Inter-relationship Between Vitamin D Requirements and Calcium Intake in Older Adults

Study Overview
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Brief Summary
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This winter-based placebo-controlled, single-dose vitamin D randomized controlled trial (RCT) aims to examine the impact of various levels of habitual calcium intake on dietary vitamin D requirements in older adults stratified by calcium intake. This will provide new data on the impact of different levels of calcium intake, ranging from low/moderate to high, on winter serum 25(OH)D levels, and their utilization and catabolism in adults.

Detailed Description
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The aim of this study is to perform a randomised controlled vitamin D3 intervention study in apparently healthy, free-living adults (aged 50+ y) to investigate whether different levels of habitual calcium intake, ranging from low-moderate to high, influence serum 25(OH)D concentrations and indices of vitamin D activation and catabolism during winter, when vitamin D intake is adequate versus inadequate. This research will provide new data and scientific understanding in relation to the impact of different levels of dietary calcium intake on vitamin D requirements in the older adult population. As such, this new data will inform dietary reference values for vitamin D.

Official Title
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Randomized Controlled Trial to Explore the Inter-relationship Between Vitamin D Requirements and Calcium Intake

Conditions
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Vitamin D Deficiency

Intervention / Treatment
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* Dietary Supplement: Vitamin D3 (20 micrograms/day)
* Dietary Supplement: Placebo


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Consenting white men and women aged ≥ 50 y Exclusion Criteria: Unwilling to discontinue consumption of vitamin D-containing supplements 4 wks before the initiation of the study and throughout the study. Planning to take a winter vacation (during the course of the 15-wk intervention) to a location at which either the altitude or the latitude was predicted to result in significant cutaneous vitamin D synthesis from solar radiation (e.g., a winter sun coastal resort or a mountain ski resort) Use of tanning facilities of any type. Pregnancy or planning to become pregnant during the study A severe medical illness, hypercalcaemia, Known intestinal malabsorption syndrome, Excessive alcohol use, Taking medications known to interfere with vitamin D metabolism

Ages Eligible for Study
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Minimum Age: 50 Years
Maximum Age: 80 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Prevention
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Placebo Comparator: Placebo in high calcium group<br>Placebo + habitual dietary calcium intake (>1000 mg/d) | Dietary Supplement: Placebo<br>* Placebo (0 micrograms vitamin D3/day)<br>|
| Active Comparator: Vitamin D3 in low/moderate calcium group<br>Vitamin D3 (20 microgram/day) + habitual calcium intake <700 mg/d | Dietary Supplement: Vitamin D3 (20 micrograms/day)<br>* Vitamin D3 (20 micrograms/day)<br>|
| Placebo Comparator: Placebo in low/moderate calcium group<br>Placebo + habitual calcium intake <700 mg/d | Dietary Supplement: Placebo<br>* Placebo (0 micrograms vitamin D3/day)<br>|
| Active Comparator: Vitamin D3 in high calcium group<br>Vitamin D3 (20 microgram/day) + habitual calcium intake (>1000 mg/d) | Dietary Supplement: Vitamin D3 (20 micrograms/day)<br>* Vitamin D3 (20 micrograms/day)<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Response of serum 25(OH)D concentration over winter in subjects stratified by calcium intake |  | 0, 8, 15 weeks | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Serum albumin-adjusted calcium |  | 0, 8, 15 weeks | 
| serum parathyroid hormone |  | 0, 8, 15 weeks | 
| Serum 24,25(OH)2D |  | 0 and 15 weeks | 
| Serum 1,25(OH)2D |  | 0 and 15 weeks | 
| Serum free 25(OH)D |  | 0 and 15 weeks | 
| Serum vitamin D binding protein |  | 0 and 15 weeks | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Vitamin D status, 25-hydroxyvitamin D, Vitamin D3, RCT, Calcium intake, Dietary requirement