Macular zeaxanthins and lutein – a review of dietary sources and bioavailability and some relationships with macular pigment optical density and age-related macular disease

Abstract

The retina is unique in the human body in containing three xanthophyll carotenoids; 3R,3 0 Rzeaxanthin, meso-zeaxanthin (MZ) and lutein. Humans consume 1 to 3 mg lutein per d 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. In the present review the bioavailablity of zeaxanthin and lutein is assessed using the plasma xanthophyll response to dietary intervention. 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. Responses following the intervention with the pure xanthophylls are compared with those following food intervention. Vegetables are the richest source of dietary lutein and several vegetable-feeding studies are discussed. Intervention studies with eggs, which are a good source of zeaxanthin, suggest that the xanthophyll carotenoids in egg yolk may be more bioavailable than those in other foods and are described separately. MZ has been a component of a xanthophyll supplement added to chicken feed in Mexico in the last 10 years. Egg consumption in Mexico is approximately one egg/person per d and the potential contribution of this food source of MZ to Mexican dietary intakes is described. Very limited information from human feeding studies of MZ-containing supplements suggests that MZ is less well absorbed than zeaxanthin. However, MZ is unusual in the diet and not reported in the plasma. 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. Lastly, the effects of longterm feeding with both pure and food sources of the xanthophyll pigments on macular pigment optical density is compared and the importance of previous dietary intake on the effects of intervention is discussed.

Augmentation of Macular Pigment Following Supplementation with All Three Macular Carotenoids: An Exploratory Study

“…However, it should be noted that the supplement used in the study by Thurnham et al was suspended in oil; whereas, our study used a micro-encapsulated form of the supplement suspended in starch, which may account for, at least in part, the low serum response reported here, given that oil has been shown to promote carotenoid absorption. 53 The investigation by Thurnham et al (2008) reported an average increase of 0.209 ± 0.128 μmol/L in serum concentrations of MZ (following supplementation with 8 mg per day of this carotenoid over a 22-day study period). 27 Similarly, the study by Bone et al observed augmented average serum concentrations of MZ (0.094 ± 0.071 μmol/L) following supplementation with 14 mg per day of this carotenoid over a 120-day period.…”

“…This observation is important, given that the amount of MZ in human donor eyes has been reported as ∼7.7 ng and also given that an active binding protein for Z and MZ have been identified in retinal tissue. [53][54][55] There has only been one other study to date that has measured MPOD following daily supplementation with MZ. That study, recently performed by Bone et al, in 2007, included 10 normal subjects, who were supplemented with 14.9 mg of MZ, 5.5 mg of L, and 1.4 mg of Z, for 120 days.…”

Hen egg carotenoids (lutein and zeaxanthin) and nutritional impacts on human health: a review

“…Lutein and zeaxanthin carotenoids cannot be synthesized in vivo and therefore must be obtained from the diet. Egg yolks have been reported as an important dietary source of lutein and zeaxanthin, and a range of studies have been conducted to analyze these nutrients in egg yolks, including commercial egg yolks (Goodrow et al, 2006;Olson, Ward, & Koutsos, 2008;Schlatterer & Breithaupt, 2006;Thurnham, 2007). However, under processing conditions, the highly reactive, electron-rich carotenoid molecule present in egg yolks suffers oxidation.…”

Low macular pigment optical density is associated with lower cognitive performance in a large, population-based sample of older adults

“…L and Z are entirely of dietary origin, whereas MZ is thought to derive (at least in part) from retinal L through a poorly understood bioconversion process (Bone et al, 1993), although its presence in the diet has not been comprehensively studied, and remains under investigation (Thurnham, 2007). MP is a powerful antioxidant (Khachik et al, 1997) and thus has a putative neuroprotective function in the retina.…”