Naturally enhanced eggs as a source of vitamin D: A review

•Three methods to produce eggs naturally enhanced with vitamin D was reviewed.•There is a linear inter-trial relationship between vitamin D3 in feed and vitamin D3 content in egg.•Feed is superior to UVB irradiation in regards to vitamin D enhancement in eggs.•Egg yolk can be vitamin D enhanced by direct exposure to UVB radiation.•Naturally enhanced eggs can contribute to increased vitamin D intake in the general population.