A New Look at Eye Health

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From The April 2001 Issue of Nutrition Science News

A New Look at Eye Health

By Bill Sardi

 

Many people with deteriorating vision are seeing nutritional therapy as a

successful alternative to conventional medicine or surgery. An example is

Mildred Frank of Ormond Beach, Fla., who experienced a dramatic improvement in

her vision that was not the result of lasers or lens implants. Her vision

improvement began with a can of kale.

 

Frank had two retinal disorders: macular degeneration, which is the loss of

central vision, and retinitis pigmentosa (RP), which initially manifests as

night blindness and progresses to a permanently constricted field of vision.

Frank's friend said kale might help resolve her eye troubles, so she began

eating a can of cooked kale a day. Within weeks she noticed some improvement in

her vision.

 

Although anecdotal, Frank's success with nutritional therapy isn't

unprecedented. The journal Optometry recently reported on 16 night-blind

patients with retinitis pigmentosa who took 40 mg/day lutein for nine weeks and

20 mg/day for 17 additional weeks. Ten of the participants also took 500 mg/day

docosahexaenoic acid (DHA), an essential component of retinal light-receptor

cells, along with a vitamin B complex and digestive enzymes for the entire

26-week study. Although the research was a preliminary pilot study, with no

placebo controls, improvements reportedly began two to four weeks after

supplementation started and plateaued at six to 14 weeks. Visual acuity gains

were four times greater in blue-eyed people compared to those with dark eyes.1

 

Vision researchers recognize that lutein and zeaxanthin—plant pigments plentiful

in collards, kale, mustard greens and spinach—play important roles in

maintaining a healthy visual system. Lutein supplements have been available

since 1995; commercially, it is extracted from marigold flower petals. A

February 2001 study between Johns Hopkins University and the Chinese University

of Hong Kong indicates a new rich source of zeaxanthin with traces of lutein is

an extract of the berry of Fructus Lycii (Lycium barbarum).2

 

Lutein and zeaxanthin work because they act like sunglass filters to protect the

retina. The retina, about the size of a postage stamp, contains millions of

light receptor cells. Normal, healthy retinas exhibit a yellow spot in their

visual center, the macula. Lutein and zeaxanthin are concentrated in the central

retina, overlying the macula, a pinpoint-wide zone where color vision and

central vision is produced. Yellow pigmentation of the central retina of animals

disappears when lutein and zeaxanthin pigments are removed from the diet.3

 

Both types of carotenoids—the carotenes such as beta-carotene and the

xanthophylls such as lutein and zeaxanthin—are essential to maintain human

vision. Beta-carotene converts to vitamin A in the liver and then travels to the

retina where it is converted into rhodopsin, the night-vision chemical. Intense

sunlight exposure can bleach out rhodopsin from the night-vision cells (called

rods) during the day and prolong visual adaptation at dusk.

 

Foods such as cantaloupe, carrots, sweet potato, yams and yellow squash are rich

in beta-carotene but provide no lutein. Dark-green leafy vegetables such as

collards, kale, mustard greens and spinach are rich sources of beta-carotene as

well as lutein and zeaxanthin. Blue-eyed individuals need more lutein and

zeaxanthin because they have less of these protective pigments in their retinas.

 

Although kale therapy is far from mainstream, researchers are observing

connections between nutrition and macular degeneration, cataracts, and glaucoma.

 

Reverse Macular Degeneration?

Most patients with macular degeneration are given a poor prognosis for their

failing central vision. This has been changing slowly since a 1994 report showed

that the equivalent of 6 mg lutein/day obtained from a diet rich in dark-green

leafy vegetables significantly reduces the risk of advanced macular

degeneration.4 In a pilot study with 14 patients at the North Chicago Veterans

Medical Center, Stuart Richer, O.D., Ph.D., showed that blind spots, the ability

to see shades of gray (contrast), and even visual acuity can be improved in the

short-term by eating a three-quarters portion of dark-green leafy vegetables

daily along with either 5 oz. spinach four to seven times a week or a

lutein-based antioxidant.5 Richer is now comparing a group taking 10 mg

lutein/day against another group taking lutein plus mixed supplemental

antioxidants.

 

Researchers at the Schapens Eye Research Institute in Boston report that

60-year-olds with normal levels of lutein and zeaxanthin in their retinas

exhibit the visual sensitivity of 20-year-olds.6

 

Lutein and zeaxanthin are not limited to protective roles in the retina only.

They may also prevent cataracts, a cloudy focusing lens, and glaucoma, an optic

nerve disease.

 

Protect Against Cataracts

The focusing lens of the human eye, about the size of an aspirin tablet, is the

only organ that never sheds a cell. It receives nutrients indirectly via the

aqueous fluid rather than the bloodstream. The lens of the eye is under unusual

stress because it is exposed to constant bombardment by solar ultraviolet

radiation through the transparent cornea. In order to maintain lens transparency

and thus clarity, the protective antioxidant levels in the aqueous fluid of the

eye must be higher than in the blood plasma.7 The lens loses about 1 percent of

its transparency each year, so if a person lives long enough, he or she will

likely develop cloudy cataracts. But sufficient data exist that nutritional

therapy may help prevent cataracts.

 

In 1990, James Robertson, of the Department of Epidemiology at the University of

Western Ontario in Canada, compared adults with cataracts to those without. He

found that taking 300 to 600 mg supplemental vitamin C reduced cataract risk by

70 percent and 400 IU supplemental vitamin E for more than a year reduced

cataract risk by 50 percent.8

 

The focusing lens is also sensitive to high blood-sugar levels, which can cause

inflammation, vision changes and eventually diabetic cataracts. Sugar can

oxidize and harden in the lens, a destructive process among diabetics that can

be countered by nutrients such as inositol.9 Sulfur-bearing amino acids, such as

taurine, can help to prevent diabetic cataracts.10 Bioflavonoids such as

quercetin are known to inhibit the enzyme that promotes diabetic cataracts.11

 

Diet plays a significant role in cataract risk. One study found that individuals

who consume the highest amounts of butter and salt have double the cataract risk

compared to those who consume the lowest amounts of these foods, while spinach,

peppers, melons, tomatoes and citrus fruits halve the relative risk of needing

cataract surgery.12 Individuals who do not eat five servings of fruits and

vegetables per day are 5 to 13 times more likely to develop cataracts.

Insufficient dietary vitamin C intake also dramatically increases cataract risk

4 to 11 times.13 The typical American diet provides about 110 mg/day of vitamin

C, but the minimum amount of vitamin C required to prevent cataracts is closer

to 300 mg/day—about five oranges.14,15 It is unlikely that consumers will eat

this much fruit, so vitamin C supplements are often more practical.

 

The potential to delay or avoid cataract surgery with lutein and zeaxanthin

became evident in 1992. A prospective study at Harvard Medical School in Boston

surveyed 50,828 nurses and found women who consumed spinach five or more times

per week, as well as those who took vitamin C supplements for 10 years or more,

reduced their risk of cataract extraction by more than 45 percent.16 Although

other carotenoids in spinach could have been at work, this study suggests the

benefits of dietary lutein and zeaxanthin.

 

Nutrition and Glaucoma

For decades, eye doctors have approached glaucoma as a loss of peripheral vision

resulting from optic nerve damage caused by elevated fluid pressure in the eye.

However, eyes with normal fluid pressure can also lose peripheral vision. Now

researchers suspect a nerve toxin may be involved in the common form of

glaucoma. Glaucoma patients exhibit an abnormally high concentration of

glutamate in the vicinity of the optic nerve.17 Glutamate is a primary chemical

used in the transmission of optic nerve impulses. Housed inside the nerve

sheath, it is innocuous. As optic nerves die off at a normal rate and release

small amounts of glutamate, surrounding Muller cells detoxify the area. But

glutamate may overwhelm the Muller cells and destroy surrounding cells, thus

releasing more nerve-toxic glutamate, resulting in an accelerated loss of vision

that is typically observed in the end stages of glaucoma.

 

While nerve-protective drugs may take years to develop, an array of natural

nerve protectors may be able to minimize glutamate toxicity. These include

vitamin B12 (methylcobalamin),<18 SAMe (S-adenosylmethionine),18 ginkgo (Ginkgo

biloba),19 vitamin E,19 coenzyme Q10,19 folic acid,20 and magnesium.21

Japanese researchers prescribed 28 glaucoma patients a high oral-dose of 1,500

mcg/day vitamin B12 for five years in an open-label study to evaluate the

vitamin's influence on vision. The patients receiving B12 experienced less

measurable loss of peripheral vision, more stable visual acuity, and better

control of eye fluid pressure compared to a group that did not take B12.22 The

effects of vitamin B12 are attributed to the preservation of myelin, which

insulates nerve cells. Results of this study were achieved with methylcobalamin,

a readily absorbable form of vitamin B12.

 

Cyanocobalamin, the more common form of vitamin B12 present in vitamin

supplements, has not been effective in other studies of optic nerve disorders.23

 

Various studies reveal that Greenland Eskimos have lower rates of glaucoma than

other Caucasian populations, an observation attributed to the consumption of

omega-3 fish oil. Omega-3 fats appear to help prevent optic nerve disorders. A

proprietary combination of DHA-rich fish oil, vitamin E, and vitamin B complex

widened the visual field of 30 glaucoma patients within 90 days in an

open-label, nonrandomized study.24

 

In animal studies, researchers were able to lower ocular fluid pressure, a

measure of glaucoma, by injecting a very large dose of 0.2 mL/day cod liver oil.

Reduction was from 21 mmHg to 18, with injections of 1 mL/day lowering pressure

to 14.5 mmHg.25

 

There is also evidence that lutein and zeaxanthin also help protect the optic

nerve. The nerve layer of the retina, near where nerve cells exit the eye and

connect to the brain, is protected from oxidative damage by lutein. Researchers

have found that a lack of lutein in this nerve bundle may be an early sign of

glaucoma.26

 

Other Eye Disorders

The aqueous fluid in the eye delivers antioxidants to the front of the inner

eye, which helps to keep the fluid drain unobstructed. This fluid drains out of

the eye in a controlled manner that maintains the shape and fluid pressure

inside the eye. When drainage is blocked, fluid pressure rises and can impinge

upon peripheral optic nerve cells at the back of the eye, narrowing side vision.

 

Glucosamine sulfate and vitamin C may counter fluid drain swelling. In a

preliminary, uncontrolled 1998 U.S. pilot study of two patients, an unreported

daily amount of glucosamine sulfate substantially reduced abnormally high fluid

pressure over the short term.27 Vitamin C may help by maintaining the collagen

structure of the fluid drain. 28,29 Taking 500 mg vitamin C four times a day

moderately and significantly reduces eye fluid pressure in humans.30,31 Typical

recommended dosages of glucosamine for collagen support are 1,500 mg/day.

 

Dry eye, which causes eye redness, itching, and burning, can be bothersome. It

is common among women and is often accompanied by dry skin and brittle nails.

Essential fatty acids (1,500 mg/day) derived from evening primrose, borage or

black currant seed, combined with vitamin B6 (50 & shy;75 mg/day) and vitamin C

(375 & shy;1,000 mg/day), have been shown to improve tear production and provide

symptomatic relief.32

 

With advancing age, the likelihood of macular degeneration, cataracts, and

glaucoma increases. The baby boomers will soon swell the population of retirees

in the United States, with inevitable increases in eye disease and sight loss.

The best answer to stem the tide of age-related vision problems is prevention.

Nutrition tops the list of preventive measures for age-related eye disorders.

 

Sidebars:

Glutathione: The Eye Healer Within

 

 

Bill Sardi, president of Knowledge of Health in San Dimas, Calif, is a health

journalist.

 

References

 

1. Dagnelie G, et al. Lutein improves visual function in some patients with

retinal degeneration: a pilot study via the Internet. Optometry 2000;71:147-64.

 

2. Leung IY, et al. Absorption and tissue distribution of zeathanthin and lutein

in Rhesus Monkeys after taking fructus lycii (GouQiZi) extract. IOVS 2001

Feb;42(2):466-71.

 

3. Malinow MR, et al. Diet-related macular anomalies in monkeys. Inv Oph

1980;19:857-63.

 

4. Seddon JM, et al. Dietary carotenoids, vitamins A, C, and E, and advanced

age-related macular degeneration. J Am Med Assoc 1994;272:1413-20.

 

5. Richer S. Part II: ARMD—pilot case series environmental intervention data. J

Am Optom Assoc 1999;70:24-47.

 

6. Hammond BR, et al. Preservation of visual sensitivity of older subjects:

association with macular pigment density. Inv Ophthamol 1998;39:397-406.

 

7. Stahl E, et al. Regulation of glutathione level in venous plasma and aqueous

humor in cataracta senilis provecta. Ophthalmologe 1996;93:54-8.

 

8. Robertson JM. Cataract prevention: time for a clinical trial. Br J Clin Pract

1990;44:475-6.

 

9. Ramakrishnan S, et al. Two new functions of inositol in the eye lens:

antioxidation and antiglycation and possible mechanisms. Ind J Biochem Biophys

1999;36:129-33.

 

10. Devamanoharan PS, et al. Prevention of lens protein glycation by taurine.

Mol Cell Biochem 1997;177:245-50.

 

11. Varma SD, Kinoshita KH. Inhibition of lens aldose reductase by

flavonoids—their possible role in the prevention of diabetic cataracts. Biochem

Pharm 1976;25:2505-13.

 

12. Tavani A, et al. Food and nutrient intake and risk of cataract. Ann

Epidemiol 1996;6:41-6.

 

13. Jacques PF, Chylack LT. Epidemiological evidence of a role for the

antioxidant vitamins and carotenoids in cataract prevention. Am J Clin Nutr

1991;53:352S-5S.

 

14. Taylor A. Cataract and macular degeneration: relationship to long-term

ascorbate intake. Clin Chem 1993;39:1305.

 

15. Jacques PF, et al. Long-term vitamin C supplement use and prevalence of

early age-related lens opacities. Am J Clin Nutr 1997;66:911-6.

 

16. Hankinson SE, et al. Nutrient intake and cataract extraction in women: a

prospective study. Br Med J 1992;305:335-9.

 

17. Dreyer EB, et al. Elevated glutamate levels in the vitreous body of humans

and monkeys with glaucoma. Arch Ophthamol 1996;114:299-305.

 

18. Akaike A, et al. Protective effects of a vitamin B12 analog,

methylcobalamin, against glutamate cytotoxicity in cultured cortical neurons.

Eur J Pharm 1993;241:1-6.

 

19. Ritch R. Neuroprotection: is it already applicable to glaucoma therapy? Curr

Opinion Ophthamol 2000;11:78-84.

 

20. Sattayasai J, Ehrlich D. Folic acid protects chick retinal neurons against

the neurotoxic action of excitatory amino acids. Exp Eye Res 1987;44:523-35.

 

21. Reynolds IJ. Intracellular calcium and magnesium, critical determinants of

excitotoxicity. Prog Brain Res 1998;116:225-43.

 

22. Sakai T, et al. Effect of long-term treatment of glaucoma with vitamin B12.

Glaucoma 1992;14:167-70.

 

23. Foulds WS, et al. The optic neuropathy of pernicious anemia. Arch Oph

1969;82:427-32.

 

24. Cellini M, et al. Fatty acid use in glaucomatous optic neuropathy treatment.

Acta Oph Scand 1998;227:41-2.

 

25. Mancino M, et al. A comparative study between cod liver oil and liquid lard

intake on intraocular pressure on rabbits. Prost Leuko Ess Fatty Acids

1992;45:239-43.

 

26. Schweitzer D, et al. Spectrometric investigations in ocular hypertension and

early stages of primary open angle glaucoma and of low tension

glaucoma—multisubstance analysis. Int Ophthamol 1992;16:251-7.

 

27. McCarty MF. Primary open angle glaucoma may be a hyaluronic acid deficiency

disease: potential for glucosamine in prevention and therapy. Med Hypoth

1998;51:483-4.

 

28. Higginbotham E, et al. Effects of ascorbic acid on trabecular meshwork cells

in culture. Exp Eye Res 1988;46:507-16.

 

29. Chang S, et al. Effects of ascorbic acid on the production of firbonectin

laminin and collagen type I by bovine trabecular meshwork cells in organ

culture. Inv Ophthamol 1994;35:Arvo Abstracts.

 

30. Linner E. The pressure lowering effect of ascorbic acid in ocular

hypertension. Acta Ophthamol 1969;47:685-9.

 

31. Fishbein SL, Goodstein S. The pressure lowering effect of ascorbic acid. Ann

Ophthamol 1972 Jun:487-9.

 

32. Giuffrida S, et al. Essential fatty acids (linoleic and gamma-linolenic

acids) on tear deficient dry-eye treatment. Inv Ophthamol 2000;41:Arvo Abstract

1447.

 

 

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