Dry eyes: Eat tuna to protect your eyes
Tears get a bad rap. But you'd truly have something to cry about if a malfunction in the glands around your eyes prevented you from making tears.
As simple as they may seem, tears contain a precise balance of water, salt, proteins, mucus and oil. Throw off the balance of those components and you could develop dry eye syndrome (DES); a condition that creates an irritating, sometimes gritty sensation under the eyelid, and affects about 7 in 100 people - mostly women. Chronic DES can damage the cornea and lead to vision loss.
Every time you blink, a protective tear film coats the eye. The outer layer of the film is composed of lipids, which impedes evaporation. A new study shows that a key dietary factor may provide significant prevention of DES by supporting lipid production.
Omega 3 helps prevent dry eyes
As we grow older, our bodies produce less and less oil. And this oil shortage can have a direct effect on tear composition.
A team of American researchers from Brigham and Women's Hospital and Schepens Eye Research Institute (both are affiliated with Harvard Medical School) conducted a recent study using data collected from the Women's Health Study. Dietary intake was assessed for more than 32,000 women between the ages of 45 and 84. About 1,500 subjects had been diagnosed with DES.
Analysis of the data produced these findings:
* Women who had the lowest intake of omega-3 fatty acids were 20 percent more likely to develop DES compared to women with the highest intake
* A higher ratio of omega-6 to omega-3 fatty acids was associated with a significantly higher risk of DES
* Omega-3 from tuna provided the most impressive prevention of DES: Women who ate five or more tuna servings per week reduced DES risk by more than 65 percent compared to women who had only one serving of tuna per week
Getting the right omega ratio
As many HSI members are by now aware, omega-3 fatty acids help regulate key cardiovascular functions such as heart rate, blood pressure, blood vessel dilation and blood clotting. Omega-6 fatty acids promote inflammation and have a negative impact on the body's immune system.
The most favourable omega-3 to omega-6 ratio is 1:1. But because omega-6 is abundant in processed foods (while the primary dietary source of omega-3 is fish) the omega-3 to omega-6 ratio of a typical Western diet is by some estimates more like 1:20.
In a previous e-alert I told you about dietary sources like walnuts and flaxseed that deliver omega-3 fatty acids, but only fish contains both eicosapentaenoic acid (EPA) and docohexaenoic acid (DHA). When combined, these two essential fatty acids have been shown to help prevent depression, as well as heart disease, Alzheimer's disease, arthritis, influenza, hyperactivity, and even some forms of cancer.
The drawback with fish is the mercury content present in exactly the types of fish that contain the highest concentration of omega-3: dark meat fish such as tuna, swordfish, and salmon. High-quality fish oil supplements don't contain mercury and provide an easy way to insure a good intake of omega-3 fatty acids.
Red meat is another good source of omega-3, but only when the meat comes from wild animals or commercial livestock that has not been fattened with grain feed. A previous study found grass-fed beef to have the omega ratio of 1:2. The ratio of grain-fed beef runs between 1:5 and 1:13.
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