High carbohydrate intake could harm vision over time

01/07/05 Scientists funded by the Agricultural Research Service (ARS) in Boston, Mass., have found that the higher the carbohydrate intake, the higher the odds of developing a certain type of cataract among a group of women aged 53 to 73 years. When damaged proteins gather within one or both of the eye lenses, the resulting area that becomes cloudy, or opaque, is called cataract.

Cataract is the leading cause of blindness worldwide, and about 20 million Americans older than 40 have it. The study was led by Chung-Jung Chiu and Allen Taylor at the Jean Mayer USDA Human Nutrition Research Center on Aging in Boston and is part of the Nutrition and Vision Project, a substudy of the federally funded Nurses' Health Study.

The women in the study whose average carbohydrate intake was between 200 and 268 grams per day were 2.5 times more likely to get cortical cataracts than the women whose intake was between 101 and 185 grams per day. The recommended dietary allowance for daily carbohydrate intake for adults and children is 130 grams, which is based on how much glucose the brain needs.

Cortical cataract is one of three distinguishable types of cataracts. Carbohydrates are mainly sugars and starches that the body breaks down into glucose, a simple sugar that feeds the body's cells. The potentially harmful effect of high-carbohydrate diets on the lens could be a result of increased exposure of normal lens proteins to glucose.

The scientists studied 417 women without a history of cataracts who had participated in the Nurses' Health Study. The researchers conducted eye exams and studied dietary data taken from questionnaires to assess the relationship between volunteers' newly diagnosed cataracts and their average carbohydrate intake over a 14-year period.

The degree to which these findings could be generalized to men and other age groups is unknown. But the mechanisms underlying cataract development have not been known to vary by sex or socioeconomic status.

The study was published in the June issue of the American Journal of Clinical Nutrition. ARS is the U.S. Department of Agriculture's chief scientific research agency.