pubs.acs.org/JAFC Published on Web 01/26/2010 © 2010 American Chemical Society J. Agric. Food Chem. 2010, 58, 4001–4007 4001 DOI:10.1021/jf903038r Recent Research on Polyphenolics in Vision and Eye Health † WILHELMINA KALT,* ,§ ANNE HANNEKEN, # PAUL MILBURY, ^ AND FRANCOIS TREMBLAY X § Atlantic Food and Horticulture Research Centre, Agriculture and Agri-Food Canada, 32 Main Street, Kentville, Nova Scotia, Canada B4N 1J5, # Department of Molecular and Experimental Medicine, The Scripps Institute, 10550 Torrey Pines Road, La Jolla, California 92037, ^ Antioxidants Research Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, 711 Washington Street, Boston, Massachusetts 02111-1524, and X Department of Ophthalmology and Visual Sciences, Dalhousie University and IWK Health Center, 5850 University Avenue, Halifax, Nova Scotia, Canada B3K 6R8 A long-standing yet controversial bioactivity attributed to polyphenols is their beneficial effects in vision. Although anecdotal case reports and in vitro research studies provide evidence for the visual benefits of anthocyanin-rich berries, rigorous clinical evidence of their benefits is still lacking. Recent in vitro studies demonstrate that anthocyanins and other flavonoids interact directly with rhodopsin and modulate visual pigment function. Additional in vitro studies show flavonoids protect a variety of retinal cell types from oxidative stress-induced cell death, a neuroprotective property of significance because the retina has the highest metabolic rate of any tissue and is particularly vulnerable to oxidative injury. However, more information is needed on the bioactivity of in vivo conjugates and the accumulation of flavonoids in ocular tissues. The direct and indirect costs of age-related vision impairment provide a powerful incentive to explore the potential for improved vision health through the intake of dietary polyphenolics. KEYWORDS: Flavonoids; retina; antioxidant; rhodopsin BERRY FLAVONOIDS AND HUMAN HEALTH Polyphenolics and especially the flavonoids contained in berry crops are being investigated for their potential benefits against cancer, as well as in cardioprotection, neuroprotection, urinary tract health, and antiaging effects ( 1 ). Concurrent with berry flavonoid research that employs various models of health and disease, investigations are underway to determine the in vivo bioavailability of these compounds ( 1 ). A somewhat unique yet controversial bioactivity attributed to berry anthocyanins is their benefits in vision, particularly night vision ( 2 , 3 ). There is a growing need to determine if and how anthocyanins improve human vision because their benefits are promoted commercially and are already widely familiar to consumers, particularly in Japan and Asia. Demonstration of clinical benefits to night vision by anthocyanins could be of great interest because this benefit would be easy for consumers to understand and should be demonstrable in a relatively short time frame. Recent research suggests that flavonoids may be involved in two major aspects of the diverse processes involved in vision physiology and eye health. Flavonoids may function in visual signal transduction, in ways that are as yet not well understood. Flavonoids may also function in their well-established role as antioxidants, which is particularly important in the eye, where oxidative stress is significant and its damage is implicated in a number of vision pathologies, including macular degeneration ( 4 ). Studies showing flavonoid effects on visual signal transduction or as antioxidants can be put in context once we understand whether flavonoids are absorbed by the eye and, if so, their relative distribution among ocular tissues. This paper will focus on the effects of berry polyphenolics on vision physiology, and their bioavailability in ocular tissues will be reviewed. When possible, conclusions will be made and areas for future research will be proposed. FLAVONOID EFFECTS ON VISUAL SIGNAL TRANSDUCTION IN VITRO Visual signal transduction involves two major processes: first, the light activation of rhodopsin, leading to a change in its conformation and the creation of a visual signal, and, second, the regeneration of rhodopsin to its original conformation. Rhodopsin has two components, the chromophore retinal and the protein opsin. Rhodopsin is embedded in the membranes of disks in the outer segment of rod photoreceptors (Figure 1). Rod photoreceptor cells are responsible for the retinal pathways that give rise to monochrome vision under reduced light (i.e., dark vision). Cone photoreceptors contain either short- (blue), middle- (green), or long - (red) wavelength sensitive light-absorbing molecules called iodopsins. Together the three types of cones are responsible for color vision and visual acuity in bright light. Rhodopsin and iodopsins share the same chromophore, 11-cis- retinal, but have different opsin molecules. † Part of the Berry Health Symposium 2009. *Corresponding author [telephone (902) 679-5757; fax (902) 679- 2311; e-mail wilhelmina.kalt@agr.gc.ca].