Don’t assume that sun exposure ensures adequate vitamin D levels

The results of this study suggest that “variable responsiveness to UVB radiation is evident among individuals, causing some to have low vitamin D status despite abundant sun exposure.”


Medscape has the best summary…, which I will summarize here.

  • 93 adults spent an average 22 hours each week outside without sunscreen and another 29 hours per week outside with and without sunscreen.
  • Despite this abundant sun exposure, 51% of the adults had 25-hydroxyvitamin D blood levels below 30 ng/mL — defined as “low vitamin D status.”

The bottom line?
According to the researchers, “The common clinical recommendation to allow sun exposure to the hands and face for 15 minutes may not ensure vitamin D sufficiency.”

Because the maximal 25-hydroxyvitamin D concentration produced by natural UV exposure is approximately 60 ng/mL, it seems prudent to use this value as an upper limit when taking vitamin D supplementation.

7/10/07 22:10 JR

Hi, I’m JR

John Russo, Jr., PharmD, is president of The MedCom Resource, Inc. Previously, he was senior vice president of medical communications at, a complementary and alternative medicine website.