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MIAMI BEACH -- Narrowband UVB therapy may be a better treatment for vitamin D deficiency than supplementation, Swedish researchers reported here.

In a small, single-center study, patients deficient in vitamin D₃ who were given 6 weeks of full-body UVB phototherapy had significantly greater increases in serum vitamin D levels than those who took a supplement during that time (P=0.02), reported Morten Bogh, MD, PhD, of Malmö University Hospital in Sweden, during a poster session at the American Academy of Dermatology meeting.

However, the results do not mean that patients should turn to tanning beds for UV exposure, Bogh warned. Those machines mostly generate UVA radiation, which doesn't stimulate vitamin D production in the body the way UVB does, he said.

"We would not recommend phototherapy as a source of vitamin D to the general population," Bogh said. "Vitamin D deficiency can easily be treated with oral supplementation as shown in this study and several others."

"Nevertheless," he said, "it might be a useful alternative for certain groups of patients, especially those with malabsorption problems or noncompliant patients."

To compare narrowband UVB exposure with supplementation for patients with vitamin D deficiency, as measured by serum 25-(OH)D₃ levels of 25 nmol/L or less, Bogh and colleagues enrolled 73 patients between February 2010 and May 2011, skipping the summer months of June through September when patients may have had sufficient exposure to the sun.

Patients were also excluded if they went on holiday to a sunny location during the course of their treatment.

They were randomized to either full-body narrowband UVB radiation three times per week (mean cumulative dose of 9 J/cm²) or to supplementation with 1,600 IU of vitamin D plus 1,000 mg of calcium.

A total of 32 patients completed the full 6 weeks of treatment.

During that time, the researchers found that patients treated with UVB phototherapy had significantly greater improvements in serum vitamin D levels than those taking supplements, rising from 19.2 nmol/L to 75 nmol/L in the phototherapy group compared with an increase from 23.3 nmol/L to 60.6 nmol/L with supplementation.

Bogh concluded that full-body UVB phototherapy thrice weekly is more efficient at raising vitamin D levels than supplementation, but again stressed that it should be reserved for patients with malabsorption problems or noncompliant patients.

Jeffrey Miller, MD, of Penn State University in Hershey, Pa., who moderated the session at which the findings were presented, warned that the tanning industry has promoted tanning beds as a way to build healthy vitamin D levels.

Bogh pointed out that only 1% to 5% of the UV in tanning beds is UVB.

Another audience member agreed that it would be "very dangerous" to misinterpret the findings as a suggestion that indoor tanning could treat vitamin D deficiency. However, future studies could look at using UVB phototherapy that exposes only part of the body to radiation, rather than the whole body.

"It's well known that you get maximum vitamin D with only your arms exposed for 15 minutes a day," she said. "We don't need to irradiate the whole body."

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