This is a topic that is currently
highly controversial, and there are no studies that are conclusive that
dietary supplementation affects the long term outcome of AMD or does anything
to prevent it. Designing scientific studies is difficult due to the fact
that AMD, particularly the dry form, progresses slowly over a long period
of time. When AMD is discovered in a patient, often their dietary history
over the past 20 - 30 years remains illusive. Also the definitions of
what constitutes a good diet has changed. However, the body of knowledge
regarding the role of vitamins, minerals, and herbals is exploding, and
will redefine the issues of wellness and disease prevention in the not-to-distant
There is a growing body of
evidence that antioxidant vitamins and minerals incorporated into supplemental
products may be effective slowing down or reversing eye disease. Although
mostly published in nutritional journals, more are being published in
medical journals. Regarding AMD, there has been a great deal of attention
among researchers regarding nutritional supplements and reduced incidence
and severity of macular degeneration. There is a very practical debate,
however, for supplemental nutrition. Some points of issue include the
- A growing concern over food
processing and environmental stresses upon health and maintaining health.
- Lack of time or inclination
to eat properly, especially among older adults living alone.
- Demineralization of our
soil that is sorely lacking in selenium, and is low on zinc, magnesium,
calcium, and others.
- Report by the American Medical
Association (AMA) showed that nearly 90% of Americans do not get even
the RDA of essential vitamins and minerals.
- Despite the recommendations
of the National Cancer Institute to consume 5 servings of fruits and
vegetables per day, less than 10% of Americans eat 2 - 3 servings of
fruits and vegetables, and at least 50% of Americans eat no vegetables,
and 70% eat no fruits or vegatables rich in vitamin C (from The Real
Vitamin and Mineral Book, Lieberman et al.).
- While little can be done
to alter genetic predisposition to disease, much can be done environmentally,
particularly nutrition and water supply that can greatly help.
- The "modern" diet features
an increased intake of fats and sugars, and less with complex carbohydrates
and fibers and an inadequate intake of essential vitamins and minerals.
Many experts feel that it is impossible to meet the RDIs by eating the
food available today.
- Many people currently are
seeking ways to attain a longer and healthier life. The public is becoming
more savvy in health issues and is looking for leadership in wellness.
- Certain terms must be understood
to make the following discussion regarding nutrition and AMD meaningful
Natural occuring organic compounds in plants and animals that work with
other enzymes to allow chemical reactions to occur in your body. Fat Soluble
Vitamins: A,D,E,K, and Water Soluble Vitamins B complex and C.
Elements not produced by plant or animal. Like vitamins, they function
as coenzymes that allow chemical reactions to occur in your body. There
are the macro or "bulk" minerals such as calcium, and micro or "nutrient"
minerals such as zinc and copper.
Any plant whose stems and leaves wither after the growing season each
year. Can be used as a medicine, seasoning, etc.
Unstable oxygen atoms and other compounds produced in every cell of the
body that generate oxidative damage to cells and tissues causing degenerative
Compounds that neutralize free radicals.
Compounds found in plants that normally give vegetables and fruit their
normal color. They function as a helper to the body's immune system, and
they act as scavengers of free radicals.
Catalysts or activators of chemical reactions that continuously take place
in your body. Enzymes make things happen and happen faster. They are necessary
for all body functions.
Having to do with or come from life. Carbon is the backbone of all organic
Not having been produced by plant or animal.
"Recommended Daily Allowance". Minimum daily requirement of micronutrients
to prevent deficiency diseases. Based upon gender, age, etc. Cumbersome.
Inadequate to promote wellness.
"Reference Daily Intake". Replaced RDA in 1997 as the official term and
represents average need for persons older than four years of age. Based
upon 2,000 cal for women and 3,000 cal for men.
"Optimum Daily Intake". Nutrient requirement to attain a state of optimum
health according to Lieberman and Bruning.
Understanding "free radicles"
is important and perhaps central to understanding the current thinking
about supplementation for AMD. Free radicles are by-products produced
by every living cell in the normal course of metabolism, and are atoms
or groups of atoms with one or more unpaired electrons. This results in
electrochemical instability in which free radicles then interact with
other cells taking or giving electrons randomly. This in turn destabilizes
molecules in cell walls and other cellular structures causing a cascade
of events that lead to cellular destruction. This is thought to be one
of the factors in the normal aging process of the body. Free radicles,
however, do some good to the body as well such as fighting off infection.
are antioxidants, and what role do they play in AMD?
In thinking about free radicles
in the course of degenerative disease such as AMD, antioxidants are substances
that neutralize and significantly inhibit the rate at which free radicles
operate, keeping down the population of these destructive elements. There
are vitamin antioxidants such as vitamins
A, E, and C; mineral antioxidants such as
zinc and selenium; and bioflavenoid antioxidants
such as grape seed, citrus extract, and carotenoid pigments such as the
carotenes and xanthophylls.
It is believed by many that
free radicles play some role in AMD although the exact mechanism is not
clear. The substances that you may hear most about regarding AMD are zinc,
lutein and zeaxanthin.
Lutein is a xanthophyll and
is found in spinach, kale, collard and mustard greens, and egg yolks.
Lutein is the only xanthophyll that accumulates in the eye, specifically
the macula. Closely related to lutein is zeaxanthin which seems to produce
a thicker, more protective macular pigment. It is thought that a diet
rich in these compounds increases the density of macular pigments.
Zinc is a common trace mineral
and is highly concentrated in the eye, particularly in the retina and
macular areas. Some studies have shown that zince levels are low in some
older adults either because of poor diet or poor absorption of zinc from
food. Because zinc is so important for the health of the macula, come
doctors think that zinc supplementation may slow the process of AMD. Scientific
studies here are also imcomplete, however, and there is no agreement among
doctors concerning the value of zinc supplementation. Too much zinc also
can interfere with other important trace minerals such as copper.
you consider nutritional supplementation?
As it relates to AMD, it might
be prudent if: 1) you are over the age of 50, 2) have a family history
of AMD, 3) have AMD yourself, 4) have insufficient dietary intake of vitamins
and minerals. Keep the following points in mind, however.
- Researchers do not agree if
nutritional supplementation is helpful in AMD, although it is well recognized
that for many, nutrition is not optimal, and that carefully formulated
supplements may be helpful.
- Supplements should not be
an easy way out from a balanced diet with foods rich in vitamins and minerals.
- Do not supplement yourself
without medical guidance from your physician. With supplements being available
at every corner and through many catalogues, many fall prey to the lastest
fads. Remember that too much of a good thing can be harmful, especially
with fat soluble vitamins and certain herbs, and high doses of trace minerals.
For example, the New England Journal of Medicine (1996) reported an increased
risk of acquiring lung cancer with 25,000 units of vitamin A and 30 mg
of beta-carotene taken on a daily basis.
- Remember that while nutritional
issues may contribute to the onset or worsening of AMD, other factors
too have been implicated. (See question 11)