26
0
1
2
3
EDCC Twin
Study
AREDS Beaver
Dam
NHANES POLA EUREYE
Figure 3. Association of the risk for AMD with dietary long chain omega 3 or fish (cross-sectional and case-control studies). References of the cited
studies: EDCC
(43)
; Twin Study
(45)
; AREDS
(44)
; Beaver Dam
(46)
; NHANES
(47)
; POLA
(48)
; EUREYE
(49)
intake in lutein and zeaxanthin, subjects may be at higher
risk for AMD because of decreased bioavailability, asso-
ciated with lower plasma concentrations of these com-
ponents. However, currently available studies including
plasma measurements are cross-sectional or case-control
studies, where the plasma measurements were performed
in subjects already affected by the disease. The stronger
associations found in these studies may therefore be
explained by reverse causality (i.e. plasma carotenoids
were lower because of change of dietary habits in subjects
with AMD, for instance).
Globally, the few available epidemiological studies
suggest a protective role of lutein and zeaxanthin in
AMD, but other studies are needed in this field, in
particular larger, prospective studies including die-
tary and plasma measurements.
Finally, omega 3 PUFA include a precursor (alpha-linole-
nic acid (ALA)), and three long-chain derivatives (eicos-
apentaenoic acid (EPA), docosapentaenoic acid (DPA)
and docosahexaenoic acid (DHA)). ALA is an essential
nutrient, since humans cannot synthesize it de novo and
therefore rely on diet as its sole source. Synthesis of the
long-chain derivatives is very limited in humans
(41)
, who
must therefore rely on their dietary supply, mainly by fish
and seafood. Long-chain omega-3 PUFA have important
structural and protective functions in the retina. DHA is
a major component of the photoreceptors
(42)
. They also
have protective functions, including the systemic anti-
inflammatory, anti-angiogenic and anti-apoptotic func-
tions and specific actions in the retina such as increase
in lysosomial acid lipase, leading to increased lipid deg-
radation in the retinal pigment epithelium
(42)
. As shown
in Fig. 3 and Fig. 4, seven case-control
(43-44)
or cross-
sectional studies
(45-49)
and five prospective studies
(50-54)
assessed the associations of dietary intake of long-chain
omega 3 PUFA or fish with AMD. In spite of differ-
ences in populations, methods and types of studies, all
studies showed a reduced risk for AMD in subjects with
high dietary intake of long chain omega 3 PUFA or fish,
although some of these associations did not reach statis-
tical significance. Most of these studies were grouped in
a meta-analysis performed in 2008, which concluded at
