Non-linear increase of vitamin D content in eggs from chicks treated with increasing exposure times of ultraviolet light

• Published in: The Journal of steroid biochemistry and molecular biology Vol. 148; pp. 7 - 13
• Main Authors: Kühn, Julia, Schutkowski, Alexandra, Hirche, Frank, Baur, Anja C., Mielenz, Norbert, Stangl, Gabriele I.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.04.2015
• Subjects: Animals; Bio-addition; Chickens; Egg; Eggs - analysis; Eggs - radiation effects; Laying hen; Ultraviolet Rays; UVB; Vitamin D; Vitamin D - metabolism; Vitamins - metabolism; UVB; Vitamin D; Egg; Bio-addition; Laying hen
• ISSN: 0960-0760; 1879-1220
• DOI: 10.1016/j.jsbmb.2014.10.015

•Chicks were daily exposed to UVB light.•Egg vitamin D content increased non-linear with increasing UVB exposure times.•Endogenous 7-dehydrocholesterol content was not altered by UVB treatment. Vitamin D fortified food can help to reduce the prevalence for vitamin D deficiency. Previous data provided evidence that eggs from hens exposed to ultraviolet (UV) light contain large quantities of vitamin D. In the current study, we assessed the efficacy of vitamin D enrichment in eggs upon increasing daily UVB exposure times. We further addressed the question whether extended UVB irradiation affects the skin content of 7-dehydrocholesterol. To this end, 35 hens were assigned to 7 groups of 5 animals each and were exposed to UVB light (76μW/cm2) for 0, 15, 30, 60, 120, 180 and 300min per day, respectively. Eggs from the treatment groups were collected at baseline and after 2, 3 and 4 weeks of treatment, respectively. Skin samples were gained at the end of 4 weeks. Vitamin D metabolites were quantified by liquid chromatography–tandem mass spectrometry. The contents of vitamin D3 and 25(OH)D3 in egg yolk raised non-linear in response to increasing daily UVB exposure times. The vitamin D3 content did not reach a clear-cut plateau within the chosen UVB treatment times. A daily UVB exposure time of 300min resulted in vitamin D3 contents of 28.6μg/100g egg yolk dry matter. In contrast to vitamin D3, the 25(OH)D3 content in the egg yolk achieved a maximum upon an UVB irradiation time of 60min/d. The cutaneous 7-dehydrocholesterol contents were not altered in response to the chosen UVB irradiation times. In conclusion, the data show a distinct non-linear dose-response relationship of UVB exposure times on the total vitamin D content in eggs. This article is part of a special issue entitled ‘17th Vitamin D Workshop’.