Contribution of Cow's Milk to Iodine and Selenium Status in Women of Child-bearing Age (SIMI)

Iodine is an essential trace element necessary for the synthesis of thyroid hormones which are critical for human growth and development throughout the lifecycle. Iodine is particularly important during pregnancy and infancy for brain and neurological development. Severe iodine deficiency during pregnancy can cause severe mental impairment and stillbirth while mild-to-moderate deficiency has been associated with impaired infant development. As such, pregnant women and women of child-bearing age are particularly vulnerable to the effects of iodine deficiency.

Globally, 241 million (30%) school aged children are iodine deficient. Historically, the UK and Ireland were believed to be iodine sufficient but concern has been expressed in the last decade regarding the iodine status of the UK and Irish populations. A study of Irish women in 2004 reported 55% of pregnant women in their sample population to be moderately iodine deficient and 53% of non-pregnant women to be moderately iodine deficient. A study of UK schoolgirls found that 51% were mildly iodine deficient and 16% were moderately deficient. Importantly, the prevalence of iodine deficiency was highest in Northern Ireland where 85% of those sampled were iodine deficient.

Iodine is known to interact with selenium in the conversion of the thyroid hormone thyroxine (T4) to the metabolically active triiodothyonine (T3) hormone. Selenium is also important for immune, cardiovascular and cognitive function. Selenium status has been reported to be moderately low using pooled English data on blood selenium concentrations from 1984 to 1992. In addition, the latest National Diet and Nutrition Survey reports that selenium intakes are below recommendations for several population groups including women of childbearing age where mean selenium intakes are 76% of the recommended 60µg/day. This national survey also reported that 49% of women aged 19-64 years failed to meet the lower reference nutrient intake of 40µg/day.

Milk and dairy products are the major source of iodine for the UK population and are also a source of selenium. The contribution of milk and dairy products to iodine and selenium intakes is greatest in adult females (35% and 6% respectively). Observational evidence has repeatedly reported milk consumption to be positively correlated with iodine status and iodine intakes. Research in Iceland and New Zealand has reported that milk consumption is not associated with selenium status; however it is unknown if this is true for the UK population.

To date, no randomised controlled trial has examined the effect of milk consumption on either iodine or selenium status. The possibility of increasing iodine and selenium intake by increasing milk consumption, a widely available and consumed foodstuff, in a population group vulnerable to micronutrient deficiency should be investigated. This would add valuable data to the knowledge base for iodine, where there is ongoing debate over the most appropriate means of increasing iodine intake amongst women of childbearing age in the UK where salt iodisation, the key strategy in preventing deficiency, is not implemented.

The aim of this study is to investigate the impact of cow's milk consumption on the biological status of iodine and selenium among women of child-bearing age.

The study will be a 12 week randomised-controlled human intervention study. Participants will be randomised to consume additional semi-skimmed milk in the Following amounts, control group (0mls/day), intervention group (430mls/day or 3l per week).

Study Overview

• Status: Completed
• Conditions: Selenium and Iodine Status
• Intervention / Treatment: Other: Semi-skimmed cow's milk

• Study Type: Interventional
• Enrollment (Actual): 78
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United Kingdom
  • Co.Londonderry
    • Coleraine, Co.Londonderry, United Kingdom, BT52 1SA
      • Human Intervention Studies Unit, Ulster University

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 45 years (Adult)
• Accepts Healthy Volunteers: Yes
• Genders Eligible for Study: Female

Description

Inclusion Criteria:

• Inclusion criteria
• Healthy
• Age 18-45 years
• Females
• Non smoking
• No history of thyroid or gastrointestinal conditions
• Not consuming thyroid medication or medication containing iodine or selenium
• Willing to increase their milk consumption should they be randomised into the milk group

Exclusion Criteria:

• Smoker
• Pregnant, breastfeeding or planning to become pregnant during the study
• Milk allergy
• Non-milk consumers or vegans
• Lactose intolerant individuals
• Use of dietary supplements containing iodine or selenium in previous 3 months
• Peri- or post-menopausal
• Consume more than 250ml of milk daily

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: Milk treatment group; Semi-skimmed cow's milk + normal diet for 12 weeks	Other: Semi-skimmed cow's milk; 430ml of semi-skimmed cow's milk / day for 12 weeks
No Intervention: Control group; Normal diet for 12 weeks

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Time Frame
Urinary iodine concentration	Change from baseline following 12-week intervention

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Serum thyroid hormone analysis		Baseline (week 0), mid (week 6) and post-intervention (week 12)
Urinary creatinine analysis		Baseline (week 0), mid (week 6) and post-intervention (week 12)
Serum selenoprotein P analysis		Baseline (week 0), mid (week 6) and post-intervention (week 12)
Dietary iodine and selenium intake	24-hour dietary recall	Baseline (week 0), mid (week 6) and post-intervention (week 12)
Blood pressure		Baseline (week 0), mid (week 6) and post-intervention (week 12)
Body Mass Index		Baseline (week 0), mid (week 6) and post-intervention (week 12)
Waist Hip ratio		Baseline (week 0), mid (week 6) and post-intervention (week 12)

Collaborators and Investigators

• Sponsor: University of Ulster
• Collaborators: Charite University, Berlin, Germany; University Hospital Southampton NHS Foundation Trust; LGC Limited; Northern Health and Social Care Trust; Dairy Council for Northern Ireland; Department of Agriculture and Rural Development Northern Ireland

Publications and helpful links

General Publications

• O'Kane SM, Pourshahidi LK, Mulhern MS, Strain JJ, Mackle EM, Koca D, Schomburg L, Hill S, O'Reilly J, Kmiotek D, Deitrich C, Bath SC, Yeates AJ. Cow Milk Consumption Increases Iodine Status in Women of Childbearing Age in a Randomized Controlled Trial. J Nutr. 2018 Mar 1;148(3):401-408. doi: 10.1093/jn/nxx043.

Study record dates

Study Major Dates

• Study Start: September 1, 2015
• Primary Completion (Actual): December 1, 2015
• Study Completion (Actual): December 1, 2015

Study Registration Dates

• First Submitted: May 4, 2016
• First Submitted That Met QC Criteria: May 6, 2016
• First Posted (Estimate): May 10, 2016

Study Record Updates

• Last Update Posted (Estimate): May 10, 2016
• Last Update Submitted That Met QC Criteria: May 6, 2016
• Last Verified: April 1, 2016

More Information

Terms related to this study

• Keywords: Iodine; Women; Cow's milk; Selenium; Child-bearing age
• Other Study ID Numbers: REC/15/0042

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO