Effects of Vitamin D Fortification on Vitamin D Metabolite Profiles and Status in Vitamin D Insufficient Individuals

This is a cross-sectional study designed to compare plasma/serum and urine vitamin D metabolite profiles of vitamin D sufficient and insufficient individuals.

There are two phases of this study.

Phase 1 - Consented study participants will attend a screening visit and provide a fasting blood and urine sample. Those individuals who are vitamin D insufficient based on serum 25(OH)D concentrations will be invited to participate in Phase II

Phase II - is a double-blind, randomized, control study designed to examine vitamin D status in vitamin D insufficient individuals consuming a water-soluble form of vitamin D3. Eligible participants will be asked to consume one of three beverages: i) rooibos iced-tea (control); ii) rooibos iced-tea fortified with 1000 IU of water-soluble vitamin D3; or iii) rooibos iced-tea fortified with 1000 IU of water-soluble vitamin D3 and 360 mg calcium at 240 mL of iced-tea consumed daily for 6 weeks. Participants will attend 6 weekly visits following baseline and provide a fasting blood sample for assessment of serum 25(OH)D concentrations.

Objectives: 1) To investigate plasma/serum and urine vitamin D metabolite profiles in vitamin D sufficient and insufficient individuals; and 2) To determine the effects of vitamin D3 fortification on serum 25-dihydroxy-vitamin D \[25(OH)D\] concentrations, markers of vitamin D and calcium metabolism, and vitamin D metabolite profile in plasma/serum and urine of vitamin D insufficient individuals.

Health individuals from the general public will be recruited into this cross-sectional study designed to compare plasma/serum and urine vitamin D metabolite profiles of those identified as vitamin D sufficient and insufficient individuals.

There are two objectives:

Objective 1: To investigate plasma/serum and urine vitamin D metabolite profiles in vitamin D sufficient and insufficient individuals; N=20 and will consist of 10 individuals identified as vitamin D insufficient and 10 individuals identified as vitamin D deficient individuals.

Objective 2: To determine the effects of vitamin D3 fortification on serum 25-dihydroxy-vitamin D \[25(OH)D\] concentrations, markers of vitamin D and calcium metabolism, and vitamin D metabolite profile in plasma/serum and urine of vitamin D insufficient individuals. N=45.

To achieve the objectives, the study will be conducted in two phases:

Phase 1 - Healthy males or females, ≥19 and ≤50 years of age, will be recruited from the general public. Consented study participants will provide a fasting blood and urine sample for the purpose of determination of vitamin D status (insufficient vs. deficient) based on serum 25(OH)D concentrations. Forty-five (45) individuals identified as vitamin D insufficient (having a serum 25(OH)D concentration ≥30 and ≤75 nmol/L) will proceed to phase II. A N=20 (10 vitamin D insufficient and 10 vitamin D deficient) will also be identified to satisfy objective 1.

Phase II - is a double-blind, randomized, control study designed to examine vitamin D status in vitamin D insufficient individuals consuming a water-soluble form of vitamin D3. Eligible participants will randomized to consume one of three beverages: i) rooibos iced-tea (control); ii) rooibos iced-tea fortified with 1000 IU of water-soluble vitamin D3; or iii) rooibos iced-tea fortified with 1000 IU of water-soluble vitamin D3 and 360 mg calcium at 240 mL of iced-tea consumed daily for 6 weeks. Both researchers and participants will be blinded to the beverage group assigned to each participant. Participants will then attend 6 weekly visits following the baseline visit to provide fasting blood samples for assessment of serum 25(OH)D concentrations.

Analysis of intact-PTH, alkaline-phosphatase, calcium, phosphorus, CRP, TAP and vitamin D metabolite profile and a urine sample will also be obtained for assessment of N-telopeptide and vitamin D metabolite profile will also occur at Baseline and Week 6. Fasting blood samples collected at week 3 will be used for additional assessment of serum alkaline phosphatase, calcium and phosphorus. A 3-day Food Record will be provided at week 3.

Vitamin D insufficient participants will be stratified according to their serum 25(OH)D concentrations (≥30 and ≤50, or \>50 and ≤75 nmol/L) after screening and prior to the beverage study to ensure that a range of lower and higher serum 25(OH)D concentrations are represented in each beverage group.

Eligibility Criteria:
Inclusion Criteria:

A. Inclusion Criteria for Objective 1 (Part One):

1. Adult volunteers, male or female, between 19 and 50 years of age;
2. Body mass index (BMI) ≥20 and ≤30 kg/m2 (normal to overweight);
3. Must be on a stable regime for the past three months, if taking vitamin and mineral/dietary/herbal supplements; and
4. Willing to provide informed consent.

B. Inclusion Criteria for Objective 2 (Part Two):

1. Adult volunteers, male or female, between 19 and 50 years of age;
2. Body mass index (BMI) ≥20 and ≤30 kg/m2 (normal to overweight);
3. Must be on a stable regime for the past three months, if taking vitamin and mineral/dietary/herbal supplements;
4. Vitamin D insufficient (serum 25(OH)D concentrations ≥30 and ≤75 nmol/L);
5. Willing to comply with protocol requirements; and
6. Willing to provide informed consent.

Exclusion Criteria:

1. Take a vitamin D or calcium supplement within the last three months before the start date of the study, or during the study;
2. History of vitamin D deficiency (serum 25(OH)D concentration \<30 nmol/L);
3. History of hypocalcaemia;
4. Presence of a clinically diagnosed disease affecting the circulatory, respiratory, immune, skeletal, urinary, muscular, endocrine, digestive, nervous or reproductive system that requires medical treatment;
5. Taking any medication (with the exception of birth control);
6. Daily consumption of more than three servings of dairy products;
7. Undergone significant sun exposure one month before start date of the study;
8. Use or have used a tanning booth one month before start date of the study, or during the study;
9. Plan to travel to a sunny climate during the study;
10. Currently smoking or have smoked within the last six months before start date of the study, or during the study;
11. Have allergies to tea products;
12. Pregnant or lactating; and
13. Consume excessive alcohol (\>10 drinks/week for women, \>15 drinks/week for men).