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 D3 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 D3
content, which averaged 14.3 mg/100 g dry matter (DM), followed by that from the indoor/outdoor
group (11.3 mg/100 g DM). Yolk from indoor eggs contained only 3.8 mg vitamin D/100 g DM. The
25-hydroxyvitamin D (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 farming conditions are sufficiently attractive for hens to range outside.
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 D3 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 D3
content, which averaged 14.3 mg/100 g dry matter (DM), followed by that from the indoor/outdoor
group (11.3 mg/100 g DM). Yolk from indoor eggs contained only 3.8 mg vitamin D/100 g DM. The
25-hydroxyvitamin D (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 farming conditions are sufficiently attractive for hens to range outside.
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