AI-Powered Research

Age: 18-45 years
BMI: 18.5-25 kg/m2
Mean urinary iodine concentration 100-300 mcg/L of 5 spot samples (5 different days)
Normal thyroid hormone levels (Normal hormone levels are 0.4-4.0 mIU/L for TSH, 58-161 nmol/L for total T4 and = 55 ng/mL for thyroglobulin)

Exclusion Criteria

-History of thyroid, metabolic, gastrointestinal or chronic diseases
-Chronic use of medication (except oral contraceptives)
-Use of iodine containing skin creams/products within the last month
-Use of iodine supplements within the last month
-Exposure to iodine containing X-ray/computed tomography contrast agents within the last six months
-Excess alcohol intake (defined as > 3 (men) or 2 (women) standard drinks per day)
-Smoking
-Consuming a vegan diet
-Pregnant or lactating

Study & Design

Study Type: Interventional

Study Design: Not specified

Primary Outcome Measures

Name	Time	Method
The primary outcome measures will be 24-h urinary iodine excretion (UIE), fecal iodine excretion (FIE) and the iodine intake, expressed as µg/d. The UIE will be calculated at each of the 3 balance days at all 3 test weeks (n=108). The FIE will be calculated for 2-days after ingestion of the test meal, and once prior to the ingestion of the test meal in order to control for iodine excretion from the standardized diet. The iodine intake is based on the iodine concentration of the standardized diet and the test meal. The sum of the UIE and the FIE results in the total iodine excretion (TIE). However, in order to correct for the iodine excretion of the standardized diet, the UIE of the first day of the balance periods and the FIE at day 1 and 2 of the first week will be used to calculate the contribution of the standardized diet to the TIE.

Secondary Outcome Measures

Name	Time	Method
Secondary outcome measures will be the urine completeness of the participants at all 10 days of the balance period. At the first balance day, the PABA recovery will be measured based on the ingestion of 3 PABA tablets (1 at each meal). If the recovery of PABA is below 85%, the 24-h urine collection is incomplete. During the other 9 balance days, the urine completeness will be calculated by the urinary creatinine excretion. Since creatinine is constantly excreted by the muscles, the muscle mass of the participants will be measured with BIA. If the creatinine index is below 0.7, the 24-h urine collection is incomplete. Incomplete urine collections cannot be used in the study, so will be excluded.