Dr. Grossman’s Blog

Scientists have long known that our diets influence our risk of age-related macular degeneration (AMD).  High glycemic-index diets have now been identified as a risk factor for AMD by researchers from the University of Sydney and the University of Melbourne in Australia, and the National University of Singapore.

The glycemic index (GI) is a measure of the effects of carbohydrates on blood glucose levels.  Carbohydrates that break down rapidly during digestion releasing glucose rapidly into the bloodstream have a high GI; carbohydrates that break down slowly, releasing glucose gradually into the bloodstream, have a low GI.

Scientists examined the association between the dietary glycemic index and the incidence of AMD in the Blue Mountain Eye Study population.

During 1992–1994, 3654 people aged 49 years or older attended baseline examinations.  Of these, 2335 patients were reexamined after 5 years and 1952 were examined again after 10 years.  At each examination, lens photography was performed and food-frequency questionnaires were administered.  An Australian database was used to calculate the mean glycemic index.

Over 10 years, 208 of 1810 participants developed early AMD. After adjusting for age, smoking, and other risk factors, a higher mean dietary glycemic index was associated with an increased risk of early AMD. 

Conversely, a greater consumption of predominantly lower glycemic index foods was associated with a reduced risk of incident early AMD. No relation was observed with late AMD.

Researchers concluded that a high-glycemic-index diet is a risk factor for early AMD, but they also noted that low glycemic-index foods such as oatmeal may protect against early AMD.

Learn more about the glycemic index and use a free GI database to find the GI index of your favorite carbohydrates at this University of Sydney Glycemic Index web site

SOURCE:  Kaushik, et al, Dietary glycemic index and the risk of age-related macular degeneration,  American Journal of Clinical Nutrition, Vol. 88, No. 4, 1104-1110, October 2008.

Cataracts are the leading cause of blindness around the world.  Studies suggest that oxidation is responsible for much of the damage to the lens and that antioxidants might protect the lens against formation of cataract.

Scientists at the University of Sydney and the University of Melbourne in Australia have released their investigation of the relationship between antioxidant nutrient intakes and the incidence of age-related cataract.

During 1992–1994, 3654 people aged 49 years or older attended baseline examinations as part of the Blue Mountains Eye Study.  Of these, 2464 (67.4%) of the participants were evaluated again at either 5 years or 10 years.  At each examination, lens photography was performed and food-frequency questionnaires were administered.  Antioxidants, including beta-carotene, zinc, and vitamins A, C, and E, were assessed. Cataract was assessed at each examination from lens photographs with the use of the Wisconsin Cataract Grading System.

Participants whose total intake of vitamin C (diet as well as supplements) was in the top 20% of the group had a reduced risk of nuclear cataract.  An above-median intake of combined antioxidants (vitamins C and E, beta-carotene, and zinc) was also associated with a reduced risk of incident nuclear cataract. 

Study authors concluded that higher intakes of vitamin C or the combined intake of antioxidants had long-term protective associations against development of nuclear cataract in this older population.

Learn more about antioxidants and their importance for good eye health

Read more about cataracts

SOURCE:  Tan, et al, Antioxidant nutrient intake and the long-term incidence of age-related cataract: the Blue Mountains Eye Study,  American Journal of Clinical Nutrition, Vol. 87, No. 6, 1899-1905, June 2008.