Eye Health

Eye Health

by Kim Schoenhals

Eye health is a function of numerous components, not the leastof which is a healthy diet. Without proper nutrition, eye health candeteriorate, leading to age-related macular degeneration (AMD), cataracts andeven glaucoma. Those with diabetes must pay special attention to maintaining eyehealth to avoid diabetic retinopathy.

According to the Natural Marketing Institute's (NMI) TheHealth & Wellness Trends Database--which contains three years of trendeddata (1999-2001) and represents more than 2,000 respondents--more thanone-quarter of the population (28.7 percent) reports vision problems, with men(31.1 percent) slightly more likely to experience eye troubles than women (27.9percent). Of the various eye-health-related supplements on the market, consumerswere most likely to use vitamin E (45.7 percent) and vitamin C (45.4 percent).Additional supplement use included B complex (24 percent), antioxidants (16.4percent), folic acid (14.6 percent) and lutein (8.6 percent). These nutrientsall have a function in preserving and enhancing eye health, as well aspotentially preventing the deteriorating effects of AMD, cataracts, glaucoma anddiabetic retinopathy.

The National Eye Institute (NEI) reports that AMD is a commoncause of vision loss among people over the age of 60. It occurs in two forms:dry AMD, which accounts for 90 percent of all AMD cases, and wet AMD, whichaccounts for 10 percent of total cases but 90 percent of severe vision lossassociated with the disease. The disease affects central vision but rarelycauses blindness.

Cataracts are another eye disorder that occurs most often in theelderly--more than half of all Americans age 65 and older have at least onecataract. While the cause of cataracts is unknown, some guesses include smoking,diabetes and excessive exposure to sunlight, according to NEI. The four types ofcataracts are age-related, congenital, secondary and traumatic.

Glaucoma is a group of diseases that can lead to damage of theeye's optic nerve, resulting in blindness. The forms of glaucoma includeopen-angle, low-tension, closed-angle and various secondary cause varieties.Although anyone can develop glaucoma, African-Americans over the age of 40,everyone over the age of 60, and people with a family history of glaucoma are athigher risk.

Diabetic retinopathy is a potentially blinding condition thatresults as a complication from diabetes. Diabetic retinopathy occurs whendiabetes damages the tiny blood vessels in the retina, and affects half of allAmericans diagnosed with diabetes, both Type I and Type II, according to NEI.Timely treatment prevents blindness in 90 percent of cases.

Antioxidants

Arguably, degenerative diseases of the eye are at leastpartially caused as a result of free radical damage, which is why antioxidantscome into play when dealing with this category. It has also been suggested thatcataract formation occurs in those with deficient glutathione levels,which contributes to a weakened antioxidant defense system in the eye (AltMed Rev, 6, 2:141-66, 2001) (www.thorne.com/altmedrev).To preserve the body's antioxidant defense in the eye, lipoic acid, vitaminE, vitamin C and selenium all enhance glutathione levels.

In addition, antioxidants such as vitamin A, beta-carotene,vitamin E and vitamin C can reduce oxidative damage to the eye, therebypreventing or slowing the progression of eye disease. While these vitaminsindividually impact eye health, they become increasingly effective when usedsynergistically. Recently published results from the Roche European AmericanCataract Trial (REACT) indicated that, taken together, beta-carotene (18 mg/d),vitamin C (75 mg/d) and vitamin E (600 IU/d) may be able to reduce theprogression of age-related cataracts (Ophthalmic Epidemiology, 9,1:49-80, 2002) (www.szp.swets.nl).

This same combination of antioxidants, with the addition of zinc,has also been found to reduce the risk of AMD. NEI, in collaboration with Bauschand Lomb, recently released results from its Age-Related Eye Disease Study (AREDS),which involved 4,757 participants who were given one of four treatments: 1)zinc: 80 mg as zinc oxide; 2) antioxidants: 500 mg of vitamin C, 400 mg ofvitamin E and 15 mg of beta-carotene; 3) antioxidants and zinc; or 4) placebo.The zinc groups also received copper (2 mg as cupric oxide), as copperdeficiency can occur when high amounts of zinc are present.

Results from AREDS indicated that only those who began the studywith a high risk of advanced AMD attained a benefit from supplementation. Thelargest benefits were seen in the antioxidant plus zinc group, whose risk ofdeveloping AMD was reduced by 25 percent. Taken independently, zinc andantioxidants also reduced the risk of developing AMD, although not as great areduction of risk was seen in the zinc plus antioxidants group. Contrary toREACT results, AREDS study participants did not experience a reduced risk ofcataracts in any of the treatment groups (Arch Ophthalmology, 119,10:1439-52, 2001) (http://archopht.ama-assn.org).

"Previous studies have suggested that people who have dietsrich in green, leafy vegetables have a lower risk of developing AMD," saidFrederick Ferris, M.D., director of clinical research at NEI and chairman ofAREDS. "However, the high levels of dietary supplements that were evaluatedin AREDS are very difficult to achieve from diet alone."

Another combination study regarding the effects of nutrients onAMD and cataracts found that antioxidant vitamins C and E reduced the risk ofage-related eye diseases. For 13 to 15 years, researchers from Tufts Universityin New York followed 478 women (ages 53 to 73 years old) without previouslydiagnosed cataracts and found that subjects who used vitamin C for 10 or moreyears had significantly lower rates of cataracts than women who werenon-supplement users. The same researchers also discovered that carotenoidnutrients--lutein and zeaxanthin--reduced the risk of cataracts. Women withlutein and zeaxanthin intakes above 2.4 mg/d exhibited a lower incidence ofcataracts (Arch Ophthalmology, 119:1009-19, 2001) (http://archopht.ama-assn.org).

click here

Carotenoids

Carotenoids, including lutein and zeaxanthin, area class of compounds that exhibit antioxidant abilities. While carotenoids areresponsible for the yellow and red pigments present in many fruits andvegetables, lutein and zeaxanthin are specifically responsible for macularpigment--they are the only carotenoids found in the macula.

There are two basic theories characterizing the function ofmacular pigment, according to researchers from the University of Georgia, Athens(Arch Biochem Biophys, 385, 1:41-46, 2001) (www.academicpress.com/abb).The first is that macular pigment protects the eye by reducing the damagingeffects from light and oxygen, as well as slowing the development of age-relatedeye diseases. The second theory is that macular pigment improves visualresolution by absorbing short-wave light, which is easily scattered and poorlyfocused. According to the researchers, lutein and zeaxanthin intake may improvevisual health by supporting healthy eye function.

Natural lutein esters in particular may be able to increasemacular pigment density, according to researchers from University Medical Centerin Utrecht, Netherlands (IOVS, 41:3322-26, 2000) (www.iovs.org).In this trial, researchers led by Tos Berendschot, Ph.D., had eight men take 10mg/d of lutein esters for 12 weeks. In addition to demonstrating increasedlutein blood levels, the men exhibited a 20-percent increase in macular pigmentdensity by the end of the trial.

"Other human trials have shown similar, efficientabsorption and assimilation of lutein from lutein esters," said CindySchweitzer, Ph.D., senior scientist at LaGrange, Ill.-based Cognis Nutrition andHealth, manufacturer of Xangold natural lutein esters."Indeed, lutein esters have been a popular form with scientists, asBerendschot's trial and several others demonstrate a clear increase in thedensity of the macular pigment following supplementation with lutein esters. ...A lower density macular pigment is a risk factor for, but may not be theultimate cause of, [AMD], the leading cause of blindness among senior citizensin the United States."

One theory for the reason carotenoids are useful in maintainingeye health is their antioxidant capabilities. According to researchers from theUniversity of Utah School of Medicine in Salt Lake City, lutein and zeaxanthinplay a critical role in protecting the eye from light-induced oxidative damageand aging (Exp Eye Res, 72, 3:215-23, 2001) (www.academicpress.com/eer).

"The presence of oxidative metabolites in the maculasuggests that lutein may also offer protection to the cells of the macula byacting as an antioxidant," wrote Andrew Shao, Ph.D., technical servicesmanager of vitamins and dietary supplements for Des Moines-based Kemin Foods,manufacturer of FloraGLO purified lutein (JANA, 4, 2:8-24,2001) (www.americanutra.com/jana.html)."Several investigators have published reviews proposing that antioxidants,including lutein and zeaxanthin, help ... preserve macular health by acting asfree radical quenchers."

click here

Lutein, zeaxanthin and other carotenoids are especiallyeffective at quenching free radicals when used synergistically, which may be dueto the specific physiological positioning of different carotenoids (FEBSLetters, 427:305-08, 1998). Researchers at Rutgers University conducted anin vitro study to determine the synergistic antioxidant capabilities of abranded carotenoid combination. The mixture (as Zealutein, bySabinsa Corp., which also sponsored the study) contained lutein, zeaxanthin,capsorubin, capsanthin and a branded black pepper extract (as Bioperine,by Sabinsa Corp.). This unpublished study demonstrated that the mixture hadpotent antioxidant activity and inhibited lipid peroxidation.

Macular lutein and zeaxanthin levels are also specificallylinked to a reduced risk of AMD. According to Shao, subjects possessing thehighest concentration of lutein and zeaxanthin in the macula were 99.9 percentless likely to have AMD relative to those with the lowest concentrations."[P]roviding lutein to humans from foods, marigold flower extract (luteinesters), or purified/crystalline lutein from marigold flowers, results insignificant increases in serum lutein and MPOD [macular pigment optical density,a marker of macular health] in normal subjects," he wrote.

Dietary carotenoids are also linked to a reduced risk ofcataract, according to researchers from the University of Southampton in England(Ophthalmology, 108, 11:1992-92, 2001) (www.aaojournal.org).Researchers assessed blood carotenoid levels in 372 men and women. The risk ofnuclear cataract was lowest in people with high plasma concentrations of alpha-caroteneor beta-carotene, while those with high plasma concentrations of lycopenedemonstrated a reduced risk of cortical cataract. Subjects with the highestlutein levels demonstrated the lowest risk of posterior subcapsular cataract.Researchers concluded that a diet rich in carotenoids may protect againstcataract development, although they suggested further research would be needed.

The plethora of information available in the scientificcommunity has apparently converted many eye doctors to becoming promoters oflutein. According to a study conducted by Cedar Rapids, Iowa-based JeffersonDavis Associates for Kemin Foods, more than 90 percent of eye doctors (of 150ophthalmologists and 150 optometrists surveyed) believe poor nutrition plays arole in the development of common eye diseases and that lutein plays animportant role in promoting eye health. The study authors also found that 84percent of eye doctors currently recommend lutein to their patients and that 80percent of these eye doctors believe regular use of lutein is helpful inmaintaining eye health. Other findings included that 89 percent of eye doctorsbelieve lutein is natural and safe, 71 percent believe consumers shouldsupplement their daily diet with lutein, and 58 percent believe that lutein isthe nutrient that best supports long-term eye health.

"I've always believed that lutein plays an important rolein promoting eye health," said Robert Abel, an ophthalmologist and memberof the Lutein Information Bureau Advisory Board. "I'm pleased to know thatmy colleagues agree. It's important to note that the overwhelming majority ofeye doctors also agree that regular use of lutein can minimize maculardegeneration."

In addition, NMI reported that lutein users show the highestbelief in the efficacy of their supplement products, and the most desire forspecific functionality. Among those who responded to NMI's Health &Wellness Trends Database, 33 percent of the general population reported thatvitamins and minerals are effective in treating certain health conditions, 35.5percent of those treating vision problems reported feeling vitamins and mineralsare effective, and 62.3 percent of lutein users reported a belief that theirsupplements are effective.

Additional Nutrients

While specific antioxidants and carotenoids have been shown toprevent the onset of deteriorative eye diseases, numerous other nutrients (someof which can also be categorized as antioxidants) can affect eye health.Deficiencies of many nutrients can cause a chain-reaction in the body, affectingenzyme systems, as well as antioxidant function, and eventually may lead to adeterioration of eye health (as well as general health).

The B vitamins, which consist of 11 water-solublenutrients, are considered coenzymes that help the body metabolize food intoenergy, synthesize antibodies for the immune system and provide support for cellfunction. Many of the B vitamins are also involved at least somewhat inmaintaining eye health, and a deficiency of any of them can lead to cataract andAMD development.

Riboflavin (vitamin B2) is a precursor to FAD (flavinadenine dinucleotide), an antioxidant found in the eye. A deficiency ofriboflavin leads to increased free radical damage in the eye and potentiallycataract formation, according to novel research on the topic (Am J Clin Nutr,34, 5:861-3, 1981) (www.ajcn.org). Another Bvitamin that is a precursor to antioxidants found in the eye is niacin(vitamin B3). Together with riboflavin, niacin can protect against cataracts (Ophthalmology,107, 3:450-6, 2000). Pantothenic acid (vitamin B5) also facilitatesantioxidant activity, reducing the risk of cataract formation.

Zinc deficiency, while difficult to assess in the eyebecause concentrations are preserved in the retina, is associated with adeterioration of retinal function (Biol Trace Elem Res, 75, 1-3:43-52,2000) (www.humanapress.com). Inaddition, zinc deficiency may result in night blindness, which is a symptom ofvitamin A deficiency as well. A study conducted with 202 Nepalese womendetermined that zinc supplementation increased serum zinc concentrations;however, this situation did not improve the women's night blindness. Whenvitamin A was added to the regimen, women were four times more likely to havetheir night vision restored (Am J Clin Nutr, 73, 6:1045-51, 2001).

One of zinc's other actions in the body is to assist thefunction of superoxide dismutase (SOD), an enzyme that is arguably thebody's most potent antioxidant. SOD function is also facilitated by copper,manganese and selenium. (SOD is sometimes referenced with these minerals:copper-SOD, zinc-SOD, manganese-SOD or selenium-SOD.)

All forms of SOD quench free radicals to moderate the agingprocess, according to researchers at Cheshire, United Kingdom-based DaresburyLaboratory (http://srs.dl.ac.uk). This actiondefines SOD's main role in the body--by quenching free radicals, the enzymepreserves cell health.

More specifically, it is thought that SOD can reduce theincidence of cataracts. Research conducted at Umea University Hospital in Swedendetermined that copper-zinc-SOD is an important free radical scavenger in thelens of the eye, and it may have a protective role in cataract formation (FreeRadic Biol Med, 31, 6:738-44, 2001) (www.elsevier.nl).In addition, researchers at the Centro de Investigaciones Biologicas in Madriddiscovered that SOD activity in red blood cells was altered in patients withcataracts (Gerontology, 47, 4:186-8, 2001) (www.karger.com/journals/ger/ger_jh.htm).

SOD is the main antioxidant found in the lens of the eye, andexposure to sunlight (specifically to UVB radiation) decreased the amount of SODfound in the cornea (Histology and Histopathology, 15, 4:1043-50, 2000) (www.hh.um.es).An early study demonstrated that SOD is critical to protecting the macula andthe lens from oxidative damage that occurs from sunlight (Curr Eye Res,3:1-2, 1984) (www.szp.swets.nl/szp/journals/ce.htm).

Aside from facilitating the body's use of SOD, seleniumis also responsible for activating the antioxidant enzyme glutathione peroxidase.Researchers from Wayne Sate University in Detroit discovered that amulti-antioxidant diet, including selenium, may inhibit the development ofdiabetic retinopathy (Diabetes, 50, 8:1938-42, 2001) (http://diabetes.diabetesjournals.org).

Botanicals

While numerous benefits to eye health can be obtained fromvitamins, minerals and enzymes, added benefits can be obtained from herbalsupplements. For example, bilberry (Vaccinium myrtillus) is knownto strengthen and protect veins and arteries, including those in the eye,thereby improving night vision and shortsightedness, according to HerbalRemedies, by Asa Hershoff, N.D., and Andrea Rotelli, N.D. (Avery Publishing,2001). In addition, Hershoff and Rotelli noted that bilberry protects the retinaagainst AMD, retinitis pigmentosa and retinal damage in diabetes, as well asreduces pressure in glaucoma and halts the progression of cataracts.

According to Herbal Medicine: Expanded Commission EMonographs (Integrative Medicine Communications, 2000), edited by MarkBlumenthal, Alicia Goldberg and Josef Brinckmann, bilberry has been studied forits ability to reduce symptoms associated with microcirculatory disorders suchas AMD, glaucoma and cataracts. "Possible mechanisms of action for[bilberry's] effects on ophthalmic conditions include its ability to protectagainst the breakdown of rhodopsin (retinal purple), a light sensitive pigmentlocated in the rods of the retina, and its ability to regnerate rhodopsin,"Blumenthal et al wrote. "It may also provide vasoprotection by decreasingcapillary fragility and permeability."

click here

In addition to AMD, cataracts and glaucoma, Blumenthal et almentioned research in which bilberry was studied for its effects on visionacuity in dim light, on patients with pigmentary retinitis when taken withbeta-carotene, on night vision in normal subjects, on patients with diabeticretinopathy when taken in combination with beta-carotene, on patients withsignificant diminished vision in bright light (hemeralopia) and on patients withretinal inflammation. Herbal Medicine also described bilberry'scapillarotropic activity in patients with various retinopathies, myopia,glaucoma, retinitis pigmentosa, and diabetic or hypertensive retinopathy, aswell as its effects on cataract formation in patients with senile corticalcataracts when taken in combination with vitamin E.

Grape seed extract, a well-known antioxidant, is also applicablein the realm of eye health. Grape seed extract contains procyanidins, whichstrengthen retinal capillaries to increase night vision, as well as deter eyeaging, according to Hershoff and Rotelli. Grape seed extract can also protecteyes from damage from exposure to UV radiation, as well as prevent and treatdiabetic retinopathy and arteriosclerosis in the eye.

Coleus forskohlii, sometimes called makandi, is an herb thatoriginated in India and has been used in Ayurveda for hundreds of years.According to Hershoff and Rotelli, Coleus can increase blood flow inside the eyeto decrease pressure. Forskolin (an extract from Coleus forskohlii) hasbeen used topically in human and animal studies to diminish intraocularpressure, a characterizing symptom of glaucoma (Alt Med Rev, 6, 2:141-66,2001).

Eyebright (Euphrasia officinalis) is another herb usedfor diseases of the eye. According to Hershoff and Rotelli, eyebright iseffective for conjunctivitis or eye irritation and inflammation from pollutants,allergies, cold and flu, measles and other conditions. Eyebright can relieve theeffects of eyestrain and bright lights, and has been known to soothe and healbloodshot, burning or itching eyes. In addition, eyebright can reduce lightsensitivity, the presence of sticky eye gum and acrid yellow discharges. It isused both internally and as drops.

Ginkgo biloba is well known for its ability to increasecirculation, and has been cited as an herb to avoid before going in to surgery.However, because of its circulatory effect, ginkgo is thought to increase theflow of nutrients and oxygen to the eye. In addition, ginkgo can prevent freeradical damage, protect eye capillaries and clear toxins, according to Hershoffand Rotelli. They also noted that ginkgo can be used in retinopathy, cataracts,AMD and glaucoma.

The realm of eye health is infinitely complex, with variousvitamins and minerals responsible for the maintenance of enzyme and antioxidantsystems. Nutrient deficiencies can produce a spiral effect, leading to aweakened antioxidant defense, as well as the possibility of developing any oneof a number of eye conditions. For this reason, proper nutrition is integral inpreserving healthy vision, as well as general body maintenance, and herbalproducts and other nutrients can be used as supplements to enhance eye health.Consumers can rest assured that sticking to a doctor-approved regimen ofnutrients and botanicals can sustain healthy vision for a lifetime.