid function test at baseline | day 1 | 
| T4 | thyroid function test at baseline | day 1 | 
| iodine content of standardized diet | the quantitative assessment of iodine content in the participants' standardized diet | prior to study start | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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iodine, bioavailability, milk