DIETARY LINK TO MACULAR DEGENERATION
Written by: Joe Gelb, Clinical Publicist, HPS Pharmacies
A paper published in the July 2007 issue of The American Journal of Clinical Nutrition describes the findings of a study at the Laboratory for Nutrition and Vision Research at Tufts University in Medford, Massachusetts, which suggest that certain types of carbohydrates may play a role in the development of age-related macular degeneration (MD).
The study found that eating carbohydrate-rich foods with a high glycemic index (GI) is associated with the development of macular degeneration.
GI is a measure of the rate of carbohydrate metabolism – the faster carbohydrates are broken down to glucose, the higher the index.
Researchers examined 4,099 people aged 55 to 80 who were enrolled in a larger long-term study of eye health. None of the participants had diabetes and all had 20/32 vision and a clear lens in at least one eye to allow high-definition photography.
Using these criteria, researchers examined 8,125 eyes, grading the severity of MD on a scale of 1 to 15. The researchers obtained answers to questions regarding meal frequency and calculated dietary GI for carbohydrates consumed by each participant.
After controlling for age, sex, education level, body mass index, alcohol consumption and other variables, researchers found that the higher the dietary GI, the more likely the presence of MD. Participants in the highest 20% of dietary GI had more than a 40% increased incidence of significant MD than those in the lowest 20%.
The total amount of carbohydrate consumed was not related to MD, suggesting that only carbohydrate with high GI was responsible for the increased incidence of MD.
While the exact mechanism of MD exacerbation remains unknown, researchers suggest that high glucose concentrations are harmful to the retina and the capillaries that supply blood to the eyes, and that a diet of high GI foods causes “oxidative stress” that increases inflammation. It may also be the sharp temporary increase in blood lipid levels that can follow consumption of simple carbohydrates that plays a role in damaging the delicate blood vessels.
The researchers point out that while older age, lower education levels and smoking are more significant risk factors for MD than diet, there is nevertheless a significant effect exerted on the development of MD by consumption of high GI foods.
Reference: The American Journal of Clinical Nutrition; July 2007