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TalkingNutrition

Providing perspectives on recent research into vitamins and nutritionals

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A Meta-Analysis About Cataract Risk, Dietary Antioxidants and Vitamins

By Michael McBurney

Nutrition and lifestyle have a large effect on a great number of facets of health, and eye health is no exception. Cataracts are one of the major causes of blindness in the world. The main risk factors are age, UV-light exposure, cigarette smoking, high body mass index, and presence of diabetes mellitus. But what if you are a non-smoker, wear glasses with UV protection when outside, have a healthy weight and your lifestyle otherwise lowers your risk of type 2 diabetes? Is there more you can do to prevent the leading cause of world blindness?

Cui, Jing and Pan conducted a meta-analysis to determine whether the currently published research on serum levels of vitamins and carotenoids is associated with reduced risk of cataracts. They identified 13 studies with almost 19,000 participants that contained information about cataracts and blood levels of vitamins A, C and E, and carotenoids alpha-carotene, beta-carotene, lycopene, beta-cryptoxanthin, lutein and zeaxanthin. They used the articles’ reporting of odds ratios or risk ratios when comparing the highest and lowest categories of blood levels.

The authors found some significant associations between the levels of some carotenoids and vitamins on risk of cataract. Vitamin E, alpha-carotene, lutein and zeaxanthin were all associated with significantly reduced risk of cataract. In Asian populations, vitamins A and C were also associated with reduced risk of cataracts. Beta-carotene, lycopene and beta-cryptoxanthin were also non-significantly associated with reduced risk of cataract.

These results show how important it is to eat a diet that is rich in antioxidant vitamins and carotenoids. Although it is difficult to directly relate carotenoid and vitamin intake with blood levels due to many differences in the way that individuals absorb and metabolize these dietary-acquired components, there are strong correlations between intake and blood levels. George and co-workers found reasonable correlations between diet and serum carotenoids in the USA. Wawrzyniak and colleagues also found fairly strong correlations. Of public health concern, large swathes of the population do not consume enough of the dietary sources of these antioxidants. Brightly colored fruits and vegetables are the only food-based sources of the carotenoids and vitamin C, pre-formed vitamin A can come from meat but orange and leafy green vegetables also are good sources of pro vitamin A beta-carotene. Vitamin E comes mainly from vegetable oils and seeds. Most people do not meet fruit and vegetable intake recommendations (e.g. for data from the United States, see Murphy et al.) and therefore have rather low intakes of carotenoids and vitamin C. Over half of adults do not meet recommendations for vitamins A and E (explore other options via www.micronutrientcalculator.org).

There are around 20 million people who suffer from cataract-related blindness globally according to the World Health Organisation. Meeting dietary recommendations may help individuals to reduce their  risk of vision loss due to cataracts .-jb-

 

Main reference:

Yu-Hong Cui, Chun-Xia Jing, and Hong-Wei Pan. Association of blood antioxidants and vitamins with risk of age-related cataract: a meta-analysis of observational studies. Am J Clin Nutr 2013 ajcn.053835; First published online July 10, 2013. http://dx.doi.org/10.3945/ajcn.112.053835


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