Dietary glycemic load and risk of age-related cataract.

BACKGROUND Metabolism of many of the most commonly consumed carbohydrates in the United States results in a high plasma glucose response, which can be quantified by the glycemic load. Although hyperglycemia is a risk factor for cataract, there is no information on the potential effect of a high dietary glycemic load on the incidence of age-related cataract. OBJECTIVE Our objective was to prospectively examine the association between dietary glycemic load and incident age-related cataract. DESIGN We studied 2 cohorts-71 919 women and 39 926 men-aged > or =45 y who had no previous diagnosis of cataract, diabetes mellitus, or cancer and who were followed for 14 and 12 y, respectively, for the occurrence of cataract extraction. We calculated dietary glycemic load from data reported on multiple validated food-frequency questionnaires and used pooled logistic regression models to estimate the association with incident cataract extraction. We performed analyses separately for each cohort and then calculated pooled estimates across cohorts. RESULTS During 980 683 person-years of follow-up, we confirmed 4865 incident age-related cataract extractions. After adjustment for age, cigarette smoking, body mass index, total caloric intake, dietary intake of lutein and zeaxanthin, and alcohol consumption, there was no significant relation of dietary glycemic load to risk of cataract extraction (P for trend = 0.10). The pooled relative risk between the highest and lowest quintiles of dietary glycemic load was 0.95 (95% CI: 0.81, 1.11; P for heterogeneity by cohort = 0.1). CONCLUSION These prospective epidemiologic data do not support the hypothesis that a high dietary glycemic load, primarily a result of consumption of refined carbohydrates, increases the risk of cataract extraction.