Source

Carotenoids are naturally occurring plant pigments found in nature. Over 700 carotenoids have been identified to date, which include the eye carotenoids L, Z and MZ.

An average western diet contains up to 3mg per day of L and Z combined, with up to seven times more L than Z. It has been reported that approximately 78% of dietary L and Z is sourced from vegetables, with L found in highest concentrations in dark green leafy vegetables (including spinach, broccoli, kale, and collard greens). Green leafy vegetables are the richest source of L, whereas corn and corn products are a major source of Z. Eggs are also a good source of L and Z, especially given the enhanced bioavailability (absorption) of these carotenoids in this form because of co-ingestion of fat.

To date, there has been no investigation into the quantities of MZ in the typical diet, although it has been confirmed that MZ is found in a standard diet. Research is currently underway to quantify the presence of MZ in foods. However, we do know that eggs from hens fed MZ are a rich dietary source of this carotenoid. Of note, there have been several studies confirming the presence of MZ in a standard diet, the first being published in 1986, that identified the presence of MZ in 21 species of edible fish, shrimp, and sea turtles.{} It is well known that in both rainbow trout and salmon the characteristic salmon color of the flesh is due to deposition of astaxanthin (a carotenoid from the same family as MZ). Analysis of skin from trout fed a diet rich in astaxanthin revealed significant quantities of MZ formed from the astaxanthin. Like the rainbow trout, the Atlantic salmon also deposits MZ within its skin. Birds make MZ and concentrate it and other carotenoids in their retinas within brightly coloured oil-droplets. Chicken and turkey retinas also contain significant amounts of MZ. Until recently, it was assumed that MZ within human retina was derived solely from retinal L, but this has recently and legitimately been called into question. (Nolan et al, 2013)

Brightly coloured egg yolks from hens fed MZ and fish skin are both a dietary source of MZ.