Lutein-zeaxanthin content of various fruits and vegetables
|Kale ||21,900 |
|Collard greens ||16,300 |
|Spinach (cooked, drained) ||12,600 |
|Spinach (raw) ||10,200 |
|Parsley (not dried) ||10,200 |
|Mustard greens ||9,900 |
| Dill (not dried) ||6,700 |
|Celery ||3,600 |
|Scallions (raw) ||2,100 |
|Leeks (raw) ||1,900 |
|Broccoli (raw) ||1,900 |
|Broccoli (cooked) ||1,800 |
|Leaf lettuce ||1,800 |
|Green peas ||1,700 |
|Pumpkin ||1,500 |
|Brussels sprouts ||1,300 |
|Summer squash ||1,200 |
|Corn (yellow) ||790 |
|Yellow pepper (raw) ||770 |
|Green beans ||740 |
| Green pepper ||700 |
|Cucumber pickle ||510 |
|Green olives ||510 |
Source: Mangles AR, et al.
Carotenoid content of fruits and vegetables: An evaluation of analytic data. J Am Diet Assoc. 1993; 93:284-296.
The ophthalmic literature has recently witnessed an influx of information purporting nutrition's role in eye care. Although not proven conclusively to cure or prevent ocular disease, recent studies suggest that increasing one's intake of various vegetables, fruits and over-the-counter (OTC) supplements may play a role in managing nonadvanced ocular disease.
Of the myriad eye diseases encountered by practitioners, none is more visually devastating than age-related macular degeneration (AMD), the leading cause of irreversible vision loss in people older than 65 years of age in the United States.
The cause of AMD is unknown, although dietary/nutritional deficiencies or genetic factors may be implicated. A study performed in Australia by Peteris Darzins, BM, BS, et al., and published in the May 1997 issue of Ophthalmology found no relationship between long-term sunlight exposure and AMD (Sun exposure and age-related macular degeneration, 104:770-776).
The following discussion will specifically address the potential benefit of dietary supplementation with the carotenoids lutein and zeaxanthin (beta-carotene is not found in significant amounts within the eye) in the treatment regimen of this formidable disease.
Try dark, leafy greens
Carotenoids, a family of red, orange and yellow plant pigments, give fruits and vegetables their color. The retina also contains carotenoids, of which lutein (a lipid, xanthophyll pigment) and zeaxanthin (a mixture of two stereoisomers, one of which is converted from lutein) are dominant. Lutein concentrations in crease in proximity to the macula and comprise the "yellow spot" of the macula lutea, while zeaxanthin predominates in the peripheral retina (but still exists to a limited degree within the macular region).
The macula is prone to oxidative damage by free radicals (oxygen-charged molecules) due to its inherently high levels of polyunsaturated fatty acids within the photoreceptor outer segment membranes. Lutein and zeaxanthin are thought to protect and maintain the macula's pigmentary density by functioning as antioxidants that fight free radicals, as well as reducing the region's exposure to blue light by quenching activated photosensitizers.
Because humans cannot manufacture lutein and zeaxanthin themselves, they must obtain these micronutrients from their diet. These two carotenoids are derived largely from dark green, leafy vegetables, such as spinach and kale, but may also be obtained by taking OTC lutein-zeaxanthin supplements.
Studies support supplements
Studies suggest that supplementation of lutein and zeaxanthin may be associated with a decreased risk of AMD. One study found that individuals who ate the largest amounts of food rich in these carotenoids had a 43% lower risk of developing the disease (Seddon JM, et al. Dietary carotenoids, vitamins A, C and E, and advanced age-related macular degeneration. JAMA.1994; 272:1413-1420).
Another study demonstrated that patients taking a lutein oral supplement had significantly increased macular pigment density (Bone RA, et al. One-year study of macular pigment enhancement by a lutein supplement. Invest Ophthalmol Vis Sci. Abstract Book-Part 1. 1997; 38(4):S90). Lutein intake may also improve dark adaptation by reducing bleaching of retinal photochemicals, enhance contrast and reduce chromatic aberration, glare and photosensitivity.
Current thinking is that food intake, which may provide nutrients not found within supplements and is a potentially more bioavailable source, may be more beneficial than OTC supplementation. However, nutritional supplements may also provide ocular benefits when used in isolation or in addition to natural sources. Because macular lutein levels vary quite dramatically from day to day, consistent supplementary intake is recommended.
Know when to supplement
Additionally, lutein-zeaxanthin supplements should be taken at separate times from other competing fat-soluble nutrients, such as beta carotene and vitamins A, D, E and K. The recommended intake of foods rich in these two carotenoids is at least two to four servings per week. Servings of five to six times per week are associated with an even higher reduction in AMD. Lutein-zeaxanthin supplements (available in both capsule and powder form) should be taken with meals to avoid gastrointestinal upset.
Lutein and zeaxanthin are recommended for individuals who are or have the following characteristics: female (have reduced lutein levels); light-colored irides; smokers (interferes with lutein absorption); AMD; family history of AMD; outdoor occupation or hobbies that make them susceptible to ultraviolet damage.
Supplementation may also be advised in patients taking cholesterol-lowering medications, mineral oil and consuming food containing olestra, because these may interfere with lutein-zeaxanthin absorption.
Recommendations for patients with AMD, drusen or family history of AMD
- Increase dietary intake of foods rich in lutein and zeaxanthin. Oral lutein-zeaxanthin supplements (capsules or powder form) may also be taken exclusively or used in addition to natural food sources.
- Adhere to a low-fat, high-fiber diet.
- Stop smoking.
- Avoid mineral oil and the fat substitute olestra, because these may reduce the absorption of lutein-zeaxanthin when eaten at the same time. Also be aware that cholesterol-lowering medications may have the same effect (consult your physician).
- Wear ultraviolet-absorbing eye wear (additional studies are needed to definitively determine sunlight's role, or lack thereof, in the development of AMD).
- Maintain adequate control of systemic hypertension. Both hypertension and atherosclerosis are potential risk factors in the development of AMD.
For Your Information:
- Michael J. Trad, OD, may be contacted at Medical Arts Center, 1620 Sauk Road, Dixon, IL 61021; (815) 288-7711; fax: (815) 288-5077. Dr. Trad has no direct financial interest in any products mentioned in this article, nor is he a paid consultant for any companies mentioned. Lutein-zeaxanthin content of various fruits and vegetables
- Edited by Bruce E. Onofrey, OD, RPh, who is responsible for primary care eye services at Lovelace Medical Center, Montgomery Blvd. NE, Albuquerque, NM 87111; (505) 275-4226. Dr. Onofrey has no direct financial interest in any products mentioned in this article, nor is he a paid consultant for any companies mentioned.