HOCUS-FOCUS CAN DIET PROTECT OUR EYES?It seems like magic. Our eyes transform light into nerve signals that somehow tell our brains what we see. But as we get older, the magic often starts to fade. One out of two Americans aged 65 or older has a cataract cataract, in medicine, opacity of the lens of the eye, which impairs vision. In the young, cataracts are generally congenital or hereditary; later they are usually the result of degenerative changes brought on by aging or systemic disease (diabetes). , or cloudiness in the eye's lens. Cataracts Cataracts Definition A cataract is a cloudiness or opacity in the normally transparent crystalline lens of the eye. This cloudiness can cause a decrease in vision and may lead to eventual blindness. impair the vision of roughly 3.3 million people. Surgery to remove cataracts costs $1.5 billion a year. Age-related macular degeneration Age-related macular degeneration (ARMD) Degeneration of the macula (the central part of the retina where the rods and cones are most dense) that leads to loss of central vision in people over 60. (AMD (Advanced Micro Devices, Inc., Sunnyvale, CA, www.amd.com) A major manufacturer of semiconductor devices including x86-compatible CPUs, embedded processors, flash memories, programmable logic devices and networking chips. ) is a breakdown of the center of the retina--the macula. One out of four people aged 65 or older has early signs of AMD. It's the leading cause of new cases of blindness in that age group. Is declining eyesight inevitable, or can antioxidants Antioxidants Substances that reduce the damage of the highly reactive free radicals that are the byproducts of the cells. Mentioned in: Aging, Nutritional Supplements antioxidants, n. like lutein lutein /lu·te·in/ (-in) 1. a lipochrome from the corpus luteum, fat cells, and egg yolk. 2. any lipochrome. lu·te·in n. 1. and vitamin C vitamin C or ascorbic acid Water-soluble organic compound important in animal metabolism. Most animals produce it in their bodies, but humans, other primates, and guinea pigs need it in the diet to prevent scurvy. and E --and possibly zinc or fish or omega-3 fats--keep our eyes from failing? Cataracts Q: What are cataracts? A: They are an increased cloudiness in the middle or in the back of the lens [see illustration]. Cloudiness distorts the light rays that enter the eye, which leads to blurred vision. [ILLUSTRATION OMITTED] Q: And the only treatment is surgery? A: Yes. The last time somebody counted, cataract surgery Cataract Surgery Definition Cataract surgery is a procedure performed to remove a cloudy lens from the eye; usually an intraocular lens is implanted at the same time. Purpose The purpose of cataract surgery is to restore clear vision. was the largest single item in the Medicare expenditure budget. And as the population ages, cataract surgery will become an even greater burden because the number of people over 75 will triple over the next 50 years. If we could delay a person's need for cataract surgery by ten years through preventive measures, we could cut in half the number of yearly cataract surgeries. Q: Does vision continue to decline until the surgery? A: Yes. And some people can't afford to have cataracts removed or simply aren't connected to the health-care system. Educated people of higher incomes tend to have their cataracts removed, but others may go around for many years unable to see clearly. Q: What are the risk factors for cataracts? A: Age is the strongest. Genetics is probably involved. And exposure to ultraviolet light--sunshine--may increase the risk. Smoking and diabetes also increase the risk for some types of cataract. Q: Can nutrients prevent cataracts? A: The evidence is strongest for antioxidants like vitamins E and C and for two carotenoids--lutein and zeaxanthin. But we're still in the early stages of investigating those links. People who eat healthy diets often have high intakes of many nutrients. And people who take supplements generally also eat diets that are richer in a variety of nutrients. So it's hard to know which of the nutrients they consume account for their lower risk. Q: How might antioxidants protect the eye? A: We know that oxidative damage from light produces free radicals that can cause cloudiness in the lens. Antioxidants may protect against oxidative damage by acting as scavengers for the free radicals. Another way to prevent a cataract is to repair the oxidative damage, but there is no machinery to repair the nucleus of the lens. That's why antioxidants may help. Q: What's the link between vitamin E vitamin E or tocopherol Fat-soluble organic compound found principally in certain plant oils and leaves of green vegetables. Vitamin E acts as an antioxidant in body tissues and may prolong life by slowing oxidative destruction of membranes. and the eye? A: Vitamin E is found in the lens, and it can slow the rate at which animals get cataracts. Some studies--like the Baltimore Longitudinal Study longitudinal study a chronological study in epidemiology which attempts to establish a relationship between an antecedent cause and a subsequent effect. See also cohort study. of Aging, the Lens Opacities Case-Control Study case-control study, n an investigation employing an epidemiologic approach in which previously existing incidents of a medical condition are used in lieu of gathering new information from a randomized population. , and the Beaver Dam Beaver Dam, city (1990 pop. 14,196), Dodge co., SE Wis., on Beaver Dam Lake, in a productive farm and dairy area; inc. 1856. Industries included food processing, metal and metal products fabrication, printing, and machinery manufacturing. Eye Study--find higher rates of cataracts among people who get little vitamin E from their food or from supplements or who have low levels of E in their blood. But the data are inconsistent. Q: What's the evidence for vitamin C? A: Levels of vitamin C in the lens are higher than levels in the blood. And we can increase vitamin C in the lens with supplements. In animal studies, higher levels of vitamin C protect against lens damage. In humans, an increasing body of evidence indicates that vitamin C protects against cataracts. For example, in a study of 247 nurses, the prevalence of early cataracts was 77 percent lower in women who took vitamin C supplements for at least ten years. But we still don't know Don't know (DK, DKed) "Don't know the trade." A Street expression used whenever one party lacks knowledge of a trade or receives conflicting instructions from the other party. whether that's because people who take vitamin C are also getting other nutrients or leading a healthier lifestyle. Q: What about lutein and zeaxanthin? A: The interesting thing about these sister pigments--from now on I'll just say lutein to refer to them both--is that they're the only carotenoids Carotenoids Carotenoids are yellow to deep-red pigments. Mentioned in: Vitamin A Deficiency carotenoids (k that are found in large quantities in the lens. There's a lot of beta-carotene and alpha-carotene and cryptoxanthin in our blood and our diet, but not in the lens. We also know that lutein can absorb ultraviolet light Ultraviolet light A portion of the light spectrum not visible to the eye. Two bands of the UV spectrum, UVA and UVB, are used to treat psoriasis and other skin diseases. in the blue range, which could explain how those carotenoids might protect the lens. Or, lutein may simply act as an antioxidant antioxidant, substance that prevents or slows the breakdown of another substance by oxygen. Synthetic and natural antioxidants are used to slow the deterioration of gasoline and rubber, and such antioxidants as vitamin C (ascorbic acid), butylated hydroxytoluene to prevent light from damaging the lens. The results from human studies are more consistent for lutein than for vitamins C or E. But so far, there are only three studies on lutein--on 77,000 nurses, 37,000 health professionals, and 1,400 people in Beaver Dam, Wisconsin Beaver Dam is a city in Dodge County, Wisconsin, along Beaver Dam Lake, Wisconsin's 16th largest lake, and the Beaver Dam River. The population was 15,169 at the 2000 census. The city is located within the Town of Beaver Dam. . Q: They're all large studies that followed people for years? A: Yes. In all three, diet was measured and new cataracts or new surgery for cataracts was assessed five to 12 years later. But in two of the studies, the risk of cataract surgery was only 20 percent lower in people who consumed more lutein. That might be because the researchers looked at surgery, not new cataracts. A lot of things affect whether a person has cataract surgery. People who are more educated might have healthier diets and get cataracts taken out at an early stage, so those things could have masked a potentially important association between lutein and cataracts. In contrast, in Beaver Dam we saw a relatively strong association--a 50 percent lower risk for new cataracts among people who had past diets that were higher in lutein. Of course, we don't know if it's the lutein or something else about their diets or lifestyles that lowered their risk. And we need a lot more than three studies--even if they all agree--before we can draw firm conclusions. Q: How about selenium selenium (səlē`nēəm), nonmetallic chemical element; symbol Se; at. no. 34; at. wt. 78.96; m.p. 217°C;; b.p. about 685°C;; sp. gr. 4.81 at 20°C;; valence −2, +4, or +6. ? A: Animals that are selenium-deficient get cataracts, but animals that are given too much selenium also get cataracts. The data in humans is very weak because we can't easily measure how much selenium people eat. Q: Does sodium raise the risk of cataracts, as recent results from the Blue Mountain Eye Study suggest? A: That study gives us a clue to follow up with additional research. But we have to be cautious about the finding because it's the first time we've seen an association between sodium and cataracts. Q: What advice can you give people who want to avoid cataracts? A: If you look across the body of research, many studies suggest that people with healthy diets are less likely to have or get cataracts. Because we haven't nailed down the nutrients that are responsible, it's prudent to eat diets that are rich in most vitamins and minerals. And that's easily accomplished by eating more fruits and vegetables and fewer nutrient-poor, calorie-dense foods like snacks and desserts. It's fairly boring advice, but it's important. Q: Do you recommend that people eat leafy greens to get lutein? A: Maybe Popeye was right. It makes sense to eat leafy greens--I do--because they're rich in lutein and other nutrients. But lutein is also in a wide variety of fruits and vegetables [see "The Lutein List" p. 4]. Q: Can people rely on a multivitamin-mineral to protect their eyes? A: I caution against using multis as a substitute for a good diet. We don't know how well the nutrients in multis are taken up by the body, and multis don't provide all of the chemical forms of nutrients in food that might be helpful. Vitamin E is an example. Gamma-tocopherol, which is found in food, is especially high in eye tissue. Recent research suggests that it has some unique functions that alpha-tocopherol, which is the kind of vitamin E in most supplements, cannot perform at all or as well. And there's also a report that taking alpha-tocopherol supplements reduces levels of gamma-tocopherol in the tissues. So it's added insurance to get these chemicals in the quantities and forms that foods provide and that we have evolved with. Macular Degeneration macular degeneration, eye disorder causing loss of central vision. The affected area, the macula, lies at the back of the retina and is the part that produces the sharpest vision. Q: What is age-related macular degeneration (AMD)? A: It's a disease that affects the macula--the central part of the retina that's involved in seeing fine details and in seeing what's in the center, not around the edges, of your view [see illustration p. 3]. AMD can cause blindness because it ultimately results in the loss of cones in the center of the macula. Unfortunately, there is no cure once the cones have been lost. And at this point the only common form of treatment is laser photocoagulation photocoagulation /pho·to·co·ag·u·la·tion/ (-ko-ag?u-la´shun) condensation of protein material by the controlled use of an intense beam of light (e.g. . But that only works for people who have "wet" macular degeneration, the kind where new blood vessels Blood vessels Tubular channels for blood transport, of which there are three principal types: arteries, capillaries, and veins. Only the larger arteries and veins in the body bear distinct names. are formed. AMD is the largest cause of blindness in older adults. Q: Who is at risk for AMD? A: All of us, as we get older. Women may have a higher risk than men. Smokers and people with a family history of AMD are also more likely to get the disease. Scientists are currently investigating whether having high blood cholesterol, high Cholesterol, High Definition Cholesterol is a fatty substance found in animal tissue and is an important component to the human body. It is manufactured in the liver and carried throughout the body in the bloodstream. blood pressure, or heart disease is also a risk factor. Q: Why might diet affect AMD? A: The macula has the highest rate of metabolism that produces oxygen free radicals anywhere in the body, in part because light is focused there. The macula is also high in polyunsaturated fatty acids Noun 1. polyunsaturated fatty acid - an unsaturated fatty acid whose carbon chain has more than one double or triple valence bond per molecule; found chiefly in fish and corn and soybean oil and safflower oil , which are particularly vulnerable to attack by free radicals. And that raises the question: Can antioxidants protect the macula? That part of the retina has a high concentration of antioxidants. And in animals that are chronically exposed to light, levels of vitamin E in the macula increase. Even so, it's thought that over the years, a small amount of insult--a small inability to prevent or repair the oxidative damage--can slowly lead to lesions that result in AMD. Q: Can lutein protect the macula? A: Because lutein absorbs light and quenches free radicals, and because lutein is so concentrated in the macula, we think that eating high levels might protect against AMD. In fact, the area of the macula that's involved in AMD--the macula lutea--is named for lutein. Also, you can increase lutein levels in the retina by taking lutein pills or eating foods like spinach or corn. And animals kept on a plant-free diet can totally lose their lutein. It's interesting, though, that the ability to enrich the retina with lutein varies from person to person. We have yet to figure out why some people don't respond to changes in the diet and some do. Q: What's the human evidence that lutein matters? A: The Eye Disease Case-Control Study showed that people with one form of AMD ate less lutein and had lower levels of lutein in their blood. In Beaver Dam and in a study in the United Kingdom, there was no association between lutein in the diet and macular degeneration. So the data are inconsistent. But the Beaver Dam study was small--not a lot of people developed AMD during the five years. And Beaver Dam doesn't have a wide range of lutein intakes, so we might have missed an association between lutein and AMD. We're now looking at populations where there's a greater range. Q: What about zinc? A: Zinc is concentrated in the retina--more than in other parts of the body. We know it's part of a lot of enzymes that keep the retina healthy, including those that defend against oxidative stress oxidative stress, n an imbalance of the prooxidant antioxidant ratio in which too few antioxidants are produced or ingested or too many oxidizing agents are produced. . So far, there are two clinical trials of zinc supplements in late-stage AMD. One found that a high level of zinc--100 mg a day--reduced visual loss, while the other found that zinc made no difference. So the clinical trials are inconsistent. Q: What did you find in Beaver Dam? A: People who had one of the early stages of AMD--pigmentary abnormalities--were more likely to have less zinc in their diets. That was true when we asked people about their diets ten years earlier or when we asked about their current diets and then looked for new pigmentary abnormalities. But I think the research needs to be repeated in other populations, and that's what we're doing. Q: What other nutrients affect AMD? A: Some studies suggest that higher intakes of vitamin E are associated with a lower risk for certain stages of AMD, but other studies don't. And to my knowledge, no studies have shown a link between AMD and either intake or blood levels of vitamin C. We don't know if the impact of vitamin C is so small that it hasn't been detected in these smaller studies, or whether no association exists. Q: What about fish or omega-3 fats? A: There is a theory that inflammation and possibly cardiovascular disease Cardiovascular disease Disease that affects the heart and blood vessels. Mentioned in: Lipoproteins Test cardiovascular disease might promote AMD, and omega-3s might protect against both. We're early in the investigation of this theory, but it's promising. The Blue Mountain Eye Study recently found that Australians who ate more fish had a lower risk of AMD. We didn't find it in Beaver Dam, but in Wisconsin they ate much less fish than the Australians did. It would have been hard to see a link in Beaver Dam even if one existed. Q: What diet do you recommend to prevent AMD? A: More fruits and vegetables, especially leafy greens, which are rich in lutein [see "The Lutein List" p. 4]. Q: Do you discourage people from taking special vitamins for eyes? A: Yes. I don't know that eye vites are more beneficial than regular multivitamin-minerals. And I'm concerned that levels of some of the nutrients may be too high [see "Eye Cons?"]. Q: Aren't some eye vites high in beta-carotene? A: That concerns me. It's too early to tell, but it's possible that if you take too much beta-carotene, you might have trouble absorbing lutein, for example. Q: So there's no magic bullet (jargon) magic bullet - (Or "silver bullet" from vampire legends) A term widely used in software engineering for a supposed quick, simple cure for some problem. E.g. "There's no silver bullet for this problem". ? A: That's right. There's a chance that lutein or one of the other nutrients offers an answer for aging eyes. That's especially important for macular degeneration, where there are no other answers. So we have to keep searching. But the likelihood that any one nutrient will prevent a large proportion of cataracts or macular degeneration is still a dream. It's more likely that a combination of nutrients or diets rich in many of them will have the largest benefit. Julie Mares Perlman is an associate professor of Ophthalmology ophthalmology (ŏf'thălmŏl`əjē), branch of medicine specializing in the anatomy, function and diseases of the eye. Ophthalmologists specialize in the medical and surgical treatment of eye disorders, vision measurements for and Visual Sciences at the University of Wisconsin at Madison. She is the principal investigator Noun 1. principal investigator - the scientist in charge of an experiment or research project PI scientist - a person with advanced knowledge of one or more sciences of two major studies on diet and eye disease. She spoke to NAH's Bonnie bon·ny also bon·nie adj. bon·ni·er, bon·ni·est Scots 1. Physically attractive or appealing; pretty. 2. Excellent. Liebman. THE LUTEIN LIST How much lutein is enough? In one of the largest studies, people who consumed roughly 14,000 micrograms (mcg) a day of lutein and zeaxanthin, largely from leafy green vegetables, had a lower risk of cataracts than people who consumed roughly 2,000 mcg a day.
Lutein +
Food Zeaxanthin
(mcg)
Kale, cooked (1/2 cup) 10,270
Collard greens, cooked (1/2 cup) 7,690
Spinach, cooked (1/2 cup) 6,340
Turnip greens, cooked (1/2 cup) 6,080
Spinach, raw (1 cup) 3,580
Broccoli, cooked (1/2 cup) 1,740
Corn, cooked (1/2 cup) 1,480
Lettuce, romaine (1 cup shredded) 1,480
Zucchini, raw (l/2 cup) 1,320
Peas, canned (1/2 cup) 1,150
Brussels sprouts, cooked (1/2 cup) 1,010
Green beans, cooked (1/2 cup) 440
Orange juice, from conc. (1 cup) 340
Okra, cooked (1/2 cup) 310
Baby carrots (8) 290
Orange (1) 240
Lettuce, iceberg (1 cup chopped) 190
Squash, crookneck or straightneck,
raw (1/2 cup) 190
Tomato, raw (1/2) 80
Cabbage, raw (1/2 cup shredded) 50
Source: U.S. Department of Agriculture. WHAT TO WATCH OUT FOR CATARACTS * Cloudy or blurry vision. * Problems with light. These can include headlights that seem too bright at night, glare from lamps or very bright sunlight, or seeing halos around lights. * Colors that seem faded. * Poor night vision. * Double or multiple vision (the symptom often goes away as the cataract grows). * Frequent changes in your eyeglasses eyeglasses or spectacles, instrument or device for aiding and correcting defective sight. Eyeglasses usually consist of a pair of lenses mounted in a frame to hold them in position before the eyes. or contact lenses contact lenses contact npl → verres mpl de contact contact lenses contact npl → Kontaktlinsen pl contact lenses npl . MACULAR DEGENERATION * Slightly blurred vision. You may need more light for reading or have trouble recognizing faces until you are up close. * A blind spot in the center of your vision (see illustration p. 5). [ILLUSTRATION OMITTED] * Straight lines appear wavy (see illustration). [ILLUSTRATION OMITTED] Anyone age 60 or older should have an eye exam through dilated dilated a state of dilatation. dilated cardiomyopathy see congestive cardiomyopathy. dilated pupil syndrome see feline dysautonomia (Key-Gaskell syndrome). pupils at least every two years. For more information, contact: National Eye Institute 2020 Vision Place Bethesda, MD 20892-3544 (301) 496-5248 www.nei.nih.gov Ocuvite, OcuGuard, ICaps, Eye Health Plus, See, Vision Care. The names sound so reassuring. The question is: Why would anyone buy them? First, there's cost. While some eye vitamins are reasonably priced, others are ridiculous. We bought a month's supply of Twinlab OcuGuard Plus with Lutein for $44.95 in Washington, D.C. A bottle of 200 NutriCology OcuDyne sold for $37.30. The recommended dose is "2 to 4 capsules once or twice daily with meals." Cost aside, it's not clear who should take eye vites. Most have a core list of the most publicized nutrients for eyes. So you probably start with at least 100 percent of the Daily Value (usually more) of zinc and vitamins C, E, and A (largely as beta-carotene). Depending on the brand, you may also find amino acids, copper, lutein, a couple of B-vitamins (riboflavin riboflavin: see coenzyme; vitamin. riboflavin or vitamin B2 Yellow, water-soluble organic compound, abundant in whey and egg white. It has a complex structure incorporating three rings. and niacin niacin: see coenzyme; vitamin. niacin or nicotinic acid or vitamin B3 Water-soluble vitamin of the vitamin B complex, essential to growth and health in animals, including humans. ), selenium, and any of several herbs--like bilberry bilberry Low-growing deciduous shrub (Vaccinium myrtillus) of the heath family, found in woods and on heaths, chiefly in hilly districts of Britain, northern Europe, and Asia. The stiff stems bear small egg-shaped leaves and small rosy flowers tinged with green. , eyebright eyebright, n Latin name: Euphrasia officinalis; part used: blooming plant; uses: eye irritations, nasal catarrh; uses under research: jaundice, lung infections, impaired memory; not recommended because of cytotoxic effects; precautions: can , and ginkgo biloba Ginkgo Biloba Definition Ginkgo biloba, known as the maidenhair tree, is one of the oldest trees on Earth, once part of the flora of the Mesozoic period. The ginkgo tree is the only surviving species of the Ginkgoaceae family. . If you take eye vites instead of an ordinary multivitamin-mineral supplement, you're going to miss out on a dozen or so nutrients that you may need (see NAH, April 2000). Some, like folic acid folic acid: see coenzyme; vitamin. folic acid or folate Organic compound essential to animal growth and health and needed by bacteria as a growth factor. , vitamin D vitamin D Any of a group of fat-soluble alcohols important in calcium metabolism in animals to form strong bones and teeth and prevent rickets and osteoporosis. It is formed by ultraviolet radiation (sunlight) of sterols (see steroid) present in the skin. , and vitamin B-12, could help cut the risk of serious health problems. On the other hand, if you take eye vites in addition to a regular multi, you could get too much of some nutrients. For example: * Zinc. More than 50 mg a day (on top of the 15 mg or so that you get from food) may depress your immune system immune system Cells, cell products, organs, and structures of the body involved in the detection and destruction of foreign invaders, such as bacteria, viruses, and cancer cells. Immunity is based on the system's ability to launch a defense against such invaders. over the long term. Most multis have 15 mg of zinc, but some hit 30 mg. Ocuvites have 40 mg. * Beta-carotene. At least in smokers and asbestos workers, doses of 33,000 IU to 50,000 IU a day raised the risk of lung cancer lung cancer, cancer that originates in the tissues of the lungs. Lung cancer is the leading cause of cancer death in the United States in both men and women. Like other cancers, lung cancer occurs after repeated insults to the genetic material of the cell. in two large trials (see NAH, May 2000). See has 25,000 IU. OcuGuard Plus has 40,000 IU. Add that to the 5,000 IU or more in many multis and you're approaching a risky level. * Selenium. A daily dose of OcuGuard or See has 100 micrograms (mcg) of selenium. If you're taking an ordinary multi with the Daily Value (70 mcg) and an extra 200 mcg a day to cut the risk of prostate cancer prostate cancer, cancer originating in the prostate gland. Prostate cancer is the leading malignancy in men in the United States and is second only to lung cancer as a cause of cancer death in men. , your daily total may reach 400 mcg, the Upper Level (UL) for selenium set by the National Academy of Sciences (see NAH, June 2000). Too much selenium could cause brittle or lost hair and nails--not life-threatening, but not too attractive, either. The bottom line: Stick with an ordinary multi. Many have as much C, E, and zinc as you'd get in an eye vite. Your multi may not have herbs like bilberry or eyebright, but the evidence that they matter is scanty. If you're looking for Looking for In the context of general equities, this describing a buy interest in which a dealer is asked to offer stock, often involving a capital commitment. Antithesis of in touch with. lutein, eat more leafy green vegetables (see "The Lutein List"). A separate lutein supplement is second best (since something other than the lutein in the vegetables may protect eyes), and it's safer than an eye vite. |
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