A Household-Based Dietary Intervention Study of Vitamin D Fortified Bread in Irish Families

NCT07481240 | Completed

• 1 other identifier: FamDBread_22122
• Study Type: interventional
• Target: 128
• Locations: 1 country
• Sites: 2

Brief Summary

Vitamin D deficiency is common. It is caused by limited sun availability together with a low supply of vitamin D in the food system. There is a high prevalence of low vitamin D status around the world. In Ireland, our relatively northern latitude and prevailing weather mean that UVB availability for skin synthesis of vitamin D is limited in this country and our population relies on the dietary supply of vitamin D to prevent deficiency. Thus, the endemic Irish problem of vitamin D malnutrition is due to the lack of vitamin D in our food system. Dietary guidelines cannot address this issue because foods naturally rich in vitamin D are very few and infrequently consumed. The FamDBread study will test the hypothesis that a vitamin D-fortified bread as part of a healthy diet that includes vitamin D-fortified foods is effective in preventing low vitamin D status during winter, and safe for families to consume.

Conditions

Vitamin D Deficiency

Outcome Measures

Primary Outcomes (1)

• Serum concentrations of 25-hydroxyvitamin D (25(OH)D)

  Comparison of the number of participants with low vitamin D status (e.g. \<30 nmol/L and \< 50 nmol/L serum 25(OH)D) between treatment and placebo groups

  8 weeks

Secondary Outcomes (3)

• Vitamin D intakes

  8 weeks

• Serum concentrations of albumin-corrected serum calcium concentrations as a safety measure

  8 weeks

• Circulating biomarkers of metabolic health status

  8 weeks

Study Arms (2)

Fortified bread Intervention group

EXPERIMENTAL

Fortified bread Intervention group will be supplied with vitamin D fortified bread. Fortified Bread Intervention group will be supplied with fortified bread delivering \>20μg vitamin D3 in a daily portion and will receive dietary advice to incorporate fortified foods that are commonly available on the market in their diet.

Other: Fortified Bread

Placebo Comparator

PLACEBO COMPARATOR

Control arm will receive unfortified bread and dietary advice to incorporate fortified foods that are commonly available on the market in their diet.

Other: Unfortified bread

Interventions

Fortified Bread OTHER

Intervention group will be supplied with fortified bread delivering \>20 μg vitamin D3 in a daily portion and will receive dietary advice to incorporate fortified foods that are commonly available on the market in their diet.

Fortified bread Intervention group

Unfortified bread OTHER

Placebo control group will be supplied with unfortified bread and will receive dietary advice to incorporate fortified foods that are commonly available on the market in their diet.

Placebo Comparator

Eligibility Criteria

• Age: 5 Years - 59 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Child (0-17), Adult (18-64)

You may qualify if:

• Provide written informed consent if over 16 years; informed parental consent for children under-16 years, plus age-appropriate assent for children under-16 years.
• Be a household with at least one adult ≥18 years, with at least one dependent aged 5 years or older.
• Willing to consume bread provided and have storage capacity for frozen bread.
• Be in good general health.
• Be willing to follow the assigned diet for 8 weeks and attend the required appointments.

You may not qualify if:

• Daily consumption of a vitamin D supplement with a dose exceeding \>10µg/d (400 IU) equivalent.
• Exposure to factors that may influence vitamin D status, such as winter sun holiday, ski holiday, tanning beds etc.
• Are following a medically prescribed diet.
• Have a diagnosis of a medical condition that may interfere with vitamin D absorption, such as Coeliac disease, Inflammatory Bowel Disease, cystic fibrosis, or metabolism, such as liver disease, renal disease.
• Have a history of active cancer or a diagnosis of cancer within the past 5 years.
• Have an allergy to the bread ingredients.
• Are participating in another research study with an intervention or other lifestyle programme that would interfere with the outcomes of the study.
• Are unable to read, write, or understand English.

Sponsors & Collaborators

• University College Cork: lead
• University College Dublin: collaborator

Study Sites (2)

Human Nutrition Studies Unit, School of Food and Nutritional Sciences

Cork, Co. Cork, T12 K8AF, Ireland

Location

UCD Institute of Food and Health

Dublin, Ireland

Location

MeSH Terms

Conditions

Vitamin D Deficiency

Condition Hierarchy (Ancestors)

Avitaminosis; Deficiency Diseases; Malnutrition; Nutrition Disorders; Nutritional and Metabolic Diseases

Study Officials

• Mairead Kiely, PhD

  University College Cork

  PRINCIPAL INVESTIGATOR

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: QUADRUPLE
• Who Masked: PARTICIPANT, CARE PROVIDER, INVESTIGATOR, OUTCOMES ASSESSOR
• Purpose: PREVENTION
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Professor

Model Details: Parallel Assignment

Study Record Dates

• First Submitted: March 13, 2026
• First Posted: March 18, 2026
• Study Start: November 17, 2025
• Primary Completion: April 4, 2026
• Study Completion: April 4, 2026
• Last Updated: May 15, 2026

Record last verified: 2026-05

Data Sharing

• IPD Sharing: Will not share

Locations

IE (2)