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Structure & Function
Structure & Function Of Zeaxanthin & Lutein
Zeaxanthin and lutein are key carotenoids in the prevention of Age-Related Macular Degeneration (AMD). Chrysantis, Inc. is the only company producing a natural, highly concentrated zeaxanthin-lutein compound, to help prevent the damaging effects of AMD.

Zeaxanthin and lutein are localized at the very center of the macula (the fovea) – the part of the eye rich in rod and cone photoreceptors that gives a person optimal visual acuity. There is 1.5 times more zeaxanthin than lutein in the inner retina.

Animal studies have shown zeaxanthin to be very effective in protecting both cone and rod photoreceptors. Quail fed with normal dietary levels of zeaxanthin had significantly less retinal damage than the zeaxanthin-deprived group (1).

Lutein is a natural pigment found in dark leafy vegetables and various fruits, including spinach, corn and egg yolks. Lutein helps to filter harmful blue light from the macula and acts as an antioxidant for the retinal cells. Lutein is more abundant in the eye than zeaxanthin, where it serves as a protector for precious photoreceptors.

Recent studies have shown that variations from the common distribution of macular pigments in the eye may be associated with early AMD while individuals with lesions near the foveal region (where zeaxanthin and lutein predominates) may be at a higher risk of developing late AMD. They also show that a reduced central macular pigment and a low central/total ratio are associated with atrophic spots and geographic atrophy in the unaffected eye. (2) (3).

Analyses of macular pigment concentrations in and around the center of the macula in eyes with AMD versus normal control eyes have shown a direct link between macular pigment concentration and AMD. It has been observed that there is a significant drop in pigment concentration at the edges of the fovea in eyes with AMD (4).

The evidence points to the importance of maintaining a stable amount of zeaxanthin and lutein predominantly in the fovea, but also in the macular periphery and the lens, to maintain eye health throughout our senescent years.

Zeaxanthin is 5 to 10 times less abundant than lutein in human blood serum and 10 to 20 times less prevalent in the diet. In a 2001 study, ocular tissues of human donor eyes were tested to determine the amount of carotenoids present. The level of lutein was found to be 2-7-fold higher than other common carotenoids, including ß-carotene, ∞carotene and lycopene.

Because of this, the body created a compromise molecule from the more abundant lutein – meso zeaxanthin – to complement dietary zeaxanthin and reach the levels needed in the fovea to protect the macula from damaging blue light.

We know today that this imperfect solution (the production of meso zeaxanthin) falters as we age (5), resulting in lower levels of macular pigment concentration.

A zeaxanthin-lutein supplement will definitively reduce the need for this ‘zeaxanthin-like’ molecule, thus ensuring long lasting eye protection.

Typical dietary zeaxanthin and lutein intake averages 2 milligrams per day. Various epidemiological studies have found an association between supplemental intake of zeaxanthin and lutein (around 6 milligrams per day) and a decreased risk in AMD and cataracts(6), thus suggesting a dietary gap of 4 milligrams per day. This dietary gap is greater for people age 50 and older as their dietary carotenoid intake is significantly lower than the average adult.

Dietary supplements are an important way to compensate for the low levels of zeaxanthin and lutein in food intake and provide the eye with the necessary amount to reduce the risk and/or prevent AMD from developing.

Dietary supplements for eye health should contain at least equal amounts of zeaxanthin and lutein per capsule, since zeaxanthin and its isomers represent 50 percent of the carotenoids present in the human retina(7).

Zeaxanthin is a 40 carbon long molecule, with 11 conjugated double bonds. Its molecular formula is C40H56O2 and has a molecular weight of 568.88 daltons. Zeaxanthin exists in three stereoisomeric forms that result from the configurations at its two chiral centers: the (3R,3’R), (3R,3’S) and (3S,3’S). The principal natural form of zeaxanthin is the (3R, 3’R).

Chrysantis’ marigolds produce only 3R,3’R zeaxanthin.

A three-dimensional view of zeaxanthin shows it to be a straight molecule that is able to transverse a biological cell membrane because of its hydrophilic end groups and lipophilic central chain. It tends to span the bilipid layer occupying a site that lies perpendicular to the membrane surface, while lutein apparently inserts itself in a non-orthogonal manner. Thus, zeaxanthin is in position to act as a membrane antioxidant.

Lutein’s molecular formula is C40H52O2 and has a molecular weight of 644 daltons. Both substances have the same number of double bonds, however, the position of the double bond in lutein forms a more chemically reactive allylic hydroxyl end group versus the extra conjugated double bond in zeaxanthin. Zeaxanthin has a better protective ability than lutein because of its greater conjugated, symmetrical structure.

Lutein and zeaxanthin are thought to orient themselves so they can span cell membranes inside the lipid bi-layer in the eye, increasing membrane stability. It is because of their antioxidant capacity and ability to filter out potentially phototoxic blue light and near ultraviolet radiation that zeaxanthin and lutein are believed to play an important role in protection against Age-Related Macular Degeneration (AMD) and age-related cataract formation (8). Risks of developing AMD have been found to be significantly higher in people with lower plasma concentrations of zeaxanthin (9) and lutein.

The body selectively places dietary zeaxanthin and lutein in the very center of the macula – the most critical area for central vision with the greatest need for protection. These substances also accumulate in the retinal pigmented epithelium and the most vulnerable portions of photoreceptors, where its potent antioxidant capacity can prevent oxidative damage. However, the overall distribution of zeaxanthin in the eye suggests that it has a specific function, separate from lutein.

The human lens also accumulates zeaxanthin (although it is one of the most metabolically inactive tissues in the body) where, along with lutein, may protect against aged-related increases in lens density and cataract formation (10).

(1) Invest. Ophthalmol. Vis. Sci. 2002 Nov, v 43, n 11, p 3538-3549
(2) ARVO abstracts 2003
(3) ARVO abstracts 2003
(4) Invest. Ophtalmol. Vis. Sci. 42:235-240
(5) ARVO abstracts 2003
(6) JAMA (1994) 272; 1413-1420
(7) Exp. Eye Res. (1997) 64, 211-218
(8) Invest. Ophtalmol. Vis. Sci. 42:235-240
(9) IOVS June 2003, Vol 44, No. 6
(10) Nutrition 19:21-24, 2003



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