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Lutein and Zeaxanthin: Good for Eyes, Good for General Health
It's a truism that carrots are good for eyes, but how many people eat kale and corn for lutein and zeaxanthin? Along with vitamins A, C, and E, these two little-known antioxidants confer protection against macular degeneration. Lutein and zeaxanthin are pigments chemically similar to the beta-carotene found in carrots, but unlike beta-carotene, the body cannot convert them into vitamin A. Both of these natural antioxidants are found in food. Lutein occurs in carrots, corn, greens, potatoes, tomatoes, and most fruits. Zeaxanthin is found in corn, fruit, paprika, and spinach. The body can convert lutein into zeaxanthin, but it cannot convert zeaxanthin into lutein. Both nutrients can be "trapped" in fat tissue so that they are not available to the eyes, and both are destroyed by free radicals released by tobacco smoke. The extraordinary value of these two underappreciated antioxidants derives from their role in the macula, the oval dot of yellow pigment found in the center of the retina. The macula is hardwired to the brain to provide much of its visual input. Lutein accumulates along the edges of the macula, and zeaxanthin is more heavily concentrated in the center of the macula. They function as antioxidants, and also as filters against blue light that protect the retina and the optic nerve from excessive exposure to ultraviolet rays, acting in much the same way as UV-protective lenses. Lutein and zeaxanthin interact with copper, zinc, beta-carotene and vitamins C and E to prevent macular degeneration. All seven antioxidants must be supplied by the diet or supplementation to lower risk of developing this disease, especially among people who are overweight and/or smoke. The use of supplements as "insurance" against the development of macular degeneration is confirmed by the Age Related Eye Disease Study (AREDS), but the formula that confers protection is precise. Daily dosages are: At the time of the AREDS trial, neither lutein nor zeaxanthin was available as a supplement. However, the Lutein Antioxidant Supplementation Trial found that an optimal dosage of lutein (from which the body can make its own zeaxanthin) was 10 mg a day. This about seven times the amount of lutein found in a typical American diet, and somewhat more than the body can absorb from a single meal without failing to absorb beta-carotene (which enters the bloodstream in similar ways). This means that getting adequate supplies of lutein and zeaxanthin from food is possible, but only if appropriate foods are eaten at different meals. A mere half-cup of cooked spinach, for example, provides 6 mg of lutein, which the body may use as either lutein or zeaxanthin. A cup of sweet corn provides 2.5 mg. Swiss chard (silverbeet) and turnip greens are sources of lutein approximately equal to spinach, and zeaxanthin is also supplied by egg yolks. Regular consumption of these foods, not all at the same meal, provides enough of their antioxidants, although supplementation is a more reliable option. The only drawback to consumption of maximum amounts of lutein and zeaxanthin is in relationship to skin health. These plant chemicals nourish the eyes, but they concentrate in fat. With very high consumption, they also encourage the production of sebum. For most persons over the age of 55, this side effect is actually beneficial, as sebum makes the skin more flexible and less inclined to wrinkling. If there is adult acne or rosacea, however, care should be taken not to consume too much of either lutein or zeaxanthin at any one time. |