Assessment of the Daily Average Requirement of Iodine in Lactating Women

Not Applicable

• Conditions: Healthy; Iodine Deficiency
• Interventions: Dietary Supplement: Control; Dietary Supplement: Iodide (150 μg/day); Dietary Supplement: Iodine (300 μg/day)

• Registration Number: NCT05382793
• Lead Sponsor: University Children's Hospital, Zurich

Brief Summary

Human milk is the only source of iodine during early infancy and adequate iodine intake during lactation is necessary to assure optimal thyroid function in breastfed infants. However, the physiological requirement of iodine in lactating women is uncertain and recommendations for the daily dietary average requirement are poorly defined. WHO recommends iodine supplementation to lactating women in populations with incomplete coverage of iodized salt and deficient iodine intake, but the scientific evidence is weak and the optimal dose is uncertain.

The primary objective is to assess the daily dietary average requirement for iodine in lactating women.

Secondary objectives are to:

* Estimate the daily average requirement for iodine in exclusively breastfed infants;

* Assess the dose-response of dietary iodine supplements on breast milk iodine concentration in lactating women with adequate and inadequate habitual iodine intakes;

* Estimate the maternal iodine intake required to provide exclusively breastfed infants with an adequate iodine intake via breast milk.

Detailed Description

This study is a single center, randomized, controlled, dose-response metabolic balance study with cross-over design. The study will be conducted in 24 exclusively breastfeeding women and their infants receding in Zürich, Switzerland. The study involves an initial screening, a 2 weeks run-in period and a balance period over 3 weeks. Participating women will be allocated to two groups based on their consumption of dietary iodine supplements during pregnancy. Women who consumed daily iodine supplements during pregnancy will be assigned to group 1 (n=12) and receive daily supplements containing 150 µg iodine for 2 weeks, whereas women who did not will be enrolled in group 2 and will receive no supplement during the run-in period. Breast milk and spot urine samples (mothers and infants) will be collected daily in all participants during two weeks for the measurement of breast milk and urinary iodine concentrations. During the balance period, all women will receive either no supplement, iodine supplements providing 150 µg/day, or 300 µg/day in random order with cross-over design. Each supplement dose will be assessed in a test period of 7 days, including 2 run-in days, 3 balance days and 2 wash-out days. The supplements will be consumed during the first 5 days in each test-period. During the 3 balance days, the daily iodine intake and excretion will be measured in mothers and infants, and the iodine retention will be calculated for each regimen and study group. The minimum daily average requirement will be determined as the iodine intake where the iodine retention is zero.

Study Timeline

• Status Verified: 2022-05
• Study Start: 2022-05-16
• Study First Submitted: 2022-05-16
• Study First Submitted QC: 2022-05-16
• Study First Posted: 2022-05-19
• Last Update Submitted: 2022-05-23
• Last Update Posted: 2022-05-24
• Primary Completion: 2023-11
• Study Completion: 2024-07

Recruitment & Eligibility

• Status: UNKNOWN
• Sex: Female
• Target Recruitment: 24

Inclusion Criteria

Not provided

Exclusion Criteria

Not provided

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: PARALLEL

Arm && Interventions

Group	Intervention	Description
Lactating women with assumed adequate habitual iodine intake	Control	Women who consumed iodine-containing dietary supplements during pregnancy (≥150 μg/day). Women in this group will receive a daily oral iodine supplement providing 150 μg iodine as potassium iodide for 14 days before the study start.
Lactating mothers with assumed inadequate habitual iodine intake	Iodide (150 μg/day)	Women who did not consume iodine-containing dietary supplements during pregnancy (≥150 μg/day).
Lactating women with assumed adequate habitual iodine intake	Iodide (150 μg/day)	Women who consumed iodine-containing dietary supplements during pregnancy (≥150 μg/day). Women in this group will receive a daily oral iodine supplement providing 150 μg iodine as potassium iodide for 14 days before the study start.
Lactating women with assumed adequate habitual iodine intake	Iodine (300 μg/day)	Women who consumed iodine-containing dietary supplements during pregnancy (≥150 μg/day). Women in this group will receive a daily oral iodine supplement providing 150 μg iodine as potassium iodide for 14 days before the study start.
Lactating mothers with assumed inadequate habitual iodine intake	Control	Women who did not consume iodine-containing dietary supplements during pregnancy (≥150 μg/day).
Lactating mothers with assumed inadequate habitual iodine intake	Iodine (300 μg/day)	Women who did not consume iodine-containing dietary supplements during pregnancy (≥150 μg/day).

Primary Outcome Measures

Name	Time	Method
Maternal iodine retention (μg/day)	24 hours	Calculated as iodine intake (µg/day) minus the iodine excretion (µg/day)

Secondary Outcome Measures

Name	Time	Method
Infant iodine retention (μg/day)	24 hours	Calculated as iodine intake (µg/day) minus the iodine excretion (µg/day)
Maternal iodine excretion in breast milk (μg/day)	24 hours	Estimated from measured breast milk iodine concentration (μg/L) and breast milk volume (L)

Trial Locations

Locations (1)

Nutrition Research Unit, University Children's Hospital Zurich; 🇨🇭 Zürich, Switzerland