Study: Lutein (1995, 1999, 2012) and Zeaxanthin - Cataracts
Learn more about natural treament of cataracts.
Researchers found that xanthophylls lutein and zeaxanthin are the only carotenoids which are found in the lens of the eye. They also found that large levels of antioxidant vitamins, such as carotenoids in the blood plasma and in patients' diets can be connected to a lower risk of developing cataracts.
For example, a diet that includes significant amounts of of spinach, a dark leafy green high in lutein and zeaxanthin was consistently connected with a smaller risk for cataract development. Correspondingly, high lipid antioxidant status is connected to healthier and longer eye lens functioning.
Why? The research suggests that xanthophylls block blue light which is phototoxic.
Likewise, there is a strong inverse connection between between large intakes of of dark leafy green vegetables, rich in lutein and zeaxanthin, and a lower risk for another oxidative stress related disease - cancer.
Lutein and zeaxanthin are the only carotenoids that have been reported to be present in a number of locations within the human eye: the retina, the macula, and the lens.
Published: KJ Yeum etal, "Measurement of Carotenoids, Retinoids, and Tocopherols in Human Lenses," Investigative Ophthalmology and Visual Science, December, 1995, Vol. 36. No. 13, pp. 2756-2761.
1999 Researchers found that the carotenoids lutein and zeaxanthin may be particularly effective in cataract prevention. The Harvard Medical School study included almost 80,000 females nurses and over 35,000 male health professionals. The female group completed diet questionnaires in 1980 and 1984, with follow-up until 1992. By 1992, 1471 of them had had cataracts removed. The male group completed questionnaires in 1986 and with follow-up for 8 years. By 1994 they had had 840 cataracts removed.
The researchers found that the 20% of nurses with the most lutein and zeaxanthin in their diet had 22% lower risk of cataract than did women with the least amounts in their diet. Among the men, the 20% with the highest intake had a 19% lower risk of cataracts compared to the 20% with the lowest intake.
There was a significant benefit due to spinach, kale and broccoli in the diet, but no confirmed results from pther carotenoids or vitamin A.
Researchers: Harvard Medical School
Published: Chasan-Taber, Lisa, et al. A prospective study of carotenoid and vitamin A intakes and risk of cataract extraction in US women. American Journal of Clinical Nutrition, Vol. 70, October 1999, pp. 509-16
Brown, Lisa, et al. A prospective study of carotenoid intake and risk of cataract extraction in US men. American Journal of Clinical Nutrition, Vol. 70, October 1999, pp. 517-24
Mares-Perlman, Julie A. Too soon for lutein supplements. American Journal of Clinical Nutrition, Vol. 70, October 1999, pp. 431-2 (editorial)
A meta-analysis is essential a review or study of studies. While a single small or in some other way insufficiently designed study may not conclusively demonstrate a particular result, by looking a many such studies reasonable conclusions can be drawn.
This meta-analysis looked at the ties between levels of the carotenoids lutein and zeaxanthin in the blood and the risk of developing cataracts in older patients. It accomplished this by evaluating pooled relative risks for lowest and highest levels of the nutrients in blood plasma and the incidence of cataract.
The researchers found marked inverse relatinships between nuclear cataract (the most common type of cataract, the center of the lens hardening and yellowing) and the nutrients - in other words, the lower the levels of carotenoids lutein and zeaxanthin the greater the incidence of cataract. This was especially true of zeaxanthin levels.
The meta-analysis also concluded that higher levels of these carotenoids was also indicative of reduced incidence of cortical cataract (inside the lens capsule) and subcapsular cataract (back of the lens).
Researchers: X.H. Liu, et al.
Published: Association between lutein and zeaxanthin status and the risk of cataract: a meta-analysis, Nutrients, Jan, 2014.