effects of vitamin d fortification on vitamin d metabolite profiles and status in vitamin d insufficient individuals

Conditions: Vitamin D Deficiency

Summary: 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).

Keywords: vitamin d insufficient rooibos tea calcium