The potential role of nutrition on lens pathology: a systematic review and meta-analysis

Oxidative stress is one of the main mechanisms of lens opacification, and certain nutritional antioxidants are suspected to have a protective effect. To examine the role of these nutritional antioxidants on cataract prevention, we searched major databases and reviewed current evidence regarding the protective effect of nutritive antioxidants. We included observational studies that investigate the association between one or more of the following micronutrients and cataract: vitamin A, vitamin C, vitamin E, lutein, zeaxanthin, α- and β-carotene. Two independent authors extracted data and assessed their quality. We pooled results for overall cataract incidence for all types of cataract and separately for nuclear, cortical, and posterior subcapsular cataract. We did not perform sensitivity analysis. Twenty-five studies were included in the qualitative and 24 in the quantitative part of the study, with a total of 295,821 participants over 30 years old. Results from pooled analysis showed a protective effect of antioxidants on cataract, but not all of them reached statistical significance. Statistically significant results were reached for vitamin C (odds ratio OR] = 0.88, 95% confidence interval CI] 0.81, 0.97]), beta-carotene (OR = 0.89, 95% CI 0.83, 0.95]), and lutein and zeaxanthin (OR = 0.92, 95% CI 0.85, 0.99]). We did not find statistically significant results for vitamin E (OR = 0.84, 95% CI 0.70, 1.01]), vitamin A (OR = 0.90, 95% CI 0.80, 1.00]), or alpha-carotene (OR = 0.92, 95% CI 0.85, 1.00]). The present study shows a relation between certain antioxidants and cataract, but further studies, especially interventional, are needed to confirm this hypothesis.