Suntan keeps UV rays at bay, blocks skin's Vitamin D synthesis

Turns out tanning is your skin's way of trying to protect itself from ultraviolet (UV) radiation, but the increasing pigment blocks vitamin D synthesis, limiting the skin's ability to produce more vitamin D.

A new study from Brazil found that even people exposed to high levels of sunlight may be deficient in serum vitamin D because it is mainly induced by UV irradiation and synthesized in the skin.

Lead author Francisco Bandeira from the University of Pernambuco said that the research showed that, in a large sample of individuals living in a tropical region located 8 degrees south of the equator with very high rates of sun exposure and extremely high UV irradiation, most people had serum vitamin D below 30 nanograms per milliliter, the cutoff for normal.

Bandeira added that the findings suggest that skin tanning, which is a natural protection against the harmful effects of UV irradiation, limits the progressive rise in serum vitamin D towards optimal concentrations.

The team evaluated 986 people between 13 and 82 years of age, with roughly equal numbers of males and females, living in the city of Recife, Brazil. All study participants had high rates of daily sun exposure and did not regularly use sunscreen or take vitamin D supplements.

Although the individuals with greater sun exposure had skin that was more tanned and less vitamin D deficiency than other participants, most of those with very high daily exposure had serum vitamin D levels below the normal cutoff.

The results are presented at ENDO 2016, the annual meeting of the Endocrine Society, in Boston.