Posted: July 12, 2012
The structure of the eye depends on nutrients that are contained mainly in leafy dark green vegetables
In many ways, what is good general nutrition also benefits the eye. A variety of fruits, vegetables, whole grains, nuts, seeds and legumes with low fat dairy and protein sources, and fatty fish with its special benefits, offer the foundation.
The structure of the eye, however, depends on some very specific nutrients that are contained mainly in the leafy dark green vegetables, such as kale, spinach, Swiss chard, collard greens, and spinach. These nutrients are lutein and zeaxanthin, plant pigments of the carotenoid family (a group of plant pigments which also includes alpha and beta carotene and lycopene). Lutein and zeaxanthin accumulate in the lens of the eye and in the macula of the retina, where they function as macular pigment. The lens of the eye is where cataracts form, and the duo may protect against the development of age-related macular degeneration (AMD), which is the major cause of blindness in older people. It is believed these nutrients offer protection through their roles as blue light filters and antioxidants.
There have been some significant studies linking lower risks of cataracts and advanced macular degeneration in people who consume more lutein and zeaxanthin. The protective effect may be directly linked to the nutrients themselves or to some other factor present in those same foods. It could also be that people with high levels of lutein also have other healthy habits or nutritional intake that is beneficial in eye health.
Intakes of approximately 6 milligrams/day of lutein and zeaxanthin have been associated with protection against AMD. Database information on dietary content of these pigments is limited, especially for zeaxanthin. Another issue is that levels of the two pigments are usually reported together. It is known that zeaxanthin is present in corn, but lacking in most other vegetables commonly consumed in the U.S. It is also present in egg, and zeaxanthin from egg is more available to the body. Lutein, however, is mostly in fruits and vegetables. Kale, spinach, Swiss chard and collard greens have between 7 ½ and 12milligrams of lutein + zeaxanthin per half cup of cooked vegetable. Lighter green veggies, such as peas, broccoli, romaine lettuce and Brussels sprouts have between 1 and 2 milligrams per serving and most other vegetables and fruits have less than 1 milligram per serving. Corn has about half a milligram, but can contribute a large amount of zeaxanthin in societies who consume large amounts of corn tortillas and other foods containing corn meal. In a recent study on phytonutrient intake in the U.S., it was found that overall, as a population we are far short of meeting the 6 milligrams per day threshold for eye health. The major source of lutein + zeaxanthin consumed in the United States is overwhelmingly spinach, followed by lettuce, eggs, collards and broccoli.
Though all the findings are not in, it’s not a bad idea to consume more of the dark leafy greens on a regular basis – they are rich in many other nutrients, as well. Hopefully, we will all be seeing more green!
Rayna Cooper is a Registered Dietitian and Family & Consumer Sciences/Nutrition Educator serving Penn State Extension in Adams County. Penn State is committed to affirmative action, equal opportunity, and the diversity of its workforce. Penn State Extension in Adams County is located at 670 Old Harrisburg Road, Suite 204, Gettysburg, PA 17325, phone 334-6271, email email@example.com.