Environmental Influences on Vitamin D Status

Study Overview
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Brief Summary
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Vitamin D deficiency is a common problem. The principal source of vitamin D for humans is solar exposure, with cutaneous synthesis of vitamin D by photoconversion of 7-dehydrocholesterol in the skin to pre-vitamin D3. Latitude, altitude, season, skin pigmentation, and age are recognized factors that influence how much vitamin D can be made by solar exposure. However, the relative influences of each are largely unknown and we cannot reliably answer the question of how much sun exposure an individual needs at various latitudes and at various seasons in order to ensure normal vitamin D status.

Detailed Description
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Purpose of the study: To determine the effect of environmental influences on Vitamin D status. Specific Aims To measure the prevailing 25D and Vitamin D levels in communities at diverse latitudes (Alaska and Hawaii). To collect information on variables that influence Vitamin D status such as skin color, history of sun exposure and sunscreen use, diet history, vitamin and calcium supplements used, and BMI. To collect typical food samples from the region for future analysis of their Vitamin D and 25D content. To collect a blood sample for DNA analysis of inter-individual differences in Vitamin D metabolism (Gc or Vitamin D binding protein alleles).

Official Title
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Environmental Influences on Vitamin D Status

Conditions
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Vitamin D Deficiency

Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Able to consent and come for a study visit. Male or female males and females ages 18-60. Exclusion Criteria: Unable to consent or come to a visit, taking Vitamin D supplements, anticonvulsants, barbiturates, steroids, having granulomatous disease, or liver or kidney disease as these medications and conditions interfere with Vitamin D metabolism.

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 60 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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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Alaska residents<br>50 healthy community dwelling males or females. | |
| Hawaiian residents<br>50 healthy community dwelling males or females at each site | |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| To measure the prevailing 25D and Vitamin D levels in communities at diverse latitudes |  | crosssectional | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| 2. To collect information on variables that influence Vitamin D status such to collect information on skin color, history of sun exposure and sunscreen use, diet history, vitamin and calcium supplements used, and BMI. |  | cross sectional | 
| To collect a blood sample for DNA analysis of inter-individual differences in Vitamin D metabolism (Gc or Vitamin D binding protein alleles). |  | cross sectional | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Sun, Vitamin D, Latitude, Vitamin D status