What is meso-zeaxanthin, and where does it come from?

Abstract

The carotenoids lutein (L), zeaxanthin (Z), and meso-zeaxanthin (MZ) accumulate in the central retina, where they are collectively known as macular pigment (MP). Each of these three compounds exhibit a regional dominance, with MZ, Z, and L being the dominant carotenoids at the epicentre, mid-periphery, and periphery of the macula, respectively. There is a growing and evidencebased consensus that MP is important for optimal visual performance, because of its blue light-filtering properties and consequential attenuation of chromatic aberration, veiling luminance, and blue haze. It has also been hypothesised that MP may protect against age-related macular degeneration because of the same optical properties and also because of the antioxidant capacity of the three macular carotenoids. Challenges inherent in the separation and quantification of MZ have resulted in a paucity of data on the content of this carotenoid in foodstuffs, and have rendered the study of tissue concentrations of this compound problematic. As a consequence, the few studies that have investigated MZ have, perhaps, been disproportionately influential in the ongoing debate about the origins of this macular carotenoid. Certainly, the narrative that retinal MZ is derived wholly and solely from retinal L needs to be revisited.

Response to Bernstein et al

“…Furthermore, these studies were not designed to investigate, even in those nonhuman species, whether retinal MZ was derived 'wholly and solely' from retinal L, for the reasons outlined in our review. 2 In summary, we have challenged the received wisdom that retinal MZ in humans is derived wholly and solely from retinal L. We believe that Bernstein et al would concur that there is a paucity of data on the origins of MZ in human retina, and invite these distinguished commentators and colleagues to join with us in our …”

“…Of note, our findings are consistent with all the published literature reporting on MZ in fish (see Schiedt et al, 10 Maoka et al, 9 and Katsuyma et al 11 ) with the sole exception of the recent paper by Rasmussen et al, 8 which did not detect MZ in such marine species. However, as explained above and in our Review, 2 we believe that the failure to saponify the fish and seafood samples tested precluded the identification of L, Z, and MZ in the foods tested.…”

“…Importantly, our finding of undeclared MZ in a supplement formulation (Ultra Lutein) had implications for one of our recently published supplementation trials, and hence why we felt the need to discuss this discovery in our review. 2 Indeed, these findings that MZ is present in some brands of commercially available L supplements (and not declared) remain uncontested by the supply company, and remain a concern with respect to the conclusions of Johnson et al, 7 as it is possible that the 'pure L' feed did in fact contain some MZ.…”

“…in Eye 2013. 2 In their letter, Bernstein and colleagues argue that our review article contains 'several critical errors that need to be considered. ' Bernstein and colleagues endeavour to make their points under the following headings:…”

Restoration of Central Macular Pigment Dip with Dietary RR Zeaxanthin Supplementation in Patients with AMD

“…Additionally, spectral separation diminishes media influences such as confounding age-related cataract. Scotomas within the central 20-degree visual field were assessed at 5 contrast levels (20,40,60, 80 and 100% full contrast).…”