Vitamin D–fortified bread for Irish households.

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

This study will test whether eating vitamin D–fortified bread and other fortified foods during winter prevents vitamin D deficiency in Irish families of children, teens, and adults.

Quick facts

• Phase: NA
• Study type: Interventional
• Enrollment: 390 (estimated)
• Ages: 5 Years to 59 Years
• Sex: All
• Sponsor: University College Cork (other)
• Locations: 2 sites (Cork, Co. Cork and 1 other locations)
• Trial ID: NCT07481240 on ClinicalTrials.gov

What this trial studies

This randomized, household-level dietary intervention will enroll about 390 participants from families in Ireland and randomly assign households to receive either vitamin D–fortified bread plus advice to eat other fortified foods or identical unfortified bread plus the same advice. The target intake for the treatment group is >20 μg/day vitamin D, delivered through the fortified bread and additional commercially fortified foods, over an 8-week winter period. The primary outcome is prevention of vitamin D deficiency, defined as serum 25-hydroxyvitamin D <30 nmol/L, measured before and after the intervention, and the study will monitor safety and adherence. The trial tests the feasibility of using a common staple food to improve population vitamin D status in a northern-latitude setting.

Who should consider this trial

Good fit: Ideal candidates are Irish households with at least one adult (≥18 years) and one dependent aged ≥5 years who are in generally good health, not taking high-dose vitamin D supplements, willing to store frozen bread and follow the assigned diet for 8 weeks.

Not a fit: People with conditions that impair vitamin D absorption or metabolism (such as coeliac disease, inflammatory bowel disease, cystic fibrosis, liver or renal disease), those on medically prescribed diets, or those already taking >10 µg/day vitamin D supplements are unlikely to benefit.

Why it matters

Potential benefit: If successful, the intervention could prevent wintertime vitamin D deficiency for most participants and provide a practical, food-based approach to protect bone health across families.

How similar studies have performed: Population-level vitamin D food fortification (for example of milk or margarine) has improved vitamin D status in other settings, though randomized household trials specifically using bread are limited.

Eligibility criteria

Inclusion Criteria:

1. 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.
2. Be a household with at least one adult ≥18 years, with at least one dependent aged 5 years or older.
3. Willing to consume bread provided and have storage capacity for frozen bread.
4. Be in good general health.
5. Be willing to follow the assigned diet for 8 weeks and attend the required appointments.

Exclusion Criteria:

1. Daily consumption of a vitamin D supplement with a dose exceeding \>10µg/d (400 IU) equivalent.
2. Exposure to factors that may influence vitamin D status, such as winter sun holiday, ski holiday, tanning beds etc.
3. Are following a medically prescribed diet.
4. 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.
5. Have a history of active cancer or a diagnosis of cancer within the past 5 years.
6. Have an allergy to the bread ingredients.
7. Are participating in another research study with an intervention or other lifestyle programme that would interfere with the outcomes of the study.
8. Are unable to read, write, or understand English.

Where this trial is running

Cork, Co. Cork and 1 other locations

• Human Nutrition Studies Unit, School of Food and Nutritional Sciences — Cork, Co. Cork, Ireland (NOT_YET_RECRUITING)
• UCD Institute of Food and Health — Dublin, Ireland (RECRUITING)

Study contacts

• Principal investigator: Mairead Kiely, PhD — University College Cork
• Study coordinator: Maired Kiely, PhD

Conditions: Vitamin D Deficiency