Lutein, zeaxanthin and meso-zeaxanthin content of eggs laid by hens supplemented with free and esterified xanthophylls

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The xanthophyll carotenoids lutein (L), zeaxanthin (Z) and meso-zeaxanthin (MZ) are found at the macula⁽¹⁾, the central part of the retina responsible for fine detail and central vision⁽²⁾. At this specialised location, they are referred to as macular pigment (MP) and, via their short-wavelength (blue) light filtration⁽³⁾and antioxidant properties⁽⁴⁾, protect against age-related macular degeneration (AMD)⁽⁵⁾. In addition, MP augmentation in humans has been shown to improve visual function in the AMD (diseased) retina^(6-8)and in the non-diseased (healthy) retina⁽⁹⁾. Also, studies have shown that L and Z are found in the human brain^(10,11), and recent reports suggest a role for these xanthophylls in supporting brain health and cognitive function^(11-13). Of note, the majority of studies to date have demonstrated MP augmentation and consequential visual benefits using over-the-counter carotenoid supplement preparations. Of interest, however, nutrient-enriched (functional) foods may offer an alternative to food supplements as can be seen, for example, with fatty acids (e.g. n-3 and n-6), which are now available from enriched eggs and milk^(14,15).

L and Z are present in a typically varied diet⁽¹⁶⁾, whereas MZ is only found in trace amounts in marine-sourced foods, such as salmon, trout and sardines^(17,18). Despite the differing amounts of L, Z and MZ found in foods, it is interesting to note that the ratio of these xanthophylls in the human retina is 1:1:1 (MZ:Z:L), suggesting a unique role for each of these carotenoids at this target tissue. Foods such as kale, spinach and maize contain high amounts of L and Z, rendering such foods important sources of these carotenoids. However, the complex cellular structure of these higher plants impedes the release of the chromoplast-bound carotenoids⁽¹⁹⁾. It is for this reason that the bioaccessibility and bioavailability of these compounds need to be enhanced in order to increase their concentrations in serum. This can be...