Soy. Soy contains the phytonutrient genistein, which has documented antiangiogenesis properties postulated to be the result of inhibiting VEGF (Yu 2010). This property of inhibiting blood vessel growth is important in limiting abnormal ingrowth of choroidal blood vessels. In mice, genistein inhibited retinal neovascularization and expression of VEGF (Wang 2005).
Food rich in Omega-3 fatty acids. Oily fish (e.g., salmon, tuna, and mackerel) as well as flax seeds are important sources of omega-3 fatty acids, essential for protection against macular degeneration and other diseases (Landrum 2001). A meta-analysis found that patients with a high dietary intake of omega-3 fatty acids had a 38% lower risk of late (more advanced) AMD. Additionally, an association was observed between eating fish two times a week and having a reduced risk of both early and late AMD (Chong 2008).
Macular Pigments: Lutein, Zeaxanthin, and Meso-Zeaxanthin
The relationship between the density of macular pigment (MP) and the onset of AMD is well established. The MP is composed principally of three carotenoids: lutein, zeaxanthin, and meso-zeaxanthin. They represent roughly 36, 18, and 18 percent, respectively, of the total carotenoid content of the retina. They are found within the macula and surrounding tissues, including blood vessels and capillaries which nourish the retina (Rapp 2000).
Lutein, zeaxanthin and meso-zeaxanthin ensure proper functioning of the macula by filtering out harmful ultraviolet light and acting as antioxidants (Beatty 2000; Kaya 2010). During the aging process, there is a decrease in levels of lutein and zeaxanthin; low levels of MPs are linked to AMD (Johnson 2010). An autopsy study on donated eyes found that levels of all three carotenoids were reduced in those with macular degeneration compared to control subjects. The most significant finding, however, was the sharp decrease in meso-zeaxanthin in the macula of macular degeneration subjects (Bone 2000). This postmortem study helped confirm other studies indicating the importance of all three carotenoids in maintaining the structural integrity of the macula (Krinsky 2003). These carotenoids protect the macula and the photoreceptor cells beneath via their antioxidant properties and light-filtering capabilities (Landrum 2001).
Intake of lutein and zeaxanthin is an important preventative measure, but may also reverse the degeneration process when it is ongoing (Richer 2004). Because lutein and zeaxanthin have the tissue-specific characteristic of all carotenoids, their natural tendency is to concentrate in the macula and retina. Consumption of foods rich in these substances is especially important, as they have a direct effect on macular pigment density -- the denser the pigment, the less likely a retinal tear or degeneration will occur (Stahl 2005). Fruits with a yellow or orange color (e.g., mangoes, kiwis, oranges, and vegetables of the dark green leafy, orange and yellow varieties) are sources of lutein and zeaxanthin (Bone 2000).
Unlike lutein and zeaxanthin, meso-zeaxanthin is not found in the diet, but is needed to maintain youthful macular density (Bone 2007). Patients with macular degeneration have been shown to have 30% less meso-zeaxanthin in their macula compared to individuals with healthy eyes (Quantum Nutritionals, data on file). When taken as a supplement, meso-zeaxanthin is absorbed into the blood stream and effectively increases macular pigment levels (Bone 2007).