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NUTRITION IN OPTOMETRIC PRACTICE
Nutrients in the battle against age-related eye diseasesJames G. Elliott, Ph.D., and Nancy Sumner WilliamsPart 2 of SeriesAn aging population has raised the priority of reducing therisk for age-related eye diseases that impair sight andquality of life. Chief among these diseases are age-relatedmacular degeneration (AMD) the leading cause of visionloss among older Americans and cataracts, which developin more than two thirds of Americans by age 80.1
Growing evidence suggests that nutritioncan attenuate the risk and/or progressionof age-related eye diseases. Optome-trists should inquire about theirpatients’ dietary intakes and supplementuse, and be able to counsel patients ongood nutrition for eye health.
Oxidative stress is implicated as a key pathogenic mech-anism in both conditions. A substantial body of experi-mental, observational, and clinical evidence suggests thereis reason to consider the impact of diet and specificnutrients on the development or progression of these2 eye diseases (and probably many more). Nutrientsassociated with AMD and/or cataract risk include vitaminsC and E; the vitamin A precursor beta-carotene; thexanthophylls lutein and zeaxanthin; omega-3 long-chainpolyunsaturated fatty acids (PUFA), such as docosahexae-noic acid (DHA) and eicosapentaenoic acid (EPA); some Bvitamins (folate, B6, B12, riboflavin); vitamin D; and themineral zinc.
Age-related macular degeneration
The original Age-Related Eye Disease Study nutrients:vitamins C and E, beta-carotene, zinc
The ability of a high-dose antioxidant supplement toprevent or slow the progression of AMD and/or cataractswas tested in the first Age-Related Eye Disease Study
James G. Elliott has a Ph.D. in nutritional biochemistry and is director of
DSM Nutritional Products LLC in Parsippany, New Jersey. Nancy Sumner
Williams is a consultant and writer in health communications. Opinions
expressed are those of the authors and not necessarily those of the Amer-
ican Optometric Association.
1529-1839/$ - see front matter � 2012 American Optometric Association. All r
doi:10.1016/j.optm.2011.11.006
(AREDS) of the National Eye Institute.2,3 The supplementprovided:
� 500 mg vitamin C – a water-soluble antioxidant that isconcentrated 20 times higher in the lens and aqueoushumor than in plasma; also present in the choroid andneural retina at higher concentrations than most non-ocular tissues.4
� 400 IU vitamin E – a lipid-soluble antioxidant thatprotects polyunsaturated fatty acids in cell membranesagainst oxidation, most importantly in lipid-rich neu-ral tissues. A higher intake of vitamin E can increaseretinal concentrations.5,6 (Note: vitamin E is a com-plex molecule consisting of 8 distinct moieties [bothalpha-, beta-, gamma- and delta- tocopherols and to-cotrienols], whereas the AREDS supplement containsonly 1 of these moieties – alpha tocopherol.)
� 15 mg beta-carotene – a carotenoid that can either becleaved to yield vitamin A, or, if vitamin A status isalready adequate, can remain intact and act as a lipidperoxidation chain-breaking antioxidant. As beta-carotene is not normally found in the eye, it mostlikely acts as a source of vitamin A, which is essentialfor the synthesis of rhodopsin.
� 80 mg zinc, an essential mineral that acts as a cofactorfor 1001 enzymes, including the antioxidants super-oxide dismutase and catalase, and also plays roles inimmune function, wound healing, protein synthesis,DNA synthesis and cell division. Zinc is found inhigh concentrations in the retina and plays a role inthe metabolic function of several enzymes in the cho-roid/retinal complex.7
� 2 mg copper – to prevent copper deficiency caused byhigh zinc intake.
AREDS found that this formula minimized the risk ofAMD progression in people at highest risk for developingadvanced AMD (signs of intermediate AMD or advanceddisease in 1 eye) over the duration of the study, but had noeffect on cataracts.2,3 Over the past decade, supplementa-tion with the AREDS nutrients has become a standard ofcare for AMD in patients with high-risk characteristics.Despite their effectiveness in minimizing the risk of
advanced AMD, the role of these nutrients in primaryprevention is less clear. A study in the Netherlands foundthat above-median dietary intake of the AREDS nutrientswas associated with a 56% reduced risk of incident AMD
ights reserved.
48 Practice Strategies
and, conversely, below-median intake of the AREDSnutrients was associated with a 33% increased risk ofincident AMD.8 In contrast, a meta-analysis of 9 prospec-tive cohort studies concluded that there is insufficient evi-dence to support the use of dietary antioxidants for theprimary prevention of early AMD.9
The new AREDS2 nutrients: lutein, zeaxanthin, DHA, EPA
Lutein and zeaxanthin. While the first AREDS wasin progress, evidence was accumulating to suggest thatthe dietary xanthophylls lutein and zeaxanthin – the carot-enoids present in yellow and orange fruits and vegetablesand in leafy green vegetables – may be more effective thanthe other antioxidants in reducing AMD risk. There isbiological plausibility for this hypothesis due to the highconcentration of lutein and zeaxanthin in the retina andmacula, notably in the region surrounding the fovea, theirblue light filtering and antioxidant properties, and theprobable involvement of oxidation in the pathophysiologyof AMD. Moreover, there is evidence from non-humanprimate studies that lutein and zeaxanthin (along withomega-3 long-chain PUFA) affect the development and/ormaintenance of the retinal pigment epithelium (RPE).10
Without these nutrients, RPE cells may be vulnerable topathological changes that are characteristic of AMD.The link between lutein and zeaxanthin and AMD risk
has been examined in at least 16 epidemiological studiesconducted in diverse countries.11-15 In general, the observa-tional data support the hypothesis that higher intakes and/orplasma levels of these macular pigments may be protective.The most recent studies are more persuasive because theywere conducted in large populations of subjects alreadyenrolled in eye disease studies (AREDS, Carotenoids inAge-Related Eye Disease Study [CAREDS], Blue Moun-tains Eye Study) that controlled for many variables.16-18
Factors contributing to the equivocal results of earlier stud-ies may include lower absolute dietary intakes in peoplereporting highest levels (each study ranks participantsbased on their intake, relative to all others in the study)and the severity of AMD studied.14
It is plausible that lutein and zeaxanthin may help reducethe risk for AMD by increasing macular pigment. In tissuecollected from autopsy studies, donor eyes with the highestlevels of macular pigment were 82% less likely to haveAMD than donor eyes with the lowest levels.19,20 Several ofthe key risk factors for AMD are also associated with lowmacular pigment, including advanced age, female gender,smoking, iris color, and higher body mass index(BMI).11,12 Higher macular pigment density (MPOD) hasbeen correlated with reduced risk for AMD in some,21-24
but not all,25,26 epidemiological studies.Intervention studies have demonstrated lutein and zea-
xanthin intake to be beneficial in AMD patients. One small,randomized trial found improved measures of visual func-tion in AMD patients given 10 mg per day supplementallutein alone or with co-antioxidants for 1 year, correspond-ing to improvements in MPOD.27 Another trial found that
non-advanced AMD patients with dysfunction in the centralretina had highly significant increased central responses at6 and 12 months when treated with an antioxidant formula-tion containing 10 mg of lutein, 1 mg zeaxanthin, and otherantioxidants (vitamin C, vitamin E, astaxanthin, zinc,copper), as compared to patients treated with a placebo.28
In other clinical studies ranging from 6 to 20 months,supplementation with 12 to 15 mg of lutein alone or incombination with other antioxidants resulted in significantimprovements in visual acuity and retinal function andslowed the rate of disease progression in AMD patients ascompared to placebo groups.29-32
Because of the potential importance of lutein and zea-xanthin in protecting against AMD, an expert panel wasconvened recently to come to a consensus on the value ofmacular pigment measurement as a screening tool for AMDrisk in clinical practice. The panel concluded that availablenon-invasive methods of measuring MPOD may be used toidentify individuals who may be at reduced, medium, andelevated risk for age-related eye diseases based on MPODlevels and distribution profiles, and that this knowledgemay enable individuals with low levels of MPOD to takeactions to improve their eye health.11
Omega-3 PUFA. The long-chain omega-3 fatty acidsDHA and EPA – most abundantly found in fatty fish –have the capacity to counter inflammatory processes andmodulate retinal cell gene expression, cellular differentia-tion, and cellular survival.33 DHA is highly concentrated inthe brain and retinal cell membranes, and its critical role innormal retinal function is well documented in animals34-36
and humans.33,37-39 DHA is the most abundant omega-3PUFA in the macula and peripheral retina40 and is the ma-jor structural lipid of the rod and cone cell outer segmentmembranes, where it must be continually recycled forproper retinal function.41 DHA appears to optimize photo-transduction42,43 and retinoid transport.44 Its roles arethought to be related to its protective functions in the cellmembranes, where it influences membrane integrity andpermeability, modulates the activity of enzymes and recep-tors on the membrane, and acts as a precursor for thesynthesis of other important biological molecules.33,45
Observational studies support the hypothesis that omega-3 PUFA is protective in the eye. A 2008 meta-analysisof epidemiological studies reported that a high intake ofomega-3 fatty acids and fish may reduce the risk of AMDby up to 38%.46 The authors stated that eating fish twice aweek was associated with a reduced risk of both early andlate AMD. In a 5-year follow-up study of the Blue Moun-tains Eye Study cohort, fish consumption at least once aweek was associated with a 40% reduction in incident earlyage-related maculopathy (ARM), and more frequentconsumption of fish (3 times a week) was protective againstlate ARM.47
In 2009, researchers from the AREDS group reported ona subsection of 1,837 study participants with eye changesrepresenting a moderate-to-high risk of progressing tocentral geographic atrophy (CGA) and neovascular AMD.
Practice Strategies 49
Over 12 years of study, participants with the highestomega-3 intakes had a 30 percent lower risk of developingthese advanced forms of AMD than their peers with lowerintakes.48 Other recent findings from subsets of the AREDSparticipants have been similar. A 2008 report found thatamong participants with bilateral drusen, those whoreported the highest levels of EPA and DHA intake had a50% decreased likelihood of progression to CGA as com-pared to their peers.49 A 2007 report described a 40% to50% reduced likelihood of having neovascular AMDamong AREDS participants who reported the highest levelsof omega-3 PUFA and fish intake.50
The association between dietary fat and AMD appears todepend not only on the sum total but also on the balance ofdifferent fatty acids in the diet.50-58 The ratio of omega-6 toomega-3 PUFA is of particular interest in the context of thecurrent food supply, which is dominated by omega-6PUFA. In some of the studies showing a protective effectof fish, omega-3 PUFA and/or fish consumption was mostprotective when there was also a low dietary intake ofomega-6 PUFA.55-57 A study that looked at the associationbetween total dietary fat intake and the rate of AMDprogression found that only fish and nuts (sources oflong-chain omega-3 PUFAs and alpha-linolenic acid, anomega-3 PUFA precursor to EPA) decreased the likelihoodthat AMD would progress to advanced stages related tovision loss, whereas all other fats increased the risk.55
Experimental evidence supports the notion that thebalance of fats is influential. A putative pathogenic processin AMD was examined in the form of inflammatory changesin human retinal vascular endothelial (hRVE) cells. Whereasthe omega-6 fatty acids linoleic acid and arachidonic acidpromoted inflammatory changes in hRVE cells, DHA com-pletely blocked inflammation by suppressing cytokine-induced pro-inflammatory signaling in these cells.59
It is likely that other dietary factors influence the effectsof omega-3 PUFA, and vice versa. A recent randomizedtrial examined the relative effects of supplementation withlutein alone, DHA alone, or lutein plus DHA on macularpigment density in elderly women. Lutein alone increasedMPOD around the fovea, whereas DHA alone increasedcentral MPOD, and the combination supplement producedincreases in both areas. 41 DHA also facilitated the accumu-lation of lutein in the macula in this study, supportingearlier findings that DHA status may affect the concentra-tion of lutein and zeaxanthin in the retina.10
Due to this promising body of evidence, the second study,AREDS2, sponsored by the National Eye Institute, wasinitiated (www.areds2.org) to evaluate the safety and effi-cacy of daily supplemental lutein (10 mg), zeaxanthin(2 mg), DHA (350 mg), and EPA (650 mg) in retardingprogression of AMD in people at moderate to high riskfor progression to advanced AMD. AREDS2 is a 5-year,multicenter, randomized trial of approximately 4,000 par-ticipants age 50 to 85 years.60 The trial will also provide in-formation on moderate vision loss as assessed by change invisual acuity.
B vitamins. A number of scientific articles have appearedsuggesting that AMD and cardiovascular disease share acommon risk profile, including elevated levels of homocys-teine, a sulfur-containing amino acid that is normally presentin the blood but becomes a risk factor for cardiovasculardisease (CVD) when elevated. Some epidemiological stud-ies have found higher homocysteine levels in people withAMD.61,62 Folic acid, vitamin B6, and vitamin B12 partici-pate in homocysteine metabolism, and supplementationwith these vitamins can lower homocysteine levels. A ran-domized controlled trial conducted in more than 5,000women at high risk for CVD found that long-term dailysupplementation with folic acid (2.5 mg/day) and vitaminsB6 (50 mg/day) and B12 (1 mg/day) reduced the risk ofmild AMD by about 40%.63
Vitamin D. Recent epidemiological studies have associ-ated higher vitamin D serum levels64 or intake65 withreduced risk of early AMD. In women younger than 75years of age, dietary intake of vitamin D from food andsupplements (604 IU) was associated with a reduced riskof early AMD.65 Another study compared risk in monozy-gotic twins to assess differences in behavioral and nutri-tional factors and found that twins with an earlier stageof AMD, smaller drusen size and area, and less pigmenttended to have higher dietary vitamin D intake.66
Interactive influence of nutrition and lifestyle on AMD risk
Researchers have begun to explore the interaction of riskfactors in AMD to determine whether diet and lifestyle mayattenuate risk. A study of participants in the CAREDSfound that having a combination of 3 healthy behaviors(healthy diet, physical activity, and not smoking) wasassociated with 71% lower odds for early AMD comparedwith high-risk scores.67 Another study in Irish constructionworkers found that the combined effects of cigarette smok-ing, low intakes of fruits and vegetables, and exposure tohigh amounts of sunlight approximately doubled the riskof predicted AMD development compared to the normalpopulation.68 These authors concluded that ‘‘smokingcessation and dietary modification to include leafy greens,colored fruits and vegetables and in some cases, dietarysupplementation containing the macular pigments, shouldbe advised to reduce the risk of AMD in constructionworkers or individuals with similar environmental andlifestyle traits.’’68
Several genetic risk loci variants have been identifiedthat may interact with dietary and other environmentalfactors to alter risk for AMD.13,69 For example, the Rot-terdam Study investigated whether dietary nutrients re-duced the genetic risk of early AMD conferred by thegenetic variants CFH Y402H and LOC387715/A69S.The authors concluded that ‘‘high dietary intake of nutri-ents with antioxidant properties reduces the risk of earlyAMD in those at high genetic risk. Therefore, cliniciansshould provide dietary advice in young susceptible indi-viduals to postpone or prevent the vision-disabling conse-quences of AMD.’’70
50 Practice Strategies
CataractsCataract extractions are the most common surgical proce-dure performed in the United States and are a considerableexpense for the public health care system. Cataract careconsumes about 60% of the Medicare budget for vision.71
In addition to age, risk factors for cataracts include oxida-tive damage to lens proteins, genetics, diabetes, possibly in-flammation, and dietary intakes of carbohydrates andfats.72-76 It has been estimated that if the progression of cat-aracts could be delayed by 10 years, the number of cataractextraction surgeries per year would be reduced by 45%.77
Nutrients and cataract risk
Antioxidant nutrients/cofactors. As oxidative damageto the lens is well-established as a contributing factor incataracts, many studies have attempted to explore theassociation between nutrients with antioxidant properties(vitamins C and E, beta-carotene) and nutrients acting ascofactors to enzymes with antioxidant properties (zinc,riboflavin) with the occurrence or progression of cata-racts. More than 40 studies have examined these rela-tionships, with mixed results.72,78-80 Recent analysessuggest that the inconsistencies from study to studymay be due the fact that these nutrients exert their protec-tive effects at different times during the cataract develop-ment process or that optimal nutrient intakes must beprolonged over many years, even decades, in order toconfer protection.For example, the Nurses’ Health Study (NHS) found the
prevalence of nuclear cataracts was significantly lower inwomen who used a vitamin C supplement for 10 yearsor more, compared to women who never used vitamin Csupplements.81 Similarly, women in the NHS who usedvitamin C supplements for 10 years or longer were lesslikely to have cataract surgery.82 Another analysis ofNHS data found reduced progression of cataracts in womenwho took supplemental vitamin E for 5 years.83 Subjects inthe Beaver Dam Eye study who used multivitamins or anysupplement containing vitamin C or E for more than10 years had a 60% reduced likelihood of developing cata-ract across a 5-year period, 84 and at least 4 studiespublished earlier reported similar findings.82,85-87
In some cases, studies examined populations whosenutrient intakes were not high or low enough to altervitamin concentrations in the lens. In studies where dietaryvitamin C intakes were relatively high, protective effectswere seen. For example, a study of a subset of womenenrolled in the NHS found a decreased risk of corticalcataract in women age 60 and older who had vitamin Cintakes of 362 mg or more per day.88
An analysis of observational findings suggests differentnutrients may influence the process of lens opacification atdifferent stages: studies that found a protective effect ofvitamin C tend to be those that looked at early stages ofcataract development, whereas vitamin E and riboflavin aremore often found to be protective in analyzing advancedstages of opacification.83
An inverse relationship between riboflavin intake orstatus and nuclear cataracts was reported in the BeaverDam Study,89 the Lens Opacities Case-Control Study,90 theBlue Mountains Eye Study,91 and the Nutrition and VisionProject.81 Some of these studies also reported associationsof opacity with niacin and thiamin, but because these nutri-ents are found in the same foods and vitamin supplements,independent effects could not be determined. A niacin/ribo-flavin supplement reduced cataract risk in a large clinicaltrial in China92; however, the results of most randomizedtrials, including AREDS, have seldom lived up to theexpectations of researchers. The potential of vitaminswith antioxidant properties to slow the progression ofage-related cataracts has been tested in 9 clinical trials orancillary trials; only 3 found protective effects from specificsupplements among subjects in certain subgroups, such assmokers.92-94
Dietary xanthophylls. Lutein and zeaxanthin are the onlycarotenoids detectable in the human lens, although atconcentrations considerably lower than in the macula.Their concentration is higher in the cortical lens tissuethan in nuclear lens tissue.95 The presence of lutein andzeaxanthin in the lens suggests they may act with vitaminsand enzymes with antioxidant properties to reduce harmfuleffects of ultraviolet (UV) radiation and oxygen-free radi-cals.96 Clinical findings show lens optical density is in-versely related with macular pigment optical densityamong adults age 48 to 72 years.97 The significance ofthis association is not yet known, but is suggested to be re-lated to processes affecting lens aging.96
A protective role for zeaxanthin and lutein in the lens issupported by a cell culture study in human lens epithelialcells, where both lutein and zeaxanthin inhibited UVB-induced lipid peroxidation by 47% to 57% and attenuatedactivation of the stress signaling pathways in these cells.98
As the cellular concentration of zeaxanthin was only halfthat of lutein yet showed equal protection, the authors sug-gested zeaxanthin may be more effective than lutein at pro-tecting the lens against UV damage. Moreover, whencompared to vitamin E, lutein and zeaxanthin exerted theirprotective effects at concentrations 80% less than vitaminE, suggesting that even though lutein and zeaxanthin arepresent at low levels in the lens, they may nonethelesshave important effects.Higher intake of foods rich in lutein and zeaxanthin has
been associated with a lower likelihood of having ordeveloping cataract in several epidemiological stud-ies.85,99-103 Higher plasma concentrations of lutein and/or zeaxanthin have been associated with a lower likeli-hood of having posterior subcapsular cataract,100,104 nu-clear cataract,89,105 any cataract,79 and reduced risk ofneeding cataract surgery.99 In the Physicians’ and Nurses’Health studies, only those in the highest quintile of dietarylutein and zeaxanthin intakes (6.8 mg/day among men,11.7 mg/day among women) had statistically significantreduction in cataract risk (19% for men and 22% forwomen).99,100
Practice Strategies 51
Lutein supplementation (15 mg 3 times a week for2 years) has been evaluated in a double-blind, placebo-controlled pilot study in 17 patients with clinicallydiagnosed cataracts.106 Visual function as measured byvisual acuity and glare sensitivity improved in the luteingroup. The authors suggested the association may be re-lated to a direct effect of lutein on the retina, independentof cataract progression.As AREDS2 is investigating supplemental nutrients in
cataracts as well as AMD; more information will beforthcoming after the completion of that trial in 2013.
A diet for eye healthGuidelines for a healthy diet have been fairly consistentthrough the years, with an emphasis on increasing intake offruits and vegetables, whole grains, beans, lean meats, fish,and low-fat dairy products while decreasing intake ofsaturated fats (whole fat dairy products, fatty meats), addedsugars, and refined grains. The most recent iteration of theU.S. Department of Agriculture’s (USDA) Dietary Guide-lines specifies the need to increase intake of colorful fruitsand vegetables and fish and also elaborates on healthyprotein sources to include nuts and seeds, which are oftensources of the omega-3 parent compound alpha-linoleicacid (ALA).107 These guidelines, which parallel theDASH (Dietary Approaches to Stop Hypertension) eatingpattern for heart health,108 may also be appropriate foreye health.Of particular importance are sources of lutein/zeaxanthin
and EPA/DHA, because the foods that provide these havebeen historically low in the American diet. Lutein andzeaxanthin are provided by orange and yellow fruits andvegetables (corn, yellow squash, butternut squash, orangepeppers, peaches, nectarines, oranges/orange juice), greenvegetables (spinach, kale, broccoli, green peppers, Brusselssprouts), and egg yolks, which are a highly bioavailablesource. Fruits and vegetables rich in lutein and zeaxanthinare also good sources of vitamins C and E, as well as othercarotenoids.109
EPA and DHA must be obtained directly from the diet orby conversion from ALA. ALA is found in canola oil, flaxseed, and some tree nuts such as almonds and walnuts. Asconversion of ALA to the longer-chain fatty acids in thebody is inefficient (especially for DHA), consumingpreformed sources such as salmon, herring, sardines, andtuna is a better means of altering tissue status.110,111
Maintaining a healthy balance of fats may be challengingdue to the predominance of omega-6 PUFA in the Americanfood supply, although this has begun to change. Prehistorichumans lived on a diet of fresh fruits, leafy vegetables, fish,marine bird eggs, and terrestrial animals that provided arelatively equal balance of omega-6 and omega-3 PUFA;human physiological and metabolic processes evolved onthis 1:1 ratio.112,113 In the twentieth century, animal feedingpractices and food production methods decreased theomega-3 fatty acid content of staple foods such as meats,fish, and eggs; the use of grain feed rich in omega-6 fatty
acids has altered the tissue composition of livestock. Lino-leic acid, the major dietary omega-6 PUFA (largely derivedfrom corn) is used throughout the food industry in processedproducts from crackers to hot chocolate mix.113 Due to suchchanges in the food supply, the ratio of omega-6 PUFA toomega-3 PUFA intake in North America today greatly favorsomega-6 PUFA and ranges from a ratio of 10:1 to 50:1.114
Many nutrition scientists believe that inflammatory diseasesand other chronic health conditions are related to this imbal-ance. A growing awareness and acceptance of the impor-tance of omega-3 PUFA has prompted efforts to redressthe imbalance of unsaturated fats in the American foodsupply in recent years, resulting in the availability of morefood products that either naturally contain or are enrichedwith omega-3 PUFA.115 For example, changes in poultryfeeding practices have led to the production of eggs withomega-3 PUFA; many cereals and breads containing flaxseed are now available; and spreads such as margarine andpeanut butter now offer alternatives with omega-3 PUFA.Patients who wish to follow a diet for eye health should
seek out the foods listed in Table 1.
RecommendationsResearch suggests that many people are not consumingadequate amounts of the nutrients needed to support goodeye health. (Levels of nutrients associated with benefits inhuman studies of age-related eye diseases are summarizedin Table 2.) Optometrists are ideally positioned to assesstheir patients’ dietary and supplementation habits andprovide nutrition counseling or referral to a registered die-titian. Here are a few simple steps a practitioner can take toinclude dietary assessment and counseling in a patient visit.
1. Inquire about the patient’s usual diet, especiallyregarding fruits, vegetables, and fish, as well as rele-vant dietary supplement practices. The new USDADietary Guidelines stress that half of each mealshould consist of fruits and vegetables. For eyehealth, these should include deep green and yellowfruits and vegetables. Patients should also seek outpre-formed sources of omega-3 PUFA (seafood),as well as products that contain ALA or have beenfortified with omega-3 PUFA.
2. Review the patient’s eye health history, heredity forAMD, and other risk factors for age-related eye dis-eases.
3. If the patient is at risk for AMD, it may be appropri-ate to measure MPOD and provide guidance abouthow to raise MPOD.
4. If the patient is at risk for cataracts, prevention shouldstart as early as possible and generally include highlevels of vitamins C and E, which may need to be ob-tained via supplements. However, to prevent possibleadverse outcomes, preventive measures should be ini-tiated in cooperation with other physicians who carefor the patient. (For example, some research suggests
Table 1 Food sources of major vision nutrients*
Nutrient (s) Good food sources
Vitamin A Liver, egg yolks, fortified milk and dairy products, margarineFolate Green leafy vegetables, citrus fruits and juices, dried beans and peas, enriched breads, cereals,
flours, corn meals, pastas, rice and other grain products (in the United States)Vitamin B6 Fortified breakfast cereals, fish, pork, chicken, bananas, beans, peanut butter, many vegetablesVitamin B12 Fish, meat, poultry, eggs, milk and milk products, fortified breakfast cerealsRiboflavin Milk, dairy products, eggs, lean meats, poultry, fish, legumes, green vegetables,
enriched breads and cerealsVitamin C Citrus fruits, melons, berries, tomatoes, potatoes, cabbage, broccoli, fortified cerealsVitamin E Vegetable oils, nuts and seeds, wheat germ, whole grains, green leafy vegetablesBeta-carotene Carrots, sweet potatoes, spinach, cantaloupe, mango, apricots, papaya, yellow squash,
dark green leafy vegetablesLutein and zeaxanthin Oranges, honeydew, kiwi, red and green grapes, pumpkin, yellow squash, yellow corn,
spinach, kale, orange and green peppers, egg yolksOmega-3 PUFA Salmon, herring, sardines, tuna provide DHA and EPA; canola oil and flax seed provide the
parent compound, alpha-linolenic acidZinc Shellfish, meat, liver, eggs, whole grains, dried beans and peas, nuts
* For nutrient content of foods, visit www.ars.usda.gov/ba/bhnrc/ndl.
52 Practice Strategies
cardiovascular risk is higher in certain patients’ reti-nal disease who take high doses of vitamins E and C.)
5. Provide patient education materials and/or referpatients to sites such as those offered on the Ameri-can Optometric Association (AOA) Web site(www.aoa.org) for information about diet, nutrition,and eye health.
It should be emphasized that consultation with the otherphysicians managing a patient is always a prudent stepwhen recommending nutritional supplements or dietarychanges. As the authors hope articles in this series willillustrate, nutrients can be a powerful force in preventing orminimizing the effects of many eye conditions. However,like pharmaceuticals, nutrients hold the potential for pos-sible adverse outcomes. Optometrists should never hesitate
Table 2 Levels of nutrients associated with benefits inhuman studies of age-related eye diseases
Nutrient (s) Dietary and/or supplement levels
Vitamin A 600-1300 mcg retinol equivalentsFolate Up to 2.5 mgVitamin B6 Up to 2.2 mgVitamin B12 Up to 1 mgRiboflavin 3 mgNiacin 40 mgVitamin C 360 - 500 mgVitamin E 400 IUVitamin D 600 IUBeta-carotene Up to 15 mgLutein and zeaxanthin 10 - 15 mg lutein, 2 mg zeaxanthinOmega-3 PUFA 1000 mg DHA and EPA combinedZinc Up to 80 mg
to check with a patient’s other physicians when counselingon nutrition. Beyond helping to ensure that the patientis properly advised on the best possible path to bettereye health, such consultations can help to establish theoptometrist in the mind of the consulted physician as aknowledgeable provider of state-of-the-art eye care and avalued member of the patient’s health care team.Optometrists today are offering a wide range of eye and
vision care products and services for their patients. In manycases, optometrists are also attempting to see more patientseach day, or see them in a more efficient manner, in order toensure the economic viability of their practices. Somepractitioners may wonder if they have the time to incorpo-rate nutritional assessment and counseling into their prac-tices. However, by taking the steps outlined here andmaking use of good patient education tools, optometristscan easily and effectively introduce nutrition counselinginto even the busiest practices. In many cases, they mayfind it is an effective way of distinguishing an optometricoffice as a state-of-the-art practice in an increasinglycompetitive eye and vision care market.
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Practice Strategies 53
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