Monday, August 23, 2010

Age-related Macular Degeneration (AMD)

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We all know that eating large amounts of dietary fat not only puts on the pounds, it can increase our risk for heart disease. But here’s a surprise – a high fat diet can also speed up age-related macular degeneration (AMD).
I’ve told you that AMD is the leading cause of irreversible visual impairment and blindness in people over the age of 50). I have also told you how devastating this disease is for its victims and their families. So anything that can slow down the progression of this disease is indeed good news – especially if it’s something as simple as changing the way we eat.
Out of sight
Just to recap: There are two forms of AMD, dry and wet. The most typical form of the disease is the dry variety, which occurs when the light-sensitive macular cells break down. This type of AMD can take years to develop and the most common symptoms are a gradual shift in perception (normally straight objects appear bent or wavy) and a dark or blurry spot in the center of your vision.
Less common, but much more debilitating, is wet macular degeneration. Wet AMD occurs when new blood vessels behind the retina grow toward it and leak blood and fluid. This form of macular degeneration causes a very sudden – and severe – loss of central vision.
And while family history can up your risk of developing AMD, researchers have also known that bad habits (smoking and too much sun) can also increase your odds. But according to this new study, you can now add another bad habit to the list: eating too much fat.
Fat chance
The study, which was conducted by researchers at the Massachusetts Eye and Ear Infirmary in Boston, involved 261 patients over the age of 60 that all had some signs of AMD in at least one eye. Participants were followed for an average of 4.6 years and completed food frequency questionnaires designed to measure the amounts and kinds of foods eaten in the previous week.
After reviewing the data, the researchers found that higher levels of dietary fat intake were associated with the progression of AMD to the advanced stages associated with visual loss. The biggest culprits were saturated, monounsaturated, polyunsaturated and trans-fats. The very fats we eat everyday!
Ok, so we know that saturated and trans-fats are bad for us on a number of levels. But monounsaturated and polyunsaturated fats; these fats are supposed to be good for you. And they are – in small amounts. These beneficial fats play a critical role in building cell membranes, producing hormones and helping the body absorb and utilize fat soluble vitamins (A, D, E and K). But Americans have trouble practicing moderation – especially when it tastes so good.
The problem is, say the researchers, foods with higher levels of these fats, particularly processed baked goods, increase the risk of accelerating AMD by about two-fold.
Whether or not limiting these fats also prevents AMD is something the researchers didn’t explore. But, as I’ve said before, for optimum health, it’s wise to limit the amount of saturated and polyunsaturated fat you consume – and try to completely avoid the synthetic trans-fats found in many processed foods.
Fish in a nutshell
The news isn’t all bad though. According to the study, the fat in nuts and fish were the exception with protective effects on eye health. That’s not surprising since nuts are rich in eye-friendly zinc and vitamin E. And fish is loaded with omega3 essential fatty acids (EFAs) – specifically docosahexaenoic acid (DHA).
A few years ago, a study by Harvard researchers found that, while consuming large amounts of linolenic acid (found in corn and safflower oil) increased the risk of AMD, eating fish high in DHA four times a week actually lowered the risk of developing the disease by 35 percent.
If you suffer from AMD and want to retain your vision longer, try adding omega3-rich fish like salmon, tuna or mackerel to your diet at least four times a week. But for maximum protection, supplement with essential fatty acid capsules containing both DHA and EPA fatty acids. By boosting your intake of these healthy fats, you may just be able to say “Here’s looking at you” for years to come.
One last thing . . .
The Massachusetts researchers also noted that the carotenoids zeaxanthin and lutein are powerful weapons against AMD. In fact, these two nutrients can slash your risk by 40 percent. One reason, according to a recent study in the Journal of Nutrition, is that supplemental lutein and zeaxanthin can enormously increase macular pigment density. By boosting the pigment, and hence the thickness of the macula, these two nutrients protect the eye from light damage.
While egg yolks, kale, spinach, broccoli and collard greens are good sources of these carotenoids, you would need to eat massive quantities to get the 6 mg. a day you need to stave off AMD. You can, however, get this protective amount by taking supplements. But don’t look for a separate zeaxanthin supplement. Since this carotenoid can’t be chemically separated from lutein, all lutein supplements contain zeaxanthin.

Bone RA, et al. “Lutein and zeaxanthin dietary supplements raise macular pigment density and serum concentrations of these carotenoids in humans.” Journal of Nutrition. 2003;133:1953.
Brown NA, et al. “Nutrition supplements and the eye.” Eye. 1998;12:127-33.
Cho E, et al. “Prospective study of dietary fat and the risk of age-related macular degeneration.” American Journal of Clinical Nutrition. 2001;73:209-218.
“Dietary fats may increase the risk of age-related macular degeneration.” Reuters. 8 Dec 2003.
“Drugs ‘don’t work on many people.’” BBC News. 8 Dec 2003.

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