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TalkingNutrition

Providing perspectives on recent research into vitamins and nutritionals

young-woman-eye

Improving Nutritional Status to Support Eye Health: Reading, Listening, Acting

By Michael McBurney

Of the five senses, sight and sound are the most important for learning. While all senses are important, many people particularly fear the loss of eyesight. Boyers and colleagues sought to determine if scientific effort is an accurate reflection of the global burden of eye and vision disease.

Their detailed examination of the Cochrane Database of Systematic Reviews found gaps in the literature. Age-related diseases (cataract, glaucoma and macular degeneration) received the most attention, sometimes overrepresented relative to eye disease and disorder prevalence, whereas nutrition-related (vitamin A deficiency), communicable disease-related (trachoma and onchocerciasis), and refraction and accommodation disorders were underrepresented.  Let’s focus on nutrition and eye health.

The eye requires several essential nutrients to function properly. One of the first nutritional diseases to be identified was night blindness. Vitamin A was discovered to be an essential precursor for visual pigments in rods and cones of the retina in the early 1900s. With this insight and modern technologies, it is known that 3 plant carotenoids (β-carotene, α-carotene and β-cryptoxanthin) are converted to vitamin A within our bodies with varying efficiencies.

Visual cells (as well as all cells in the body) require essential long-chain polyunsaturated fatty acids (LCPUFA) to  maintain cell membrane fluidity and facilitate signaling and transport activities by proteins traversing cell membranes.  An adequate intake of the omega-3 fatty acid docosahexaenoic acid (DHA) is important for visual function and eye health.

Carotenoids also function as antioxidants within the body. Two, lutein and zeaxanthin, out of over 60 commonly consumed carotenoids, are concentrated in the macula lutea of the retina. Co-location of these antioxidants in the retina helps prevent LCPUFA and DHA from being oxidized.  Macular pigment optical density (MPOD), a measure of the amount of lutein and zeaxanthin present in the macula of the retina, is a biomarker of visual health. Low MPOD is often a reflection of infrequent consumption of green and yellow fruit and vegetables and egg yolks. Lutein and zeaxanthin also represent 70% of the carotenoids in the brain. MPOD has been correlated with cognitive function.

Many are not adhering to dietary recommendations with respect to fruit, vegetables, and seafood. The consequence is that beta-carotene/vitamin A, DHA, lutein and zeaxanthin intakes are inadequate to maintain optimal tissue concentrations.

Here’s hoping that more people will read this blog, listen to the advice, and take steps to increase their intake of these nutrients.

Main Citation

Boyers LN, Karimkhani C, Hilton J, Richheimer W, Dellavalle RP. Global burden of eye and vision disease as reflected in the Cochrane Database of Systematic Reviews. 2014 JAMA Opthalmol doi: 10.1001/jamaopthalmol.2014.3527

Other Citations

Dowling JE, Wald G. Vitamin A deficiency and night blindness. 1958 Proc Natl Acad Sci 44(7): 548-661

Birch EE, Carlson SE, Hoffman DR, Fitzgerald-Gustafson KM, Fu VLN, Drover JR, Castneda YS, Minss L, Wheaton DKH, Mundy D, Marunycz J, Diersen-Schade DA. The DIAMOND (DHA Intake And Measurement Of Neural Development) study: a double-masked, randomized controlled clinical trial of the maturation of infant visual acuity as a function of the dietary level of docosahexaenoic acid. 2010 Am J Clin Nutr doi: 10.3945/ajcn.2009.28557

Zhu W, Wu Y, Li G, Wang J, Li X. Efficacy of polyunsaturated fatty acids for dry eye syndrome: meta-analysis of randomized controlled trials. 2014 Nutr Rev doi: 10.1111/nure.12145

Elliott JG, Williams NS. Nutrition and optometric practice: Functional roles of lutein and zeaxanthin in visual performance. 2011 Optometry doi: 10.1016/j.optm.2011.09.004.

Kesse-Guyot E, Andreeva VA, Ducros V, Jeandel C, Julia C, Hercberg S, Galan P. Carotenoid-rich dietary patterns during midlife and subsequent cognitive function. 2014 Br J Nutr doi:1017/S0007114513003188


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