Blue Light Damage & lutein and zeaxanthin. Eye health supplement for Photodamaged Eye

POTENTIAL BENEFITS OF ZEALUT-DENA (LUTEIN AND ZEAXANTHIN) IN INDIVIDUALS EXPOSED TO BRIGHT LIGHT

Excessive light is known to damage the retina [1], in particular by inducing apoptosis (cell death) of photoreceptor cells [2] and causing complex post-exposure retinal remodeling, which eventually becomes irreversible [3]. Excessive light is particularly damaging in patients with degenerative retinal diseases because it synergistically accelerates photoreceptor cell death [3]. Damage caused by bright light and by these diseases may involve similar mechanisms, because late-stage retinal remodeling after light damage is similar to the anatomical changes observed in advanced age-related macular degeneration (AMD) [4]. Collectively, retinal damage from bright light is known as solar retinopathy, or solar retinitis, regardless of whether it is caused by sunlight or an artificial source of bright light [5].

 

Sunlight exposure is a known risk factor for AMD [6]. A detailed study conducted among 838 boat workers in Chesapeake Bay (Maryland and Virginia), analyzed the effects of exposure to different wavelengths of visible light (400–450 nm, 400–500 nm, and all visible light, 400–700 nm) and UV (UV-A, 320–340 nm; UV-B, 290–320 nm) over 20 years on the development of eye diseases, including AMD [7]. The authors found that exposure to visible light (400–500 nm or 400–700 nm) but not to UV light was significantly associated with advanced AMD. Analysis of the results of the 5-year Beaver Dam Eye Study (conducted in Wisconsin) obtained between 1987 and 1990 found that exposure to sunlight (as estimated from the amount of time spent outdoors in summer) was positively associated with advanced AMD, whereas the use of hats with brims and sunglasses protected against AMD [8].

 

The National Health and Nutrition Survey, conducted in 1971–1974, revealed a positive association between cataract extraction without implantation of an ultraviolet/blue light absorbing intraocular lens and AMD development, apparently because of an increase in retina exposure to harmful irradiation in the absence of the lens [9]. Exposure to sunlight, especially to its UV component, promotes oxidation of lens proteins and plays an important role in cataract development [10, 11].

 

Thus, exposure to excessively bright light is a risk factor in the development of both AMD and cataract; in both cases induction of reactive oxygen species appears to play a role [12]. Although artificial light sources do not emit UV light (unless they are specifically designed to do so), they do emit blue light, which may damage the retina [13]. In particular, light emitted by light-emitting diodes (LED) used in some modern energy-efficient light bulbs has been found to be damaging to the retina, presumably because of oxidative stress from reactive oxygen species this light generates [14].

 

The carotenoids lutein and zeaxanthin are thought to have protective effects in the retina [15] thanks to their ability to filter out most damaging irradiation [16, 17] and to scavenge reactive oxygen species [18]; they may also have anti-inflammatory effects in the retina [19]. Although most lutein and zeaxanthin in the eye is concentrated in the retina (especially in the macula), they are the only carotenoid species present in the lens [20, 21]. These carotenoids efficiently protect human lens epithelial cells against UVB-induced damage [22].

 

Multiple carotenoid species are present in blood plasma, but only lutein and zeaxanthin are able to cross the hemato-ophthalmic barrier and accumulate in the eye tissues, including the retina, where their concentration is four orders of magnitude higher than in the blood [11, 23]. Dietary supplementation is an efficient way to increase the content of these carotenoids in the eye, especially in individuals with poor diet who receive insufficient amounts of lutein and zeaxanthin with food, as concluded by AREDS2 (The Age-Related Eye Disease Study 2), a large multicenter study conducted in 2006–2012 [24, 25]. The content of lutein and zeaxanthin in the eye tissues follows changes in the dietary intake of these carotenoids with a delay of two to three weeks [26].

 

The data from a number of studies demonstrate beneficial effects of lutein and zeaxanthin supplementation in patients with AMD and their association with reduced risk of cataract development. For example, two independent studies found that daily intake of lutein and/or zeaxanthin significantly improves contrast sensitivity in patients with early AMD [27, 28]. The AREDS2 study revealed a protective effect of lutein and zeaxanthin against the onset of AMD in subjects whose dietary intake of these carotenoids was within the lowest quintile [24, 29]. Although this study did not assess the contribution of bright light into the onset of AMD in participants, these results consider together with the fact that light is a risk factor for the onset of AMD are compatible with the ability of lutein and zeaxanthin supplementation to mitigate the harmful effect of light on the macula. Lutein (10 mg/day) and zeaxanthin (2 mg/day) have been recommended as components of the AREDS formulation [30].

 

The Beaver Dam Eye Study mentioned above found that lutein and zeaxanthin were the only carotenoids associated with the reduced risk of nuclear cataract development: their intake in the highest quintile reportedly reduced the risk by as much as half [31]. These results suggested a protective effect of these carotenoids in individuals at risk of cataract development and were corroborated by two larger-scale studies conducted in the last quarter of the 20th century. The Nurses’ Health Study, which enrolled female registered nurses, found that increased intake of lutein (≥6 mg/day) and zeaxanthin reduced the number of required cataract surgeries [32]. The parallel Health Professionals Follow-Up Study, which enrolled male health professionals, reported similar result. This study found a decrease in the need for cataract surgeries as a result of increased intake of lutein and zeaxanthin (6.9 mg/day) [33]. A recent meta-analysis of 13 observational studies (18,999 participants in total) concluded that the blood levels of both lutein and zeaxanthin (the two carotenoid species were analyzed separately) are inversely associated with risk of age-related cataract [34]. As in the case of AMD, since sunlight increases the risk of cataract development, these data are compatible with the ability of lutein and zeaxanthin supplementation to mitigate the effect of sunlight on the lens.

 

Overall, although studies to directly assess the benefits of lutein and zeaxanthin supplementation in humans exposed to bright light (either sunlight or light from artificial sources) are yet to be conducted, the facts that (1) bright light increases the risk of AMD and cataract and (2) lutein and zeaxanthin supplementation has positive effects in patients with both diseases make it reasonable to recommend supplementation with these carotenoids in individuals whose lifestyle or profession results in an increased exposure of their eyes to potentially damaging light levels, at least as an appropriate cautionary measure. This may be especially important for individuals with low dietary intake of these carotenoids [24, 29]. As average dietary consumption of lutein plus zeaxanthin in the USA is estimated at only 1.7 mg/day, the American Optometric Association currently recommends taking supplements that increase the intake to >6 mg/day [35]. In this respect, taking even one capsule of Zealut-Dena daily (i.e.: 11 mg lutein plus zeaxanthin) is expected to be sufficient to mitigate any deficit of lutein and zeaxanthin intake with food. It should be also noted that the safety of long-term lutein and zeaxanthin supplementation has been confirmed [36, 37].

 

References

  1. Ham, W.T., Jr. Ocular hazards of light sources: review of current knowledge. J Occup Med 25, 101-103 (1983).
  2. Wenzel, A., Grimm, C., Samardzija, M. & Reme, C.E. Molecular mechanisms of light-induced photoreceptor apoptosis and neuroprotection for retinal degeneration. Prog Retin Eye Res 24, 275-306 (2005).
  3. Organisciak, D.T. & Vaughan, D.K. Retinal light damage: mechanisms and protection. Prog Retin Eye Res 29, 113-134 (2010).
  4. Marc, R.E. et al. Extreme retinal remodeling triggered by light damage: implications for age related macular degeneration. Mol Vis14, 782-806 (2008).
  5. Chen, K.C., Jung, J.J. & Aizman, A. Solar retinopathy: etiology, diagnosis, and treatment. Retinal Physician 10, 46-50 (2013).
  6. Snodderly, D.M. Evidence for protection against age-related macular degeneration by carotenoids and antioxidant vitamins. Am J Clin Nutr 62, 1448S-1461S (1995).
  7. Taylor, H.R. et al. The long-term effects of visible light on the eye. Arch Ophthalmol 110, 99-104 (1992).
  8. Cruickshanks, K.J., Klein, R. & Klein, B.E. Sunlight and age-related macular degeneration. The Beaver Dam Eye Study. Arch Ophthalmol 111, 514-518 (1993).
  9. Liu, I.Y., White, L. & LaCroix, A.Z. The association of age-related macular degeneration and lens opacities in the aged. Am J Public Health 79, 765-769 (1989).
  10. Sliney, D.H. UV radiation ocular exposure dosimetry. J Photochem Photobiol B 31, 69-77 (1995).
  11. Stringham, J.M. & Hammond, B.R., Jr. Dietary lutein and zeaxanthin: possible effects on visual function. Nutr Rev 63, 59-64 (2005).
  12. Glickman, R.D. Ultraviolet phototoxicity to the retina. Eye Contact Lens 37, 196-205 (2011).
  13. Youssef, P.N., Sheibani, N. & Albert, D.M. Retinal light toxicity. Eye (Lond) 25, 1-14 (2011).
  14. Lougheed, T. Hidden blue hazard? Environ Health Perspect 122, A81 (2014).
  15. Stahl, W. Macular carotenoids: lutein and zeaxanthin. Dev Ophthalmol 38, 70-88 (2005).
  16. Junghans, A., Sies, H. & Stahl, W. Macular pigments lutein and zeaxanthin as blue light filters studied in liposomes. Arch Biochem Biophys 391, 160-164 (2001).
  17. Krinsky, N.I., Landrum, J.T. & Bone, R.A. Biologic mechanisms of the protective role of lutein and zeaxanthin in the eye. Annu Rev Nutr 23, 171-201 (2003).
  18. Ahmed, S.S., Lott, M.N. & Marcus, D.M. The macular xanthophylls. Surv Ophthalmol 50, 183-193 (2005).
  19. Izumi-Nagai, K. et al. Macular pigment lutein is antiinflammatory in preventing choroidal neovascularization. Arterioscler Thromb Vasc Biol 27, 2555-2562 (2007).
  20. Bernstein, P.S. et al. Identification and quantitation of carotenoids and their metabolites in the tissues of the human eye. Exp Eye Res 72, 215-223 (2001).
  21. Yeum, K.J., Shang, F.M., Schalch, W.M., Russell, R.M. & Taylor, A. Fat-soluble nutrient concentrations in different layers of human cataractous lens. Curr Eye Res 19, 502-505 (1999).
  22. Chitchumroonchokchai, C., Bomser, J.A., Glamm, J.E. & Failla, M.L. Xanthophylls and alpha-tocopherol decrease UVB-induced lipid peroxidation and stress signaling in human lens epithelial cells. J Nutr 134, 3225-3232 (2004).
  23. Whitehead, A.J., Mares, J.A. & Danis, R.P. Macular pigment: a review of current knowledge. Arch Ophthalmol 124, 1038-1045 (2006).
  24. Andreatta, W. & El-Sherbiny, S. Evidence-based nutritional advice for patients affected by age-related macular degeneration. Ophthalmologica 231, 185-190 (2014).
  25. Pinazo-Duran, M.D. et al. Do nutritional supplements have a role in age macular degeneration prevention? J Ophthalmol 2014, 901686 (2014).
  26. Loughman, J., Nolan, J.M. & Beatty, S. Impact of dietary carotenoid deprivation on macular pigment and serum concentrations of lutein and zeaxanthin. Br J Nutr 108, 2102-2103 (2012).
  27. Ma, L. et al. Effect of lutein and zeaxanthin on macular pigment and visual function in patients with early age-related macular degeneration. Ophthalmology 119, 2290-2297 (2012).
  28. Sabour-Pickett, S. et al. Supplementation with three different macular carotenoid formulations in patients with early age-related macular degeneration. Retina (2014).
  29. Pinazo-Duran, M.D. et al. Oxidative stress and its downstream signaling in aging eyes. Clin Interv Aging 9, 637-652 (2014).
  30. Group, T.A.-R.E.D.S.A.R. Lutein + zeaxanthin and omega-3 fatty acids for age-related macular degeneration: the Age-Related Eye Disease Study 2 (AREDS2) randomized clinical trial. JAMA 309, 2005-2015 (2013).
  31. Lyle, B.J., Mares-Perlman, J.A., Klein, B.E., Klein, R. & Greger, J.L. Antioxidant intake and risk of incident age-related nuclear cataracts in the Beaver Dam Eye Study. Am J Epidemiol 149, 801-809 (1999).
  32. Chasan-Taber, L. et al. A prospective study of carotenoid and vitamin A intakes and risk of cataract extraction in US women. Am J Clin Nutr 70, 509-516 (1999).
  33. Brown, L. et al. A prospective study of carotenoid intake and risk of cataract extraction in US men. Am J Clin Nutr 70, 517-524 (1999).
  34. Cui, Y.H., Jing, C.X. & Pan, H.W. Association of blood antioxidants and vitamins with risk of age-related cataract: a meta-analysis of observational studies. Am J Clin Nutr 98, 778-786 (2013).
  35. American Optometric Association. Lutein and Zeaxanthin - Eye-Friendly Nutrients. http://www.aoa.org/patients-and-public/caring-for-your-vision/nutrition/lutein-and-zeaxanthin?sso=y
  36. Bahrami, H., Melia, M. & Dagnelie, G. Lutein supplementation in retinitis pigmentosa: PC-based vision assessment in a randomized double-masked placebo-controlled clinical trial [NCT00029289]. BMC Ophthalmol 6, 23 (2006).
  37. Berson, E.L. et al. Clinical trial of lutein in patients with retinitis pigmentosa receiving vitamin A. Arch Ophthalmol 128, 403-411 (2010).