Nutrition and Retina Health

AREDS taught us some things about this relationship, but there’s much left to learn.

STEVE LENIER, CONTRIBUTING EDITOR

The Age-Related Eye Disease Study 2 (AREDS2) is ongoing, with results anticipated in 2013. But there is already plenty of evidence of a link between good nutritional habits and a healthy retina. Healthier eating overall may certainly slow the development of age-related macular degeneration. Authors of one study concluded that their results suggested that eating various meats may differently affect AMD risk. Their data showed that higher consumption of red meat was associated with an increasing prevalence of early AMD, and higher consumption of chicken was more likely associated with late AMD.¹

In women, a better overall diet significantly lowered the odds of developing early AMD (Figure). Women who maintained diets that scored in the highest quintile on the modified 2005 Healthy Eating Index were shown to be 46% less likely to develop early AMD than women whose diets fell into the lowest quintile of that scale.²

ROLE OF ANTIOXIDANTS, ZINC

Specific nutrients can also make a difference. The original AREDS study showed that “taking high levels of antioxidants and zinc can reduce the risk of developing advanced AMD by about 25%.”³

With exposure to blue light (including the blue light found in sunshine), low combined levels of vitamin C, zeaxanthin, vitamin E, and dietary zinc were associated in one study with neovascular AMD, and the authors of that study recommended that people in the general population should follow the dietary guidelines for these key nutrients.⁴

It’s important to stress to patients that eating fruits and vegetables is good for health in general, not just retinal health.

In a study of twins who both had AMD, the twin with the higher intake of dietary vitamin D, betaine, or methionine tended to be at an earlier stage of AMD, with smaller drusen size and area and less pigment.⁵

Recently, a report showed that increased intake of lutein and zeaxanthin, available in green vegetables, such as spinach, kale, and broccoli, among other sources, could improve early functional abnormalities of the central retina.⁶

Figure. Early AMD showing a single druse.

ANTICIPATING AREDS2

Evidence has also suggested omega-3 fatty acids aid in the prevention of advanced AMD.^7,8 The AREDS2 study is looking at these nutrients, and the results should provide a more definitive answer as to how helpful they are.

David Boyer, MD, a retina specialist practicing in Los Angeles, is looking forward to seeing the results of that study. He currently puts patients with stage 3 disease on medication, following the AREDS formula, except substituting lutein for beta carotene and sometimes also adding fish oil.

“I’m waiting to see if the AREDS2 will give us a bigger improvement or better stabilization than the original AREDS, but it’s going to be hard to know,” Dr. Boyer says. “The results may not be statistically significant because you might get 1% or 2% improvement, so it’s going to be hard to see, but I’d like to see the trends and the tendencies to be able to make an intelligent decision about what to put the patient on.”

When asked whether he thought AREDS2 would support that observational data suggesting that lutein, zeaxanthin, and fish oil are useful in fighting AMD, Dr. Boyer says, “There is a lot of anecdotal evidence, but there are not a lot of randomized, clinical trials. There are some retrospective reviews, and looking at them, I can tell you that’s why we do randomized, clinical trials — to try to check results and to be able to better advise our patients.

“Anecdotal results or case series are good. They’re helpful in the designing of randomized, clinical trials. But because this is such a major health epidemic, we have to rely on the data that come out of these trials and transfer them to our patients.”

Michael Lange, OD, of Ocala, FL, who is certified as a nutritional specialist by the American College of Nutrition and is a member of the Ocular Nutrition Society, has a somewhat different view. Regarding AREDS2, Dr. Lange says, “I can already say I think the results are going to be much better than the original AREDS, because we know beyond the shadow of a doubt that lutein and zeaxanthin help replenish macular pigment density and we think that patients who have AMD are more prone to having decreases in their macular pigment density.”

Dr. Lange believes that rather than following a predetermined formula for nutrients, patients should be approached individually. He initially tests all of his patients for nutritional deficiencies and works with each patient to balance out his or her levels.

LIFESTYLE ADJUSTMENTS ARE ALSO IMPORTANT

There is no difference of opinion as far as a healthy lifestyle is concerned. Drs. Boyer and Lange both tell AMD patients they need to stop smoking and eat healthy diets. These recommendations are especially important for anyone with a family history of AMD, but as Dr. Boyer notes, there is very little downside to anyone eating a healthy diet.

Dr. Lange points out that it is important for patients to be at a healthy weight, because lutein, zeaxanthin, mesozeaxanthin, and astaxanthin have predispositions to be stored in the fat in the body, so if patients are overweight, these supplements will not go to the retina, where they are needed, but to the fat in the patients’ bodies instead.

So both Drs. Lange and Boyer recommend that their patients eat dark green leafy vegetables, such as kale and spinach (Dr. Lange says these foods should be cooked, not consumed raw, to reduce the amount of oxalic acid and increase the amount of lutein released), as well as other vegetables, such as corn and orange bell peppers. Dr. Lange also suggests goji berries, which have a very high content level of zeaxanthin. He recommends that patients avoid beta carotene, because it blocks the absorption of lutein.

FISH, TEA, AND EXERCISE

Drs. Boyer and Lange also both recommend that their patients eat a lot of fish. Dr. Lange specifies it be wild Alaskan salmon and says it is very important to eat the skin, which we often leave on the plate, for the mesozeaxanthin it contains.

Dr. Lange goes on to suggest drinking green tea for the polyphenols and red wine, specifically pinot noir, for the resveratrol. These substances act not only as anti-inflammatories but that also have some anti-VEGF activity, he says.

A proper diet can also benefit circulation. Decreased choroidal blood flow and volume have been found to be associated with increased drusen in patients with nonexudative AMD.⁹ A low-fat and low-cholesterol diet can help prevent fatty plaque deposits, which can develop in the macular vessels and hamper blood flow.¹⁰

In addition to dietary changes, Dr. Lange suggests that patients get plenty of cardiovascular exercise to pump the needed nutrients to the capillaries in the eye and that they wear blue-blocking sunglasses when outside.

THE ROLE OF NUTRITION IN DIABETIC RETINOPATHY

The Centers for Disease Control and Prevention predict that by the 2050, one in three US adults could have diabetes, the leading cause of new cases of blindness among adults younger than 75 years old.¹¹ Between 2005 and 2008, 4.2 million (28.5%) people older than 40 who had diabetes developed diabetic retinopathy. Of those, almost 700,000 (4.4% of those with diabetes) had advanced diabetic retinopathy.¹²

Good nutrition can help fight obesity, a leading cause of diabetes, and can help keep blood-sugar levels under control. Keeping those levels low has been shown to reduce the risk of developing retinopathy.¹³

In 2007, researchers at the National Eye Institutes found that the omega-3 fatty acids EPA and DHA, which can be obtained by eating fish, and the omega-6 fatty acid arachidonic acid may have an effect on the loss of blood vessels, the regrowth of healthy vessels, and the growth of abnormal destructive vessels.¹⁴

The NEI’s study results showed a nearly 50% decrease in retinopathy in mice with higher amounts of omega-3. The authors noted that retinopathy in the mouse shares many characteristics with retinopathy of prematurity in humans, and they also noted there are aspects of the disease process that could apply to diabetic retinopathy and AMD.

More recently, researchers found that maintaining mice on a diet high in omega-3 polyunsaturated fatty acids “efficiently stalled the deterioration of retinal visual function associated with DR before any vasoprotective effects.” These researchers believe that this finding suggests that omega-3 polyunsaturated fatty acids have the capacity to protect cellular function in diabetic retinopathy and thus delay the early events of diabetes-induced neuronal dysfunction in the retina.¹⁵

However, these results are early. As Dr. Boyer pointed out, “We don’t have any studies that are performed to the degree of the AREDS.”

CONCLUSION

Good nutrition is something everyone should strive for. There is already evidence that healthier eating can improve retina health, and clinical testing has shown definite relationships between certain nutrients and certain effects. Continued research will show these relationships more clearly and provide further direction on achieving better nutrition to keep eyes healthier. RP

REFERENCES

1. Chong EW, Simpson JA, Robman LD, et al. Red meat and chicken consumption and its association with age-related macular degeneration. Am J Epidemiol. 2009;169:867-876.

2. Mares JA, Voland RP, Sondel SA, et al. Healthy lifestyles related to subsequent prevalence of age-related macular degeneration. Arch Ophthalmol. 2011;129:470-480.

3. National Eye Institute. The AREDS formulation and age-related macular degeneration. Summary. Available at: http://www.nei.nih.gov/amd/summary.asp. Accessed October 23, 2012.

4. Fletcher AE, Bentham GC, Agnew M et al. Sunlight exposure, antioxidants, and age-related macular degeneration. Arch Ophthalmol. 2008;126:1396-1403.

5. Seddon JM, Reynolds R, Shah HR, Rosner B. Smoking, dietary betaine, methionine, and vitamin D in monozygotic twins with discordant macular degeneration: epigenetic implications. Ophthalmology. 2011;118:1386-1394.

6. Ma L, Dou HL, Huang YM, et al. Improvement of retinal function in early age-related macular degeneration after lutein and zeaxanthin supplementation: a randomized, double-masked, placebo-controlled trial. Am J Ophthalmol. 2012;154:625-634.

7. Seddon JM, Rosner B, Sperduto RD, et al. Dietary fat and risk for advanced age-related macular degeneration. Arch Ophthalmol. 2001;119:1191-1199.

8. Chiu C-J, Klein R, Milton RC, Gensler G, Taylor A. Does eating particular diets alter the risk of age-related macular degeneration in users of the Age-Related Eye Disease Study supplements? Br J Ophthalmol. 2009;93:1241-1246.

9. Berenberg TL, Metelitsina TI, Madow B, et al. The association between drusen extent and foveolar choroidal blood flow in age-related macular degeneration. Retina. 2012;32:25-31.

10. AMD Alliance International. Good advice which could keep age-related macular degeneration at bay. Available at: http://www.amdalliance.org/4-simple-steps-to-decrease-your-risk-of-age-related-macular-degeneration.html. Accessed October 23, 2012.

11. Center for Disease Control and Prevention. U.S. Dept of Health and Human Services. Press Release. Centers for Disease Control and Prevention; Atlanta, GA; Oct 22, 2010.

12. American Diabetes Association. Diabetes statistics, 2012. Available at: http://www.diabetes.org/diabetes-basics/diabetes-statistics/. Accessed October 23, 2012.

13. National Diabetes Information Clearinghouse. U.S. Dept of Health and Human Services. DCCT and EDIC: The Diabetes Control and Complications Trial and Follow-up Study. Available at: http://diabetes.niddk.nih.gov/dm/pubs/control/. Accessed October 23, 2012.

14. National Institutes of Health, National Eye Institute. Omega-3 fatty acids protect eyes against retinopathy, study finds — Retinopathies may be prevented or lessened by a change in diet [press release]. National Institutes of Health; Bethesda, MD; June 24, 2007.

15. Sapieha P, Chen J, Stahl A, et al. Omega-3 polyunsaturated fatty acids preserve retinal function in type 2 diabetic mice. Nutr Diabetes.2012;2:e36.