Lutein & Zeaxanthin (eye carotenoid for patients with eye cataract. & Zealut-Dena Supplement. Vitaminized - mail order supplements online

BENEFITS OF ZEALUT-DENA (LUTEIN AND ZEAXANTHIN) INTAKE IN SUBJECTS AT RISK OF CATARACT DEVELOPMENT

Oxidative stress is known to contribute to the onset and progression of a number of eye diseases [1]. Cataracts, along with age-related macular degeneration, are a major cause of blindness in the elderly. Oxidative stress, especially that caused by UV light, plays an important role in cataract development by promoting oxidation of lens proteins [2, 3]. The carotenoids lutein and zeaxanthin are thought have a dual protective effect: they filter out the most damaging short-wavelength irradiation (blue light and UV) and scavenge reactive oxygen species. 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 [4, 5]. Over the last ~30 years, a number of studies have been conducted to determine whether lutein and zeaxanthin may reduce the risk of age-related cataracts.

 

The 5-year Beaver Dam Eye Study, which enrolled 1354 subjects and was conducted between 1988 and 1995, 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 6. These results were corroborated by two larger-scale studies. The Nurses’ Health Study, which was conducted in the USA and enrolled female registered nurses, found that increased intake of lutein (≥6 mg/day) and zeaxanthin reduced the number of required cataract surgeries [7]. The parallel Health Professionals Follow-Up Study, which enrolled male health professionals, reported similar results: 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) [8]. However, some other studies at that time failed to find a significant association between cataract risk and carotenoid supplementation, and a Food and Drug Administration review conducted in 2006 concluded that there was no reliable evidence for the ability of lutein and zeaxanthin to reduce the risk of cataracts [9]. Nevertheless, a number of other studies published the same year and later have confirmed the beneficial effects of one or both of these carotenoids with respect to cataract development.

 

The results of two studies, also published in 2006, may shed light on possible reasons for the above discrepancies. The POLA study (Pathologies Oculaires Liées à l’Age – Age-Related Eye Pathologies), which was conducted in France and Switzerland and enrolled 2584 participants, found a significant association between high plasma levels of zeaxanthin and a reduced risk of any cataracts and specifically nuclear cataracts [10]. Yet, no significant association was found between the risk of cataracts and either combined plasma lutein and zeaxanthin or lutein alone [10]. These results suggest that zeaxanthin may be more important than lutein in protecting the lens from cataract development. If so, the discrepancies between earlier studies could be due to the fact that dietary intake of zeaxanthin and its natural content in ocular tissues is only 10–20% of that of lutein [11, 12] (this natural proportion is taken into account in the Zealut-Dena formulation: 10 mg lutein and 1 mg zeaxanthin). Therefore, any specific effects of zeaxanthin would be more challenging to measure than those of lutein or both carotenoids combined.

 

The Melbourne Visual Impairment Project, which analyzed separately the incidence of cortical, nuclear, and posterior subcapsular cataracts in 1,841, 1,955, and 1,950 subjects, respectively, over a period of three to seven years, reported an inverse association between high dietary intake of lutein and zeaxanthin and prevalence of nuclear cataract, but not of the other two cataract types [13]. Although nuclear cataract is the prevalent type (more than half of total cataract cases in the Melbourne Visual Impairment Project were represented by this type [13]), the absence of the effect on other cataract types may have been another confounding factor in earlier studies.

 

The Carotenoids in Age-Related Eye Disease Study (CAREDS), a multi-center study conducted in the USA and supported by the National Eye Institute and Research to Prevent Blindness, enrolled 1,802 women over 50 who had the highest percentile (>78%) or the lowest percentile (<28%) of lutein and zeaxanthin intake according to the data from an earlier study in which they participated [14, 15]. The CAREDS study found that women with the highest intake of both carotenoids were 32% less likely to have nuclear cataract (the only cataract type assessed) than women with the lowest intake. A similar but weaker association was found in women who took lutein-only supplement [14], which is in line with the conclusion of the POLA study [10] that zeaxanthin may have a stronger beneficial effect than lutein.

 

A study conducted in Finland investigated the association between the plasma levels of lutein and zeaxanthin in 1,689 elderly subjects (aged 61–80 years) and the risk of nuclear cataract (only five out of 113 age-related cataracts in this study were of other types) [16]. This study found that subjects who had the highest percentile (>75%) of plasma concentrations of lutein and zeaxanthin had 42% and 41% lower risks of nuclear cataract, respectively, in comparison with those who had the lowest percentile (<25%). Thus, this study confirmed the beneficial effect of these carotenoids but did not reveal any differential effects of lutein and zeaxanthin.

 

The availability of data from multiple studies on the association between lutein and zeaxanthin and the risk of cataract development makes it now possible to perform meta-analyses across different studies. Three such meta-analyses were published in 2013–2014. On the basis of meta-analysis of 13 observational studies (18,999 participants in total), Cui and coworkers [17] concluded that blood levels of both lutein and zeaxanthin (the two carotenoid species were analyzed separately), but not those of three other carotenoids (β-carotene, lycopene, and β-cryptoxanthin), are inversely associated with the risk of age-related cataract.

 

A meta-analysis of the results of one cohort study and seven cross-sectional studies confirmed that high concentrations of lutein and zeaxanthin in the blood are associated with a significantly reduced risk of nuclear cataract but probably not of other cataract types, although a marginally significant association between lutein and subcapsular cataract was noted [18]. In line with the conclusions of the POLA study, zeaxanthin was found to have a stronger effect, although only in European studies [18]. Finally, a meta-analysis of six prospective cohort studies (41,999 participants; 4,416 cataract cases) addressed not only the association between dietary lutein and zeaxanthin intake and the risk of age-related cataract, but also the dose-dependence of this association [19]. This meta-analysis confirmed a statistically significant association between the intake of these carotenoids and a reduced risk of nuclear cataract, but not of cortical and posterior subcapsular cataract. An increase of 0.3 mg/day in dietary lutein and zeaxanthin intake was found to be associated with a 3% reduction in the risk of nuclear cataract [19].

 

In conclusion, despite some doubts and inconsistencies in the results of earlier studies, it is now firmly established that increased intake of lutein and zeaxanthin is associated with a reduced risk of nuclear cataract; to what extent these carotenoids may reduce the risk of other cataract types remains to be ascertained. As the 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 [20]. In this respect, taking even one capsule of Zealut-Dena daily (i.e., 11 mg lutein plus zeaxanthin) is expected to reduce the risk of age-related nuclear cataract.

 

References

  1. Khandhadia, S. & Lotery, A. Oxidation and age-related macular degeneration: insights from molecular biology. Expert Rev Mol Med12, e34 (2010).
  2. Stringham, J.M. & Hammond, B.R., Jr. Dietary lutein and zeaxanthin: possible effects on visual function. Nutr Rev 63, 59-64 (2005).
  3. Sliney, D.H. UV radiation ocular exposure dosimetry. J Photochem Photobiol B 31, 69-77 (1995).
  4. 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).
  5. 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).
  6. 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).
  7. 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).
  8. 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).
  9. Trumbo, P.R. & Ellwood, K.C. Lutein and zeaxanthin intakes and risk of age-related macular degeneration and cataracts: an evaluation using the Food and Drug Administration's evidence-based review system for health claims. Am J Clin Nutr 84, 971-974 (2006).
  10. Delcourt, C., Carriere, I., Delage, M., Barberger-Gateau, P. & Schalch, W. Plasma lutein and zeaxanthin and other carotenoids as modifiable risk factors for age-related maculopathy and cataract: the POLA Study. Invest Ophthalmol Vis Sci 47, 2329-2335 (2006).
  11. Seddon, J.M. et al. Dietary carotenoids, vitamins A, C, and E, and advanced age-related macular degeneration. Eye Disease Case-Control Study Group. JAMA 272, 1413-1420 (1994).
  12. Thurmann, P.A., Schalch, W., Aebischer, J.C., Tenter, U. & Cohn, W. Plasma kinetics of lutein, zeaxanthin, and 3-dehydro-lutein after multiple oral doses of a lutein supplement. Am J Clin Nutr 82, 88-97 (2005).
  13. Vu, H.T., Robman, L., Hodge, A., McCarty, C.A. & Taylor, H.R. Lutein and zeaxanthin and the risk of cataract: the Melbourne visual impairment project. Invest Ophthalmol Vis Sci 47, 3783-3786 (2006).
  14. Mares, J.A. et al. Associations between age-related nuclear cataract and lutein and zeaxanthin in the diet and serum in the Carotenoids in the Age-Related Eye Disease Study, an Ancillary Study of the Women's Health Initiative. Invest Ophthalmol Vis Sci 47, E-Abstract 4724 (2006).
  15. Moeller, S.M. et al. Associations between age-related nuclear cataract and lutein and zeaxanthin in the diet and serum in the Carotenoids in the Age-Related Eye Disease Study, an Ancillary Study of the Women's Health Initiative. Arch Ophthalmol 126, 354-364 (2008).
  16. Karppi, J., Laukkanen, J.A. & Kurl, S. Plasma lutein and zeaxanthin and the risk of age-related nuclear cataract among the elderly Finnish population. Br J Nutr 108, 148-154 (2012).
  17. 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).
  18. Liu, X.H. et al. Association between lutein and zeaxanthin status and the risk of cataract: a meta-analysis. Nutrients 6, 452-465 (2014).
  19. Ma, L. et al. A dose-response meta-analysis of dietary lutein and zeaxanthin intake in relation to risk of age-related cataract. Graefes Arch Clin Exp Ophthalmol 252, 63-70 (2014).
  20. 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