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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 |