Vitamin D Deficiency Clinical Trial
Official title:
A Double Blind Randomised Controlled Trial to Investigate the Effect of Vitamin D3 Supplementation on Iron Absorption and Hepcidin Response in Marginally Deficient and Iron Deficient Women
Iron is one of the most vital elements in humans as it plays a role in physiological functions such as transferring and storing oxygen, transporting electrons and catalysing numerous reactions, from oxidative metabolism to cellular proliferation. Iron deficiency can be attributed to poor absorption that leads to insufficient iron to meet body requirements. Oral iron supplements have been extensively used to treat iron deficiency and iron deficiency anaemia. However, the use of iron compounds in fortifying foods is one of the best practical approach to combat iron deficiency, while improving diet and food pattern involves long-term goal which can be challenging. Vitamin D has recently been shown to affect hepcidin levels, which in turn has effects on iron status but there are a limited number of studies investigating the hepcidin profile in humans following iron supplementation, and few data are available, especially in humans, despite its role as a primary iron absorption and homeostasis regulator. Although several studies have been carried out using iron fortified products, there is limited data on the potential effect of vitamin D on iron metabolism amongst iron deficient women in particular. Therefore, the present study aims to investigate the effect of vitamin D3 supplementation (1500 IU) consumed with iron fortified breakfast cereals on haematological indicators and hepcidin response in iron deficient women.
Recruitment And Sampling Strategy :
Participants will be recruited within the University of Chester, UK only. Emails and
posters/leaflets will be used as a medium of advertisement to the target group (staff and
students). A total of 62 pre-menopausal women aged between 19 to 40 years old will be
included in the study based on criteria described below. Eligibility will be based upon serum
ferritin and also vitamin D concentrations at screening before the start of the study.
Participants will be required to complete a screening questionnaire which will provide
information about participant's health status, drugs/medication/supplement usage, and recent
occurrences of illness/trauma/injury. A 6 ml venous blood will be drawn to assess
concentrations of plasma ferritin vitamin D, haemoglobin and full blood counts, Participants
with plasma ferritin concentrations below 20.0 µg/L and vitamin D concentration below 250
nmol/l will be included in the study. If the levels of haemoglobin are found to be in severe
stage of anaemia, the potential participant will be notified and advised to consult their
General Practitioner (GP) (haemoglobin levels < 8.0 g/dL). All eligible participants will be
briefed on the study protocol before the beginning of the study, and the eligible
participants will be given a Participant Information Sheet (PIS) and asked to provide written
informed consent.
An 8 week, double blind, randomised controlled trial will be carried out in Chester, United
Kingdom (UK). The 8 week intervention period was selected since more than 1 month is
appropriate to generally enlarge the erythropoietic marrow and observe changes in red blood
cell indices, especially in non-anaemic groups. Most vitamin D studies have used a supplement
concentration of 1000 IU and reported no adverse effects in the participants. Some studies
have used higher doses of 1600 or 4000 IU with no reported adverse outcomes in the
participants.
Participants will be randomly allocated to 2 groups:
1. Fe group (iron fortified breakfast cereals and placebo)
2. Vitamin D group (iron fortified breakfast cereals and vitamin D3).
Each participant will consume 60 grams of iron fortified breakfast cereals containing a total
of 9 mg of iron daily for 8 weeks with either vitamin D3 placebo or vitamin D3 (1500 IU)
according to their assigned group. The participants will consume the iron fortified breakfast
cereals in the morning, with 200 ml of semi-skimmed milk daily for a period of 8 weeks. The
participants will consume the vitamin D or placebo in the evening with 200 ml of water.
Participants will be asked to maintain their dietary habits and physical activity during the
course of study. Participants will also be asked not to donate blood during the course of the
study. The remaining supplements will be returned at the final clinic (week 8), and
compliance will be estimated.
Participants will be required to attend 3 clinics in total over a period of 8 weeks, and they
will be assessed at baseline (Day 0), interim (Week 4) and post intervention (Week 8).
Participants will be requested to fast overnight for approximately 8 hours before all
clinics. At each clinic, a 30 ml blood sample will be taken and both height (cm) and weight
(kg) will be measured. Before the start and the end of the study, participants will be
required to keep a 3-day food diary which includes 2 weekdays and 1 weekend day to represent
the habitual dietary intake of the participant. Blood samples will be batch analysed at the
end of the intervention to assess all biomarkers of iron status and vitamin D metabolism.
Sample size and justification :
Sample size was estimated using iron supplementation data from a study carried out by
Scholz-Ahrens et al. (2004) in which a serum ferritin concentration post intervention at 8
weeks (mean ± S.D) of 17.7 ± 11.8 ug/l (Fe fortified milk group) and 10.6 ± 8.1 ug/l (non
fortified milk group) was reported. With an effect size of 0.7015447, the total sample size
required for each group in the proposed study is 26. Taking into account a 20% drop out rate,
the total sample size required is 31 (Power = 0.80). Therefore, the total sample size needed
for the whole study is 62. Sample size was estimated using of G Power Software Version 3.1.7.
Statistical Analysis:
All statistical analyses will be conducted with International Business Machines (IBM)
Statistical Package for the Social Sciences (SPSS) Statistic Data Editor Software (Version
21). Assuming that the data is normally distributed after performing a Shapiro Wilks
normality test, one-way analysis of variance (ANOVA) with repeated measures will be conducted
to compare the mean differences for all measured parameters within each group at baseline,
interim and post intervention. The changes in the measured parameters between the periods of
the study will be analysed using paired t-test. Pearson's correlation test will be performed
to investigate the relationship between hepcidin profile and iron status biomarkers. A
non-parametric approach will be adopted if the data is not normally distributed for all
analyses. Differences will be considered significant with a p value ≤ 0.05.
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