Earlier studies found links between the consumption of these nutrients and a reduced risk of cataracts in older adults. However, none of the existing research examined the links from a wider point of view.
To address this, researcher Hong Jiang, together with his colleagues from Xi'an Jiaotong University (XJTU) and the University of South Australia, conducted a meta-analysis of 20 studies on the subject. Eight were randomized controlled trials (RCTs) while the others were cohort studies.
All of the studies looked into the relationship between age-related cataract risk and the intake of dietary vitamins and carotenoids.
The results of Jiang and his team's meta-analysis were published in The American Journal of Clinical Nutrition. (Related: B vitamins are CRUCIAL to heart health, brain health and eye health.)
Consuming more vitamins A, C and E and carotenoids lowers the risk of cataracts
The XJTU researchers reported that the intake of most vitamins and carotenoids is linked to a significantly lower risk of age-related cataracts in the cohort studies. Vitamins A, C and E reduced the risk of clouding in the lenses of the eyes. So did the carotenoids beta-carotene, lutein and zeaxanthin.
In contrast, vitamin E and beta-carotene intake did not reduce the risk of cataracts significantly compared with the placebo.
In the cohort studies, Jiang's team also found that for every 10 milligrams per day (mg/d) increase in the intake of lutein and zeaxanthin, the risk of cataract development decreased by 26 percent.
Increasing the intake of other nutrients also yielded similar results. For instance, the risk of cataract decreased by 18 percent for every 500 mg/d increase in vitamin C, by eight percent for each five mg/d increase in beta-carotene intake, and by six percent for every five mg/d increase in vitamin A intake.
“If we could delay the onset of ARC by 10 years, it could halve the number of people requiring surgery,” said one of the authors in a statement.
The scientific jury remains divided over vitamins and carotenoids' effect on cataract formation
Several studies have looked into the effects of various vitamins and carotenoids on the development of cataracts. Their results, unfortunately, varied greatly.
A 2012 study by researchers from the University of Eastern Finland (UEF) linked lutein and zeaxanthin with the prevention of cataracts. The researchers reported that both carotenoids can prevent oxidative stress from harming the lens of the eye. This antioxidant effect contributes to the prevention of cataracts. The researchers also noted that the protective effects of lutein and zeaxanthin were similar to those of vitamin E.
Meanwhile, the findings by Swedish researchers clashed with those of a later study conducted by their British counterparts. In 2010, Karolinska Institute (KI) researchers identified 2,497 cases of cataract extraction after following 24,593 women from the Swedish Mammography Cohort for more than eight years. They found that among women aged 65 and above, vitamin C intake increased the risk of cataract by 38 percent.
In contrast, the findings of a King's College London study in 2016 revealed that high intake of vitamin C can prevent the progression of cataracts. So the jury may still be out on the matter. Read more at EyeHealth.news.
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