The health of the body is often reflected in the eyes. Circulatory problems, which are hidden elsewhere in the body, can manifest visibly in these organs. Similarly, the antioxidant status of the aging body often will have a profound effect upon the eyes. Age-related macular degeneration (AMD, a deterioration in the retina at the point at which images are focused) is a typical result of the aging process, as the formation of cataracts (opaque defects in the transparency of the lens of the eye). Prevent Blindness America estimates that AMD may affect 13 million individuals in this country. Cataracts impair the vision of roughly four million Americans. Some authorities estimate that thirty percent of all adults aged 70 and older suffer from some form of vision impairment.
Diet, through its effects upon antioxidant status, may play a significant role in these age-related degenerations. Indeed, the eyes are especially prone to certain types of oxidative damage. In one study of 40 to 70 year olds, for instance, those who consumed fewer than 3.5 servings of fruits and vegetables per day had five times the risk for developing one type of cataract and 13 times the risk for developing another type of cataract when compared to those who ate more than 3.5 servings of fruits and vegetables daily.1 Hence, a prudent plan would be to use diet and supplements to insure the intake of a comprehensive combination of nutrients which support the various aspects of visual functioning and which help to maintain optimal ocular antioxidant status.
LUTEIN AND ZEAXANTHIN, EYE SAVERS?
Lutein and zeaxanthin are important antioxidants used by the body for a number of physiological functions. Of all the currently recommended nutrients for the eyes, these have perhaps received the widest general endorsement. They are found in a variety of foods and now are also available in significant amounts in supplemental form.
Lutein is a carotenoid, which does not supply vitamin A activity to the body. It is chemically distinctive in that it lacks part of the terminal “ring” structure of the other carotenoids. Like its close relative zeaxanthin, lutein is what is termed a xanthophyll carotenoid. Both of these related carotenoids are better antioxidants than is beta-carotene under normal oxygen conditions. Lutein is the more important of the two. According to Optometry (the Journal of the American Optometric Association), “Lutein can be metabolized into zeaxanthin and is therefore the more essential carotenoid.” Zeaxanthin has been shown to be present in the center of the macula. Lutein and zeaxanthin are usually found together in leafy green vegetables, such as kale, broccoli, spinach and mustard greens.
One of the primary functions of lutein and zeaxanthin is to provide protection against oxidative and free radical damage. These yellow-colored carotenoids are found in high concentrations within the macula lutea (the yellow spot in the center of the retina) and in smaller amounts throughout the retina and the eye lens. They are also concentrated in the skin, breast and cervical tissues. These stores, however, appear to diminish at an increasing rate with age if not regularly replenished through dietary means.
FOOD SOURCES OF LUTEIN
Vegetable (1/2 cup serving)
Lutein Content (mg)
Source: Journal of the American Dietetic Association 1993:284-95
LUTEIN/ZEAXANTHIN AND THE AMD CONNECTION
Age-related macular degeneration (AMD) is the leading cause of irreversible blindness in people over age 65. The exact cause of AMD is not yet known, although the protective role of nutrition against the condition is being researched at major universities and other institutions. A study published in the Journal of the American Medical Association concluded that a daily intake of six mg per day of lutein led to a 43 percent lower risk of developing AMD.2
Scientists believe that lutein and zeaxanthin contribute to the density of macular pigment3—the component of the retina of the eye which typically absorbs and filters out 40 to 60 percent of damaging near-ultraviolet blue light (near-UV blue light) which strikes the retina. The denser the pigment, the more the inner retina is protected from light-induced damage. Lutein/ zeaxanthin also helps limit blue light damage to the inner retina by inhibiting lipid peroxidation and by neutralizing free radicals.
LUTEIN/ZEAXANTHIN AND HEALTH OF THE EYE LENS
Considerable evidence shows the importance of lutein and zeaxanthin in reducing changes in the opacity of the eye lens as we age. A study published in the British Medical Journal examined cataract formation among 50,000 women over an eight-year period.4 The results clearly showed that the consumption of spinach, which is an excellent source of lutein and zeaxanthin, led to a much lower level of such eye lens changes than did the consumption of other vegetables, such as carrots, sweet potatoes and winter squash, which contain primarily betacarotene and very little lutein. Similarly, according to a study published in the Journal of the American Medical Association, people who eat foods rich in lutein—particularly kale and spinach—are less likely to develop macular degeneration.5 The intake of carotenoids other than beta-carotene, that is, alpha-carotene, lutein and lycopene, has been inversely correlated with the risk of developing cataracts. In other words, the more alpha-carotene, lutein and lycopene consumed, the lower the incidence of cataracts.6 Protection most likely comes from the scavenging of free radicals. Oxidative/free radical damage to the eye lens is believed to play an important part in the development of cataracts. Lutein/zeaxanthin prevent peroxidation in the lens, thus limiting damage to the opacity of this tissue. However, there is no evidence that lutein/ zeaxanthin can help to reverse an existing cataract.
BILBERRY: FOOD FOR THE EYES
Another food that has an especially strong affinity for the eyes is bilberry. The bilberry (Vaccinium myrtillus) is a close relative of American blueberry. It grows in Northern Europe, Canada, and in parts of the Northern United States, where the berries are known as huckleberries. There are over 100 species with similar names and fruit. The English call bilberries whortleberries. The Scots know them as blaeberries.
The bilberry has many historical or traditional uses based upon both the dried berries and the leaves. It has been used as a medicinal herb since the 16th century. Modern interest in the bilberry is partly based on the fruit’s use by British pilots during the Second World War. These pilots noticed that their night vision improved when they ate bilberry jam prior to night bombing raids. In the intervening years, scientists discovered that anthocyanosides, the bioflavonoid complex in bilberries, are potent antioxidants.7 Many of the traditionally suggested uses of bilberry, such as against scurvy and urinary tract complaints, no doubt reflect the antioxidant, vitamin C-sparing and anti-inflammatory properties of the berry. However, the astringent qualities of the dried bilberry fruit and of bilberry tea also may provide some benefits and help to explain the use of these in folk medicine to soothe the gastrointestinal tract.8 In Europe, bilberry extracts are accepted conventionally as a normal part of health care for the eyes.
Much of the modern research on bilberry extract has focused upon the benefits to the eyes. Bilberry anthcyanosides provide three primary benefits to these organs. First, these highly colored plant pigments nourish the retina. Night vision depends upon the retina’s ability to constantly regenerate visual purple (rhodopsin), and anthocyanosides serve as “building blocks” for this important substance. Tests have confirmed these benefits. When subjects with normal vision supplemented with bilberry extract, it was found that the acuity of their nighttime vision improved, as did the speed at which they adjusted to darkness and the rate at which they recovered from blinding glare.9,10 After reviewing the literature, some authors have suggested that bilberry extract provides benefits even in cases of myopia.11 These findings may reflect the importance of visual purple for visual acuity in general.
The benefits of bilberry anthcyanosides extend beyond the regeneration of visual purple, however. The eye depends upon a very high relative blood flow and is exposed to large amounts of oxygen. Such factors mean that the eye is extremely vulnerable to problems arising from capillary fragility and that prevention of damage by free radicals plays a major role in maintaining eye health. In Europe, bilberry extracts are widely supplemented by individuals who are known to be subject to eye capillary permeability and retinopathy. The expected benefit is improved integrity of the collagen that is integral to the support structure of the capillaries.12
Similarly, several types of deterioration, which are typical of aging eyes, such as cataracts and macular degeneration, appear to be influenced by the rate of generation of free radicals. In laboratory trials, changing the diets from commercial laboratory chow to "well-defined" diets rich in flavonoids has been shown to be beneficial.13,14 Interesting results have been found with human trials in which bilberry extract was supplemented, either alone or in combination with vitamin E.15,16
GRAPE SEED EXTRACT AND GINKGO BILOBA EXTRACT
Both grape seed extract and Ginkgo biloba extract enhance the circulatory health of the eyes. Grape seed extract has been studied very widely for it ability to reduce capillary fragility and excessive permeability.18 It benefits to the circulatory system are not in doubt; nor are its antioxidant benefits. Somewhat surprising, however, are grape seed extract's benefit with regard to recovery from glare, an important aspect of night vision. It now appears that grape seed extract complements the benefits in the area of night vision that are found with bilberry.
As is true of the Chinese herbal tradition, the Indian Ayurvedic healing tradition associates Ginkgo with long life. Modern Western research supports these beliefs from two ancient healing traditions and has led to Ginkgo biloba extract becoming one of the most widely used of all herbal products.19 The extract often is recommended for improving memory and reaction time20, for improving circulation21, and for protecting against free radical damage. Ginkgo biloba also is suggested in traditional practices for improving the physiologic effects of other herbs and nutrients.
SUPPORTING ANTIOXIDANT AND GLUCOSE METABOLISM
The eyes are particularly vulnerable to certain of the long-term effects of poor blood sugar control. As is true of the nerves, the eyes can be damaged by the products of the enzyme known as aldose reductase. Poor control of blood sugar levels also places the tissues of the body under oxidative stress. Blood glucose-related vulnerabilities need to be taken into account when considering eye health. Alpha-lipoic acid has been shown to be a potent antioxidant for the eye in both cataract22 and glaucoma.23 It is complemented in these actions by the flavonoid quercitin, an inhibitor of the actions of aldose reductase.
The eyes are vulnerable organs, but deterioration can be protected against to a remarkable degree through sound dietary practices. Dark green vegetables and fruits in shades of blue, purple and red can be highly protective. The secret is to consume these items daily, or at least several times per week. A judicious use of special herbs and other supplements will complement—not substitute for—these dietary measures.
- Jacques PF, Chylack LT Jr. Epidemiologic evidence of a role for the antioxidant vitamins and carotenoids in cataract prevention. Am J Clin Nutr. 1991 Jan;53(1 Suppl):352S-355S.
- Seddon JM, Ajani UA, Sperduto RD, Hiller R, Blair N, Burton TC, Farber MD, Gragoudas ES, Haller J, Miller DT, et al. Dietary carotenoids, vitamins A, C, and E, and advanced age-related macular degeneration. Eye Disease Case-Control Study Group. JAMA. 1994 Nov 9;272(18):1413.20.
- Johnson EJ, Hammond BR, Yeum KJ, Qin J, Wang XD, Castaneda C, Snodderly DM, Russell RM. Relation among serum and tissue concentrations of lutein and zeaxanthin and macular pigment density. Am J Clin Nutr. 2000 Jun;71(6):1555.62.
- 4 Hankinson SE, Stampfer MJ, Seddon JM, Colditz GA, Rosner B, Speizer FE, Willett WC. Nutrient intake and cataract extraction in women: a prospective study. BMJ. 1992 Aug 8;305(6849):335.9.
- Seddon JM, Ajani UA, Sperduto RD, Hiller R, Blair N, Burton TC, Farber MD, Gragoudas ES, Haller J, Miller DT, et al. Dietary carotenoids, vitamins A, C, and E, and advanced age-related macular degeneration. Eye Disease Case-Control Study Group. JAMA. 1994 Nov 9;272(18):1413. 20; Jacques PF. The potential preventive effects of vitamins for cataract and age-related macular degeneration. Int J Vitam Nutr Res. 1999 May;69(3):198.205.
- Mares-Perlman JA, Brady WE, Klein BE, Klein R, Haus GJ, Palta M, Ritter LL, Shoff SM. Diet and nuclear lens opacities. Am J Epidemiol. 1995 Feb 15;141(4):322.34.
- Salvayre R, Braquet P, et al. Comparison of the scavenger effect of bilberry anthocyanosides with various flavonoids. Proceed Int'l Bioflavonoids Symposium, Munich, 1981, 437.42.
- Grieve M. A Modern Herbal, vol. 1. (New York: Dover Publications, 1971)385.6.
- Jayle GE, Aubert L. Action des glucosides d'anthocyanes sur la vision scotopique et mesopique du sujet normal. Thereapie 1964;19:171.85.
- Caselli L. Clinical and electroretinographic study on activity of anthocyanosides. Arch Med Int 1985;37:29.35.
- Mowrey D. Next Generation Herbal Medicine. (Comorant Books, 1988)15ff.
- Mian E, et al. Anthocyanosides and the walls of microvessels: Further aspects of the mechanism of action of their protective effect in syndromes due to abnormal capillary fragility. Minerva Med 1977;68:3565.81.
- Hess H, et al. Dietary prevention of cataracts in the pink-eyed RCS rat. Lab Anim Sci 1985;35:47.53.
- Pautler EL, et al. A pharmacologically potent natural product in the bovine retina. Exp Eye Res 1986;42:285.8.
- Bravetti G. Preventive medical treatment of senile cataract with vitamin E and anthocyanosides: Clinical evaluation. Ann Ottamol Clin Ocul 1989;115:109.
- Scharrer A, Ober M. Anthocyanosides in the treatment of retinopathies. Klin Monatsbl Augenheilkd 1981;178:386.9.
- Delacrois P. Double-blind study of Endotelon in chronic venous insufficiency. La Revue De Med. 1981;27:28.31.
- Boissin JP, Corbe C, Siou A. [Chorioretinal circulation and dazzling: use of procyanidolic oligomers (Endotelon)]. Bull Soc Ophtalmol Fr. 1988;88(2):173-4, 177.9. [French text]
- Castleman M. The Healing Herbs (Rodale Press, 1991).
- Schmidt U, Rabinovici K, Lande S. Enfluss eines Ginkgo biloba Specialextraktes auf doe befomdlickeit bei zerebraler Onsufficizienz. Muench Med Wochenschr 1991;133( Suppl. 1): S15-S18.
- Ernst E. Pentoxifylline for intermittent claudication. A critical review. Angiology 1994 ;45: 339.45.
- Maitra I, Serbinova E, Trischler H, Packer L. Alpha-lipoic acid prevents buthionine sulfoximine-induced cataract formation in newborn rats. Free Radic Biol Med. 1995 Apr;18:823.9.
- Filina AA, Davydova NG, Endrikhovskii SN, Shamshinova AM. [Lipoic acid as a means of metabolic therapy of open-angle glaucoma] Vestn Oftalmol 1995 Oct-Dec.;111 : 6.8.