This pilot study demonstrates that a portable tanning device emitting UVB could maintain or improve vitamin D status in patients with CF or SBS during the winter months. Studies in SBS patients helped to define the UVB dose chosen for the CF study. In CF subjects, all were vitamin D deficient, despite taking regular vitamin D supplementation, due to malabsorption. During the winter, 8 weeks of the Sperti sunlamp resulted in a 25% increase in serum 25(OH)D concentration, and the prevalence of severe vitamin D deficiency [defined as 25(OH)D <20 ng/ml] decreased from 60% to 20%. All subjects demonstrated an increase in serum 25(OH)D concentrations, which achieved statistical significance. Similar results were found in the early pilot study in two SBS subjects. The use of a desktop tanning unit was well tolerated and no significant adverse events were reported by either group.
Sunlight, in particular UVB between the wavelengths of 290 and 315 nm, is the main source for producing vitamin D in the skin and is the primary source of vitamin D for the body. It is estimated that 90% of the daily body requirements are met by sunlight exposure (16
). One minimal erythemal dose (MED) of UVB exposure to 6% of the body surface area is equivalent to the ingestion of 600–1000 IU of vitamin D (18
). Thus, exposure of the hands, face and arms two to three times a week is sufficient to meet the daily body vitamin D requirements in most individuals during the spring, summer and fall (18
). Owing to the zenith angle of the sun during the winter months, very little UVB penetrates the earth above 351 latitudes, and thus sunlight exposure at this time will not result in sufficient vitamin D production (19
). For example, a third of healthy adults living in Boston were demonstrated to be vitamin D deficient at the end of winter (21
In areas where there is limited sunlight or in situations where patients cannot absorb vitamin D from the diet, phototherapy using UV light has been used to correct vitamin D deficiency. In the early 20th century, mercury arc lamps were used to treat children with rickets in Russia. Indoor beds or tanning devices have been reported to be an effective alternative method to maintain or raise vitamin D status especially during the winter months in individuals with malabsorption (1
). Subjects who use an indoor tanning bed at least once a week have 150% higher 25(OH)D levels at the end of winter and higher BMD than matched healthy controls (13
). Several other studies have used UVB from artificial sources in raising body vitamin D status (23
Vitamin D insufficiency and metabolic bone disease remains a major health problem in patients with CF. The cause for decreased bone density in CF is multifactorial; however, due to the inability to absorb fat soluble vitamins, vitamin D insufficiency is a major contributing factor (8
). Serum 25(OH)D in CF patients is positively correlated with BMD (29
). A recent Johns Hopkins Hospital study found 109 out of 134 CF adults in the clinic to be vitamin D deficient [serum 25(OH)D <30 ng/ml], and none of the 33 CF subjects who finished 1 200 000 IU of oral vitamin D2
over 4 months showed correction in their vitamin D status (10
). The CF consensus guidelines for bone health suggest the use of UV lamps in subjects who fail to achieve optimal vitamin D status; however, no standard protocols have been established (8
). A recent case–control study from Sweden demonstrated that CF subjects exposed to UV lamps one to three times weekly for 6 months showed an increase in circulating 25(OH)D from 20 to 50 ng/ml (27
One of the weaknesses of our study is that we did not have randomized control subjects during the same months. Our small sample size also limits the power of our data analysis; however, the study subjects were exposed to the tanning light for just 8 weeks, which significantly increased their serum vitamin D levels by 25%. However, the values failed to reach the newly established levels to define vitamin D insufficiency [25(OH)D >32 ng/ml] (30
). This suggests that the protocol may need to be extended for a longer time. Also, during this limited timeframe, we failed to show a significant decline in serum PTH concentration. Another limitation was that compliance could not be well assured in our second study with CF subjects because of the use of the tanning device at home.
In summary, we found that a portable tanning device used for tanning could be used to improve vitamin D status in selected individuals with intestinal malabsorption of vitamin D. Eight weeks of exposure to the sunlamp increased circulating 25(OH)D levels by 25% and reduced the prevalence of severe vitamin D deficiency. Further research is needed to determine the optimal duration of UVB exposure and to determine the long-term benefits of correcting vitamin D status by UVB on musculoskeletal health in these at-risk patients.