“Of the 600 carotenoids identified in nature, only about 25 are found in
human serum and tissues, and only lutein and its isomer zeaxanthin
preferentially accumulate in the macular region of the retina to form
macular pigment. Lutein and zeaxanthin protect the macula from short
wavelength blue light and oxidative stress. In infants, lutein and
zeaxanthin may also play a role in the maturation of cells in the
developing macula. Therefore, lutein may be important for visual de-
velopment, maintenance of ocular tissues as well as protection against
age-related macular degeneration (AMD), a leading cause of visual
impairment and blindness in the United States. Increased intake of
lutein is related to a decreased risk of AMD. Similarly, the dietary
information from the Age-Related Eye Disease Study (AREDS 1) found that
dietary intakes of lutein and zeaxanthin were related to protection
against de- veloping AMD. AREDS 2, a multicenter randomized clinical
trial, assessed the effects of oral supplemen- tation of lutein and
zeaxanthin (10 and 2 mg, respectively), and/or eicosapentaneoic acid
(EPA) and docasa- hexaenoic acid (DHA) (650 and 350 mg, respectively) as
a treatment for AMD. In secondary analysis, lutein and zeaxanthin
supplements on top of the AREDS 1 formula (500 mg vitamin C, 400 IU
vitamin E, 15 mg beta-carotene, 80 mg zinc, 2 mg copper) lowered the
progression to advanced AMD in persons with low dietary lutein and
zeaxanthin.
Scientific evidence is accumulating that lutein may be important for
brain function as well. The brain is espe- cially vulnerable to free
radical attacks due to its relatively low antioxidant content, high
polyunsaturated fatty acid concentrations, and its high metabolic
activity. Increased lipid peroxidation and nucleic acidoxidation are
found early in Alzheimer’s disease (AD), and increased levels of
inflammatory markers and pro-inflammatory cytokines have been found in
the central nervous system of individuals with early AD as well as with
mild cognitive impairment. If increases in sensitivity to oxidative
stress and inflammation in the aging brain lead to cognitive deficits,
dietary antioxidant and anti-inflammatory agents may delay the extent of
oxidative damage to neural tissues and may have an enormous impact on
neural health. Lutein functions as both antioxidant and
anti-inflammatory agent. Therefore, intake of this dietary component may
be important for neural health across the lifespan.
In a recent study evaluating the carotenoid content in infant brain
tissue, lutein, zeaxanthin, beta-crypto- xanthin and beta-carotene were
the major carotenoids found in the infant brain tissues. Lutein was the
pre- dominant carotenoid, accounting for 59% of total carotenoids.
Lutein was higher than all other detected carotenoids in regions of the
infant brain that are associated with memory, executive function, vision
and hearing. Preterm infants had significantly lower concentrations of
lutein in their brain compared to full-term infants despite similarity
in postmenstrual age. Brain lutein concentrations were not different
between breast-milk-fed and formula-fed term decedents. The data
suggested preferential accumulation and maintenance of lutein in the
infant brain despite relatively lower intakes among the dietary
carotenoids.
Lutein was also found to be the dominant carotenoid in various regions
of geriatric brain tissue. On the con- trary, beta-carotene and lycopene
were predominant in matched serum, which more closely reflects dietary
intake. These findings suggest that although not predominant in the
diet, there seems to be a preferential uptake of lutein from the
circulation into the brain, similar to what occurs in the macula. In
infant brain tis- sue, the relative contribution of lutein to the total
carotenoids is twice that found in adults, accounting for more than half
the concentration of total carotenoids (4). Therefore, the greater
proportion of lutein in the pediatric brain suggests a need for lutein
during neural development. The mechanism of a neuroprotective effect of
lutein is not known. It has been suggested that lutein’s actions involve
decreased oxidative stress, activation of anti-inflammatory pathways
and modulation of functional properties of synaptic membranes along with
changes in physicochemical and structural features. However, a
neuroprotective effect of lutein may not be due to an antioxidant effect
alone.
Research has shown that there is an association between macular pigment
(MP) density and cognitive func- tion suggesting that lutein and
zeaxanthin embedded in neural tissue are capable of influencing
cognitive function in the elderly (6, 7). Higher MP densities likely
reflect higher brain lutein and zeaxanthin concent- rations which may
function in cognition. Among the carotenoids, lutein seems to be the
most consistently associated with a range of cognitive measures. A role
for lutein in cognitive function was evaluated in a randomized,
placebo-controlled double-blind study in healthy elder women who
received docasahexaenoic acid (800 mg/d), lutein (12 mg/d), a
combination of docasahexaenoic acid and lutein or placebo (8). Fol-
lowing supplementation, verbal fluency scores improved significantly in
the DHA, lutein, and combined treat- ment groups. Memory scores and rate
of learning improved significantly in the combined treatment group, who
also displayed a trend toward more efficient learning. Measures of
mental processing speed, accuracy and mood were not affected by
supplementation. These findings suggest that DHA and lutein supplemen-
tation may work together in an additive/synergistic manner to improve
cognitive functions in older adults. Although lutein is not an essential
nutrient, evidence is accumulating to suggest that lutein is important
to optimize neural health. Given this, efforts may be warranted to
establish recommended intakes for this dietary component.”
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