Condition category
Not Applicable
Date applied
Date assigned
Last edited
Retrospectively registered
Overall trial status
Recruitment status
No longer recruiting
Publication status
Results overdue

Plain English Summary

Not provided at time of registration

Trial website

Contact information



Primary contact

Dr Georg Lietz


Contact details

School of Agriculture
Food and Rural Development (AFRD)
University of Newcastle
Kings Road
Newcastle upon Tyne
United Kingdom

Additional identifiers

EudraCT number number

Protocol/serial number


Study information

Scientific title

Do genetic polymorphisms in a beta-carotene metabolising key enzyme influence dietary vitamin A requirements?


Study hypothesis

Vitamin A (retinol) is an essential nutrient for vision, embryonic development, maturity of organs, cellular proliferation andthe immune response. It is obtained from the diet per se or through provitamin A sources that are cleaved enzymatically
in the body to produce retinol. Vitamin A deficiency occurs largely due to increases in physiological requirements (growth, pregnancy, lactation, infection) together with a low dietary intake.

Currently, the mean daily intake of vitamin A is below the recommended intake levels for men and women aged 19 to 24 years. This means that young individuals in the UK rely to over 50% on provitamin A sources, beta-carotene being the main one, to cover their vitamin A needs. Since a significant proportion of young British individuals have a low vitamin A intake and since the Expert Group on Vitamins and Minerals has recommended to limit the use of beta-carotene in food supplements, there is growing concern that young men and women in the UK might develop subclinical deficiencies, therefore increasing their susceptibility to infectious diseases. This concern is especially valid for young pregnant women who will experience a higher physiological need for vitamin A.

Given the fact that a high proportion of the British population relies on beta carotene to cover their vitamin A needs, it is important to note that the amount of retinol produced after ingestion and conversion of beta-carotene is highly variable between healthy individuals. Several studies have shown a large disparity between individuals who are efficient or inefficient converters of beta-carotene, with variations of up to 8-fold. It is possible that the observed differences in obtaining retinol from beta-carotene may be due to genetic polymorphisms in genes involved in aspects of beta-carotene conversion. Indeed, results from our laboratory have shown that two genetic variants exists in the key enzyme responsible for beta-carotene conversion.

Ethics approval

Newcastle and North Tyneside Local Research Ethics Committees approved on the 19th May 2009 (ref: 09/H0904/20)

Study design

Single centre non-randomised interventional trial

Primary study design


Secondary study design

Non randomised controlled trial

Trial setting


Trial type


Patient information sheet

Not available in web format, please use the contact details below to request a patient information sheet


Topic: Generic Health Relevance and Cross Cutting Themes; Subtopic: Generic Health Relevance (all Subtopics); Disease: Public Health Research


The intervention will last 14 days. However, first contact with the study participants will be 2 months prior to the start of the intervention to explain the study. A capsule containing 2 mg dose of beta-carotene and 1 mg retinyl acetate stable isotope will be orally adminstered to volunteers on day 1. Blood samples will be drawn at 7 time points on day 1, with subsequent samples being taken on days 2, 3, 7, and 14.

Intervention type



Not Applicable

Drug names

Primary outcome measure

Blood concentrations of administered beta-carotene/retinyl acetate, and derived metabolites. Primary outcome measures will be taken at 0, 2, 4, 6, 8, 12 hours on day 1. Then at days 2, 3, 7, and 14.

Secondary outcome measures

No secondary outcome measures

Overall trial start date


Overall trial end date


Reason abandoned (if study stopped)


Participant inclusion criteria

1. Aged 18 - 45 years
2. Generally fit and healthy adults
3. Males and females

Participant type


Age group




Target number of participants

Planned sample size: 200

Participant exclusion criteria

1. Smokers
2. Pregnant females
3. Diabetics
4. Liver disease
5. Gastrointestinal disorders

Recruitment start date


Recruitment end date



Countries of recruitment

United Kingdom

Trial participating centre

School of Agriculture, Food and Rural Development (AFRD)
Newcastle upon Tyne
United Kingdom

Sponsor information


Newcastle University (UK)

Sponsor details

School of Agriculture Food and Rural Department
Claremont Road
Newcastle Upon Tyne
United Kingdom

Sponsor type




Funder type

Research council

Funder name

Biotechnology and Biological Science Research Council (BBSRC) (UK)

Alternative name(s)

Funding Body Type

Funding Body Subtype


Results and Publications

Publication and dissemination plan

Not provided at time of registration

Intention to publish date

Participant level data

Not provided at time of registration

Basic results (scientific)

Publication list

Publication citations

Additional files

Editorial Notes

31/10/2019: No publications found, verifying study status with principal investigator. 21/07/2016: No publications found, verifying study status with principal investigator.