Eating whole grains and avoiding refined carbohydrates may slow the progression of age-related macular degeneration (AMD), a leading cause of vision loss in older people.
AMD affects the macula, the central part of the retina, and can impair the ability to read or drive. There is no treatment for the early stages of the disease, but research has indicated that certain vitamins and minerals may slow its progression.
Recent results from a long-term project called the Age-Related Eye Disease Study (AREDS) also suggest that the types of carbohydrates in the diet affect AMD progression. Diets that have a high “glycemic index” are associated with an increased risk of AMD progression, and diets with a low glycemic index are associated with a reduced risk of progression.
The glycemic index ranks carbohydrates according to the extent to which they raise blood sugar levels. In general, high-fibre foods have a lower glycemic index and less effect on blood sugar levels, and refined carbohydrates have a greater effect.
AREDS showed that diets with an overall high glycemic index are associated with an eight per cent increased risk of AMD progression over a five-year period compared with low glycemic index diets, according to Chung-Jung Chiu, a study researcher and assistant professor of ophthalmology at Tufts University in Boston. Participants whose AMD was more severe had a 17 per cent increased risk of progression if their diet had a high glycemic index.
The study involved nearly 4,000 people between the ages of 55 and 80 years who were at risk for AMD progression.
Chiu and his colleagues estimate that widespread adoption of a low glycemic index diet among seniors would eliminate more than 100,000 new cases of advanced AMD over five years in the U.S. alone.
Foods that contribute to a lower dietary glycemic index include legumes, rolled oats, basmati rice, whole bran, whole grains and pasta if it is cooked al dente (slightly hard). Foods that contribute to a higher glycemic index include instant oatmeal, overcooked pasta, white bread, and many types of potatoes.