Even people exposed to high levels of sunlight may be deficient in serum vitamin D because it is mainly induced by UV irradiation and synthesised in the skin, researchers from University of Pernambuco Medical School in Brazil said.

Researchers evaluated 986 people between 13 and 82 years of age, with roughly equal numbers of males and females.

All study participants had high rates of daily sun exposure and did not regularly use sunscreen or take vitamin D supplements.

Researchers evaluated each participant's Fitzpatrick skin phototype scale to estimate the response of different skin types to UV light.

In general, higher Fitzpatrick scale scores indicate deeper colour and tendency to tan rather than burn in the sun.

They also calculated each participant's sun index, the number of hours of sun exposure per week multiplied by the fraction of body surface area exposed.

They measured everyone's serum vitamin D levels and compared them with their skin phototype and sun index scores.

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.

Overall, 72 percent of participants had vitamin D deficiency, and their mean vitamin D level was only 26.06 ng/ml.

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