April 2019 Issue

Eye Health: Lutein — An Underrecognized Antioxidant That Can Help Preserve Sight
By Ginger Hultin, MS, RDN, CSO
Today’s Dietitian
Vol. 21, No. 4, P. 10

Eye health has a unique and direct link to nutrition status. Critical sensory organs, the eyes require specific nutrients for protection and functionality. Many nutrients help support eye health, but carotenoid antioxidants in particular continue to surface as among the most essential. The carotenoid lutein protects the eye’s macula, both shielding damage from light and supporting better vision.1 While lutein commonly is sold in eye health supplements or added to supplemental eye health formulas, it’s also found in an array of healthful foods. Dietitians play a unique role in their ability to provide guidance for patients on how to eat to maintain eye health.

Role of Nutrients
Visual impairment is a major and debilitating health concern worldwide. According to the World Health Organization report on visual impairment in 2010, globally cataracts accounted for 33% of vision loss; age-related macular degeneration (AMD) and diabetic retinopathy each were responsible for 1%. Leading causes of blindness on a global scale have similar proportions; cataracts are the most common at 51% of cases, followed by glaucoma at 8% and AMD at 5%. However, in industrialized countries, including the United States, AMD is the leading cause of blindness and has limited treatment options in people older than 65.1

In normal vision, the eye’s lens collects light and focuses it on the retina, formulating an image that the brain can process. When the lens becomes oxidized through genetic factors or environmental damage such as oxidative stress, excessive light exposure, or smoking, it can become cloudy, resulting in cataracts.2 Likewise, the macula, the portion of the retina responsible for central vision, can be damaged through similar environmental factors and/or with age, especially in those 50 and older, causing the center of the visual field to appear blurry or dark.2,3

While the latter risk factors are relatively well known, awareness of the role nutrition plays in eye health is growing as well, with lutein emerging as a star player.1,3 Other nutrients that support eye health include dietary omega-3 polyunsaturated fatty acids, beta-carotene, vitamins C and E, zinc, and copper.4

What Is Lutein?
Lutein is a xanthophyll, a yellow/brown carotenoid pigment; in conjuncture with its related antioxidant zeaxanthin, it’s been extensively studied and determined to help delay the onset of cataracts and AMD.1,3,5 Lutein and zeaxanthin are stereoisomers, meaning they differ only in the spatial arrangement of their atoms, and often are found in the same foods. The body can’t manufacture lutein, so it must be consumed in the diet.2 Studies estimate that the standard American diet contains 1 to 3 mg per day of lutein and zeaxanthin, while 6 mg daily is needed to reduce the risk of AMD.1,6

Once consumed, lutein and zeaxanthin are transported in the blood stream and deposited into the retina (especially into the macula); they’re the only carotenoids to do so.1,2,7 High concentrations of lutein and zeaxanthin in the retina absorb up to 90% of blue light, helping protect the macula from damage and maintain optimal vision.8 Furthermore, there’s evidence that lutein in the macula may improve visual acuity and help protect the eyes from free radical damage, with the strongest evidence demonstrating a delay in cataract and AMD onset.1

Aside from eye health, lutein also may be useful in treating diabetes and CVD, improving cognitive function, and preventing cervical, breast, esophageal, prostate, lung, and colon cancers. However, the most convincing evidence of lutein’s efficacy is for the management of eye health, and more studies are needed to explore its uses for other health conditions.5

Dietary Sources
There are many food sources of lutein, including green veggies (eg, parsley, spinach, kale, broccoli, lettuce, peas, Swiss chard), egg yolk, and whole grains (eg, einkorn, corn, durum wheat).1 Although there are no recommended daily intakes set for lutein, 10 mg in supplement form has been shown to possibly support eye health, a level that’s easily achieved through food sources (just 1 cup cooked dark leafy greens provides well over 10 mg lutein, with cooked kale providing almost 24 mg).2 In one study, older adults who consumed one whole egg per day experienced a 26% increase in serum lutein (p<0.001) after five weeks compared with placebo.9

The American Optometric Association recommends meeting needs through food or supplements,2 but food sources may be better absorbed.5 Another consideration is that lutein in eggs may be more bioavailable than that in plant sources.5 Lutein, along with other carotenoids, is best absorbed when consumed with a fat source, so preparing lutein-containing foods with oil, avocado, or nuts and seeds, for example, may increase bioavailability.8

Supplements
Because the standard American diet generally lacks lutein, the National Eye Institute recommends lutein supplementation if dietary sources don’t meet current recommendations.2 Taking as much as 15 mg/day of supplemental lutein has been shown to be safe for as long as two years.5 In addition, a total daily lutein intake of as much as 20 mg from both supplement and dietary sources appears to be well tolerated and causes no adverse effects.5,6

Lutein supplements aren’t known to interact with any drugs, though taking beta-carotene or vitamin E supplements with lutein may alter the bioavailability and/or decrease intestinal absorption of beta-carotene and vitamin E.5 That said, supplements that combine lutein with other antioxidants, including vitamin E, may support eye health; in a notable example, Age-Related Eye Disease Study researchers formulated an evidence-based eye health supplement that includes vitamin C, vitamin E, zinc, copper, omega-3 fatty acids, lutein, and zeaxanthin.10 As it is in food, lutein in supplement form is fat soluble, so RDs should encourage clients to look for oil-based supplements to increase absorption.8 Taking lutein as part of a combination supplement may be more effective for AMD prevention than taking lutein supplements alone.4

Future Research and Exploration
Researchers are increasingly interested in establishing Dietary Reference Intake–like guidelines for nonessential bioactive compounds that play critical roles in health, including lutein.6 Future intake recommendations, both for the general population and those at higher risk of visual impairment and blindness given genetic or lifestyle factors, can reduce incidence of sight loss. Many studies have included both food and supplement sources of lutein in investigations, so more research can determine the most efficacious way clients and consumers can meet lutein needs for eye health.4,5 In addition, further studies are needed to evaluate the role of lutein and other carotenoids in slowing progression of cataracts or damage from diabetic retinopathy.8

Recommendations for RDs
Dietitians can educate clients about the benefits of lutein for eye health and help them optimize intake through dietary sources when possible, as these foods are rich in other antioxidants, fiber, vitamins, and minerals. Dietitians also can help guide clients to the most effective and safest lutein supplements, if needed. In doing so, RDs can have a significant impact on clients’ quality of life through preserving their sight, especially as the higher-risk older adult population grows.

— Ginger Hultin, MS, RDN, CSO, is a nutrition and health writer and certified specialist in oncology nutrition based in Seattle. She’s past chair of the Vegetarian Nutrition Dietetic Practice Group, past president of the Chicago Academy of Nutrition & Dietetics, and owner of concierge nutrition practice Champagne Nutrition LLC.

References
1. Abdel-Aal el-SM, Akhtar H, Zaheer K, Ali R. Dietary sources of lutein and zeaxanthin carotenoids and their role in eye health. Nutrients. 2013;5(4):1169-1185.

2. Lutein & zeaxanthin. American Optometric Association website. https://www.aoa.org/patients-and-public/caring-for-your-vision/diet-and-nutrition/lutein. Accessed February 2, 2019.

3. Facts about age-related macular degeneration. National Institutes of Health, National Eye Institute website. https://nei.nih.gov/health/maculardegen/armd_facts. Updated November 2018. Accessed February 2, 2019.

4. Kohn JB. Are there nutrients that support eye health? J Acad Nutr Diet. 2015;115(9):1548.

5. Lutein. Natural Medicines Database website. https://naturalmedicines.therapeuticresearch.com/databases/food,-herbs-supplements/professional.aspx?productid=754. Updated April 6, 2018. Accessed February 2, 2019.

6. Ranard KM, Jeon S, Mohn ES, Griffiths JC, Johnson EJ, Erdman JW Jr. Dietary guidance for lutein: consideration for intake recommendations is scientifically supported. Eur J Nutr. 2017;56(Suppl 3):37-42.

7. Rasmussen HM, Johnson EJ. Nutrients for the aging eye. Clin Interv Aging. 2013;8:741-748.

8. Carotenoids. Oregon State University, Linus Pauling Institute, Micronutrient Information Center website. https://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/carotenoids. Updated August 2016. Accessed February 1, 2019.

9. Goodrow EF, Wilson TA, Houde SC, et al. Consumption of one egg per day increases serum lutein and zeaxanthin concentrations in older adults without altering serum lipid and lipoprotein cholesterol concentrations. J Nutr. 2006;136(10):2519-2524.

10. For the public: what the AREDS means for you. National Institutes of Health, National Eye Institute website. https://nei.nih.gov/areds2/PatientFAQ. Updated May 2018. Accessed February 21, 2019.