“Our 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,” said study author Dr. Francisco Bandeira, of the University of Pernambuco Medical School in Recife, Brazil.
For the study, researchers examined nearly 1,000 males and females from Recife who were between 13 and 82 years old. All had significant daily sun exposure and none routinely used sunscreen or took vitamin D supplements.
Using the Fitzpatrick skin phototype scale, which is a numerical measure of skin color and type used by dermatologists, the researchers assessed the response of different skin types to UV light. Generally, higher scores indicate darker skin tones and the tendency to tan, not burn.
The participants’ sun index was also calculated by multiplying the number of hours on sun exposure they got on a weekly basis by the fraction of exposed skin.
The researchers compared the participants’ sun index scores and skin type with their blood level of vitamin D. Most of the participants with very high daily exposure to the sun had lower-than-normal serum vitamin D levels.
Overall, 72% of the participants were deficient in vitamin D. Those lacking this nutrient tended to be older and have lower sun index values, the study found.
“Our 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 ng/ml, the cutoff for normal,” Bandeira said in a news release from the Endocrine Society.
This findings were presented Saturday at the annual meeting of the Endocrine Society, in Boston.
I frequently see low levels of serum vitamin D here in S. Florida. Much of it is from the use of sunscreens and clothing to protect our skin. Now here is study that shows excessive sun exposure also reduces vitamin D production.
Somewhere in between is the balance. I don’t like sunscreen and opt for UV protective clothing when I’m on the boat or in the water. If I’m on the boat all day (next week we move the boat to the Keys for a month), then I will apply sunscreen to my face and neck.
However, for my early morning runs I wear a pair of shorts and nothing else. I also play tennis on the weekends but reserve the court for 8 AM. The early morning and late afternoon sun is more indirect. This reduces the harmful UV rays but still can stimulate vitamin D production.
The Bottom Line:
Don’t tan to “get a good tan” but get some natural sunlight on your skin every day if at all possible. Have your serum vitamin D levels checked. Oh, by the way, this study was presented at the Endocrine Society because vitamin D is a hormone, not really a vitamin.
Source: April 4, 2016 National Institutes of Health