Estimation of the Dietary Requirement for Vitamin D in Ethnic Groups

Anthropometric measurements - weight (kg)

Weight (kg)

Time frame: Baseline and 12 weeks

Anthropometric measurements - height (m)

Height (m)

Time frame: Baseline and 12 weeks

Anthropometric measurements - height (cm)

Height (cm)

Time frame: Baseline and 12 weeks

Anthropometric measurements - waist circumference (cm)

Waist circumference measurement (cm)

Time frame: Baseline and 12 weeks

Anthropometric measurements - hip circumference (cm)

Hip circumference measurement (cm)

Time frame: Baseline and 12 weeks

Concentration of serum calcium (nmol/L)

Measure dose-response change in serum calcium measured in nmol/L

Time frame: 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

Time frame: Baseline and 12 weeks

Concentration of serum albumin (g/L)

Measure dose-response change in serum albumin measured in g/L

Time frame: Baseline and 12 weeks

Concentration of C-Reactive Protein (CRP) (mg/L)

Measure dose-response change in CRP measured in mg/L

Time frame: Baseline and 12 weeks

Complete blood count

Measure change in complete blood count

Time frame: Baseline and 12 weeks

Change in immune parameters

Measure change in gene expression in white blood cells

Time frame: Baseline and 12 weeks

Number of participants with Acute Respiratory Tract Infections (ARTIs)

Measure the frequency of ARTIs using a validated questionnaire

Time frame: 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.

Time frame: Baseline and 12 weeks

Muscular strength and endurance using a sit-to-stand test

Number of sit to stands in 30 seconds

Time frame: Baseline and 12 weeks

Blood analytes - micronutrient status

Measure dose-response change in micronutrient status from blood samples

Time frame: Baseline and 12 weeks

Blood analytes - lipid profile (mg/dL)

Measure change in lipid profile from blood samples measured in mg/dL

Time frame: 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.

Time frame: Baseline and 12 weeks

Physical activity questionnaire

Assess level of physical activity using an International Physical Activity Questionnaire (short form)

Time frame: 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)

Time frame: Baseline

Ultraviolet B radiation (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.

Time frame: 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

Time frame: Baseline