Vitamin D and Skin Pigmentation in Healthy Humans Exposed to UVB
试验速览
- 阶段
- 不适用
- 状态
- 已完成
- 入组人数
- 43
- 试验地点
- 2
- 主要终点
- Change in serum 25(OH)D
研究概览
简要总结
Skin pigmentation (melanin) absorbs ultra violet type B (UVB) radiation found in sunlight and is believed to be responsible for darker-skinned persons' generally low 25(OH)D status. This phenomenon is found in immigrants living in Northern countries and their 25(OH)D responses to UVB-irradiation seem low.
We hypothesized that objectively measured skin pigmentation and/or pigment genes influence UVB-induced 25(OH)D increase significantly in combination with other influential parameters.
The influence of objectively measured constitutive and facultative skin pigmentation on UVB-induced 25(OH)D increase over time was investigated together with other possible influential parameters. These other influential parameters include sex, age, weight, height, BMI, number of fatty fish meals per week, Fitzpatrick Skin Type and 25(OH)D start level. The genetic parameters include 33 Vitamin D receptor and pigment SNPs.
This is a single-centre, open and non-blinded clinical trial. No randomisation was used, as the participants were allocated into two groups based on their Fitzpatrick Skin type and ethnic origin. The light-skinned group included participants with Fitzpatrick Skin type II-IV and were of Northern origin (Denmark, the Faroe Islands and the UK). The darker-skinned included Fitzpatrick Skin Types V-VI originating from countries located at latitudes below 50 degrees N. Thus, it could be ensured that the participants represented a wide range of skin pigmentation. The light-skinned (N = 22) and the darker-skinned subjects (N = 18) were exposed to identical UVB doses on identical body areas over nine weeks with weekly measurements of 25(OH)D. The UVB-induced 25(OH)D synthesis was investigated in summer-pigmented skin with melanin throughout the epidermis and during winter when ambient UVB exposure is negligible. Demographic data (gender, age, weight, height, Fitzpatrick Skin Type, measured constitutive and facultative skin pigmentation (PPF)) was collected/measured and registered in prior to study start. The number of daily consumed fatty fish meals was recorded in a questionnaire. Serum 25(OH)D was analysed weekly.
详细描述
Background. Melanin molecules (pigment) in skin, absorb UVB and presumably reduce the photo-conversion of 7-dehydrocholesterol. Epidemiological studies have reported poor vitamin D status in relatively darker-skinned immigrants residing in countries located at high latitudes. It is therefore commonly believed that skin pigmentation is a major influencer of vitamin D status. However, controlled UVB intervention studies have yielded conflicting results regarding the influence of skin pigmentation on UVB induced vitamin D increase.
Study hypothesis. The investigators hypothesized that objectively measured skin pigmentation (assessed as Pigment Protection Factor) and/or pigment genes influence UVB-induced 25-hydroxyvitamin D (25(OH)D) increase significantly in combination with other influential parameters. These other influential parameters include sex, age, weight, height, BMI, number of fatty fish meals per week, Fitzpatrick Skin Type and 25(OH)D start level. The genetic parameters include 33 Vitamin D receptor- and pigment-SNPs.
Study design. This is a single-centre, open and non-blinded clinical trial.
Intervention. The study was planned so that all included participants would receive identical UVB doses gradually increasing over nine weeks from November to January. The total UVB dose during the nine weeks was planned to be 26 kilo Joules/m2 (56 standard erythema doses). Irradiation time would be determined and regulated by measuring UV intensity with a Sola-Hazard spectroradiometer at study start, after five weeks and at the end of the exposure period. To avoid erythema, the standard erythema dose must be below the lowest measured UVB tolerance in the participants included. Based on previous experience of measurement on light-skinned individual, the UVB treatment dose was set to a maximum of 1.4 kilo Joules/m2 (3 standard erythema doses).
Methodological aspects.
研究设计
- 研究类型
- Interventional
- 分配方式
- Na
- 干预模型
- Single Group
- 主要目的
- Basic Science
- 盲法
- None
入排标准
- 年龄范围
- 18 Years 至 —（Adult, Older Adult）
- 性别
- All
- 接受健康志愿者
- 是
入选标准
- •Fitzpatrick Skin type I-IV (light-skinned)
- •Fitzpatrick Skin type V-VI (darker-skinned).
排除标准
- •Vitamin D supplementation exceeding 10 µg/day one month prior to study start
- •Vitamin D supplementation during study period
- •Sun holiday south of latitude 45 degrees N one month prior to or during the study start
- •Use of solarium one month prior to or during the study period
- •Chronic disease
- •Skin disease
- •Intake of cholesterol-lowering or photosensitising medication
- •Pregnancy
- •Drug addiction
- •Psychiatric disorder
- •Physical disabilities.
研究组 & 干预措施
Long-term UVB radiation
All participants received repeated UVB radiation for nine weeks. The treatment was identical for all participants.
干预措施: UVB radiation (Radiation)
结局指标
主要结局
Change in serum 25(OH)D
时间窗: Measured at study start and weekly over nine weeks
Serum 25(OH)D is a marker of vitamin D increase induced by UVB
次要结局
未报告次要终点