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

Not Applicable

Completed

• Conditions: Vitamin D Deficiency
• Interventions: Dietary Supplement: Placebo; Dietary Supplement: Vitamin D3 (20 micrograms/day)

• Registration Number: NCT01990872
• Lead Sponsor: University College Cork

Brief Summary

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

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.

Study Timeline

• Study Start: 2012-10
• Status Verified: 2013-11
• Primary Completion: 2013-11
• Study Completion: 2013-11
• Study First Submitted: 2013-11-08
• Study First Submitted QC: 2013-11-21
• Last Update Submitted: 2013-11-21
• Study First Posted: 2013-11-25
• Last Update Posted: 2013-11-25

Recruitment & Eligibility

• Status: COMPLETED
• Sex: All
• Target Recruitment: 125

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

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: PARALLEL

Arm && Interventions

Group	Intervention	Description
Placebo in high calcium group	Placebo	Placebo + habitual dietary calcium intake (\>1000 mg/d)
Vitamin D3 in low/moderate calcium group	Vitamin D3 (20 micrograms/day)	Vitamin D3 (20 microgram/day) + habitual calcium intake \<700 mg/d
Placebo in low/moderate calcium group	Placebo	Placebo + habitual calcium intake \<700 mg/d
Vitamin D3 in high calcium group	Vitamin D3 (20 micrograms/day)	Vitamin D3 (20 microgram/day) + habitual calcium intake (\>1000 mg/d)

Primary Outcome Measures

Name	Time	Method
Response of serum 25(OH)D concentration over winter in subjects stratified by calcium intake	0, 8, 15 weeks

Secondary Outcome Measures

Name	Time	Method
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 albumin-adjusted calcium	0, 8, 15 weeks
serum parathyroid hormone	0, 8, 15 weeks
Serum vitamin D binding protein	0 and 15 weeks

Trial Locations

Locations (1)

Human Dietary Studies Facility, School of Food and Nutritional Sciences, University College Cork, Cork, Ireland; 🇮🇪 Cork, Ireland