Study: Antioxidants (1998, 2001-2, 05, 13) and Cataract Prevention
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Researchers evaluated the relationship between the presence of antioxidants in the eye tissue and blood levels and the risk of development of cataracts. The study was called the Longitudinal Study of Cataract and involved 764 patients.
At the beginninng of the study the scientists collected dietary information, use of vitamin supplements, and blood samples measuring levels of vitamin E. In addition eye exams with specific data about lens clarity were taken including use of lens photographs which were graded according to a standard clarity protocol. This information and data was again collected on yearly follow-up visits.
The scientists wanted to determine whther nutrition was a factor in development of cataracts over time. They found that the risk of cataract formation decreased in the regular users of multivitamin supplements (1/3 decrease in risk), vitamin E supplements, and in the people with higher blood levels of vitamin E (1/2 the risk). The results were similar to earlier research and were observed only, not clinical trials.
Researchers:Leske MC; Chylack LT Jr; He Q; Wu SY; Schoenfeld E; Friend J; Wolfe J
Published: Antioxidant vitamins: the longitudinal cataract study, Ophthalmology (United States) May 1998
Researchers find that different antioxidants can help prevent varying types of cataract as follows:
- People with the highest blood concentrations if either beta- or alpha-carotene were 30-50% less likely to develop nuclear cataracts, which are those located in the central part of the lens.
- People with high blood levels of lycopene (found in high concentration in cooked tomatoes) were associated with a 60% lower risk if cortical cataracts, which are those located in the outer layer of the lens.
- People with high lutein concentrations were 50% less likely to develop posterior subcapular cataracts, which are those located toward the bottom rear of the lens.
So in essence the study shows that a diet rich in antioxidants can reduce the risk of cataracts.
Study 1: C.R. Gale, N.F. Hall, D.I. Phillips, et al., Plasma antioxidant vitamins and carotenoids and age-related cataract, Ophthalmology, 2001
Study 2: P.F. Jacques, L.T. Chylack Jr., S.E. Hankinson, et al., Long-term nutrient intake and early age-related nuclear lens opacities, Archives of Ophthalmology, 2001
Researchers report that people with healthy diets that include 18mg of beta-carotene daily, 750mg of vitamin C daily, and 600mg of vitamin E daily are able to slow the progression of cataracts. This is according to the results of the Roche European-American Cataract Trial results.
The trial involved almost 300 U.S. and U.K. patients, randomly receiving supplements or placebo. Followup was done for two years for 231 of them, for three years for another 158, and for four years for 36 more patients.
All patients began with four months of placebo; following that period they were divided into two groups for placebo or nutrients and monitored every four months.
At the beginning of the study there was no difference between control and test subjects' eyes. After two years of treatment there was a small positive effect for the non-placebo group in the U.S. and after three years positive results were noticed for non-placebo groups in the U.S. and the U.K.
Researchers: L.T. Chylack, Jr, N.P. Brown, A. Bron, M. Hurst, W. K÷pcke, U. Thien, W. Schalch
Published: The Roche European American Cataract Trial (REACT): a randomized clinical trial to investigate the efficacy of an oral antioxidant micronutrient mixture to slow progression of age-related cataract, Ophthalmic Epidemiology, February, 2002
In 1993 researchers noted amounts of fruit and vegetables consumed by nearly 40,000 women medical professionals. Most of them were free of cataracts at that time. Ten years later their vision health was again evaluated and it was found that the women in the lowest 1/5th of fruit and vegetable consumption had the highest levels of cataract. Women in the highest 1/5th of fruit and vegetable consumption had about 10-15% lower risk of cataract.
Researchers: W. G. Christen, et al.
Published: Fruit and vegetable intake and the risk of cataract in women, American Journal of Clinical Nutrition, June 2005.
Research has consistently indicated that the levels of antioxidants and/or vitamins in the blood are associated with lowered risk of developing cataracts. The researchers did a meta-analysis to verify that such association is valid.
A meta-analysis is essentially a study of studies. While small studies, or studies that are lacking controls, or randomization, or are not double-blind may or may not be valid, by looking at all such studies together as though they are one larger study, statistical significance can be determined.
The researchers evaluated 13 studies involving nearly 19,000 patients. They concluded that:
- Vitamin E, alpha-carotene, lutein and zeaxanthin were inversely related to age-related cataract. (The greater the levels of those nutrients, the lower the risk of cataract.)
- Vitamins A and C were inversely related to cataract in Asian populations (not western peoples).
- Beta-carotene, lycopene and beta-cryptoxanthin were not statistically significant.
Researchers: Y.H. Cui, C.X. Jing, H.W. Pan
Published: Association of blood antioxidants and vitamins with risk of age-related cataract: a meta-analysis of observational studies, American Journal of Clinical Nutrition, September, 2013.