Eating for Eye Health

Eating for Eye Health
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As America ages, it’s more important than ever to prioritize vision-protective nutrients and foods.

According to the World Health Organization, global average life expectancy continues to rise and is increasing faster than it has at any other time during the last 50 years. Approximately 9 percent of the world’s population is 65 or older; this number is expected to grow to 17 percent by 2050. With longer life comes more years of living with chronic diseases and disabilities. For instance, the rate of vision impairments nearly triples for Americans as they age from 65 to 85 and older.

Age-related macular degeneration, or AMD, is a leading cause of vision loss in older people in the United States and, as the name indicates, the risk of the condition increases with age. AMD affects 2.5 percent of white Americans 50 and older and more than 14 percent of white Americans 80 and older — significantly more than people who are black, Latino or other races. Between 2000 and 2010, the number of people in the U.S. with AMD grew 18 percent. By 2050, the number is expected to reach 5.4 million.

While risk for AMD partially is impacted by genetics, lifestyle factors including smoking, physical activity and dietary patterns also can modify risk. Research suggests Americans are not eating enough of the foods and nutrients that protect eye health, particularly the antioxidant carotenoids lutein and zeaxanthin. Foods rich in these nutrients include dark leafy greens and green vegetables. Lutein and zeaxanthin are found in high amounts in the retina, and lutein has the ability to absorb blue light that is harmful to the eye.

According to antioxidants and eye health researcher Elizabeth Johnson, PhD, FACN, FICS, “If a generally healthy adult is following the 2015-2020 Dietary Guidelines for Americans, they should get approximately 6 milligrams per day of lutein, which epidemiological research suggests is the amount related to decreased risk of age-related eye disease.” For reference, one cup of cooked kale contains about 6 milligrams of lutein and zeaxanthin.

There is no dietary reference intake, or DRI, for lutein or zeaxanthin and neither is mentioned in the 2015-2020 Dietary Guidelines for Americans. Based on criteria to evaluate if a nonessential bioactive is ready to be considered for specific dietary recommendations, some researchers believe there is enough evidence to develop intake recommendations for lutein. The American Optometric Association recommends consuming 10 milligrams of lutein and 2 milligrams of zeaxanthin per day to slow AMD progression.

Additional antioxidants may play a role in eye health. Catechins found in green tea are thought to positively impact the eyes. Drinking green tea has been linked with significantly reduced risk of age-related cataracts and glaucoma. There is in vitro evidence that melatonin may protect against oxidative stress in retinal cells, and a link has been found between serum melatonin levels and risk of AMD as well as diabetic retinopathy, a condition that causes eye damage in people with diabetes. More research on each of these associations is needed before any certain conclusions may be drawn.

Eating more vitamin A (found in sweet potatoes, spinach, carrots, cantaloupe, peppers and mangoes), vitamin C (found in peppers, oranges, kiwifruit, broccoli, strawberries and Brussels sprouts) and vitamin E (found in sunflower seeds, almonds, hazelnuts, sunflower oil and wheat germ) has been linked with lower risk of cataracts and AMD.

A 2017 meta-analysis found a significant association between vitamin D deficiency and diabetic retinopathy. Researchers also are investigating mechanisms by which vitamin D seems to lower AMD risk. Additionally, evidence points to a diseasespecific association between AMD and osteoporosis in older women; researchers suspect vitamin D may play a role. Vitamin D-rich foods include salmon, tuna, UV-exposed mushrooms and fortified juices and dairy and plant-based milks. Researchers also have found lower rates of AMD in people who consume higher amounts of zinc, which is found in oysters, crab, beef, pork, baked beans and cashews.

Optimal Dietary Patterns
Eating styles rich in vegetables and fruits are associated with lower risk for cataracts, glaucoma and AMD; high meat consumption, especially red meat, has been linked to increased risk of these conditions. Although research on amounts and types of dietary fat are complex and require further study in a variety of populations, Mediterranean-style eating patterns have been associated with lower risk for AMD. Researchers have found that nutrient-dense eating patterns are most effective for lowering risk of AMD when implemented along with other healthful lifestyle behaviors.

Addressing Dietary Supplements
The National Eye Institute has conducted two large clinical trials investigating the impact of specific supplements on risk for and progression of advanced AMD among older people. In 2001, researchers from the Age-Related Eye Disease Study, or AREDS, reported that the AREDS supplement (vitamins C and E, beta-carotene, copper and zinc) reduced the risk of advanced AMD by 25 percent over five years. Beginning in 2006, a second study called AREDS2 investigated variations of the original formula including one with added omega-3 fatty acids DHA and EPA and another with lutein and zeaxanthin instead of beta-carotene. Results showed no significant benefit from DHA and EPA. Lutein and zeaxanthin in place of beta-carotene slightly reduced risk of advanced AMD; this was especially useful for smokers, since supplemental beta-carotene was found to increase risk of lung cancer in people who smoked. Currently, AREDS formulations are the only treatment for AMD.

Based on AREDS and AREDS2 data, to slow AMD progression, the American Optometric Association recommends consuming 500 milligrams per day of vitamin C, 400 milligrams per day of vitamin E and 40 to 80 milligrams per day of zinc. The American Academy of Ophthalmology recommends considering the AREDS and AREDS2 supplements for patients with intermediate and advanced AMD. Supplements may help treat AMD if a person’s diet does not contain adequate amounts of specific nutrients. There may be no benefit or harm in taking supplements if a person’s diet already contains adequate amounts of specific nutrients. Talk with a health care provider before taking any dietary supplements.

Key Takeaways
An abundance of evidence links eating more vegetables and fruits with better eye health as one ages. Following the Dietary Guidelines for Americans should be sufficient for most people. For those already affected by AMD, health care providers may recommend supplementation. Registered dietitian nutritionists should consider incorporating the topic of eye health into conversations with older patients and clients: It’s another reason to consume ample amounts of vegetables and fruits.

References

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Age-Related Macular Degeneration (AMD). National Eye Institute website. Accessed April 17, 2019.
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Taylor Wolfram
Taylor Wolfram, MS, RDN, LDN, is a dietetics content manager at the Academy of Nutrition and Dietetics and associate editor of Food & Nutrition.