Vitamin D's ability to boost health still uncertain

Key Points

EDITOR'S NOTE: Despite many widely reported studies, the evidence is still inconclusive as to whether higher serum levels of vitamin D improve health outcomes, dermatologists say. In this issue, we examine some of the current research. We also explore whether indoor tanning is addictive ("Craving the rays? Study: About a third of sunbed users meet criteria for addiction"), and our online story looks at the state of suncreens (see http://www.dermatologytimes.com/sunscreens).

National report - Although recent vitamin D research suggests that higher vitamin D levels might improve some health outcomes, these data are largely inconclusive and sometimes contradictory, dermatologists say. Moreover, they continue to recommend oral supplementation rather than intentional sun exposure for those interested in elevating their levels.

Results of recent studies are inconsistent, dermatologists say.

Indeed, a recent review published by the Agency for Healthcare Research and Quality concludes that "The majority of findings concerning vitamin D, calcium or a combination of both nutrients on health outcomes were inconsistent," which makes formulating recommendations difficult (http://www.ahrq.gov/clinic/tp/vitadcaltp.htm#Report).

Some research links higher vitamin D levels to poorer outcomes.

In a prospective study involving male smokers, Dr. Rigel says, "High vitamin D levels were associated with a threefold increased risk for pancreatic cancer (Stolzenberg-Solomon RZ, Vieth R, Azad A, et al. Cancer Res. 2006 Oct 15;66(20):10213-10219)."

He says many recent vitamin D studies extend or confirm previous findings regarding vitamin D and various health outcomes.

However, he says, vitamin D synthesis in various skin types represents a fairly new avenue of investigation.

In this regard, one study shows that in the winter, darker and lighter skin types can synthesize vitamin D to the same extent with UV exposure (Bogh MK, Schmedes AV, Philipsen PA, et al. J Invest Dermatol. 2010 Feb;130(2):546-553).

"This article suggests that the innate ability of skin to synthesize vitamin D is the same for darker or lighter skin types," Dr. Lim says. "But during summer, the darker skin types would tan, because they possess more melanin, which blocks the synthesis of vitamin D."

The study is relatively small, and its findings require confirmation in larger studies, he says.