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Spinach and Seafood Excel as Eye Sun-Shields
6/30/2011
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By now, it’s pretty clear that the omega-3 DHA in fish fat is very good for human vision ... for prior research, see Omega-3s & Eye Health” in our news archive.
 
This is in part because DHA is an essential component of the retina ... see our sidebar “Why your eyes need omega-3 DHA”, below.
 
And the carotene-class “antioxidants” in egg yolks and dark, leafy greens – beta carotene, lutein (loo-teen), and zeaxanthin (zee-ah-zan-thin) – are also vital to both basic and optimal eye health.
 
Recently, a study in Dutch people susceptible to macular degeneration found that those who ate higher levels of zinc, dark, leafy greens, or fish-type omega-3s – were one-third less likely to develop the disease (Ho L et al. 2011).
 
Age-related macular degeneration accounts for half of all cases of blindness, and this vision-sapping erosion of the retina occurs in more than six out of every 100 American adults over 40.
 
Why your eyes need DHA
The retina uses specialized photoreceptor cells called rods and cones to process light. Rod and cone cells are extraordinarily rich in omega-3 DHA. A shortage of dietary DHA leads to a shortage of retinal DHA, which in turn reduces visual acuity.
 
But lack of dietary omega-3s—from fatty fish or fish oil supplements—can bring more ominous threats, like age-related macular degeneration.
 
Omega-3 DHA in the retina’s cells is used to make a substance called neuroprotectin D1. This substance protects retinal pigment cells from damage and destruction. In addition, DHA itself helps protect the retina’s pigment cells.
 
These twin protective actions help explain why people who eat fish more than once a week have significantly lower rates of AMD, according to the results of population studies.
And as the Dutch research team wrote, “To achieve this benefit, it does not appear necessary to consume excessive amounts of these nutrients; the recommended dietary allowance will suffice” (Ho L et al. 2011).
 
(The U.S. recommended dietary allowance for zinc is 11mg for men and 8mg for women. Men and women alike are advised to consume at least 500 mg of omega-3 fatty acids (EPA + DHA) daily.)
 
Good sources of zinc include oysters, red meat, nuts, and beans. Oily fish like salmon, tuna, and sardines are the best food sources of omega-3s, while beta carotene abounds in peppers (chili and bell), carrots, and sweet potatoes.
 
Lutein and zeaxanthin are concentrated in egg yolks, dark green leafy vegetables (e.g., spinach, collard greens, kale, chard, turnip greens, broccoli, zucchini, and Brussels sprouts), and in whole yellow corn or cornmeal.
 
Supplemental lutein is usually made from marigolds … which are also fed to many commercial chickens, to make their skin look more yellow and appealing in the meat case.
 
Lutein shines in summer eye protection study
To judge by a Japanese study in mice, the apparent eye health benefits of lutein – a carotene-class compound concentrated in green leafy vegetables and egg yolk – may extend to protection against the damaging effects of strong light (Sasaki M et al. 2011).
 
Findings published recently in the Journal of Nutritional Biochemistry showed that lutein may protect the DNA of “photoreceptor” cells in the retina from the harmful effects of strong light.
 
Now, Japanese researchers report that visual impairment produced by strong light exposure was greatly reduced in mice fed supplemental lutein.
 
For the new study the researchers divided mice into two groups and fed them different diets for 10 days before being exposed to strong light.
 
Both were fed normal chow, but one group had chow supplemented with 0.1 percent lutein.
 
The lutein group showed a smaller range of detrimental effects associated with light exposure, including less visual impairment, and less thinning of the layer of photoreceptor cells.
 
In addition, the researchers note that a marker of DNA damage was up-regulated in the normal chow-fed animals, but not in the lutein-fed animals.
 
Finally, DNA repair was increased in the lutein group, which also had less light-induced oxidative stress in the retina, and less light-induced visual impairment.
 
So if you spend time in strong sun, be sure to get plenty of dark, leafy greens, egg yolks, and fish … it’s a wonderfully tasty “prescription” for eye health that brings many other health benefits.
 
 
Sources
  • Ho L, van Leeuwen R, Witteman JC, van Duijn CM, Uitterlinden AG, Hofman A, de Jong PT, Vingerling JR, Klaver CC. Reducing the Genetic Risk of Age-Related Macular Degeneration With Dietary Antioxidants, Zinc, and {omega}-3 Fatty Acids: The Rotterdam Study. Arch Ophthalmol. 2011 Jun;129(6):758-66.
  • Sasaki M, Yuki K, Kurihara T, Miyake S, Noda K, Kobayashi S, Ishida S, Tsubota K, Ozawa Y. Biological role of lutein in the light-induced retinal degeneration. J Nutr Biochem. 2011 Jun 8. [Epub ahead of print]
  • Thomson LR, Toyoda Y, Delori FC, Garnett KM, Wong ZY, Nichols CR, Cheng KM, Craft NE, Dorey CK. Long term dietary supplementation with zeaxanthin reduces photoreceptor death in light-damaged Japanese quail. Exp Eye Res. 2002 Nov;75(5):529-42.
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