Variation in nutritional quality in UK retail eggs

Fatty acid (FA), carotenoid and vitamin contents of UK eggs were assessed for four production systems (caged (CA), free-range (FR), organic (OR) and extensive organic (EO)) as well as season. The impact of enforced housing, due to avian influenza, was also investigated. Production system did not alter vitamin D₃, B₂ or B₉ content, but significantly influenced nutritionally desirable FA, carotenoid and vitamins A and E - concentrations decreased as production intensity increased, although for most, CA and FR did not differ significantly. Vitamin E and FA profiles for OR and EO were also similar, although carotenoids were higher in EO eggs. In contrast, FA, carotenoids, vitamins E and B₉ were consistent throughout the year, unlike vitamins A, D₃ and B₂, which fluctuated with season; D and B₂ were higher in July than January and lower vitamin A was the only detected implication from enforced housing of FR and OR birds.