Cataract surgery is the most common operation performed in the UK with more than 300,000 procedures carried out each year.
There was an estimated cataract rate of 19.3% in European adults in 2007. This prevalence increases with age from 5% for those aged 52–62, 30% for those aged 60–69 and 64% for over 70s.
The study led by King’s College London looked at the progression of cataracts in 324 pairs of female twins over ten years.
Photographs were examined of the participant’s lenses showing the opacity of the lens in detail. Participant intake of vitamin C was also measured using a food questionnaire.
Participants with high levels of dietary vitamin C had a 33% reduced risk of cataract progression and ‘clearer’ lenses after ten years than those who had consumed less dietary vitamin C.
“The findings of this study could have significant impact, particularly for the ageing population globally by suggesting that simple dietary changes such as increased intake of fruit and vegetables as part of a healthier diet could help protect them from cataracts,” said Professor Chris Hammond, consultant eye surgeon and lead author of the study from the Division of Diabetes and Nutritional Sciences at the university.
“While we cannot avoid getting older, diabetes and smoking are also risk factors for this type of cataract, and so a healthy balanced diet and lifestyle generally should reduce the risk of needing a cataract operation.”
Vitamin C tears
The study’s authors believed that eye fluid that bathed the lens is high in vitamin C. This helps to stop the lens becoming cloudy.
They suggested increased vitamin C intake exerted a preventative effect on cataract progression by increasing the vitamin C available in this fluid.
“The human body cannot manufacture vitamin C, so we depend on vitamins in the food we eat,” said Kate Yonova-Doing, the study’s first author.
“We did not find a significantly reduced risk in people who took vitamin tablets, so it seems that a healthy diet is better than supplements.”
Conflicting studies
Studies on the effect of dietary vitamin C intake, serum vitamin C concentrations, and vitamin C supplementation on nuclear cataract formation have given conflicting results in the past.
Similarly, dietary and supplemented vitamin E intake and vitamin E blood concentrations have been shown to be related inversely with nuclear cataract.
Meanwhile vitamin A has been associated with a reduced risk of nuclear cataract, as have lutein and zeaxanthin.
Landmark studies
The results of this latest study are similar to those of the Carotenoids in Age-Related Eye Disease Study, which showed vitamin C intake assessed with an food frequency questionnaire ten years before cataract assessment was protective against cataracts.
The Blue Mountains Eye Study also found vitamin C intake, through both diet and supplements, resulted in a lower nuclear cataract incidence over ten years.
This study is the first to show that dietary vitamin C intake protects against progression of nuclear lens opacity.
Source: Ophthalmology
Published online ahead of print, doi.org/10.1016/j.ophtha.2016.01.036
“Genetic and Dietary Factors Influencing the Progression of Nuclear Cataract.”
Authors: E. Yonova-Doing, Z. A. Forkin, P. G. Hysi, K. M. Williams, T. D. Spector, C. E. Gilbert and C. J. Hammond