Black skin color but not VDR gene represent a risk factor for low serum levels of vitamin D in self-declared black individuals.

BACKGROUND: The absorption of vitamin D occurs via two main pathways: first, through the biosynthesis in the skin under the exposure of UV from sunlight; and second, through the intake of certain foods. However, its levels can be influenced by both genetic and environmental factors, which can generate changes such as vitamin D deficiency (hypovitaminosis D), a condition that black adults have a high potential to suffer from.

OBJECTIVE: The aim of this work is to study the association of skin color (self-reported: black, brown and white), food consumption, and the BsmI polymorphism in the vitamin D receptor gene (VDR) on serum levels of vitamin D in a group of adults.

METHODS: This was a cross-sectional analytical study. Individuals in the community were invited to participate in the research and, After signing the informed consent, a structured questionnaire was applied containing identification data, self-declaration of race/color, and nutritional data (Food frequency questionnaire (FFQ) and 24 h); afterwards, blood was collected for biochemical analysis, vitamin D was measured by Chemiluminescence and RT-PCR was used to evaluate the BsmI polymorphism of the VDR gene. Data was analyzed using a statistical program (SPSS 20.0) and differences between groups using p < 0.05.

RESULTS: A total of 114 persons was evaluated between black, brown and white individuals. It was found that a large part of the sample presents hypovitaminosis D, and blacks stand out with an average serum vitamin D level of 15.9 ng/dL. The group demonstrated that dietary intake of vitamin D is low, with the present study is a pioneer in associating the polymorphism of the VDR gene (BsmI) with the consumption of foods that are considered to have a higher content of vitamin D in their composition.

CONCLUSION: The VDR gene does not represent a risk factor for the consumption of vitamin D in this sample, and it was found that the self-declaration of "black" skin color was an independent risk factor for low serum levels of vitamin D.