Estimation of the Dietary Requirement for Vitamin D in Ethnic Groups

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

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.

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.

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