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Free-range chicken eggs have at least 3X more vitamin D – Oct 2013

Free-range farming: a natural alternative to produce vitamin D-enriched eggs

Julia Kühn, Dipl., Alexandra Schutkowski (Dr.), Holger Kluge (Dr.), Frank Hirche (Dr.),
Gabriele I. Stangl (Dr.) gabriele.stangl at landw.uni-halle.de
Institute of Agricultural and Nutritional Sciences, Martin-Luther-University Halle-Wittenberg, 06120 Halle (Saale), Germany

Objective: Food-based strategies need to be developed to improve the vitamin D status of individuals. Recent studies identified UVB irradiation as an efficient method to enrich mushrooms and eggs with vitamin D. These findings prompted us to test, whether free-range farming of hens could provide a valuable method to produce vitamin D-enriched eggs.

Methods: Laying hens were randomly assigned to three groups of 33/34 animals each, and were kept either indoors (indoor group), outdoors (outdoor group) or with an indoor/outdoor option (indoor/outdoor group) over 4 weeks.

Results: Here we show that the vitamin D3 content of egg yolk was 3- to 4-fold higher in the groups that were exposed to sunlight (outdoor group and indoor/outdoor group) compared to the indoor group (P<0.001). Egg yolk from the outdoor group revealed the highest vitamin D3 content which averaged 14.3 μg/100 g dry matter (DM), followed by that from the indoor/outdoor group (11.3 μg/100 g DM). Yolk from indoor eggs contained only 3.8 μg vitamin D/100 g DM. The 25(OH)D3 content of egg yolk was also influenced by sunlight exposure, although less pronounced than the vitamin D content (P<0.05). In contrast, free-range eggs randomly acquired from supermarkets had relatively low vitamin D contents.

Conclusion: Free-range farming offers an efficient alternative to fortify eggs with vitamin D, provided that the farming conditions are sufficiently attractive for the hens to range outside.

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