A nutritionist's take on eye health

Talking points on diet and weight to help patients achieve optimal ocular health.

By Ruth Frechman, MA, RDN, CPT

About the Author
	Ruth Frechman, MA, RDN, DPT is National Spokesperson for the Academy of Nutrition and Dietetics and author, of The Food Is My Friend Diet, winner of a 2012 National Indie Excellence award. Her e-mail is ontheweigh@usa.net.

Of the five senses, sight may be the most treasured. It also happens to be the sense affected most by diet and nutrition. Studies have shown that the general public may not be getting enough nutrients to maintain ideal eye health,¹ so the ophthalmologist very much has a role in addressing nutrition with patients.

USDA's MyPlate symbol replaces the traditional food pyramid, making it an easy guide to eating healthy.

As with most health problems, proper nutrition plays a big role in prevention. For ophthalmologists whose schedules don't allow them to devote the time patient education may require, a registered dietitian nutritionist (RDN) can be a valuable asset in preventing vision loss from age-related eye diseases. Whichever route you choose, here's what your patients need to know about diet, and some ideas for addressing it with them.

EYES BIGGER THAN STOMACHS

Weight control and ocular health

Many people want to know what's good for their health, but may not think about protecting and preserving their vision through diet until it's too late. Says Maria Sakowitz, MS, RD, CLT, president of Nutrition Associates of East Brunswick in New Jersey: “The people I have seen for eye health issues are diabetics.”

The reason for the increasing number of diabetics, of course, is the rising rate of obesity in the United States. Besides essential nutrients, a healthy weight is also a priority to protect vision. Helping people maintain a normal weight and avoid type 2 diabetes should be a priority for ophthalmologists. Further, a discussion about weight can be a good segue to a discussion about nutrition in general.

When thinking about good vision and eye health, beta-carotene is the nutrient that typically comes to mind, but there's more to eye health than carrots. Research has shown that fruits, vegetables, nuts, seeds, oils and milk may offer protection and reduce the risk of glaucoma, cataract and AMD, so make sure your patients are aware of this.

Following the US Department of Agriculture's (USDA) 2010 Dietary Guidelines is a good way to eliminate nutritional deficiencies, reduce the risk of chronic diseases and maintain eye health (www.health.gov/DietaryGuidelines/).

Targets for fruits and vegetables

Fruits and vegetables provide many of the important nutrients for eye health. For a 2,000-calorie diet, consuming 2 cups of fruits and 2½ cups of vegetables is recommended. The USDA's MyPlate symbol,² which replaces the food pyramid, makes it easy for patients to visualize a healthy way to eat and put the guidelines into practice, so you may want to display it.

Patients need a variety of fruits and vegetables. Don't just eat broccoli, for example, nor only oranges. The Dietary Guidelines divide the vegetable group into five subgroups with similar nutrients in amounts to be consumed in a week.² A daily intake of 2½ cups of vegetables should add up to these amounts in a week:

• 1½ cups dark green vegetables (spinach, broccoli, kale, turnip greens, collard greens).
• 5½ cups red and orange vegetables (carrots, red peppers, squash, pumpkin, sweet potatoes, tomatoes).
• 1½ cups beans and peas (black beans, lentil, pinto beans, garbanzo beans, soybeans, split peas).
• 5 cups starchy vegetables (potatoes, corn, green peas, lima beans).
• 4 cups other vegetables (green beans, asparagus, beets, cabbage, zucchini, cauliflower, okra).

The raw and the cooked

Eating both raw and cooked fruits and vegetables ensures the most complete nutrient absorption. Chopping and cooking carrots and broccoli breaks down the cell walls of the plant and increases the body's ability to absorb it. A small amount of fat, such as oil in salad dressing, will also increase absorption and availability of carotenoids in a salad.

Despite the USDA's Dietary Guidelines, Americans are still falling short of the recommended amounts of fruits and vegetables. We currently eat slightly more than a cup each of fruits and vegetables a day.³ Suggest patients boost their consumption by starting with favorite fruits and vegetables and then adding a new vegetable every week.

BEST NUTRIENTS FOR EYE HEALTH

The nutrients patients need to know about for good eye health are lutein, zeaxanthin, vitamin C, beta-carotene, vitamin E, zinc, and omega 3 fatty acids. Many of these nutrients are antioxidants and may protect eyes by reducing oxidative stress.

AREDS2 stars: lutein and zeaxanthin

Lutein and zeaxanthin (L/Z) are members of the xanthophylls family of carotenoids. L/Z are yellow pigments found in the lens and retina and concentrated in the macula. They may act as potent antioxidants to filter out damaging blue and ultraviolet light. Some evidence has suggested that consuming 6 mg per day of L/Z may lower the risk of AMD and slow the progression of cataract.⁴ The current average intake of L/Z is around 2 mg per day.⁵

The best sources found in commonly eaten foods include kale, spinach, collard greens, egg yolks, pistachios, corn and corn products. Other sources include summer squash, green peas, winter squash, persimmons, Brussel sprouts and broccoli.

Many people avoid eating eggs for fear of raising cholesterol, but studies have shown that blood L/Z increase without much change to cholesterol levels.⁶ Some people don't eat corn, because they believe it doesn't have any nutritional value, but is merely sugar. Nutrition education provides an opportunity for the physician to correct misconceptions among patients.

To increase L/Z levels, add spinach and corn to scrambled eggs. For people who dislike vegetables, adding spinach to smoothies is one way of adding vegetables. The spinach is tasteless in a smoothie.

For another lutein/zeaxanthin fix, see my recipe for kale chips (“Crispy, crunchy and delicious”).

Almost half of Americans have low macular pigment optical density,⁷ which means low L/Z levels. This could be an important risk factor to consider when evaluating eye health.

More than lutein and zeaxanthin

Other nutrients essential for eye health are:

• Vitamin C. As an antioxidant, vitamin C blocks damage from radiation and helps make blood vessels. Vitamin C is found in citrus fruits, berries, tomatoes, melons and potatoes.
• Beta-carotene. An orange carotenoid, beta-carotene is necessary for healthy eyes. The body converts beta-carotene into vitamin A, which the retina needs to detect light. Good sources of beta-carotene are carrots, carrot juice, sweet potatoes, canned pumpkin and that “superfood,” spinach.
• Vitamin E. As an antioxidant, vitamin E may protect the eyes from free radical damage. Good sources include vegetable oils, nuts, especially almonds, sunflower seeds and wheat germ.
• Zinc. Zinc is found in the macula and assists vitamin A in making melanin to protect eyes. Oysters, beef, dry beans, lentils, yogurt and whole grains are good sources of zinc. One easy way to consume more zinc is to drain, rinse and add a can of beans to a salad. Keep in mind, however, that high amounts of zinc can cause a copper deficiency.
• Omega-3 fatty acids. Studies have suggested that the long chain omega-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), may not only play a role in preventing cardiovascular disease, they may also protect the retina.⁸ DHA is found in the brain and in the eyes. Fatty acids may prevent or slow the progression of eye disease by protecting the blood vessels. Good sources of EPA and DHA include salmon, tuna, trout, herring and sardines. The American Heart Association recommends eating fatty fish twice a week. Fish oil supplements may be indicated for the fish-averse.

Sodium intake and the eyes

We know that salt intake can affect blood pressure, but what's good for the coronary arteries may also good for the ocular blood vessels. To protect these tiny blood vessels from bursting, you may want to address sodium restriction with patients. The 2010 Dietary Guidelines for Americans recommend limiting sodium to 1,500 mg a day among these groups:

• Patients age 51 years or older.
• Hypertensives.
• Diabetics.
• Chronic kidney disease sufferers.
• African Americans.

ROLE OF SUPPLEMENTS

Latest knowledge from AREDS2

While the AREDS supplements in the Age-Related Eye Disease Study (AREDS2) showed promising results for people at risk for advanced AMD, they did not reduce the risk of cataract unless perhaps subjects had low levels of L/Z.⁹ The high-dose supplement cocktail reduced the progression of AMD 25% over five years.^10,11 Overall, the L/Z supplement may be safer than beta-carotene, which may raise the risk of lung cancer in smokers or ex-smokers.¹²

With the new AREDS formulation, adding DHA and EPA and lowering zinc did not have an effect or add benefits. However, diet alone cannot provide as high a level of vitamins and minerals as the supplement. If the high-dose AREDS supplement is the best option for a patient, be sure to check for medication interactions.

Moreover, in AREDS2 the formulation did not show benefits in subjects with no or early AMD.¹³ People often take vitamin/mineral supplements as insurance, but the AREDS2 formulation appears to be unnecessary except in the setting of intermediate or advanced AMD.

Buyer beware

If a patient has an unhealthy diet or limited access to certain foods, supplements for the key eye nutrients may be an option. However, the supplement industry is not regulated, so make sure your patients are aware of that. Consumers may be getting too much or not enough of a particular nutrient in their supplement of choice. Further, the supplement may contain other substances not on the label. Inform patients who decide to go the supplement route to look for USP on the label. It indicates the US Phamacopeial Convention has tested it for strength and purity.

The ‘eyes’ have it

In the eyes of a registered dietitian nutritionist, good nutrition is the name of the game to keep not only bodies healthy, but also eyes. Aging, genetics, race and gender are risk factors for eye disease that cannot be controlled — smoking, obesity and diet, on the other hand, can be controlled. Doctors need to continually remind patients of this. Despite the critical role of diet and nutrition in protecting eyes and prevent future vision loss, fewer than 5% of Americans follow the 2010 Dietary Guidelines.¹⁴

Ophthalmologists and registered dietitian nutritionists have their work cut out for them. OM

Crispy, crunchy and delicious

Making kale chips is a fun and tasty way to eat kale, while getting a healthy dose of lutein and zeaxanthin. Try this quick kale recipe.

Crunchy Kale Chips

Wash and chop kale into small 1-inch pieces. In a large mixing bowl add kale and one tablespoon of vegetable oil. Mix until coated. Spread kale on baking sheets. Bake in a preheated oven at 375° for 20 minutes. Toss kale after 10 minutes. Kale will look crispy. When done, sprinkle lightly with salt. Eat and enjoy. The kale chips stay crunchy for days.

REFERENCES

1. El-Sayed M, Abdel-Aal E-SM, Humayoun A, Zaheer K, et al. Dietary Sources of Lutein and Zeaxanthin Carotenoids and Their Role in Eye Health. Nutrients 2013 5:1169-1185.

2. US Department of Agriculture. ChooseMyPlate.gov Website. Washington, DC. Accessed August 2013.

3. State of the Plate 2010 Study on America's Consumption of Fruits & Vegetables. Produce for Better Health Foundation.

4. Seddon JM, Ajani UA, Sperduto RD, et al. Dietary carotenoids, vitamins A, C, and E, and advanced age-related macular degeneration. Eye Disease Case-Control study Group. JAMA 1994 272(18):1413-1420.

5. Koushan K, Rusovici R, Chalam K. The Role of Lutein in Eye-Related Disease. Nutrients 2013 5(5):1823-1839.

6. Vishwanathan R, Gendron CM, Goodrow-Kotyla EF, Wilson TA, Nicolosi RJ. Increased consumption of dietary cholesterol, lutein, and zeaxanthin as egg yolks does not decrease serum concentrations and lipoprotein distribution of other carotenoids, retinol, and tocopherols. Nutr Res. 2010 Nov;30:747-755.

7. Wooten BR, Hammond BR. Macular pigment: influences on visual acuity and visibility. Prog Retin Eye Res. 2002 Mar;21: 225-240.

8. Lutein: Protection from the Eye to the Brain-Egg Nutrition Center. http://www.eggnutritioncenter.org/wp-content/uploads/2012/04/ENC-Closeup-summer-2012-Newsletter.pdf.

9. Age-Related Eye Disease Study 2 (AREDS2) Research Group, Chew EY, SanGiovanni JP, Ferris FL, Wong WT, Agron E, Clemons TE, Sperduto R, Danis R, Chandra SR, Blodi BA, Domalpally A, Elman MJ, Antoszyk AN, Ruby AJ, Orth D, Bressler SB, Fish GE, Hubbard GB, Klein ML, Friberg TR, Rosenfeld PJ, Toth CA, Bernstein P. Lutein/zeaxanthin for the treatment of age-related cataract: AREDS2 randomized trial report no. 4. JAMA Ophthalmol. 2013 Jul;131:843-50.

10. Age-Related Eye Disease Study Research Group. A Randomized, Placebo-Controlled, Clinical Trial of High-Dose Supplementation With Vitamins C and E, Beta Carotene, and Zinc for Age-Related Macular Degeneration and Vision Loss. AREDS Report No. 8. Arch Ophthalmol. 2001 October; 119:1417-1436.

11. Mathew MC, Ervin AM, Tao J, Davis RM. Antioxidant vitamin supplementation for preventing and slowing the progression of age-related cataract. Cochrane Database Syst Rev. 2012 Jun 13;6:CD004567.

12. Age-Related Eye Disease Study 2 Research Group. Lutein + zeaxanthin and omega-3 fatty acids for age-related macular degeneration: the Age-Related Eye Disease Study 2 randomized clinical trial. JAMA. 2013 May 15;309:2005-2015.

13. Chew EY, Clemons, TE, Agron E, et al. Long-Term Effects of Vitamins C, E, Beta-Carotene and Zinc on Age-Related Macular Degeneration: AREDS Report No. 35. Ophthalmol, 2013:120: 1604-1611.

14. Reeves, M. Rafferty, A. Healthy Lifestyle Characteristics Among Adults in the United States, 2000. Arch Intern Med 2005;165: 854-857.