Estimation of the Dietary Requirement for Vitamin D in Ethnic Groups

Study Overview
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Brief Summary
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The aim of this study is to perform a double-blind, randomised, dose-response trial of vitamin D3 supplementation in United Kingdom (UK)-dwelling adults of white European, South Asian, and black African/Caribbean ethnicity to investigate the distribution of dietary intakes needed to maintain adequate vitamin D status in winter, as indicated by serum 25(OH)D concentrations at ranges of >25 to 50 nmol/L. In addition, this study will investigate the effect of vitamin D3 supplementation on immune health, muscular strength, and overall health.

Detailed Description
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The aim of this study is to perform a double-blind, randomised, dose-response trial of vitamin D3 supplementation in United Kingdom (UK)-dwelling adults of white European, South Asian, and black African/Caribbean ethnicity to investigate the distribution of dietary intakes needed to maintain adequate vitamin D status in winter, as indicated by serum 25(OH)D concentrations at ranges of >25 to 50 nmol/L. In addition, this study will investigate the effect of vitamin D3 supplementation on immune health, muscular strength, and overall health. Recruited participants will be randomised to take 400, 1000, or 2000 IU for 12 weeks. Fasting blood samples collected at baseline and 12 weeks will measure biochemical markers of vitamin D status (serum 25(OH)D, calcium, parathyroid hormone, albumin), lipid profile, ferritin, micronutrient status, and immune and inflammatory biomarkers. Muscular strength will be measured using sit-to-stand and grip strength tests. Questionnaires, food diaries, and dosimeters will be used to gather data on lifestyle, physical activity, dietary intake, and sun exposure.

Official Title
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Estimation of the Dietary Requirement for Vitamin D in Ethnic Groups: a Double-blind, Randomised, Dose-response Trial

Conditions
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Immune Health, Vitamin D Deficiency, Muscle Function

Intervention / Treatment
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* Dietary Supplement: Vitamin D Supplement


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: British white European, black African/Caribbean, or South Asian (self-reported) Living in England for >2 months Aged >18 years No significant health issues English or Urdu speaker Exclusion Criteria: Medical condition or history which might impact study measurements (e.g., ischaemic heart disease, type 1 and type 2 diabetes, thyroid disease, osteoporosis, haematological disease, malignancy) Medications known to affect vitamin D metabolism (i.e., hormone replacement therapy, anti-oestrogens treatment, antiepileptic drugs, and breast cancer treatment) Pregnant or planning pregnancy during the study period Regular use of sun beds Having a sun holiday one month prior to commencing study or plans for a sun holiday within the study period. A sun holiday is generally defined as a holiday in a sunny resort outside of the UK. The researchers will assess this on a case-by-case basis depending on the time of year and expected weather conditions Reported participation in another clinical trial occurring simultaneously Previous intolerance or allergic reaction to vitamin D

Ages Eligible for Study
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Minimum Age: 18 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
Interventional Model Description: Recruited participants will be randomised to take 400,1000, or 2000 IU for 12 weeks.
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: Vitamin D Supplement 400 IU<br>400 IU (10 µg) of Vitamin D3 | Dietary Supplement: Vitamin D Supplement<br>* Vitamin D Supplement<br>|
| Active Comparator: Vitamin D Supplement 1000 IU<br>1000 IU (25 µg) of Vitamin D3 | Dietary Supplement: Vitamin D Supplement<br>* Vitamin D Supplement<br>|
| Active Comparator: Vitamin D Supplement 2000 IU<br>2000 IU (50 µg) of Vitamin D3 | Dietary Supplement: Vitamin D Supplement<br>* Vitamin D Supplement<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Concentration of serum 25(OH)D (nmol/L) | A blood sample will be analysed using liquid chromatography tandem mass spectroscopy (LC-MS). Dose-response change in serum 25(OH)D will be measured in nmol/L. | Baseline and 12 weeks | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Anthropometric measurements - weight (kg) | Weight (kg) | Baseline and 12 weeks | 
| Anthropometric measurements - height (m) | Height (m) | Baseline and 12 weeks | 
| Anthropometric measurements - height (cm) | Height (cm) | Baseline and 12 weeks | 
| Anthropometric measurements - waist circumference (cm) | Waist circumference measurement (cm) | Baseline and 12 weeks | 
| Anthropometric measurements - hip circumference (cm) | Hip circumference measurement (cm) | Baseline and 12 weeks | 
| Concentration of serum calcium (nmol/L) | Measure dose-response change in serum calcium measured in nmol/L | Baseline and 12 weeks | 
| Concentration of plasma parathyroid hormone (PTH) (pg/mL) | Measure dose-response change in plasma parathyroid hormone (PTH) measured in pg/mL | Baseline and 12 weeks | 
| Concentration of serum albumin (g/L) | Measure dose-response change in serum albumin measured in g/L | Baseline and 12 weeks | 
| Concentration of C-Reactive Protein (CRP) (mg/L) | Measure dose-response change in CRP measured in mg/L | Baseline and 12 weeks | 
| Complete blood count | Measure change in complete blood count | Baseline and 12 weeks | 
| Change in immune parameters | Measure change in peripheral blood mononuclear cell (PBMC) profile | Baseline and 12 weeks | 
| Number of participants with Acute Respiratory Tract Infections (ARTIs) | Measure the frequency of ARTIs using a validated questionnaire | 12 weeks | 
| Muscular strength using a handgrip strength test (kg) | Muscular strength measured using a dynamometer (measured to the nearest 0.1kg). The participant will squeeze the dynamometer with maximum effort for 5 seconds. | Baseline and 12 weeks | 
| Muscular strength and endurance using a sit-to-stand test | Number of sit to stands in 30 seconds | Baseline and 12 weeks | 
| Blood analytes - micronutrient status | Measure dose-response change in micronutrient status from blood samples | Baseline and 12 weeks | 
| Blood analytes - lipid profile (mg/dL) | Measure change in lipid profile from blood samples measured in mg/dL | Baseline and 12 weeks | 
| Vitamin D consumption from diet | Vitamin D intake will be measured through a 4-day food diary which participants will fill out for 4 day at home before and after the study. | Baseline and 12 weeks | 
| Physical activity questionnaire | Assess level of physical activity using an International Physical Activity Questionnaire (short form) | Baseline | 
| Sun exposure behaviour questionnaire | Measures amount of time spent in the sun (often, occasionally, never) and what parts of the body are exposed (head, hands, arms, legs, torso) over summer, spring, autumn and winter. Also questions any summer holidays abroad, in what month, what country was visited, number of hours of sun per day and what body parts were exposed (head, hands, arms, legs, torso) | Baseline | 
| UVB sun exposure | Sun exposure will be measured by a dosimeter, which measures UVB exposure. Participants wear this like a badge for 4 days before and after the study. | Baseline and 12 weeks | 
| Lifestyle questionnaire | Measures: - Skin type (Fitzpatrick scale) Questions: Questions what ethnicity they identify with, Holidays abroad, Education, Origin, Health, Pregnancy, Sun behaviours (what body parts are usually exposed to the sun, clothing, sun bathing, sunscreen use, sun bed use), Smoking, Drinking, Recreational drug use, Knowledge around vitamin D, supplement use, Milk, egg, oily fish and liver consumption | Baseline |