Serum 25(OH)D levels after oral vitamin D3 supplementation and UVB exposure correlate.
BACKGROUND
The inter-individual variation in 25(OH)D3 increase (Δ25(OH)D3 ) after vitamin D3 supplementation was determined and compared with the UVB irradiation response.


METHODS
Nineteen Danish participants received 85 μg vitamin D3 (cholecalciferol) daily for nine weeks with regular serum 25(OH)D3 measurements. These participants had three years earlier taken part in a 9-week controlled UVB study. The Δ25(OH)D3 was not confounded by ambient UVB, BMI or ethnicity.


RESULTS
Δ25(OH)D3 was 53 nmol L-1 and almost identical to Δ25(OH)D3 (52 nmol L-1 ) after UVB. Δ25(OH)D3 ranged from 17 to 91 nmol L-1 (span 74 nmol L-1 ) and was about half of that observed after UVB irradiation (span 136 nmol L-1 ). The interquartile ranges for vitamin D3 supplementation (38.8-71.4 nmol L-1 , span: 32.6 nmol L-1 ) and UVB irradiation (35.7-65.4 nmol L-1 , span: 29.7 nmol L-1 ) were similar indicating a comparable response of the two interventions. As the 25(OH)D3 start levels (R2  = 0.398, P = 3.8 × 10-3 ), 25(OH)D3 end levels (R2  = 0.457, P = 1.5 × 10-3 ) and Δ25(OH)D3 (R2  = 0.253, P = 0.028) between both interventions were correlated, this suggested a possible common individual background for the variation. Four pigment SNPs influenced the variation in the vitamin D3 -induced and UVB-induced Δ25(OH)D3 . A combined model including the influence of these four SNPs and the 25(OH)D3 start level explained 86.8% (P = 1.6 × 10-35 ) of the individual variation after vitamin D3 supplementation.


CONCLUSION
The inter-individual variation in the two interventions was comparable and had no common demographic but a partly common genetic background.
['Datta|Pameli|P|https://orcid.org/0000-0001-5590-8671', 'Philipsen|Peter Alshede|PA|https://orcid.org/0000-0002-9656-733X', 'Olsen|Peter|P|', 'Andersen|Jeppe Dyrberg|JD|https://orcid.org/0000-0002-4395-5232', 'Morling|Niels|N|https://orcid.org/0000-0002-9463-5087', 'Wulf|Hans Christian|HC|https://orcid.org/0000-0001-8060-6413']
D000328:Adult D002112:Calcifediol D002762:Cholecalciferol D005260:Female D006801:Humans D008297:Male D008875:Middle Aged D012621:Seasons D014466:Ultraviolet Rays
25(OH)D vitamin D3 supplementation UVB inter-individual variation pigment genes