Recent studies support the role of lutein in preventing age-related macular degeneration and cataracts and have paved the way for the carotenoid to attain GRAS status. This regulatory reward has given lutein a safety seal to enter into mainstream food and beverage markets such as cereals and juices. Andaleeb Ahmed investigates.
The discovery of lutein is one of the major breakthroughs in the recent history of medical sciences. This carotenoid, a naturally occurring yellow pigment widely distributed in fruits, vegetables, egg yolk and the human macular pigment in the eye, is gaining recognition as an effective antioxidant. The benefits for vision health associated with lutein, particularly in preventing age-related macular degeneration (AMD) and cataracts, have led to extensive research in this direction.
Lutein promotes long-term eye maintenance by acting as a filter against the damaging effect of the sun, particularly retinal damage and macular degeneration. Researchers have indicated that the decreased concentration of lutein in the macula with ageing and exposure to UV light leads to chronic eye diseases such as cataracts and AMD. However, because the body cannot manufacture lutein, the dietary consumption of lutein-rich foods such as kale, collard, spinach and supplements is essential to maintain optimum lutein levels in the eye.
The GRAS (Generally Recognized As Safe) affirmation status, confirmed by the Food and Drug Administration in June 2003, is opening doors for lutein in the food and beverage markets. Many new avenues have opened for lutein since its gaining of GRAS status, which began with Kemin Foods? patented free lutein, FloraGLO, which is GRAS at various levels for specific foods and drinks. The GRAS movement has continued with Cognis? lutein ester, Xangold, as well as with products by DSM and others.
Numerous studies documenting the positive effects of lutein supplementation on improved visual function have boosted the position of this carotenoid. Despite a little slowdown in the dietary supplements market in the last two to three years, lutein supplements and lutein-fortified products have shown substantial sales growth.
Sights set on the macula
AMD is the leading cause of irreversible blindness among people over the age of 65 years. The macular pigment in the retina contains large amounts of a sub-class of carotenoids called xanthophylls, which includes lutein and its isomer, zeaxanthin.1 However, lutein content decreases with age and exposure to sunlight, contributing to the progression to AMD and ultimately leading to impaired vision.
To determine whether eating lutein-rich foods increases serum lutein levels, a clinical evaluation of seven subjects treated them with spinach and corn for 15 weeks in their daily diet. A battery of tests was made to analyse carotenoid and macular pigment density at baseline, four, eight, 15 weeks and then two months after the study. Results showed concentrations of lutein increased significantly and peaked at eight weeks. 2
To examine the effects of lutein on macular density, researchers at Florida International University in Miami conducted a study on the damaging effect of blue light—the shortest wavelength on the visible spectrum, which causes photo-oxidation in the macula. Two subjects were treated with 30mg/day lutein for 140 days, with measurements being made of their macular pigment optical density before, during and after the treatment period. Twenty to 40 days after the subjects commenced taking the lutein supplement, their macular pigment optical density began to increase uniformly at an average rate of 1.13+/-0.12 milliabsorbance units/day. During this same period, the serum concentration of lutein increased roughly tenfold, approaching a steady-state plateau.
The optical density curve eventually levelled off 40 to 50 days after the subjects discontinued the supplement. During the same 40 to 50 days, the serum concentration returned to baseline. Thereafter, little or no decrease in optical density was observed. The mean increases in the macular pigment optical density were 39 per cent and 21 per cent in the eyes of the two subjects, respectively. Based on the results from this study, researchers concluded that even this modest duration of lutein consumption led to a 30?40 per cent decrease in vulnerability to AMD.3
A recent study evaluated the relationship between dietary carotenoids and AMD in the Age-Related Eye Disease Study. Scientists examined how the lutein and zeaxanthin concentrated in the macular portion of the eye protect the retina. A total of 4,513 subjects participated in this case-control analysis. Researchers concluded that higher intake of lutein and zeaxanthin was associated with a decreased chance of AMD progression.4
Another recent study demonstrated that higher levels of lutein and zeaxanthin correlate to better AMD outcomes. In a study of 93 AMD eyes and 220 normal eyes, researchers discovered an average of 32 per cent lower levels of lutein and zeaxanthin in AMD eyes compared to normal elderly control eyes. Those who consumed high-dose lutein supplements (greater than 4mg/day) had average macular pigment levels in the normal range and had significantly higher levels than AMD patients not consuming these supplements.5
Further, data collected from epidemiological studies have indicated that people with low levels of carotenoids and other antioxidants are more vulnerable to AMD, and that lutein and zeaxanthin were most strongly associated with reduced risk.6
In cataract formation, the eye?s normal protective mechanisms are unable to prevent free radical damage. Cataracts develop when protein deposits form on the lens of the eye, clouding vision. A diet high in lutein as well as its fellow xanthophyl, zeaxanthin, may reduce the risk of developing cataracts.
The Nurses Health Study reported a reduced need for cataract surgery with a regular dietary intake of lutein, an average of 6mg/day.8 After 12 years of follow-up on 77,466 women, those with the highest intake of lutein and zeaxanthin had a 22 per cent decreased risk of cataract extraction compared with those in the lowest quintile. Many of the same researchers found that, among 36,644 men, those in the top quintile of lutein and zeaxanthin intake had a 19 per cent lower risk of cataracts relative to those in the lowest one-fifth.8
A two-year, double-blind, placebo-controlled pilot study result has been reported on the long-term effect of antioxidant supplementation (lutein and vitamin E) on serum levels and visual performance in cataract patients. Seventeen patients were treated with 15mg dietary lutein and 100mg alpha-tocopherol three times a week for two years. Serum concentrations of lutein and alpha-tocopherol increased with supplementation, although statistical significance was reached only in the lutein group. Visual performance (visual acuity and glare sensitivity) improved in the lutein group, whereas there was a trend toward the maintenance of and decrease in visual acuity with alpha-tocopherol and placebo supplementation, respectively. No significant side effects or changes in biochemical or hematologic profiles were observed in any of the subjects during the study.9
How much lutein is required?
Researchers studied the effect of lutein and zeaxanthin on serum due to dietary intake on early- and late-stage age-related maculopathy among 8,222 persons over age 40. Results indicated that higher lutein levels were related to lower chances of abnormalities.10
Ongoing studies are providing more documentary evidence to establish the optimal supply of antioxidants for maintaining eye health, with more emphasis on lutein. So far, there is no recommended daily reference intake for lutein. However, studies suggest that a 6mg/day dosage for prevention should be followed.6 In Seddon?s seminal 1994 study, 6mg/day lutein led to a 57 per cent decreased risk of AMD.
Of note is emerging science that indicates AMD is, in fact, a nutrition-responsive disorder and could actually be reversed at doses of 10mg/day of lutein. A group led by Stuart P Richer, PhD, OD, at the Veteran?s Affairs Medical Center in Chicago, designed a prospective 12-month, placebo- controlled, double-blind crossover study of lutein and lutein with antioxidants on 90 mostly male veterans with atrophic AMD. After one year of supplementation, macular pigment density increased 50 per cent in both treatment groups. Both groups also experienced a statistically significant improvement in some measures of visual function including glare recovery, contrast sensitivity and visual acuity both near and distant. The group that took the lutein with added antioxidants trended better but not to the point of statistical significance. This study is reportedly in press at the Journal of Optometry.
More investigative research is needed to validate the maximum daily dosage as well as to determine any adverse side effects or toxicity. To date, there are no reported statistically significant adverse effects during short-term or long-term prospective studies. However, lutein?s bioavailability may be reduced with concomitant intake of beta-carotene, as both carotenoids compete equally for absorption.11
Because lutein?s mechanism of action in the eye is to quench free radicals and absorb blue light, researchers are investigating whether orally ingested lutein can also work in a skin-health platform. From a functional standpoint, the two organs—the eye and skin—are both exposed to high-energy blue light.
However, do not expect to find lutein in suntan lotion any time soon. UVA and UVB rays penetrate only the outer layers of the skin, and that makes those rays the focus of sunscreen. Blue light, on the other hand, penetrates the entire depth of skin. Because of that, researchers are beginning to look at lutein for preventing skin damage from sun exposure, as well as the downstream effects of skin cancer.
1. Yeum K, et al. Measurement of carotenoids, retinoids and tocopherols in human lenses. Inves Ophthalmol Vis Sci 1995;36:2756-61.
2. Johnson EJ, et al. Relation among serum and tissue concentrations of lutein and zeaxanthin and macular pigment density. Am J Clin Nutr 2000 Jun;71(6):1555-62.
3. Landrum JT, et al. A one-year study of the macular pigment: the effect of 140 days of a lutein supplement. Exp Eye Res 1997 Jul;65(1):57-62.
4. Emily YC, et al. AREDS. Dietary carotenoids and risk for age-related macular degeneration.2003 Oct. NIH Research Festival.
5. Bernstein PS, et al. Resonance Raman measurement of macular carotenoids in normal subjects and in age-related macular degeneration patients. Ophthalmology 2002 Oct;109(10):1780-7.
6. Seddon JM, et al. Dietary carotenoid, vitamins A, C and E and advanced age-related macular degeneration. Eye Diseases Case-Control Study Group. JAMA 1994;271(18):1413-20.
7. Chasan-Taber L, et al. A prospective study of carotenoid and vitamin A intakes and risk of cataract extraction in US women. Am J Clin Nutr 1999 Oct;70(4):509-16.
8. Brown L, et al. A prospective study of carotenoid intake and risk of cataract extraction in US men. Am J Clin Nutr 1999 Oct;70(4):517-24.
9. Olmedilla B, et.al. Lutein, but not alpha-tocopherol, supplementation improves visual function in patients with age-related cataracts: a 2-y double-blind, placebo-controlled pilot study. Nutrition 2003;19:21-4.
10. Tyssandier V, et al. Vegetable-borne lutein, lycopene, and beta-carotene compete for incorporation into chylomicrons, with no adverse effect on the medium-term (3-wk) plasma status of carotenoids in humans. Am J Clin Nutr 2002 Mar;75(3):526-34.
11. Mares-Perlman JA, et al. Lutein and zeaxanthin in the diet and serum and their relation to age-related maculopathy in the third national health and nutrition examination survey. Am J Epidemiol 2001 Mar 1;153(5):424-32.