Dr. Frank R. de Gruijl and Dr. Stan Pavel of Leiden University in Holland have carried out a study comparing the effects of low-level UV irradiation and orally-administered vitamin D supplements on the participants' vitamin D levels and their likelihood of catching a cold. For the purposes of the study, they set up three groups. The first group used a sunbed three times a week (in line with EU safety guidelines). The second group took daily supplements of 1000 IU/d vitamin D. The third (control) group did neither.
At the end of the trial, the vitamin D levels in the control group had fallen. The vitamin D levels in the group which took the supplements had increased significantly, however, the highest vitamin D levels were observed in the group which had used the sunbeds.
"The study shows that the use of modern sunbeds which conform to EU standards can significantly increase vitamin D levels. In the northern hemisphere, there is insufficient sunlight between September and March to ensure that vitamin D can be synthesized via the skin. So moderate, regular exposure using modern sunbeds can help to prevent vitamin D deficiencies during the winter months", Ad Brand of the Sunlight Research Forum (SRF) explains.
Source:
Frank R. de Gruijl and Stan Pavel: The effects of a mid-winter 8-week course of sub-sunburn sunbed exposures on tanning, vitamin D status and colds, Photochem. Photobiol. Sci., 2012, 11, 1848