Eye to the Future

Eye to the Future

Why wait? Let’s go straight to the good news.

A simple dietary change could reduce the number of cases of advanced age-related macular degeneration (AMD) by eight percent over five years. The result: about 100,000 middle-aged and elderly people might avoid loss of sight.

That’s the assessment of Allen Taylor, Ph.D. – the director of the Laboratory for Nutrition and Vision Research at Tufts University.

As I’ve noted in previous e-Alerts, AMD is the number one cause of blindness among people over the age of 50. But as Dr. Taylor and his fellow researchers reveal, that statistic isn’t written in stone.

Looking good

Just this past month, in the e-Alert “Future Vision” (10/1/07), I told you about a study in which researchers evaluated data taken 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.

Okay – we’ll come back to that in a moment. Meanwhile, Dr. Taylor’s research also put to use data collected from AREDS.

STUDY PROFILE:

• Nearly 4,000 subjects, aged 55-80, participated in the AREDS project
• Among these 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

Your eyes are what you eat

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, honeydew, 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
• Honeydew GI = no listing
• 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 exception is honeydew melon, which is neglected by the GI lists I checked. Honeydew is nutrient-rich (potassium, folate, vitamin A), but scores somewhat high in carbs, so its GI is probably comparable to mango and kiwifruit.

In other words, stick to the vegetables (and eggs) on the lutein/zeaxanthin list, along with other low GI foods, and you’ll help avoid type 2 diabetes while enjoying reduced risk of AMD in the bargain. 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.

Sources:
“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
“High GI Diet May Favor Age-Related Sight Loss” Stephen Daniells, Food Navigator- USA, 10/8/07, foodnavigator-usa.com