Narrowband ultraviolet B three times per week is more effective in treating vitamin D deficiency than 1600 IU oral vitamin D3 per day: a randomized clinical trial.

BACKGROUND: It is known that narrowband ultraviolet B (NB-UVB) radiation and oral vitamin D(3) supplementation can both improve serum levels of vitamin D, expressed as 25-hydroxyvitamin D(3) [25(OH)D(3) ]. However, surprisingly few studies have compared the effects of the two interventions in treating vitamin D deficiency. OBJECTIVES: To compare the effect of NB-UVB exposure with oral vitamin D(3) supplementation on vitamin D levels in patients with vitamin D deficiency. METHODS: Seventy-three participants with vitamin D deficiency [25(OH)D(3) ≤ 25 nmol L(-1) ] were consecutively enrolled from February 2010 to May 2011, avoiding the summer period (June to September). The participants were randomized into two groups, one receiving full body NB-UVB exposure three times per week, the other receiving 1600 IU (40 µg) oral vitamin D(3) per day together with 1,000 mg calcium. Thirty-two participants completed the 6-week study period, 16 in each group. In both groups blood samples were obtained at baseline and after 3 and 6 weeks. RESULTS: We found a significantly greater increase in 25(OH)D(3) levels (mean) in the NB-UVB treated group (from 19·2 to 75 nmol L(-1) ) compared with the oral vitamin D(3) treated group (from 23·3 to 60·6 nmol L(-1) ) after 6 weeks of treatment (P = 0·02), accompanied by a significant decrease in parathyroid hormone for the whole group (from 5·3 to 4·2 pmol L(-1) , P = 0·028). CONCLUSIONS: Full body NB-UVB three times per week is more effective in treating vitamin D deficiency than prescription of a daily oral intake of 1600 IU (40 µg) vitamin D(3) .

The relation between sunscreen layer thickness and vitamin D production after ultraviolet B exposure: a randomized clinical trial.

BACKGROUND: Sunscreens absorb ultraviolet B (UVB) and it is a major concern that sunscreen use may lead to vitamin D deficiency. OBJECTIVES: To investigate the relation between the amount of sunscreen applied and the vitamin D serum level in humans after UVB exposure under controlled conditions. METHODS: Thirty-seven healthy volunteers with fair skin types were randomized to receive an inorganic sunscreen with sun protection factor (SPF) 8 of 0 mg cm(-2) , 0.5 mg cm(-2) , 1 mg cm(-2) , 1.5 mg cm(-2) , or 2 mg cm(-2) thickness on the upper body, approximately 25% of the body area. Participants were irradiated with a fixed UVB dose of 3 standard erythema doses 20 min after sunscreen application. This procedure was repeated four times with a 2- to 3-day interval. Blood samples were drawn before the first irradiation and 3 days after the last to determine the serum vitamin D level expressed as 25-hydroxyvitamin D(3) [25(OH)D]. RESULTS: The vitamin D serum level increased in an exponential manner with decreasing thickness of sunscreen layer in response to UVB exposure. For all thicknesses of sunscreen, the level of 25(OH)D increased significantly after irradiation (P<0.05), except for the group treated with 2 mg cm(-2) , in which the increase in 25(OH)D was not statistically significant (P=0.16). CONCLUSIONS: Vitamin D production increases exponentially when thinner sunscreen layers than recommended are applied (<2 mg cm(-2) ). When the amount of sunscreen and SPF advised by the World Health Organization are used, vitamin D production may be abolished. Re-evaluation of sun-protection strategies could be warranted.

A small suberythemal ultraviolet B dose every second week is sufficient to maintain summer vitamin D levels: a randomized controlled trial.

BACKGROUND: It is known that ultraviolet (UV) B radiation increases serum 25-hydroxyvitamin D(3) [25(OH)D] level. However, there is uncertainty about the relationship between the maintenance of vitamin D status and UVB. OBJECTIVES: To define the frequency of UVB exposure necessary for maintaining summer 25(OH)D levels during the winter. METHODS: In total, 60 participants were included from October 2008 to February 2009 (16weeks) and randomized for UVB exposure of 1 standard erythema dose (SED) to ∼88% body area once a week (n=15 completed), every second week (n=14 completed) or every fourth week (n=12 completed). The controls (n=14 completed) had no intervention. Vitamin D was measured at baseline, every fourth week before exposure, and 2days after the last UVB exposure. RESULTS: The 25(OH)D levels (mean) after UVB exposure once a week increased significantly (from 71·9 to 84·5nmolL(-1) ) (P<0·0001), whereas UVB exposure every second week maintained 25(OH)D levels (P=0·16). A significant decrease in mean 25(OH)D levels (from 56·4 to 47·8nmolL(-1) ) (P<0·0001) was found after UVB exposure once every fourth week and for the control group (from 64·8 to 40·1nmolL(-1) ) (P<0·0001). The development in 25(OH)D levels during the 16-week study period were negatively correlated with baseline 25(OH)D (P<0·0001). Further, the increase in 25(OH)D after the last UVB exposure was negatively correlated with the 25(OH)D level just before the last UVB exposure (P<0·0001). CONCLUSIONS: Exposure to a UVB dose of 1 SED every second week to ∼88% body area is sufficient for maintaining summer 25(OH)D levels during the winter.

Interdependence between body surface area and ultraviolet B dose in vitamin D production: a randomized controlled trial.

BACKGROUND: Ultraviolet (UV) B radiation increases serum vitamin D level expressed as 25-hydroxyvitamin-D(3) [25(OH)D], but the relationship to body surface area and UVB dose needs investigation. OBJECTIVE: To investigate the importance of body surface area and UVB dose on vitamin D production after UVB exposure. METHODS: We randomized 92 participants to have 6%, 12% or 24% of their skin exposed to 0·75 (7·5 mJ cm(-2) at 298 nm using the CIE erythema action spectrum), 1·5 (15 mJ cm(-2) ) or 3·0 (30 mJ cm(-2) ) standard erythema doses (SED) of UVB. Each participant underwent four UVB exposures at intervals of 2-3 days. Skin pigmentation and 25(OH)D levels were measured before and 48 h after the final exposure. RESULTS: The increase in 25(OH)D after irradiation [Δ25(OH)D] was positively correlated with body surface area (P = 0·006; R(2) = 0·08) and UVB dose (P < 0·0001; R(2) = 0·28), and negatively correlated with baseline 25(OH)D (P < 0·0001; R(2) = 0·18), for the entire data sample. However, when analysing each body surface area separately, we found a significant UVB response correlation for 6% (P < 0·0001; R(2) = 0·48) and 12% (P = 0·0004; R(2) = 0·35), but not for 24%. We also found a significant skin area response correlation for 0·75 SED (P < 0·0001; R(2) = 0·56), but not for 1·5 and 3·0 SED when analysing each UVB dose separately. The relationships did not change significantly after adjustment of Δ25(OH)D for baseline 25(OH)D. CONCLUSION: The increase in 25(OH)D depends mainly on the UVB dose; however, for small UVB doses the area of irradiated body surface is important.