How a dietary change might do wonders for your vision health

Taking the Low Road

“Low carb”

Those two words are all it takes to send certain nutrition “experts” around the bend. And the phrase “low glycemic” often has the same effect. Not surprising, of course – if you follow a low-glycemic regimen then you’ll be cutting virtually all simple, refined carbs from your diet.

While those experts busy themselves belittling a diet that’s been shown to be ideal for type 2 diabetics, we’ll take a look at another excellent reason to take the low- glycemic road: your vision health.

Looking good

As I’ve noted in previous e-Alerts, age-related macular degeneration (AMD) is the number one cause of blindness among people over the age of 50. But a study from the Laboratory for Nutrition and Vision Research at Tufts University could help change all that.

In the e-Alert “Future Vision” (10/1/07), I told you about a study that collected data from the Age-Related Eye Disease Study (AREDS). Dietary records and vision health were compared in more than 4,500 subjects over the age of 60. Results showed that high intake of lutein and zeaxanthin (antioxidant-rich carotenoids found in colorful fruits and vegetables) reduced AMD risk.

We’ll come back to lutein and zeaxanthin in a moment. Meanwhile, the Tufts team also put to use data collected from AREDS.

STUDY PROFILE:

• Among nearly 4,000 subjects, about 7,230 eyes without AMD were divided into three groups
• Group One: Eyes with small drusen (tiny deposits of protein-like material that build up and calcify in the retina – an early warning that AMD may be developing)
• Group Two: Eyes with intermediate drusen or pigmentary abnormalities
• Group Three: Eyes with large drusen
• Dietary glycemic index was evaluated for each subject based on food frequency questionnaires (Glycemic index (GI) is a scale that categorizes food items according to their effect on blood sugar levels)
• Drusen changes and dietary factors were followed for more than five years
• When subjects with high GI diets were compared to subjects with low GI diets, results showed that high GI was associated with a significantly higher risk of developing advanced AMD

Researchers hypothesize that if the low-glycemic diet were widely followed, the number of AMD cases might be reduced by eight percent over five years. The result: about 100,000 middle-aged and elderly people might avoid loss of sight.

From L to Z

Low GI foods (such as meat and many fruits and vegetables) prompt a slow increase in blood sugar levels, while high GI foods (such as foods with added sugar, processed baked goods, and starchy foods) produce a quick spike in blood sugar levels. A heavy intake of high GI foods promotes a gradual insensitivity to insulin, sharply increasing risk of type 2 diabetes.

Now…back to lutein and zeaxanthin.

Leafy green vegetables are the best sources of lutein. Zeaxanthin is plentiful in yellow corn, orange pepper, kiwifruit, squash, mango, broccoli, and egg yolks. So I went to glycemicindex.com (and a couple of other GI sources) to check the GI for each of these foods. GI ranking ranges from zero to 100.

• Spinach GI = 15
• Yellow corn GI = 59
• Orange pepper GI = no listing
• Kiwifruit GI = 58
• Squash GI = no listing
• Mango GI = 51
• Broccoli GI = 10
• Egg yolks GI = no listing

And just for comparison…

• Chicken GI = no listing
• Cheerios GI = 74

“No listing” means the food isn’t rated because its ranking is zero or very close to zero.

The GI index is also an excellent resource for choosing foods in weight-loss diets. High GI food intake tends to make you hungry more often, and hungrier for high GI foods. Talk to your doctor before making significant changes in your diet.

Sources:
“Effect of a Low-Glycemic Index or a High-Cereal Fiber Diet on Type 2 Diabetes” Journal of the American Medical Association, Vol. 300, No. 23, 12/17/09, jama.ama-assn.org
“Dietary Carbohydrate and the Progression of Age-Related Macular Degeneration: A Prospective Study From the Age- Related Eye Disease Study” American Journal of Clinical Nutrition, Vol. 86, No. 4, October 2007, ajcn.org