Dietary carbohydrate in relation to cortical and nuclear lens opacities in the melbourne visual impairment project.

PURPOSE: In vitro and in vivo animal studies suggest that dietary carbohydrates play a role in cataractogenesis. Few epidemiologic studies have been conducted to evaluate this association. The objective of this study was to examine the cross-sectional associations between total carbohydrate intake, dietary glycemic index (dGI), and the risk of cortical and nuclear cataracts. METHODS: After excluding 864 persons from 2473 eligible participants, 1609 eligible nondiabetic participants (mean age, 57.6 years, 55.9% female) in the Melbourne Visual Impairment Project (VIP) were enrolled. Dietary information derived from a semiquantitative food-frequency questionnaire and cataract status graded by the Wilmer protocol (cortical cataract: opacity >or=4/16; nuclear cataract grade >or=2) were collected. With the use of the generalized estimating approach to logistic regression to account for the lack of independence between the eyes of an individual, the associations between dietary carbohydrates and risk of cataract in eyes with no or a single type (pure) of cataract were examined. RESULTS: Multivariate adjustment showed that pure cortical cataract (197 eyes) was significantly associated with total carbohydrate intake (odds ratio [OR] comparing the highest quartile with the lowest quartile = 3.19, 95% confidence interval [CI] = 1.10-9.27; P(trend) = 0.017). The OR for nuclear cataract (366 eyes) comparing the third quartile of dGI with the first quartile (OR = 1.64, 95% CI = 1.02-2.65) was significant, but there was not a consistent dose-response association (P(trend) = 0.75). CONCLUSIONS: Carbohydrate intake may be optimized to prolong eye lens function. Because of the high proportion of subjects with missing covariates, these results warrant further study.