Fish Oil and Your Health...About Rhode Island Fish:
Eating seafood, especially those high in omega 3 fatty acid, can
provide you with many health benefits. We take many steps
to ensure consistent quality and grading and take pride in the
fact
that we produce some of the purest, most wholesome seafood
available today.
fish
oil and your health
by
Paul B. Addis, Ph.D.
INTRODUCTION
The
discovery that fish oil may have unique benefits in the fight
against coronary heart disease has stimulated a tremendous
amount of research which this publication summarizes. Although
the subject is complex, the study of fish oils is very
worthwhile because it provides a totally new perspective on the
relationship of diet to coronary heart disease.
We
have been inundated with oversimplified information about the
effects of diet on blood cholesterol. It has led most people to
believe that low blood cholesterol achieved by eating a low
cholesterol diet is the one and only key to good health,
particularly good heart health. Because of this, when the health
benefits of fish oil were first reported, most people assumed
that its primary benefit is the lowering of blood cholesterol.
The health benefits of fish oil, however, are primarily related
to the reduction of platelet activity, not the reduction of
blood cholesterol. While some studies do show that fish oil
moderately reduces blood cholesterol, it has been shown to
increase blood cholesterol in many other studies. While
attaining a low blood cholesterol is considered healthy, it is
only one of many factors affecting heart disease which must be
considered. This publication explains more fully the
relationship of diet to coronary heart disease and the health
benefits of fish oil.
THE BENEFITS OF FISH OIL
Fish
oil has many names. One of the most common is omega-3 fatty
acid or its scientific abbreviation, N-3. N3 fatty
acids are found mostly in fish, but are contained in other foods
as well. Fish oil is the best food source of these fatty acids.
The
primary benefit of N-3 fish oil is the reduction of platelet
activity (blood clotting) and plaque formation which in turn can
prevent heart attacks. Here's how it works.
Platelets
are clot-forming blood cells which prevent excessive bleeding.
Overly active platelets, however, may speed the build-up of
plaque, a deposit of fatty or fibrous material which narrows a
blood vessel wall. Elevated blood cholesterol also contributes
to the acceleration of plaque formation. When plaque narrows an
artery it is easier for a blood clot to get stuck in the artery
and this can cause a heart attack. Because platelets also form
blood clots, this is likely to occur. That's why it is desirable
to reduce platelet activity and why N-3 fatty acid, fish oil, is
beneficial.
ATHEROSCLEROSIS
Plaque
build-up and narrowing of an artery is called atherosclerosis.
It is a disease of aging which begins early in life. The process
of this disease is complicated, involving monocytes
(white blood cells), platelets, various tissue cells,
low-density lipoproteins (LDL), as well as cholesterol, as
commonly believed, but also fat, smooth muscle cells, calcium,
and other components.
Atherosclerosis
starts when the cells which cover the inner surface of a blood
vessel become injured. Monocytes and platelets, both found in
plaque, adhere to the injured area and attempt to repair it.
Monocytes encourage the formation of foam cells and platelets
stimulate the movement of smooth muscle cells into the injured
area. All of these cells begin to accumulate in the blood vessel
and it becomes progressively more narrow.
Fish
oil, N-3 fatty acid, reduces the activity of monocytes and
platelets, cell production, narrowing of the arteries, and
production, narrowing of the arteries, and the chance of blood
clots and heart attack. Some research indicates that fish oil
reduces the risk of heart attack even in people who already have
extensive atherosclerosis.
POLYUNSATURATED,
SATURATED, N-6, AND N-3 FATTY ACIDS
There
are more than twenty different types of fatty acids commonly
found in food. In general, all foods contain most of the twenty
types of fatty acids to some degree. Saturated and
polyunsaturated fatty acids are two types we hear a lot about.
As all foods and oils contain most of the different types of
fatty acids to some extent, even polyunsaturated vegetable and
fish oils contain some saturated fat. Fish oil, the most
polyunsaturated of all oils, contains 15% to 30% saturated fat.
Thus the terms polyunsaturated and saturated are inadequate to
accurately describe fat or oil.
All
polyunsaturated fatty acids are different and so have different
health effects. And all fats, polyunsaturated or saturated, have
both health benefits and drawbacks. For example, vegetable oil,
an N-6 polyunsaturated oil, is often promoted for lowering blood
cholesterol and undesirable low-density lipoproteins (LDL).
However, it may increase the chance of heart attack by lowering
high-density lipoproteins (HDL) which keep arteries clean, and
by increasing the activity of platelets and monocytes, which is
reduced by N-3 oils (von Schacky 1987). Advertisements which
promote the health benefits of one oil over all others are again
providing oversimplified information. Every oil has its health
benefits and drawbacks. None is a cure-all. The important N-3
and N-6 fatty acids of foods are shown in the table below.
Some
Important N-3 and N-6 Fatty Acids of Foods
|
Fatty
Acid
|
Abbreviationon
|
Major
Type Sources
|
|
alpha-linolenic
|
alpha-LA
|
flax,
canola, fish oil
|
|
eicosapentaenoic
|
EPA
|
oily
fish
|
|
docosahexaenoic
|
DHA
|
oily
fish
|
|
linoleic
|
LA
|
soybean,
safflower, sunflower, corn oils
|
|
arachidonic
|
AA
|
traces
in meat, fish, poultry
|
HOW
N-3 AND N-6 FATTY ACIDS AFFECT Health
N-3
and N-6 fatty acids have negative and positive health effects.
N-6 fatty acids encourage the formation of eicosanoids called
prostaglandins and leukotrienes. These are potent chemicals
which can increase platelet and monocyte activity respectively,
thus increasing the risk of heart attack. The good news is that
both N-6 and N-3 fatty acids reduce certain lipoproteins which
carry plasma lipids (fatty materials) in the blood plasma.
Plasma lipids consist party of cholesterol and triglycerides.
The reduction of lipoproteins in effect reduces plasma lipids
and ultimately helps preven atherosclerosis and heart disease.
N-6
and N-3 fatty acids compete with each other. Therefore, the
amount of N-6 and N-3 fatty acids, the N-6/N-3 ratio, is very
important. Americans eat 17 times as much N-6 fatty acid,
usually in the form of vegetable oil, as they eat N-3, which is
very unhealthy. Ideally people should eat approximately 5 times
as much N-6 fatty acid as N-3 fatty acid, a 5/1 ratio. The
health benefits are an increase in prostacyclin and a decrease
in thromboxane. Prostacyclin reduces platelet activity
(clotting) and prevents heart attacks by preventing arterial
spasms. A decrease in thromboxane is also desirable because it
increases platelet activity and arterial spasms, the opposite
effect of prostacyclin.
THE N-3 FATTY ACID IN FISH
The
amount of N-3 oils varies in different types of fish. It is
commonly believed that only salt water fish contain significant
levels of N-3 fatty acid. This is not true. Freshwater
fish from cold northern waters, including Lake Superior, can
have significant levels as well (Want et al. 1990).
The
following are recommended saltwater and freshwater fish with a
high N-3 oil content:
-
albacore
-
black
bass
-
bluefish
-
carp
-
channel
catfish
-
herring
-
lake
herring
-
lake
trout
-
mackerel
-
pompano
-
salmon
-
tuna
(Water-packed)
-
whitefish
Fish
not recommended are those with low levels of N-3 oils. They are:
-
cod
-
flounder
-
haddock
-
halibut
-
grouper
-
pike
-
shark
-
snapper
-
sole
-
walleye
-
whiting
For
maximum benefits, fish with high N-3 oil content should be
prepared without additional oil by baking, broiling, or
grilling. Preparing fish with batter, breading, or frying
reduces health benefits significantly. The result is a less
desirable N-3/N-6 ratio when vegetable oil (N-6) is added during
preparation.
Fish
oils, like any food, have disadvantages as well as benefits.
Because fish oils are highly polyunsaturated they become rancid
quickly. Although this usually has no effect on the nutritional
value, eating rancid fish is obviously not a good idea. Because
rancid fish smell fishy, they are not very appetizing. Proper
storage and short storage periods can alleviate the problem of
rancidity.
ALTERNATIVE SOURCES OF N-3 FATTY ACIDS
There
are other sources of N-3 fatty acids such as fish oil capsules,
canola oil, and flax oil. Use of fish oil capsules should be
done only with the recommendation of your doctor, who should
also specify the brand. Canola and flax oils have less potent
forms of N-3 fatty acids and would need to be eaten in
approximately 20 times the amount to get comparable benefits of
consuming fish oil rich in N-3 fatty acids.
DIETARY RECOMMENDATIONS
It
is best to eat a variety of oils in moderate quantities given
the wide range of effects of different oils. In general, you
should eat more N-3 fatty acids and less N-6 vegetable oil to
attain a more balanced N-3 /N-6 ratio. Recent studies suggest
that eating 0.5 to 1 gram of fish oil daily reduces the risk of
heart disease death in middle-aged American men by 40 percent.
The most efficient way to add these important oils to your diet
is to eat two meals per week of fish rich in N-3 fatty acids
prepared without additional oil.
References
-
Addis,
P.B. 1990. Omega-3 fatty acid content of Lake Superior fish.
St. Paul: Minnesota Extension Service. University of
Minnesota. HE-FO-5618-B.
-
Lands,
W.E.M. 1986. Fish and human health. New York: Academic
Press.
-
Leaf,
A., and P.C. Weber. 1987. A new era for science in
nutrition. Amer. J. Clin. Nutr. 45:1048
-
Leaf,
A., and P.C. Weber. 1988. Cardiovascular effects of N-3
fatty acids. New England J. Med. 318:549.
-
Schafer,
W. 1990. Preserving fish. St. Paul:Minnesota Extension
Service. University of Minnesota. HE-FS-1087.
-
von
Schacky, C. 1987. Prophylaxis of atherosclerosis with marine
omega-3 fatty acids. Ann. Internal Med. 107:890.
-
Wang,
Y.J., L.A. Miller, M. Perren, and P.B. Addis. 1990. Omega-3
fatty acids in Lake Superior fish. J. Food Sci. 55:71.
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