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