Risk For Cataract

Higher consumption of certain vitamins and carotenoids is with a significantly decreased risk for age-related cataract (ARC) in cohort studies, according to a meta-analysis published in the January issue. Hong Jiang, from Xi’an Jiaotong University Health Science Center in China, and colleagues conducted a meta-analysis of randomized controlled trials (RCTs) and cohort studies published through June 2018 to assess dietary vitamin and carotenoid intake and ARC risk.
The authors included eight RCTs and 12 cohort studies in the analysis. The researchers found that most vitamins and carotenoids significantly with a reduced risk for ARC in the cohort studies; including vitamin A (relative risk [RR]; 0.81), vitamin C (RR, 0.8), vitamin E (RR, 0.9), β-carotene (RR, 0.9); lutein or zeaxanthin (RR, 0.81). In RCTs, compared with placebo, vitamin E or β-carotene did not significantly reduce the risk for ARC.

Lutein or zeaxanthin intake

In cohort studies, the risk for ARC significantly decreased by 26 % or every 10-mg/d increase in lutein or zeaxanthin intake; as well as by 18 % for each 500-mg/d increase in vitamin C intake; by 8 % for each 5-mg/d increase in β-carotene intake, and by 6 % for every 5-mg/d increase in vitamin A intake.
If they could delay the onset of ARC by 10 years; it could halve the number of people requiring surgery; a coauthor said in a statement. The findings from the present meta-analysis suggested significant inverse associations between intakes of most dietary vitamins and carotenoids and ARC risk in cohort studies; whereas vitamin E or β-carotene supplementation did not
significantly reduce ARC risk in RCTs.

The cellular metabolism

Therefore significant dose-response relations observed, especially lutein or zeaxanthin and vitamin C. As by-products of cellular metabolism or UV radiation in the lens; ROS could exert a toxic effect on multiple lens constituents that have implicated in the development of ARC (6, 39). But cumulatively elevated ROS levels may lead to the formation of disulfide-linked dimers or precipitation in crucial enzymes and/or membrane proteins.

Free radicals can initiate an autocatalytic chain reaction of lipid peroxidation; thereby disturbing the optimal homeostasis within the cell; so leading to subsequent cell and tissue dysfunction. As important nonenzymatic antioxidative agents; vitamins and carotenoids have a beneficial effect on maintaining the structural integrity and function of the lens. In a case-control study of ARC, Theodoropoulou, et al.

In conclusion, reported that subjects with high intakes of vitamins C and E had 50% lower odds of ARC. This result is consistent with the finding of Jacques et al., who noted that a decreased risk of nuclear opacification was with higher consumption of antioxidants in the Nurses’ Health Study. In a 7-y RCT in ARC patients, supplementation with vitamin C, vitamin E, βcarotene, and zinc resulted in a nonsignificant decrease in the risk of ARC progression or visual acuity loss.