D-Light Intervention (D-Light)

D-Light Intervention: A Randomised Controlled Human Intervention Study to Assess the Impact of Vitamin D From Milk and Supplements on Functional Health Outcomes and Future Vitamin D Synthesis From UV Exposure

Vitamin D insufficiency has become a global concern, with low vitamin D status associated with bone disorders, cardiovascular disease and certain cancers. The United Kingdom (UK) and Ireland are at particular risk of vitamin D deficiency owing to the northerly latitude, increased use of sunscreen, decreased sun exposure and a high level of cloud cover. A recent survey in the UK showed that more than 50% of UK adults have insufficient vitamin D status, with lower levels noted in the winter months. Variations in vitamin D status have been known to vary between summer and winter, owing to our northern latitude (52-55°N) the Ultraviolet (UV)-B intensity in Northern Ireland is inadequate to promote the dermal synthesis of vitamin D during the winter months, causing us to rely on dietary sources. The aim of this intervention is to investigate the main effects of vitamin D3-fortified milk and supplemental vitamin D3 on vitamin D status and functional health outcomes during the winter, and how this intervention will affect subsequent dermal synthesis of vitamin D from UV exposure. Participants will be recruited from the local community. Blood samples will be collected from each participant at two timepoints (September/October and March/April). Pre- and post-intervention blood pressure, grip strength, height, weight, waist and hip circumferences will be measured, in addition participants will undergo a dual energy x-ray absorptiometry (DXA) scan to assess body composition and bone mineral density. Information on general health, lifestyle, physical activity, dietary intake and typical behaviours in the sun will be collected. Following the dietary intervention, a subset of participants will be invited to participate in a follow-up study, examining UV exposure during the summer months, when they will wear a personal wrist dosimeter for 1 month, complete a sun dairy and provide 2 additional blood samples.

Study Overview

• Status: Completed
• Conditions: 25-hydroxyvitamin D Concentration (Vitamin D Status)
• Intervention / Treatment: Dietary supplement: Fortified milk (10µg vitamin D3); Dietary supplement: 10µg vitamin D3 supplement; Dietary supplement: Placebo supplement; Dietary supplement: Unfortified milk (placebo)

• Study Type: Interventional
• Enrollment (Actual): 52
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United Kingdom
  • Coleraine, United Kingdom, BT52 1SA
    • Human Intervention Studies Unit

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 20 years to 40 years (Adult)
• Accepts Healthy Volunteers: Yes
• Genders Eligible for Study: All

Description

Inclusion Criteria:

• 20-40 years old
• Apparently healthy
• Living on the island of Ireland

Exclusion Criteria:

• Below 20 years and aged 40 years or above
• Not living on the island of Ireland
• Pregnant or lactating women and those planning to become pregnant
• Individuals who have been taking a vitamin D or calcium containing supplement in the previous three months
• Those with food intolerances or allergies that would affect their ability to consume study milk
• Individuals following a diet which excludes milk (e.g. vegans)
• Those with a diagnosed chronic medical condition or on prescribed medication known to effect vitamin D metabolism
• Those who are planning a sun holiday during the winter months (Oct-Mar)
• Adults with learning, or any other difficulties that would prevent them from completing the study protocol

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Randomized
• Interventional Model: Factorial Assignment
• Masking: Double

Number of Arms

4

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Treatment 1; 500ml fortified milk (10µg vitamin D3) +1 supplement capsule (10µg vitamin D3) daily for 24 weeks	Dietary supplement: Fortified milk (10µg vitamin D3); Dietary supplement: 10µg vitamin D3 supplement
Experimental: Treatment 2; 500ml fortified milk (10µg vitamin D3) +1 supplement capsule (placebo) daily for 24 weeks	Dietary supplement: Fortified milk (10µg vitamin D3); Dietary supplement: Placebo supplement
Experimental: Treatment 3; 500ml unfortified milk (placebo) +1 supplement capsule (10µg vitamin D3) daily for 24 weeks	Dietary supplement: 10µg vitamin D3 supplement; Dietary supplement: Unfortified milk (placebo)
Placebo Comparator: Treatment 4; 500ml unfortified milk (placebo) +1 supplement capsule (placebo) daily for 24 weeks	Dietary supplement: Placebo supplement; Dietary supplement: Unfortified milk (placebo)

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in vitamin D status (25-hydroxyvitamin D serum concentration)	Blood analysis	Baseline + post-intervention (24weeks)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in body composition	Assessed by dual energy X-ray absorptiometry (DXA)	Baseline + post-intervention (24weeks)
Change in muscle strength	Assessed by grip strength	Baseline + post-intervention (24weeks)
Change in inflammation status	Blood analysis	Baseline + post-intervention (24weeks)
Change in lipid profile	Blood analysis	Baseline + post-intervention (24weeks)
Change in glucose levels	Blood analysis	Baseline + post-intervention (24weeks)
Change in insulin concentrations	Blood analysis	Baseline + post-intervention (24weeks)

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
UV exposure (follow-up)	Assessed by UV wrist monitors	8 weeks post-intervention (32-40 weeks)

Collaborators and Investigators

• Sponsor: University of Ulster
• Collaborators: Dairy Council for Northern Ireland; Agri-food & Biosciences Institute; Center for Nutrition and Health, RIVM (The Netherlands)

Study record dates

Study Major Dates

• Study Start: September 1, 2014
• Primary Completion (Actual): October 1, 2015
• Study Completion (Actual): October 1, 2015

Study Registration Dates

• First Submitted: May 11, 2015
• First Submitted That Met QC Criteria: July 10, 2015
• First Posted (Estimate): July 13, 2015

Study Record Updates

• Last Update Posted (Estimate): January 15, 2016
• Last Update Submitted That Met QC Criteria: January 14, 2016
• Last Verified: January 1, 2016

More Information

Terms related to this study

• Keywords: Vitamin D; Supplementation; Body Composition; Blood pressure; Healthy adults; Muscle function; Fortified milk; UV exposure; Winter
• Additional Relevant MeSH Terms: Physiological Effects of Drugs; Micronutrients; Bone Density Conservation Agents; Calcium-Regulating Hormones and Agents; Vitamin D; Cholecalciferol; Vitamins; Ergocalciferols
• Other Study ID Numbers: 13/NI/0091