Loss of central vision with age may be linked to quality of dietary carbohydrates

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Public release date: 6-Jun-2006

Contact: Siobhan Gallagher

617-636-6586

Tufts University

Loss of central vision with age may be linked to quality of dietary

carbohydrates

Boston-- Age-related macular degeneration (AMD) is one of the leading

causes of vision loss in older adults and a person's risk may partly

depend upon diet. When it comes to carbohydrates, quality rather than

quantity may be more important, according to new research by

, PhD, director of the Laboratory for Nutrition and Vision

Research at the Mayer USDA Human Nutrition Research Center on

Aging (HNRCA) at Tufts University, and colleagues. Their findings

were reported in the April 2006 issue of the American Journal of

Clinical Nutrition.

and colleagues analyzed data from a sub-group of participants

in the Nurses' Health Study (NHS) who were enrolled in the Nutrition

and Vision Program. The researchers looked at the total amount of

carbohydrates consumed over 10 years and the dietary glycemic index,

which is a measure of the quality of overall dietary carbohydrate.

" Women who consumed diets with a relatively high dietary glycemic

index had greater risk of developing signs of early age-related

macular degeneration when compared with women who consumed diets with

a lower dietary glycemic index, " says lead author Chung-Jung Chiu,

DDS, PhD, scientist in the Laboratory for Nutrition and Vision

Research at the HNRCA and an assistant professor at Tufts University

School of Medicine. High total carbohydrate intake, however, did not

significantly increase the risk factor for AMD.

" In other words, the types of carbohydrates being consumed were more

important than the absolute amount, " explains , senior author.

A high-glycemic-index diet is one that is rich in high-glycemic-index

foods, which are converted more rapidly to blood sugar in the body

than are low-glycemic-index foods.

Chiu, , and colleagues examined the eyes of more than 500 women

between 53 and 73 years of age, looking for changes indicative of

early AMD. The researchers also analyzed the participants' diets, as

reported in questionnaires that had been administered periodically

over the course of 10 years preceding their eye exams.

" Dietary glycemic index may be an independent and modifiable risk

factor for early AMD, " concludes , who is also a nutrition,

ophthalmology and biochemistry professor on the Tufts health sciences

campus in Boston. " The likelihood of having abnormalities

characteristic of AMD on eye exam more than doubled for women who

consumed diets with the highest glycemic index, regardless of other

factors already known or suspected to increase the risk of AMD, such

as age, high blood pressure, cigarette smoking, and obesity. "

AMD primarily and irreversibly affects central vision, which is

critical for many activities, such as reading and driving. The

disease is caused by the gradual breakdown of light-sensitive cells

in the region of the eye's retina called the macula. It is estimated

that 1.75 million Americans 40 years of age and older have some

manifestation of AMD.

Prior to the current study, the association between AMD and dietary

carbohydrate had not been evaluated. " We are interested in studying

the role of glucose in age-related diseases like AMD, " says,

" because evidence suggests that problems with glucose metabolism, as

in diabetes, may cause damaging by-products to accumulate in

sensitive tissues and contribute to disease. "

" We cannot say, based on these data, whether or not consuming a diet

with a high glycemic index causes AMD, " says . He points out

that there are other possible explanations for the relationship he

and his colleagues observed. " Perhaps a high-glycemic-index diet is a

marker for an overall dietary or lifestyle pattern that increases the

risk of developing AMD. " A diet high in high-glycemic-index foods

like white bread and french fries has a higher overall glycemic index

than a diet based more heavily on low-glycemic-index foods, such as

lentils and yams.

is cautious in his interpretation of this data, but he

believes that further research is critical, as it may ultimately

prove helpful in preventing or delaying the onset of such potentially

debilitating and costly diseases.

###

Chiu C-J, Hubbard LD, Armstrong J, G, Jacques PF, Chylack LT,

Hankinson SE, Willet WC, A. American Journal of Clinical

Nutrition. 2006 (April); 83(4): 880-886. " Dietary glycemic index and

carbohydrate in relation to early age-related macular degeneration. "

If you are interested in learning more about this topic, or speaking

with a faculty member at the Friedman School of Nutrition Science and

Policy at Tufts University, or another Tufts health sciences

researcher, please contact Siobhan Gallagher at 617-636-6586 or Peggy

at 617-636-3707.

http://www.eurekalert.org/pub_releases/2006-06/tu-loc060606.php