Macular xanthophylls and their effects on vision and cognition
A substantial body of evidence suggests that the macular xanthophylls, lutein and zeaxanthin, have a protective effect against age-related macular degeneration (AMD), a neurodegenerative disease characterized by infiltration of blood vessels, leakage, inflammation, and compromised vision. AMD currently affects approximately 1.75 million people in the United States, and treatments are limited in scope and efficacy.
Dr. Paul Bernstein, Professor of Ophthalmology and Visual Sciences at the University of Utah’s MoranEyeCenter, discussed the potential relationship between the xanthophyll binding proteins, which his lab identified (GSTP1 binds zeaxanthin - 2004 study; StARD3 binds lutein - 2011 study). A borderline association of GSTP1 variants has been correlated with a risk of AMD, and GSTP1 expression may be lower in AMD eyes, Bernstein explained. StARD proteins still need to be examined.
Bernstein’s ongoing research involves 53 Moran Eye Center patients who are participating in the national Age-Related Eye Disease Study 2 (AREDS2). Continuing through 2012 or 2013, Bernstein’s study involves annual measurements of macular pigments, skin carotenoids, and serum carotenoids. The current data suggests that skin and serum carotenoid measurements are not reliable biomarkers for macular pigment optical density. Notably, 70% of Bernstein’s subjects had high baseline levels of lutein and zeaxanthin; many reported taking supplements for years before the study. This may be due to their location: Utah is known as the “Silicon Valley” of nutritional supplements and accounts for one-fifth of all dietary supplement production in the United States, according to a February 2011 report published in WestlawBusinessCurrents.
Dr. John Paul SanGiovanni, a co-director of AREDS2, underscored the importance of large-scale genotypic projects in the field, referring to work in Bernstein’s lab and elsewhere. While the gene studies may not lead directly to clinical applications, taking the data in the context of the known relationship between macular xanthophylls and AMD can lead to new approaches in the study of macular xanthophylls and their metabolites in humans.
Current macular xanthophyll research isn’t limited to diseased eyes. Dr. B. Randy Hammond, Principal Investigator of the Vision Sciences Laboratory at the University of Georgia, discussed his ongoing research into the effects of lutein and zeaxanthin supplementation on healthy vision. His data suggests that supplementation of lutein and zeaxanthin does improve a person’s ability to withstand glare and recover quickly from a blinding flash of light.
Evidence also exists suggesting neuroprotective effects of lutein and, possibly to a lesser extent, zeaxanthin. Dr. Elizabeth Johnson, a research scientist at the Jean Mayer USDA Human Nutrition Research Center on Aging, reviewed some of the evidence to date, which suggests that lutein intake (as well as DHA, an omega-3 fatty acid) correlates with slower cognitive decline in older adults, healthy as well as those with varying degrees of dementia. Johnson’s recent research examines whether macular pigment density can be used as a biomarker for brain levels of lutein and zeaxanthin. The data does suggest a correlation between the pigment levels in the retina and various parts of the brain.
