Clinical trial NCT02474446: Getting Vitamin D Dosing Right
Official title: Determining the Effects of Race, Skin Colour and Genotype on the Response to Vitamin D Therapy
Study type: INTERVENTIONAL
Overall status: COMPLETED
Phase: NA
Conditions: Vitamin D Status
Lead sponsor: Sheffield Children's NHS Foundation Trust
Sponsor class: OTHER
First posted: 2015-06-17
Enrollment: 60
Sex: MALE
Minimum age (years): 18
Maximum age (years): 25
Standard ages: ADULT
Accepts healthy volunteers: yes
Allocation: NA
Intervention model: SINGLE_GROUP
Primary purpose: DIAGNOSTIC

Brief summary: The investigators want to make sure that people get the right dose of Vitamin D treatment. They will therefore investigate how skin colour, body mass index, ethnicity, vitamin D binding protein and genetic variation affect the response to a standard course of vitamin D in young adults, as a prelude to further studies in younger children.

Detailed description: The Department of Health and the Chief Medical Officer have identified vitamin D deficiency as a key area of interest and concern for public health.

The main function of vitamin D is to enable dietary calcium to be absorbed from the intestine. Low levels of vitamin D can lead to diseases of bone such as rickets and osteomalacia and are linked to a higher risk of fracturing bones in older women with osteoporosis.

Vitamin D levels may be affected by the skin colour, body mass index (BMI), lifestyle or environment in which someone lives, and by their genetic makeup. Vitamin D levels tend to be lower in people with higher BMI and / or darker coloured skin or if the skin is covered by clothing because a lot of vitamin D is made from the action of sunlight on natural chemicals in the skin.

Vitamin D does occur naturally in the diet in foods like oily fish, and also vitamin D can be given as a supplement either on its own or as part of a multivitamin tablet.

There is natural variation from one person to another in how well the system controlling vitamin D blood levels works. Vitamin D circulates bound to a carrier protein, vitamin D binding protein (VDBP). When vitamin D levels are measured, both vitamin D bound to the protein and "free" vitamin D are measured.

A recent study in America showed that when "free" vitamin D levels (total vitamin D minus vitamin D bound to VDBP) are measured, they correlate very closely with other factors that help determine blood calcium levels.This variation is determined in part by a person's genetic makeup, and recent large studies have identified specific genetic variations that are linked to blood levels of vitamin D; some of these vary with the person's ethnic origin.

At present if someone has low vitamin D levels that put them at increased risk of bone problems, a course of vitamin D treatment is given.

When the investigators assessed their regular treatment given to children recently, they found some individuals developed very high blood vitamin D levels and others didn't.

They don't know how VDBP levels affect the response to treatment with vitamin D.

Further variation can occur because of the distribution of vitamin D into fat tissue. The investigators will measure height and weight, and waist and hip circumference and calculate Body Mass Index, body surface area (BSA) and waist: hip ratio as proxy measures of fat mass.

They will also evaluate whether blood or saliva tests give better information about vitamin D levels. The information about how these factors affect the response to vitamin D will help the clinicians choose the right dose of vitamin D for studies in younger children who are still growing.

Eligibility criteria: Inclusion Criteria:

* Healthy young male adults aged 18 25 years
* Free from any condition affecting bone health, general nutrition, growth and glucose metabolism.

Exclusion Criteria:

* Subjects with any chronic illness involving the liver and kidney
* Use of steroids, anticonvulsants or any medication that might affect calcium and vitamin D metabolism.
* Potential participants who have made plans to travel abroad during the study period.

Primary outcomes:
measure: Increase in serum 25 hydroxyvitaminD (25OHD) levels
timeFrame: Participants will be followed for the duration of the study, an expected average of 4 weeks
Secondary outcomes:
measure: Determine if dark skin colour or South Asian heritage reduces the increase in serum 25OHD.
timeFrame: Participants will be followed for the duration of the study, an expected average of 4 weeks
measure: Change in serum calculated free vitamin D
timeFrame: Participants will be followed for the duration of the study, an expected average of 4 weeks
measure: Determine if variation in Group specific component(GC) genotype is associated with variation in the increase in serum 25OHD.
timeFrame: Participants will be followed for the duration of the study, an expected average of 4 weeks
measure: Determine the extent of parathyroid hormone (PTH) suppression in relation to overall increases in total and free serum 25OHD
timeFrame: Participants will be followed for the duration of the study, an expected average of 4 weeks
Other outcomes:
measure: Evidence of hypercalciuria
timeFrame: Participants will be followed for the duration of the study, an expected average of 4 weeks
Locations:
city: Sheffield
country: United Kingdom
facility: Sheffield Children's NHS Foundation Trust
state: Sheffield (South Yorkshire district)
Study officials:
affiliation: Investigator
name: Sujatha Gopal
role: PRINCIPAL_INVESTIGATOR
References: