The January 14, 2008 issue of the American Medical Association journal Archives of Ophthalmology published the discovery of Harvard researchers that women whose diets are high in lutein, zeaxanthin, and vitamin E have a reduced risk of developing cataracts. Lutein and zeaxanthin are antioxidant xanthophylls which occur in yellow or dark, leafy vegetables. Improved intake of lutein and zeaxanthin has been linked with a lower risk of another eye disease—age-related macular degeneration.
For the current study, William G. Christen, ScD, of Brigham & Women’s Hospital and Harvard Medical School and his colleagues utilized data from 35,551 participants in the Women’s Health Study. Dietary questionnaires completed upon enrollment in 1993 were analyzed for levels of antioxidants including alpha and beta-carotene, beta cryptoxanthin, lycopene, lutein and zeaxanthin, vitamin C and vitamin E in food and multivitamin supplements. The women, who were 45 years of age or older, were followed for an average of 10 years.
Over the course of follow up, 2,031 women developed cataracts. Women whose lutein and zeaxanthin intake was in the top one-fifth of participants experienced an 18 percent lower risk of developing cataracts than women whose intake was in the bottom fifth. When vitamin E was examined, those whose intake was in the top fifth at approximately 262.4 milligrams per day had a 14 percent reduction in risk compared with women whose intake was lowest at only 4.4 milligrams per day. Beta-carotene and vitamin C showed weaker protective associations.
Lutein, zeaxanthin and vitamin E are believed to help protect against cataracts by reducing the formation of damaging free radicals. “The oxidative hypothesis of cataract formation posits that reactive oxygen species can damage lens proteins and fiber cell membranes and that nutrients with antioxidant capabilities can protect against these changes,” the authors explain. Additionally, lutein and zeaxanthin, which exist in the eye’s lens, help filter blue light which can have an adverse effect over time.
“These prospective data from a large cohort of female health professionals indicate that higher intakes of lutein/zeaxanthin and vitamin E are associated with decreased risk of cataract,” the authors conclude. “Although reliable data from randomized trials are accumulating for vitamin E and other antioxidant vitamins, randomized trial data for lutein/zeaxanthin are lacking. Such information will help to clarify the benefits of supplemental use of lutein/zeaxanthin and provide the most reliable evidence on which to base public health recommendations for cataract prevention by vitamin supplementation.”
The benefits of dietary supplements for of cataracts are widely documented. Free-radical action is directly linked to cataracts and is a major cause of damage to eyes and cataract formation. Numerous studies have documented the effects of supplements, including their ability to reduce free-radical damage and reverse the damage in some cases.
Low plasma levels of vitamin E increase the risk of lens opacities. Selenium works with alpha-lipoic acid to increase cellular concentrations of glutathione, which protects the eye lens from free radical damage. Taking 400–800 IU daily of vitamin E and 200–400 mcg daily of selenium is prudent to protect the lens from cataract formation and maintain overall good health. Carotenoids are fat-soluble, yellowish pigments found in some plants, algae, and photosynthetic bacteria. Carotenoids are light-gathering pigments that provide protection from the toxic effects of oxygen free radicals and singlet oxygen which are generated in the presence of light and oxygen. Lutein and zeaxanthin are carotenoids found in high concentrations in the macula of the retina. Lutein and zeaxanthin protect the eye from age-related macular degeneration and cataract formation. Lutein is derived from dark green leafy vegetables (spinach, broccoli, kale, and collard greens). Zeaxanthin is found in yellow fruits and vegetables (corn, peaches, and mangoes).
A lens with cataracts has decreased concentrations of potassium and magnesium. Potassium and magnesium are often deficient in aging humans. Supplementation with 400 mg of elemental potassium and 800 mg of elemental magnesium increases availability of these minerals to the lens and protects the arterial system.
Scientists long ago discovered that the carotenoids lutein and zeaxanthin help protect the macular region of the eye from harmful forms of light that can cause photoxidative damage to the eyes. New research has uncovered a third carotenoid, meso-zeaxanthin that the aging macula requires to maintain its structural density.
Up until recently there has not been a good dietary source of meso-zeaxanthin or availability as a dietary ingredient. New extraction processes can now extract meso-zeaxanthin from similar sources of lutein and zeaxanthin.