Some nutrients can stave off vision loss and ocular diseases that occur as we age.
Even if you are reading this without glasses, it's not too early to start taking your eye vitamins. Some nutrients can stave off the burdensome vision loss and eye disease that occur as we age, mounting research suggests.
But claims by supplement manufacturers about the powers of eye-friendly antioxidants are frequently overblown. Although carrots have long been touted as a magical sight-booster, other foods, including dark, green leafy vegetables, might have a stronger impact on your peepers.
More than 150 million Americans use glasses or contacts to correct refractive errors such as nearsightedness or farsightedness, according to a report from the eye health organization Prevent Blindness America. And the prevalence of blindness and sight problems rises with age. In people older than 40, the most common diseases include age-related macular degeneration (AMD), cataracts, diabetic retinopathy and glaucoma.
Studies over the past few decades suggest that people whose diets are high in specific antioxidants such as vitamin C, E, zinc or carotenoid plant pigments such as beta-carotene or lutein are less likely to develop common age-related eye diseases, said Julie Mares, a professor of ophthalmology and visual sciences at the University of Wisconsin-Madison.
But Mares cautions that it's better to get these nutrients through whole foods, rather than supplements, which usually provide only single nutrients and might be lacking other critical compounds. Researchers are finding that those who eat a wide range of healthy foods "have much lower odds for having age-related diseases," Mares said.
Still, sales of vision supplements in the United States reached $370 million in 2010, a 6 percent increase over the previous year, according to estimates by Nutrition Business Journal. Lutein, multivitamins and fish oil are the most popular eye-related products, NBJ said.
Here's a look at which nutrients show the most promise of improving eye health and where researchers are still in the dark.
Antioxidant vitamins + zinc
What's clear: The antioxidant vitamins C, E, beta carotene and zinc reduced the risk of developing advanced AMD by about 25 percent, according to the National Eye Institute's original Age-Related Eye Disease Study.
Still foggy: They haven't been shown to prevent or delay the onset of AMD, only to slow its progression in people who already have it. Current data also don't support the use of antioxidants -- or herbal medications -- to prevent or treat cataracts, glaucoma or diabetic retinopathy, according to researchers at Oregon Health Science University.
Lutein and zeaxanthin
What's clear: Lutein and zeaxanthin could help younger people improve vision, new data suggest. This might be because the carotenoids can absorb blue light, which is especially damaging to the back of the eye or retina, Mares said.
Still foggy: So far, there's no association between lutein and zeaxanthin and vision in non-glare conditions. Moreover, early data suggest that some people are low responders and might not be able to increase the lutein levels in their eyes as easily as others can, even with supplements, Mares said.
Omega-3 fatty acids
What's clear: Essential fatty acids could help treat dry-eye syndrome, which occurs when the eye can't produce enough tears for lubrication, according to a 2011 study from the Mount Sinai School of Medicine. The American Optometric Association recommends eating fish or taking a nutritional supplement that contains a polyunsaturated fatty acid to help with dry eye. The essential omega-3 fatty acid decosahexanoic acid (DHA), found in breast milk, is crucial for vision and brain development in infants.
Still foggy: It is known that formula-fed infants do not see as well as infants who are fed breast milk. But adding DHA to infant formula hasn't been shown to improve vision, so other nutrients might be at play.
What's clear: Made by the body when the skin is exposed to sunlight, vitamin D also helps lower inflammation and slows the development of abnormal blood vessels that contribute to AMD.
Still foggy: Beyond a certain level, higher levels of D didn't have greater impact. Mares' research also suggests that vitamin D might enhance the benefit of other aspects of diet.