HOCUS-FOCUS: CAN DIET PROTECT OUR EYES?

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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, or cloudiness in the eye's lens. Cataracts impair the vision of roughly 3.3 million people. Surgery to remove cataracts costs $1.5 billion a year.

Aged-related macular degeneration (AMD) 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 like lutein and vitamins C 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.

Q: And the only treatment is surgery?
A: Yes. The last time somebody counted, cataract surgery 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 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 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 of Aging, the Lens Opacities Case-Control Study, and the Beaver Dam 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 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 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 in the blue range, which could explain how those carotenoids might protect the lens. Or, lutein may simply act as an antioxidant 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.

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?
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 ant 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 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. But that only works for people who have "wet" macular degeneration, the kind where new blood vessels 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 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, 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.

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 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 betacarotene?
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?
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.

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 or contact lenses.
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).
Straight lines appear wavy (see illustration, this page).
Anyone age 60 or older should have an eye exam through dilated 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
EYE CONS?
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 close is "2 to 4 capsules once or twice daily with meals."

Cost aside, it's not clear who should take eye rites. Most have a core list of the most publicized nutrients for eyes. So you probably start with at least I00 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 and niacin), selenium, and any of several herbs--like bilberry, eyebright, and ginkgo biloba.

If you take eye vices instead of an ordinary multivitamin-mineral supplement, you're going to miss out on a dozen or so nutrients that you ma), need (see NAH, April 2000). Some, like folic acid, vitamin D, and vitamin B- 12, could help cut the risk of serious health problems. On the ocher hand, if you cake 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 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 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, 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 lutein, eat more leafy green vegetables (see "The Lutein List," p. 4). 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.

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.

Legend for Chart:

A - Food
B - Lutein + Zeaxanthin (mcg)

A B

Kale, cooked (1/2 cup) 10,270
Collard greens, cooked (1/2 cup) 7,690
Spinach, cooked (1 1/2 cup) 6,340
Turnip greens, cooked (1 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 (1/2 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.
PHOTO (COLOR): Normal vision.

PHOTO (COLOR): The same scene as it might be viewed by a person with age-related macular degeneration (AMD).

PHOTOS (BLACK & WHITE): On the left is what a grid normally looks like, and on the right is how it might look to someone with age-related macular degeneration (AMD). These grids are reduced in size; ask your doctor for a full-size grid to use at home.

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By Mares Perlman

Mares Perlman is an associate professor of Ophthalmology and Visual Sciences at the University of Wisconsin at Madison. She is the principal investigator of two major studies on diet and eye disease, She spoke to NAH's Bonnie Liebman.

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