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

Objective: Food-based strategies need to be developed to improve the vitamin D status of individuals. Recent studies identified ultraviolet B irradiation as an efficient method to enrich mushrooms and eggs with vitamin D. The aim of this study was to determine 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 to 34 animals each, and were kept either indoors (indoor group), outdoors (outdoor group), or with an indoor/outdoor option (indoor/outdoor group) over 4 wk. Results: The study shows that the vitamin D-3 content of egg yolk was three- to fourfold higher in the groups that were exposed to sunlight (outdoor and indoor/outdoor groups) compared with the indoor group (P < 0.001). Egg yolk from the outdoor group revealed the highest vitamin D-3 content, which averaged 14.3 mu g/100 g dry matter (DM), followed by that from the indoor/outdoor group (11.3 mu g/100 g DM). Yolk from indoor eggs contained only 3.8 mu g vitamin D/100 g DM. The 25-hydroxyvitamin D (25[OH]D-3) 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 farming conditions are sufficiently attractive for hens to range outside. (C) 2014 Elsevier Inc. All rights reserved.