Chemistry Reference
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to be particularly supporting because they outline that many AMD risk factors are associated either
with a relative dietary lack of key nutrients including lutein and zeaxanthin (Nolan et al. 2006), or
with a reduced MPOD (Nolan et al. 2007b).
13.8.2.2 Clinical Evidence
The question whether lutein and zeaxanthin can contribute to lowering the risk for AMD cannot
be answered unequivocally by epidemiological studies. Only randomized controlled trials (RCTs)
during the course of which xanthophylls are supplemented in a double-blind, placebo-controlled,
and randomized manner, and in which results are evaluated according to clear predei ned efi cacy
criteria (Seddon and Hennekens 1994) have the potential to provide dei nitive answers. The spe-
cii c long-term time-course and intricate nature of AMD make the design of such studies difi cult,
however.
To date, no results from large RCTs evaluating whether supplementation with lutein and/or zeax-
anthin inl uences disease-specii c endpoints has been published. One reason for this is that lutein
and zeaxanthin supplements have only recently become available for human consumption. In 1992,
the National Eye Institute initiated the AREDS in 3600 people (AREDS Research Group 1999).
The results indicated that regular ingestion of a dietary antioxidant supplement containing vitamins
E and C,
-carotene, zinc, and copper could reduce the progression of advanced AMD relative
to controls (AREDS Research Group 2001). Recently, another RCT (AREDS II) was initiated by
the NEI. Early in 2007, this trial began recruiting the planned 4000 subjects. The supplements for
this study provide daily doses of 10 mg lutein and 2 mg zeaxanthin in combination with long-chain
polyunsaturated fatty acids (LCPUFAs). The effects of combining LCPUFAs with xanthophylls has
been evaluated by at least two research groups in the meantime (Huang et al. 2008, Johnson et al.
2008a,b) with results indicating that addition of LCPUFA did not change the plasma levels of the
supplemented xanthophylls.
What have been published are small-scale lutein supplementation studies. One (Dagnelie et al.
2000) reported signii cantly improved visual function in 16 patients with congenital retinal degen-
erations who were supplemented with 20-40 mg lutein/day for 26 weeks. A case-control study
found improvements in a number of visual function tests, including contrast sensitivity in patients
who consumed lutein-rich spinach at an intake level of 30 mg of lutein/day for 26 weeks (Richer
1999). A larger and longer double-blind, placebo-controlled supplementation study with lutein and
an antioxidant mixture in 90 subjects, showed statistically signii cant improvements in selected
visual functions of AMD patients who took either 10 mg/day of lutein alone, or 10 mg/day of lutein
incorporated in an antioxidant formula, compared with those taking placebo (Richer et al. 2004). In
another study, 21 patients diagnosed with RP and 8 normal subjects were supplemented with a daily
dose of 20 mg of lutein for a period of 6 months (Aleman et al. 2001). Plasma lutein concentrations
increased in all participants but MPOD, as measured by HFP, increased signii cantly only in half
of them. These “retinal responders” had a less severe course of the disease than the nonresponders.
Inner retinal thickness, measured by optical coherence tomography, correlated positively with the
level of MP density at 0.5° eccentricity, a relationship that was signii cant for patients, but not for
healthy controls. In contrast, results of a recent study indicate that central retinal thickness is indeed
directly correlated with MPOD in healthy subjects (Liew et al. 2006). Parisi et al. (2008) supple-
mented 15 early AMD patients with an antioxidant mixture providing, among other substances,
daily amounts of 10 mg lutein and 1 mg zeaxanthin for 12 months. When comparing the patients'
multifocal ERG recordings with those of an untreated control group they noted that supplementation
had induced an improvement of retinal function, which was specii c for the central retina but was
not noted in peripheral retinal areas. While this is a preliminary i nding in a small group of patients,
it indicates that lutein and zeaxanthin supplementation may have had a “therapeutic” effect that
could be measured by a functionally important parameter. The authors conclude that the improved
ERG signal is indicative of a functional improvement of preganglionic elements. If this were true,
a retinal element other than the photoreceptors and the RPE would have been positively altered by
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