By: Nutrition expert- Vidula Kozarekar, Mumbai.
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Lutein (L) and zeaxanthin (Z) are dietary carotenoids derived from dark green leafy vegetables, orange and yellow fruits that form the macular pigment of the human eyes. It was hypothesized that they protect against visual disorders and cognition diseases, such as age-related macular degeneration (AMD), age-related cataract (ARC), cognition diseases, ischemic/hypoxia induced retinopathy, light damage of the retina, retinitis pigmentosa, retinal detachment, uveitis and diabetic retinopathy (1).
The mechanism by which they are involved in the prevention of eye diseases may be due to their physical blue light filtration properties and local antioxidant activity. In addition to their protective roles against light-induced oxidative damage, there are increasing evidences that L and Z may also improve normal ocular function by enhancing contrast sensitivity and by reducing glare disability. Surveys about L and Z supplementation have indicated that moderate intakes of L and Z are associated with decreased age-related macular degeneration (AMD) risk and less visual impairment. (1)
Macular Pigment and visual performance:
Macular pigment enhances visual function in a variety of ways. The filtration of blue light (400–500 nm) reduces chromatic aberration, which can enhance visual acuity and contrast sensitivity (CS). L and Z also reduce discomfort associated with glare and improve photo stress recovery time, macular function, and neural processing speed. Discomfort glare is a term used to describe photophobia and discomfort experienced when intense light enters the eye. (2)
Stringham et al. analysed the photophobic response in normal subjects and found that those with higher Macular Pigment(MP) levels tolerated xenon light better. They concluded that light containing short-wavelength energy appeared to be especially discomforting and that MP appeared to act as a spatially integrated filter, serving to attenuate photophobia to a great extent. (3) Similarly, Wenzel et al. showed a direct correlation between MP level and photophobia threshold. (4)
- A study conducted by Stringham and Hammond demonstrated that subjects with higher Macular Pigment (MP) levels maintained better visual acuity than subjects with lower levels when exposed to both bright white light and short wavelength (blue) light. Additionally, photo-stress recovery time, after exposure to xenon-white light, was significantly shorter for subjects with higher MP levels. (5)
- A more recent study showed that higher Macular pigments optical density (MPOD) resulted in faster photo-stress recovery times, lower disability glare contrast thresholds, and lower visual discomfort. (6)
- Hammond et al. reported that daily oral supplementation with L (10 mg/day) and Z (2 mg/day) in 57 patients for 12 months resulted in a significant increase in serum levels of L and Z and in Macular pigments optical density (MPOD) and significantly improved chromatic contrast and photo-stress recovery time. (7)
- Participants from the Rotterdam Study were enrolled into a case–control study investigating whether dietary nutrients could reduce the genetic risk of early Age related Macular Degeneration (AMD). Participants from a large population-based cohort at risk of AMD were followed for a mean of 8.6 years. They reported that high dietary intake of nutrients with antioxidant properties such as L and Z, β-carotene, omega-3 fatty acids, and zinc reduced the risk of early AMD in those at high genetic risk. (8)
- Retinal ischemia can lead to neovascularization, haemorrhage and blindness. Oxidative stress plays a role in the pathogenesis of both conditions and in a review of literature Xiaoming Gong and Lewis P. Rubin found that antioxidant supplementation may prevent disease progression. (9)
Dietary sources of Lutein and zeaxanthin: (10)
Lutein and zeaxanthin are found together in many food sources. Dark green leafy vegetables are the primary source of lutein and zeaxanthin, but they are also present in lesser amounts in other colourful fruits and vegetables, such as broccoli, orange peppers, corn, peas, persimmons and tangerines.
Hence it can be concluded that; taking an eye vitamin with enough dietary (natural) zeaxanthin and lutein can replenish your stores of these nutrients and fully protect your vision.