Nutritional supplements to prevent age-related visual problems
Chronic, age-related visual problems such as cataract,
macular degeneration and glaucoma have one basic similarity. These are
degenerative conditions caused by excessive oxidation (free radical damage).
Remember that free radicals are toxic by-products of your everyday metabolism.
With aging, the production of these free radicals increases, whereas your body
defences against them (i.e. the production of natural antioxidants in an attempt
to neutralise free radicals) becomes less effective. As a result, free radicals
destroy proteins, enzymes and DNA causing chronic damage to your tissues.
So, this is oxidation in a nutshell. Apart from oxidation,
another important process implicated in aging is that of glycation. This is when
sugar and similar molecules attack your proteins and DNA, causing abnormal
chemical bonds between individual molecules. Free radicals then make matters
worse by facilitating this destruction of your tissues. In the end, there is an
increased amount of abnormal, twisted and deformed proteins in your body,
worsening the risk of developing age-related chronic conditions. In the case of
the eye, these deformed proteins may cause visual impairment through cataract,
macular degeneration or glaucoma.
Cataract
Cataract is a common age-related condition and affects one
in four people over the age of 65. Basically, it is caused when the proteins
inside the lens of the eye (called crystallins) become damaged. Glycation is the
main culprit here, which causes the crystallins to bind to each other, clump
together and become misshapen, forming opaque plaques in the lens of the eye.
As a result, light cannot pass through the lens and reach
properly the inside of the eye, so vision is impaired. This progressive damage
is made worse by free radical action on the already damaged crystallins. For
more detailed information about cataract see my most recent book The Cataract
Cure.
Age-Related Macular Degeneration (ARMD)
Another degenerative condition is ARMD. This happens when
a particular part of the retina, called the macula, becomes damaged by free
radicals that cause the arteries and cells of the retina to malfunction.
Environmental pollution, increased ultraviolet (UV)
radiation or other toxic damage, cause and increased production of free radicals
in the retina. So, a logical way of preventing or treating ARMD is by using
antioxidants to reduce the concentration of free radicals in the eye (1). The
use of antioxidants in preventing ARMD has been studied in a variety of
scientific trials, usually with positive results. For example, it was recently
reported from the Department of Ophthalmology, Biochemistry, and Medicine, Emory
University, Atlanta, Georgia in the US, that antioxidants prevent oxidation of
vital amino acids in patients with ARMD (2).
The role of oxidation as a cause of ARMD was explored
further by a team of researchers from the Chemistry and Biochemistry Department,
Northern Illinois University. The researchers suggested that one of the reasons
why the macula is easily affected by free radicals is because, with aging, the
melanin pigment of the retina loses its ability to withstand damage (3). It
makes sense to suggest that, in order to prevent this deterioration of the
melanin pigment, antioxidant therapy must be helpful.
Glaucoma
The third most common chronic eye condition is glaucoma. This is when the fluid inside different parts of the eye does not flow properly,
causing increased pressure inside the eye with consequent loss of vision. The
blockage is caused when free radicals damage the trabecular meshwork, a part of
the eye that produces and then reabsorbs the fluid.
Italian scientists from the Department of Health Sciences,
University of Genoa, have recently reported the following: “There is growing
evidence that reactive oxygen species (free radicals) play a key role in the
pathogenesis of glaucoma. The occurrence of oxidative DNA damage in the
trabecular meshwork has been demonstrated by measuring the increase of
8-hydroxy-2'-deoxyguanosine, the most abundant DNA oxidative alteration, which
is significantly increased in glaucoma-bearing subjects as compared to
unaffected controls.”
They believe that there are several factors supporting the
theory that free radicals play a fundamental role in glaucoma. Some of these
reasons are:
- In the presence of hydrogen peroxide (a well known
free radical), the pressure of the fluid inside the eye increases. This is
because hydrogen peroxide compromises the integrity of the trabecular
meshwork.
- The trabecular meshwork is normally rich in natural
antioxidants.
- Patients who have glaucoma have significant increase
in free radical activity.
- These patients appear to have a genetic
predisposition rendering them susceptible to free radical damage.
The scientists concluded: “These considerations could bear
relevance for glaucoma prevention and suggest that … the use of drugs or dietary
measures attenuating the effects of free radicals could be useful tools
contributing to the control of this disease.” (4)
In summary, these three chronic eye conditions develop on
a background of both oxidation and glycation. It is logical to assume that in
order to prevent or even reverse this damage is necessary to use a combination
of chemicals which work both against oxidation (i.e. antioxidants) and against
glycation.
N-acetyl carnosine
The most recent development in the prevention of
age-related eye diseases is the nutrient N-acetyl carnosine. This is a natural
chemical closely related to carnosine, which itself is a combination of two
amino acids (alanine and histidine). Carnosine has been investigated extensively
and there are over 1000 scientific reports discussing its biological actions. It
is active in almost all body tissues and works both as an antioxidant and as an
anti-glycator.
N-acetyl carnosine (NAC) works the same way as carnosine,
namely preventing free radical damage and reducing the risk of glycation. But
NAC is particularly useful within the eye, because it remains biologically
active for longer. Once inside the eye tissues NAC transforms into pure
carnosine and prevents free radicals from further destroying eye tissues such as
the crystallins. It also reverses glycation, in other words, it may be useful in
curing already existing eye damage. N-acetyl carnosine is a very important
discovery because it shows that cataract may be cured without the need to resort
to an operation (5).
Commercially available N-acetyl carnosine: The beneficial
actions of NAC against cataract and other eye conditions have been recognised by
a variety of commercial companies who are now offering NAC in eye drop form.
However, it is important to realise that NAC is very sensitive both during the
manufacturing and during the application stages, so it is necessary to use only
a reputable supplier. Also, some commercial eye drops contain chemicals which
may not be beneficial when applied directly in the eye. For example, although
vitamins given by mouth may help prevent age related eye conditions as will be
discussed below, if these vitamins are given directly into the eye, they may
cause damage to the eye tissues. In addition, the Russian scientists who
developed the original NAC drops (Can-C) claim that the combination of
stabilising agents and other chemical factors needs to be taken into account
when using NAC and this makes their Can-C drops the best available choice at
present.
Apart from carnosine, other good anti-glycators are the
agents metformin and aminoguanidine. Both work to reduce the risk of glycation
of proteins within the lens of the eye and thus prevent the harm caused to the
proteins of the lens. By helping to improve microcirculation of the blood in the
eye these can be useful both in macular degeneration and glaucoma.
By-products of glycation (called AGEs –Advance Glycation
End-products) are frequently found in several parts of the eye, including the
retina (6). It has now been proven that there are special receptors for these
AGEs within the retina and this means that the blueprint for the slow and
chronic destruction of the retina has already been put in place by nature. (7)
However, antiglycators such as carnosine, metformin and aminoguanidine can fool
nature by reducing AGEs before these have the chance to combine with the
receptors and affect the eye.
It may not be enough to only use one remedy in order to
prevent or even reverse chronic eye conditions. Taking additional supplements
will ensure that you are getting the extra insurance necessary to keep free
radical action at low levels and reduce the risk of further harm to the eyes.
The following are some relevant nutritional factors that have a role to play in
improving vision. Current research supporting their actions is highlighted for
each supplement.
Ginkgo Biloba Extract
Ginkgo is the extract of the maidenhair tree, used in
order to improve memory and blood circulation problems. It is also a very good
antioxidant, particularly if used correctly. Many people buy the ‘raw leaf’
preparation of ginkgo which may not contain a standard amount of the active
ingredients. It is best to use the standardised extract at a dose of 120 mg once
or twice a day.
Scientists from the Department of Ophthalmology, Tang Du
Hospital, Shanxi in China have studied the effects of ginkgo extracts on the
retina. They first injected glutamate (a known brain chemical which is toxic in
high amounts) into the retinas of one group of rabbits. This caused an increased
production of free radicals which, in turn, caused the retinal cells to wither
and die. They then injected ginkgo biloba extracts into another group of rabbits
before injecting them with glutamate. What they found was that ginkgo protected
these retinas from any harm caused by free radicals. (8) This confirms that
ginkgo may be able to protect the retina against age-related oxidation, and that
gingko may thus be useful against all chronic eye conditions including macular
degeneration.
Although this particular experiment was performed on
laboratory animals, newer research has confirmed that ginkgo can also be useful
in human eye problems. In a clinical trial performed by Polish researchers from
the Department of Clinical Ophthalmology, Medical Academy of Poland, gingko was
given to a group of 15 patients who had an increased risk of retinal damage (in
this case through diabetes). They found that ginkgo improved these patients’
colour vision test results, concluding that: “Ginkgo seems to be good adjuvant
in patients with long lasting diabetes mellitus” (which can cause retinal
damage). (9)
Finally, ginkgo can protect not only against macular
degeneration, but also against cataract, by reducing the injury caused by
oxidation on the lens of the eye. It turns out that ginkgo increases the
antioxidant enzymes superoxide dismutase and glutathione peroxidase in the eye.
This makes it less likely that free radicals caused by radiation, (such as UV
for example) can damage the lens (10).
Grape Seed Extract
It is well known that both grapes and their seeds contain
antioxidants such as flavonoids (catechin, epicatechin, procyanidins and gallic
acid). These are strong natural chemicals with antioxidant power up to 20 times
more than vitamin E, and 50 times more than vitamin C. Flavonoids from grape
seeds help to protect the eyes from UV radiation and to improve overall vision.
In addition, these compounds can help improve blood circulation particularly in
the small arteries of organs including the eye. (11)
In a landmark experiment preformed by researchers from the
Research and Development Division, Kikkoman Corporation, Japan, it was confirmed
that grape seed extracts prevent the progression of cataract formation. The
researchers investigated the anti-cataract activity of grape seed extracts
(containing 38.5% procyanidins) on laboratory rats with cataract. The rats were
divided into two groups. The first group was fed a standard diet containing no
grape seed extracts. The second was given 0.213% grape seed extract in addition
to the standard diet, for 27 days. As a result, the clarity of the lens was
significantly better in the treatment group compared with the control group. The
scientists concluded that: “these extracts significantly prevented and postponed
development of cataract formation in the active group” (12).
Vinpocetine
Although vinpocetine is a well known nootropic (brain
booster), it has also a role to play in preventing chronic eye conditions,
particularly if used in combinations with other supplements.
Some years ago, scientists working at the Romanian
University of Medicine and Pharmacy, have reported that diseases in other parts
of the body, such as liver disease, can have an adverse impact upon the retina.
Nutritional supplements such as vinpocetine can prevent this kind of damage by
improving blood circulation both in the liver and in the arteries of the eye. In
this way, the likelihood of visual problems associated with systemic diseases
can be reduced. (13)
More recently, Russian scientists found that vinpocetine
can improve optic nerve atrophy caused by head injury. It improved the
sensitivity of the retina and protected the optic nerve which transmits visual
signals from the eye to the brain. Finally, it improved blood flow within the
arteries of the eye, which means that more nutrients could reach vital eye
tissues. (14)
Lutein
and zeaxanthin
The two most well known supplements for eye protection are the carotenoids
lutein and zeaxanthin. There is quite a lot of scientific evidence confirming
that consumption of these two chemicals reduces the risk of age-related
cataract. Lutein and zeaxanthin are the only two carotenoids present in the
lens, and their role is to protect the lens against free radicals caused by UV
radiation from the sun.
In an experiment performed at the Ohio State University in the USA, scientists
compared these two chemicals and vitamin E used against free radical action in
lenses obtained from human eyes. They first applied the different chemicals
(such as lutein, zeaxanthin, vitamin E, and astaxanthin - see below) on the
lenses, and then they irradiated these lenses with UV radiation. They found that
all these chemical protect the lens against free radical damage. Specifically,
there was an inhibition of ‘cell stress signalling’, meaning that the irradiated
cells did not produce any toxic chemicals following the irradiation. Lutein and
zeaxanthin was more powerful than vitamin E in this respect. (15)
References
1. Gakhramanov FS. Effect of natural antioxidants
on antioxidant activity and lipid peroxidation in eye tissue of rabbits with
chemical burns. Bull Exp Biol Med. 2005;140(3):289-91.
2. Moriarty-Craige SE, Adkison J, Lynn M, Gensler G, Bressler S, Jones DP,
Sternberg P Jr. Antioxidant supplements prevent oxidation of cysteine/cystine
redox in patients with age-related macular degeneration. Am J Ophthalmol.
2005;140(6):1020-6.
3. Wang Z, Dillon J, Gaillard ER. Antioxidant properties of melanin in retinal
pigment epithelial cells. Photochem Photobiol. 2006;82(2):474-9.
4. Izzotti A, Di Marco B, De Flora S, Sacca S. Open angle glaucoma:
epidemiology, pathogenesis and prevention. Recenti Prog Med. 2006;97(1):37-45.
5. Babizhayev M, Deyev A, Yermakova V, Brickman I, Bours J. Lipid peroxidation
and cataracts: N-acetyl carnosine as the therapeutic tool to manage age-related
cataracts in human and canine eyes. Drugs R D. 2004;5(3):125-139.
6. Kaji Y, Usui T, Oshika T, et al. Advanced glycation end products in diabetic
corneas. Invest Ophthalmol Vis Sci. 2000;41(2):362-8.
7. Yamada Y, Ishibashi K, Bhutto IA, Tian J, Lutty GA, Handa JT. The expression
of advanced glycation endproduct receptors in rpe cells associated with basal
deposits in human maculas. Exp Eye Res. 2006;82(5):840-8.
8. Li YJ, Yang XG, Gao MR.Effects of extracts of ginkgo biloba (EGB) on levels
of nitric oxide and apoptosis in the retina induced by glutamate in adult
rabbits. Zhongguo Zhong Yao Za Zhi. 2003;28(10):961-4.
9. Bernardczyk-Meller J, Siwiec-Proscinska J, Stankiewicz W, Fichna P, Pecold K.
Influence of Eqb 761 on the function of the retina in children and adolescent
with long lasting diabetes mellitus--preliminary report. Klin Oczna.
2004;106(4-5):569-71.
10. Ertekin MV, Kocer I, Karslioglu I, Taysi S, Gepdiremen A, Sezen O, Balci E,
Bakan N. Effects of oral Ginkgo biloba supplementation on cataract formation and
oxidative stress occurring in lenses of rats exposed to total cranium
radiotherapy. Jpn J Ophthalmol. 2004;48(5):499-502.
11. Shi J, Yu J, Pohorly JE, Kakuda Y. Polyphenolics in grape seeds-biochemistry
and functionality. J Med Food. 2003;6(4):291-9.
12. Yamakoshi J, Saito M, Kataoka S, Tokutake S. Procyanidin-rich extract from
grape seeds prevents cataract formation in hereditary cataractous (ICR/f) rats.
J Agric Food Chem. 2002;50(17):4983-8.
13. Cusnir V, Slepova O, Dumbrava V, Zaiteva N, Cusnir R, Midrigan I. Ocular
manifestations of hepatitis B. Oftalmologia. 1997;41(2):25-7.
14. Aznabaev MT, Khalikov VA, Zagidullina ASh. Use of instenon in complex
treatment of patients with optic nerve atrophy caused by craniocerebral trauma.
Vestn Oftalmol. 2003;119(6):12-4.
15. Chitchumroonchokchai C, Bomser JA, Glamm JE, Failla ML Xanthophylls and
alpha-tocopherol decrease UVB-induced lipid peroxidation and stress signalling
in human lens epithelial cells. J Nutr. 2004;134(12):3225-32.
16. Waagbo R, Hamre K, Bjerkas E, Berge R, Wathne E, Lie O, Torstensen B.
Cataract formation in Atlantic salmon, Salmo salar L., smolt relative to dietary
pro- and antioxidants and lipid level. J Fish Dis. 2003;26(4):213-29.
