~ Zeaxanthin and Aging Eyes - Scientific Abstracts

May 2004

Zeaxanthin

Are lutein and zeaxanthin conditionally essential nutrients for eye health? The carotenoids lutein and zeaxanthin are found in the macula in high concentrations and may play a role in the pathogenesis of age-related macular degeneration (ARMD). Lutein and zeaxanthin may protect the macula and photoreceptor outer segments throughout the retina from oxidative stress and play a role in an antioxidant cascade that safely disarms the energy of reactive oxygen species. Although lutein and zeaxanthin are not essential nutrients, studies are beginning to suggest that they fit the criteria for conditionally essential nutrients. Low plasma lutein and zeaxanthin concentrations or dietary intake are associated with low macular pigment density and increased risk of ARMD. Dietary deprivation of lutein and zeaxanthin in primates causes pathological changes in the macula. Should controlled clinical trials show lutein and/or zeaxanthin supplementation protects against the development or progression of ARMD and other eye diseases, then lutein and zeaxanthin could be considered as conditionally essential nutrients for humans.

Med Hypotheses. 2003 Oct;61 (4):465-72

Biologic mechanisms of the protective role of lutein and zeaxanthin in the eye. The macular region of the primate retina is yellow in color due to the presence of the macular pigment, composed of two dietary xanthophylls, lutein and zeaxanthin, and another xanthophyll, meso-zeaxanthin. The latter is presumably formed from either lutein or zeaxanthin in the retina. By absorbing blue-light, the macular pigment protects the underlying photoreceptor cell layer from light damage, possibly initiated by the formation of reactive oxygen species during a photosensitized reaction. There is ample epidemiological evidence that increased macular pigment is correlated with reduced incidence of age-related macular degeneration, an irreversible process that is the major cause of blindness in the elderly. The macular pigment can be increased in primates by either increasing the intake of foods that are rich in lutein and zeaxanthin, such as dark-green leafy vegetables, or by supplementation with lutein or zeaxanthin. Although increasing the intake of lutein or zeaxanthin might prove to be protective against the development of age-related macular degeneration, a causative relationship has yet to be experimentally demonstrated.

Annu Rev Nutr. 2003;23:171-201. Epub 2003 Feb 27

Evidence for protection against age-related macular degeneration by carotenoids and antioxidant vitamins.

Epidemiologic data indicate that individuals with low plasma concentrations of carotenoids and antioxidant vitamins and those who smoke cigarettes are at increased risk for age-related macular degeneration (AMD). Laboratory data show that carotenoids and antioxidant vitamins help to protect the retina from oxidative damage initiated in part by absorption of light. Primate retinas accumulate two carotenoids, lutein and zeaxanthin, as the macular pigment, which is most dense at the center of the fovea and declines rapidly in more peripheral regions.

The retina also distributes alpha-tocopherol (vitamin E) in a nonuniform spatial pattern. The region of monkey retinas where carotenoids and vitamin E are both low corresponds with a locus where early signs of AMD often appear in humans. The combination of evidence suggests that carotenoids and antioxidant vitamins may help to retard some of the destructive processes in the retina and the retinal pigment epithelium that lead to age-related degeneration of the macula.

Am J Clin Nutr. 1995 Dec;62(6 Suppl):1448S-1461S

C-reactive protein concentration and concentrations of blood vitamins, carotenoids, and selenium among United States adults.

OBJECTIVE: To examine the relationships between circulating concentrations of C-reactive protein and concentrations of retinol, retinyl esters, vitamin C, vitamin E, carotenoids, and selenium. DESIGN: Cross-sectional study using National Health and Nutrition Examination Survey III (1988-1994) data. SETTING: United States population. SUBJECTS: Up to 14,519 US noninstitutionalized civilian men and women aged > or=20 y. RESULTS: C-reactive protein concentration (dichotomized at the sex-specific 85th percentile) was inversely and significantly associated with concentrations of retinol, retinyl esters, vitamin C, alpha-carotene, beta-carotene, cryptoxanthin, lutein/zeaxanthin, lycopene, and selenium after adjustment for age, sex, race or ethnicity, education, cotinine concentration, body mass index, leisure-time physical activity, and aspirin use. CONCLUSIONS: These results suggest that the inflammatory process, through the production of reactive oxygen species, may deplete stores of antioxidants. Whether increased consumption of foods rich in antioxidants or supplementation with antioxidants can provide health benefits to people characterized by elevated C-reactive protein concentrations may be worthy of further study.

Eur J Clin Nutr. 2003 Sep;57 (9):1157-63

Nutritional and clinical relevance of lutein in human health.

Lutein is one of the most widely found carotenoids distributed in fruits and vegetables frequently consumed. Its presence in human tissues is entirely of dietary origin. Distribution of lutein among tissues is similar to other carotenoids but, along with zeaxanthin, they are found selectively at the centre of the retina, being usually referred to as macular pigments. Lutein has no provitamin A activity in man but it displays biological activities that have attracted great attention in relation to human health. Epidemiological studies have shown inconsistent associations between high intake or serum levels of lutein and lower risk for developing cardiovascular disease, several types of cancer, cataracts and age-related maculopathy. Also, lutein supplementation has provided both null and positive results on different biomarkers of oxidative stress although it is effective in increasing macular pigment concentration and in improving visual function in some, but not all, subjects with different eye pathologies. Overall, data suggest that whereas serum levels of lutein have, at present, no predictive, diagnostic or prognostic value in clinical practice, its determination may be very helpful in assessing compliance and efficacy of intervention as well as potential toxicity. In addition, available evidence suggests that a serum lutein concentration between 0.6 and 1.05 micromol/l seems to be a safe, dietary achievable and desirable target potentially associated with beneficial impact on visual function and, possibly, on the development of other chronic diseases. The use of lutein as a biomarker of exposure in clinical practice may provide some rationale for assessing its relationship with human health as well as its potential use within the context of evidence-based medicine.

Br J Nutr. 2003 Sep;90(3):487-502

Dietary lutein/zeaxanthin decreases ultraviolet B-induced epidermal hyperproliferation and acute inflammation in hairless mice.

Lutein and zeaxanthin are carotenoids found in green leafy vegetables with interesting antioxidant properties. They are present in high concentrations in the fovea centralis of the human retina and their role in the prevention of age-related macula degeneration has been reported. We have investigated the effect of orally administered lutein and zeaxanthin in the cutaneous response to ultraviolet B irradiation. Female hairless SKh-1 mice receiving 0.4% and 0.04% lutein plus zeaxanthin-enriched diet for 2 week were exposed to single doses of ultraviolet B radiation. Skin biopsies were taken at 24 and 48 hours after irradiation and analyzed for the presence of apoptotic cells, proliferating cells, and expression of proliferating cell nuclear antigen. Our results show a clear ultraviolet-induced dose-dependent inflammatory response. Orally administered 0.4% lutein and zeaxanthin decreased significantly the edematous cutaneous response (p<0.01) as determined by the reduction of the UVB-induced increase of ear bifold thickening. Additionally, dietary carotenoids were efficient in reducing the ultraviolet B-induced increases in the percentage of proliferating cell nuclear antigen (p<0.05), bromodeoxyuridine (p<0.05), and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labeling-positive cells (p<0.01). These data demonstrate that oral supplementation of lutein and zeaxanthin diminishes the effects of ultraviolet B irradiation by reducing acute inflammatory responses and ultraviolet-induced hyperproliferative rebound.

J Invest Dermatol. 2003 Aug;121 (2):399-405

Effect of dietary zeaxanthin on tissue distribution of zeaxanthin and lutein in quail.

PURPOSE: The xanthophyll carotenoids (lutein and zeaxanthin) are hypothesized to delay progression of age-related macular degeneration. The quail has a cone-dominant retina that accumulates carotenoids. The purpose of these experiments was to characterize the carotenoid composition of retina, serum, liver, and fat in quail and to determine whether dietary enrichment with zeaxanthin alters zeaxanthin or lutein concentrations in these tissues.

METHODS: Quail were fed for 6 months with a commercial turkey diet (T group; n = 8), carotenoid-deficient diet (C- group; n = 8), or a carotenoid-deficient diet supplemented with 35 mg 3R, 3'R-zeaxanthin per kilogram of food, (Z+ group; n = 8). Zeaxanthin was derived from Sphingobacterium multivorum (basonym Flavobacterium). Carotenoids in serum, retina, liver, and fat were analyzed by HPLC. RESULTS: As in the primate fovea, the retina accumulated zeaxanthin, lutein, and cryptoxanthin, and preferentially absorbed zeaxanthin (P < 0.005). In contrast, lutein was preferentially absorbed by liver (P < 0.01) and fat (P < 0.0001). In supplemented females, zeaxanthin increased approximately 4-fold in retina, and 74-, 63- and 22-fold in serum, liver, and fat, respectively. In males, zeaxanthin was elevated approximately 3-fold in retina, and 42-, 17-, and 12-fold in serum, liver, and fat, respectively. Birds fed the Z+ diet absorbed a higher fraction of dietary lutein into serum, but lutein was reduced in the retina (P < 0.05). CONCLUSIONS: Xanthophyll profiles in quail mimic those in primates. Dietary supplements of zeaxanthin effectively increased zeaxanthin concentrations in serum, retina, liver, and fat. The robust response to zeaxanthin supplementation identifies the quail as an animal model for exploration of factors regulating delivery of dietary carotenoids to the retina.

Invest Ophthalmol Vis Sci. 2002 Apr;43(4):1210-21

Aging Eye

Blood and lens lipid peroxidation and antioxidant status in normal individuals, senile and diabetic cataractous patients.

PURPOSE: Oxidative mechanisms are believed to play an important role in the pathogenesis of cataract, the most important cause of visual impairment at advanced age. To determine the body's antioxidant status as well as its lipid peroxidation levels, both blood and lens parameters were evaluated. METHODS: This study was performed on the blood samples and lenses obtained from 46 patients diagnosed as having cataract and 20 control subjects. The control group was composed of 10 women and 10 men who do not smoke. Control subjects without any lens opacity or vacuoles when observed with a slit lamp were recruited on the same exclusion criteria as far as disease and treatment were concerned. No antioxidant medicines were used. They were all healthy individuals without any systemic diseases. Superoxide dismutase (SOD), glucose-6-phosphate dehydrogenase (G6PD), glutathione reductase (GSSG-Red) activities in red blood cell (RBC) lysates as well as whole blood glutathione (GSH) and plasma thiobarbituric acid reactive substances (TBARS), the indicator of lipid peroxidation concentrations, were determined quantitatively both in the blood samples and the lenses of the patients with senile and diabetic cataracts. RESULTS: Whole blood GSH values, and erythrocyte SOD activities were significantly lower in the cataractous patients than those in the control group. The values in the diabetic cataractous group were also less than those in the senile cataractous group. Significantly decreased erythrocyte GSSG-Red and G6PD activities were detected in the diabetic cataractous group. Plasma TBARS values were higher both in the senile and diabetic groups when compared to those in the control group. Significantly decreased values were observed for GSSG-Red activities and TBARS values in the lenses of the senile cataractous patients in comparison with those in the diabetic cataractous patients. The lens GSH values were found to be higher in the senile cataractous group than the values obtained in the diabetic cataractous group. CONCLUSIONS: A strong correlation was found between lens GSH and lens TBARS concentrations in the diabetic group. This emphasized the vital role of GSH as an antioxidant in the lens over the other antioxidant parameters, e.g., enzymes, and the oxidative stress is at the highest level in lens.

Curr Eye Res. 2002 Jul;25(1):9-16

Long-term intake of vitamins and carotenoids and odds of early age-related cortical and posterior subcapsular lens opacities.

BACKGROUND: Proper nutrition appears to protect against cataracts. Few studies have related nutrition to the odds of developing cortical or posterior subcapsular (PSC) cataracts. OBJECTIVE: We assessed the relation between usual nutrient intakes and age-related cortical and PSC lens opacities. DESIGN: We studied 492 nondiabetic women aged 53-73 yeas from the Nurses' Health Study cohort who were without previously diagnosed cataracts. Usual nutrient intake was calculated as the average intake from 5 food-frequency questionnaires collected over a 13-15-year period before the eye examination. Duration of vitamin supplement use was determined from 7 questionnaires collected during this same period. We defined cortical opacities as grade > or = 0.5 and subcapsular opacities as grade > or =0.3 of the Lens Opacities Classification System III. RESULTS: Some lenses had more than one opacity. No nutrient measure was related to prevalence of opacities in the full sample, but significant interactions were seen between age and vitamin C intake (P = 0.02) for odds of cortical opacities and between smoking status and folate (P = 0.02), alpha-carotene (P = 0.02), beta-carotene (P = 0.005), and total carotenoids (P = 0.02) for odds of PSC opacities. For women aged <60 years old, a vitamin C intake > or = 362 mg/d was associated with a 57% lower odds ratio (0.43; 95% CI: 0.2, 0.93) of developing a cortical cataract than was an intake <140 mg/d, and use of vitamin C supplements for > or = 10 y was associated with a 60% lower odds ratio (0.40; 0.18, 0.87) than was no vitamin C supplement use. Prevalence of PSC opacities was related to total carotenoid intake in women who never smoked (P = 0.02). CONCLUSIONS: Our results support a role for vitamin C in diminishing the risk of cortical cataracts in women aged <60 years old and for carotenoids in diminishing the risk of PSC cataracts in women who have never smoked.

Am J Clin Nutr. 2002 Mar;75 (3):540-9

Vitamin C is associated with reduced risk of cataract in a Mediterranean population.

Cataract is an important visual problem of older people and a substantial health care cost in many countries. Most studies investigating risk factors for cataract have been conducted in the United States, and there is less information on the possible role of dietary factors in European populations. We conducted a case-control study to investigate the association of antioxidant vitamins (vitamin C, vitamin E, vitamin A, beta-carotene, alpha-carotene, beta-cryptoxanthin, lycopene, zeaxanthin andlutein) and minerals (zinc and selenium) and risk of cataract in a Mediterranean population. Cases with cataract (343) and 334 age/sex frequency-matched controls aged 55 to 74 years old were selected from an ophthalmic outreach clinic in Valencia, Spain. Participants were interviewed about their diet using a Food Frequency Questionnaire, and other information on potential confounders, such as smoking, alcohol, and education. Blood samples were analyzed by a colorimetric method for vitamin C and by reversed-phase HLPC for other blood antioxidants. Blood levels of vitamin C above 49 micromol/L were associated with a 64% reduced odds for cataract (P < 0.0001). Dietary intake of vitamins C, E and selenium were marginally associated with decreased odds (P = 0.09, P = 0.09, P = 0.07, respectively), whereas moderately high levels of blood lycopene (>0.30 micromol/L) were associated with a 46% increased odds of cataract (P = 0.04). Our results strengthen the evidence for a protective role for vitamin C on the aging lens as this effect was seen in a population characterized by high vitamin C intakes.

J Nutr. 2002 Jun;132(6):1299-306


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