157
Preventive AMD Treatments
of 1,700 patients was subject to a 5-year follow-up eye
examination, showed that a high intake of carotenoids
and vitamin E is associated with a lower risk of developing
large drusen. High dietary zinc intakes would be associ-
ated with a lower number of retinal pigment epithelium
anomalies
(39)
.
In 2001,
AREDS report no. 8
, a large multicentric, ran-
domised clinical trial, revealed that the risk of progression
to advanced AMD was reduced by 28% in patients with
intermediate AMD treated with high doses of antioxidant
supplements (vitamins C and E, zinc and
β
-carotene),
when compared to the placebo group (odds ratio: 0.72;
99% confidence interval: 0.52-0.98). This study did not
specifically investigate whether antioxidant supplements
were effective in the primary prevention of early AMD in
individuals without signs of this condition
(40)
.
In 2004,
AREDS report no. 13
evaluated mortality rates
in patients with ocular disorders taking high doses of anti-
oxidants or zinc. Results showed that mortality was lower
in patients taking zinc (alone or with antioxidants) (12%
reduction), when compared to those not taking this min-
eral (RR: 0.73; 95% CI: 0.61-0.89)
(41)
.
In 2005, the
Rotterdam Study
, a population-based study
involving 4170 participants, showed that an above-average
intake of the 4 AREDS trial nutrients protected against
AMD development or early AMD, as indicated by large
drusen, and was associated with a 35% reduction in the
risk of AMD (HR: 0.65; 95% CI: 0.46-0.92)
(42)
.
In 2007,
Chong and colleagues
undertook a systematic
review and meta-analysis of nine prospective cohort stud-
ies and three randomised clinical trials. The results from
the first studies indicated that vitamin A, vitamin C, vita-
min E, zinc, L, Z, alpha-carotene, beta-carotene, beta-
cryptoxanthin and lycopene have little or no effect in the
primary prevention of early AMD. The three randomised
clinical trials failed to show that antioxidant supplements
prevented early AMD
(43)
.
In 2008, a systematic review and meta-analysis under-
taken with the objective of examining available evidence
as to whether antioxidant vitamin or mineral supplements
are able to prevent AMD development or delay its pro-
gression was published online. No evidence was found
that antioxidant (vitamin E or beta-carotene) supplements
are able to prevent AMD (RR 1.03; 95% CI; 0.74-1.43).
Some evidence was found that antioxidant (beta-carotene,
vitamin C and E) and zinc supplements were able to
delay progression to advanced AMD and prevent loss of
visual acuity in individuals displaying signs of the disease
(adjusted odds = 0.68; 95%CI: 0.53-0.57, and 0.77; 95%
CI: 0.62-0.96, respectively)
(44)
.
3.2.2 Key points
According to current evidence, antioxidant vitamin supple-
ments are unable to prevent AMD.
Patients with AMD or early AMDmay benefit from taking
AREDS trial supplements.
High-dose antioxidant supplementation may increase the
risk of lung cancer in smokers (beta-carotene), heart fail-
ure in individuals with vascular disease or Diabetes (vita-
min E) and hospitalisation in patients with genitourinary
conditions.
3.3 Dietary fatty acids
3.3.1 Docosahexaenoic acid (DHA) and eicosapentae-
noic acid (EPA)
The role of fatty acids in AMD was initially investigated
because of the hypothesis that AMD and cardiovascular dis-
ease may share a similar pathogenesis and fat intake has been
associated with atherosclerosis and cardiovascular disease.
Fatty acids may be divided into three types:
•
Saturated fat from dairy products and meat.
•
Monounsaturated fatty acids (MUFA) from olive
oil.
•
Polyunsaturated fatty acids (PUFA), especially
from fish and seafood.
Omega-3 fatty acids, also known as Long-Chain
Polyunsaturated Fatty Acids (LCPUFAs), are essential to
human health. Omega-3 fatty acids include alpha-linolenic
acid (a short-chain omega-3 fatty acid) and long-chain
omega-3 fatty acids docosahexaenoic acid (DHA) and
eicosapentaenoic acid (EPA).
Omega-3 fatty acids, especially DHA, have morphological,
functional and protective roles in the retina:
1. Morphological role – DHA is the main PUFA
found within the outer segments of rods and has
anti-apoptotic, anti-inflammatory and antiangio-
genic functions.
2. Functional role – DHA provides an adequate
environment for conformational changes in
rhodopsin.
3. Protective role - DHA protects against aging of
the retina and may reduce lipofuscin accumula-
tion in the retinal pigment epithelium and lipid
deposits in Bruch’s membrane.
Several epidemiological studies have evaluated the rela-
tionship between total and specific fat intake and the risk
of advanced AMD. Results confirm that higher intakes
