Lutein and Zeaxanthin are xanthophyll carotenoids that constitute the two major components of the macular pigment of the retina. In the retina, it is the macula lutea or “yellow spot” that is responsible for central vision and visual acuity. Lutein and Zeaxanthin are the only two carotenoids found in both the macula and lens of the human eye and hence play an essential role in eye health. They have dual functions in both tissues – to act as powerful antioxidants and to filter high-energy blue light.
Structurally both Lutein and Zeaxanthin differ from other carotenoids as both have two hydroxyl groups, one on each side of the molecule. Zeaxanthin is a stereoisomer of Lutein, wherein there is a difference in the location of a double bond in one of the hydroxyl groups. Owing to their chemical structure, these xanthophylls are more hydrophilic than other carotenoids found in blood and tissues. It is reported that the hydroxyl groups appear to control the biological function of both Lutein and Zeaxanthin.
Studies also indicate that Lutein appears to have an affinity for the peripheral retina and rods, while Zeaxanthin seems to be preferentially taken up by the cones of the macula (Bone et al., 1998).
Vast research has been directed using in vitro cell cultures, in vivo animal models and human studies to the potential role of Lutein and Zeaxanthin in offering protection against several chronic diseases, particularly age-related macular degeneration (AMD) and cataract.
Lutein and Zeaxanthin are the powerful antioxidants, and Lutein is widely known as the primary nutrient for protecting ocular function. They may prevent cellular damage by quenching singlet oxygen (i.e. oxygen free radical) or neutralizing photo-sensitizers.
They have the potential to filter out high energy blue light, which may otherwise cause damage to the retina. This is because blue light, acting on photo-sensitizers, is able to promote the formation of reactive oxygen species (ROS) in the retina. Lutein and Zeaxanthin effectively quench free radicals, thus offering improved eye health.