Thurnham has written a very interesting review of macular zeaxanthins and luteins.
Thurnham (2007) Macular zeaxanthins and luteins-a review of dietary sources and bioavailability and some relationship with macular pigment optical density and age-related macular disease. Nutritional Research Reviews vol 20 163-179.
The retina is unique in the human body in containing three xanthophyll carotenoids: 3K,3’R-zeaxanthin. meso-zeaxanthin (MZ) and lutein.
We eat 1 to 3 mg lutein per day and the lutein: zeaxanthin ratio in the diet is about 5:1 .Xanthophyll pigments occur widely in vegetables and fruits but MZ is found in only a few foods such as the shrimp carapace and fish skin.
In spite of the amounts of the different xanthophylls in the diet, zeaxanthin and MZ occur in approximately equal amounts in the eye, and their combined concentration can exceed that of lutein. A number of studies have used single and mixed sources of the pure xanthophylls to achieve steady-state plasma responses. Mostly these have been with lutein and zeaxanthin but two using MZ are also described.
Vegetables are the richest source of dietary lutein Intervention studies with eggs, which are a good source of zeaxanthin. suggest that the xanthophyll carotenoids in egg yolk may be more bioavailablc than those in other foods
Very limited information from human studies of MZ-containing supplement. suggests that MZ is less well absorbed than zeaxanthin. Thus plasma responses may not reflect true absorption if it takes MZ longer to equilibrate with body tissues than the other xanthophylls and competition with zeaxanthin may lower the relative concentrations of MZ in plasma.
It would be nice if a xanthophyll carotenoids rich diet kept the retrina healthy, but this has yet to be proven
- Martin Eastwood