Beneficial effects of Fish oil to Human Health- A review

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AGRICULTURAL RESEARCH COMMUNICATION CENTRE
www.arccjournals.com / indianjournals.com
Agric. Rev.,
30 (3) : 199-205 , 2009
BENEFICIAL EFFECTS OF FISH OIL TO HUMAN HEALTH: A REVIEW
S. Das, B.N. Paul, J. Sengupta and A.K. Datta
Wastewater Aquaculture Division
Central Institute of Freshwater Aquaculture P.O. Rahara. Kolkata-700118, India
ABSTRACT
The Omega (αα
αα
α)-3 and αα
αα
α-6 poly unsaturated fatty acids are dietary essential
constituents of human diet. As our body cannot de novo synthesize it, so, it must be
consumed through diet. Fish oil is a major source of ω−ω−
ω−ω−
ω−3 and ω−ω−
ω−ω−
ω−6 essential fatty
acids. It prevents major heart diseases, cancer, diabetes, mental disorder, arthritis
and many other health problems. So fish oil contributes a large number of beneficial
effects to us. It must be consumed as per the recommended dosages. Consumption
of 1.0g fish oil daily will help the human being to combat the coronary heart disease.
Fish oil supplements have numerous benefits over consumption of fish directly.
Key words: Fish oil, Coronary heart disease, Polyunsaturated fatty acids,
Eicosapentaenoic acid, Docosahexaenoic acid
Fatty acids are aliphatic
monocarboxylic acids derived from, or
contained in esterified form in an animal or
vegetable fat, oil, or wax. Essential fatty acids
(EFA) are one type of fatty acids. They cannot
be de novo synthesized within our body.
Because our body lack the enzymes required
to make certain fatty acids so they must be
acquired through the diet from plant or animal
sources. But they are very essential for us as
they are involved in important biological
processes. Essential fatty acids are
polyunsaturated and grouped into two
families, the omega-6 EFAs and the ω−3 EFAs.
The body can convert one ω−3 to another ω−
3, for example, but cannot create an ω−3
from ω−6 or saturated fats. Essential fatty
acids so named because without them we
cannot survive.
Fish oil is derived from the tissues of
oily fish. It is recommended for a healthy diet
because it contains the ω−3 fatty acids,
eicosapentaenoic acid (EPA) and
docosahexaenoic acid (DHA), precursors to
eicosanoids that reduce inflammation
throughout the body as reported by Sargent
(1997). Fish oils are required to be added in
minute quantities for optimum health benefit,
cellular metabolism and normal physiological
functions (Sau and Paul, 2004). Scientists
came to know about many benefits of fish oils
in the early 1970s when Danish physicians
observed that Greenland Eskimos had an
exceptionally low incidence of heart disease
and arthritis despite the fact that they
consumed a high-fat diet. Intensive research
soon discovered that two of the fats that they
consumed in large quantities, EPA and DHA,
were actually highly beneficial. Fish oil has
numerous beneficial effects to human body. It
prevents atherosclerosis, angina, heart attack,
congestive heart failure, arrhythmias, stroke,
and peripheral vascular disease. Clinical trials
have shown that it is also effective in the
treatment of many disorders including
rheumatoid arthritis, diabetes, cancer etc
(Connor and William, 2000). It is observed that
E-mail: bnp63@yahoo.co.in

200 AGRICUTURAL REVIEWS
due to imbalance of intake of ω−3 and ω−6
fatty acids a number of serious diseases occur.
So by changing dietary habits by taking fish
oil these problems can be avoided.
Omega-3 Fatty Acids:
Important two ω−3 fatty acids are EPA
and DHA. They possess essential biochemical
functions. EPA is converted into anti-
inflammatory biochemical intermediates.
DHA can be made from EPA and is the most
abundant ω−3 fatty acid in most tissues,
present in large amounts in the brain and
retina. DHA is required for brain development
and function, central nervous system
development and optimum visual acuity.
Alpha-linolenic acid (ALA)is converted to EPA
and DHA through a series of enzymatic steps
(Steffens and Wirth,1997).
Omega-6 Fatty Acids:
Although omega-6 fatty acids are
sometimes viewed as pro-inflammatory
mediators, the physiological impact is
dependent on the type and quantity of the
omega-6 fatty acid consumed. Linoleic acid
is an essential fatty acid with cardioprotective
benefits. The linoleic acid content in adipose
tissue was found to be inversely associated
with cardiovascular disease risk; the greater
the content of linoleic acid, the lower the risk
for cardiovascular disease. Linoleic acid
converts to arachidonic acid which is the major
ù-6 fatty acid through enzymatic steps.
Ratio of ωω
ωω
ω-3 and ωω
ωω
ω-6 fatty acids:
There must be a dietary balance between
the two fatty acids. The ratio of ω-3 to omega-6
fatty acids appears to be critical in inhibiting
inflammatory responses. The body has ability
to convert ω-3 fatty acids into anti-inflammatory
mediators depends upon enzyme activity.
Because ω-6 fatty acids require the same
enzymes for conversion into their prostaglandin
and thromboxane equivalents. Sargent (1997)
reported that the ratio of ω-3: ω-6 fatty acid should
be 5:1. However, over early ancestors consumed
diets with ω-3: ω-6 ratio approximately
1:1(Simopolons, 1991).
Bio chemistry of PUFA:
As fish oil contains ω-3 and ω-6 types
of fatty acids, the mechanism of action of fish
oil reflects the action of these EFA. Both must
be obtained through the diet because they are
not synthesized de novo by vertebrates. Both
types can support important physiological and
developmental processes. They can form
eicosanoids i.e prostaglandins, leukotrienes,
lipoxins, etc. These ω-3 and ω-6 fatty acids
can be esterified. and hydrolyzed from tissue
glycerolipids, and can be metabolically
elongated and desaturated to a variety of highly
unsaturated fatty acids (Hazra
et al.
,2003).The
conversion occurs slowly. There is a
competition between alpha lenolenic acids and
linoleic acids. Linoleic acids of high level
inhibits conversion of alpha lenolenic to its
long chain derrivatives. These longer chain
fatty acids are very important. Because they
are precursors of eicosanoids. Eicosanoids
have wide range of functions including
ability to influence platelet aggregation,
blood pressure, blood clotting, inflammation
etc. Eicosanoids from ω-3 fatty acids are less
potent than ω-6 fatty acids in case of
producing inflammation, platelet
aggregation. ω-3 and ω-6 fatty acids being
a component of cell membrane, compete
with each other for incorporation into it. As
there is a competition between both of the
family of fatty acids there must be a proper
balance of their intake.
Advantages of consumption of fish oil
over whole fish:
Fish oil supplements have numerous
benefits over consuming fish directly. Fish oil
can be consumed by eating the fish directly or
by drinking fish oil which is often available in
the form of supplements such as tablets,
capsules, pills, soft gels, etc. Some of the
benefits of fish oil are listed here:

Vol. 30, No. 3, 2009 201
• Regular consumption of fish oil may lead to
reduction of anti-oxidants such as vitamin E
in the body. Certain fish oil supplements help
us to tackle this problem as they contain added
vitamin E in them.
• Sometimes, in severe cases, when we require
large dosage of fish oil for treatment and try to
take the fish oil by eating fish, we will have to
eat a lot of fish. Fish oil supplements provide
us this convenience as they contain fatty acid
in a concentrated form.
• Fish oil supplements are very handy. If we
want to consume fish oil daily, we just have to
open up the jar, pick a tablet and gulp it.
Cooking fish, on the other hand, daily becomes
very troublesome.
• Further, we have to know the exact dosage
of fish oil.
Positive Effects:
• Cardiovascular disease:
It is well established that populations
with a high consumption of oily fish have a
lower incidence of heart disease and several
studies have confirmed that fish oils EPA and
DHA are the protective components. ù-3 is
effective in reducing the incidence of
cardiovascular diseases (CVD). Fish oil, which
is abundant in ω-3 fatty acids, therefore,
reduces the risk of heart diseases and heart
arrhythmias. It helps to maintain the elasticity
of artery walls, prevent blood clotting, reduce
blood pressure, stabilize heart rhythm and help
combat inflammation. It lowers the levels of
LDL cholesterol, which is bad cholesterol, and
increases the HDL levels, which is good
cholesterol. Fish oil prevents accumulation of
triglycerides and further reduces the levels of
excess triglycerides. Arachidonic acid derived
from silver carp has pronounced effect on
blood pressure, serum lipid and platelet
function (Wirth
et.al
., 1992).Thus fish oil can
be used for preventing atherosclerosis in
coronary patients and also effective in treating
heart strokes and regular usage of fish oil can
help avoid numerous sudden cardiac deaths.
(Mori
et al
.,1997).An adequate daily intake
(about 1 gram) of EPA and DHA is essential
to maintain a healthy heart. It is believed that
fish oil has the ability to improve blood
circulation along with reducing triglyceride and
serum cholesterol levels. Haemodialysis
patients have an exceptionally high incidence
of death from cardiovascular problems. It is
due to abnormalities of lipids and platelets.
Eskimos have a low incidence of myocardial
infarction and have a high dietary intake of
fish, rich in -3 polyunsaturated fatty acids
(Rylance,1986).So Fish oil also prevents
myocardial infraction.
Atherosclerosis increases the risk of
stroke and heart attack. Because part of the
plaque on the inner wall of arteries may
dislodge and block smaller arteries in the heart
respectively and thus cut off the vital supply of
oxygenated blood. So strokes are caused by
blood clot or by burst blood vessel.
Consumption of fish and fish oils was first
associated with decreased risk of
cardiovascular disease almost 50 years ago.
Since then, a number of epidemiologic studies
have evaluated whether their consumption is
specifically associated with stroke. Ecologic/
cross-sectional and case-control studies have
generally shown an inverse association
between consumption of fish and fish oils and
stroke risk (Skerrett and Hennekens, 2003).
Fish oils have anti arrhythmic effects and help
prevent blood clotting. Fish oil supplementation
will improve plaque stability and thus help
prevent heart attack and stroke. So fish oil
consumption helps protect against stroke.
• Brain development :
The human brain is one of the largest
“consumers” of DHA. DHA makes up 15 to
20% of the cerebral cortex and 30 to 60% of
the retina. So, it is absolutely necessary for
normal development of the fetus and baby.

202 AGRICUTURAL REVIEWS
During pregnancy and lactation an adequate
intake of DHA and EPA is important. During
this time the mother must supply all the baby’s
needs for DHA and EPA. Because it is unable
to synthesize these essential fatty acids itself.
There is some evidence that an insufficient
intake of ω-3 fatty acids may increase the
risk of premature birth and an abnormally low
birth weight. Experts recommend that women
get at least 500-600 mg of DHA every day
during pregnancy and lactation. The easiest
way is to take a good fish oil supplement daily.
A normal adult human brain contains
more than 20 grams of DHA. Low DHA
levels have been linked to low brain serotonin
levels which again are connected to an
increased tendency to depression, suicide, and
violence. A high intake of fish has been linked
to a significant decrease in age related memory
loss and cognitive function impairment and a
lower risk of developing Alzheimer’s diseases
(Kalmijn
et.al
., 1997). A recent study found
that Alzheimer’s patients given an omega-3-
rich supplement experienced a significant
improvement in their quality of life
• Diabetes: Fish oil has been linked with
lowering of glucose and it controls the insulin
level. People suffering from type II diabetes often
have high blood levels of triglycerides and are
therefore prone to coronary heart disease
(McManus,
et al.,
1996 ). Fish oils are known
to be effective in lowering triglyceride levels,
but concern has been expressed that they may
also increase low-density lipoprotein (LDL)
levels and be deleterious to glucose control.
Type 1 diabetes is a disease that frequently
occurs during childhood. ω-3 fatty acids could
can safely prevent the development of type 1
diabetes in this high-risk group of children.
• Immunity:
Fish oil has the potential to enhance
the immune system of humans. Regular
consumption of fish oil increases our immunity.
So It helps to resist incidence of common
diseases such as cold, cough and flu. ω-3 fatty
acids present in fish oil benefit the immune
system by effecting cytokines and eicosanoids
present in our body .Fish oil is also beneficial
to patients suffering from lupus, which is a
disease characterized by the attacks of immune
system of the body on various organs and
tissues. Fish oil helps in reducing the pain and
inflammation that may occur in joints, eyes,
kidney, heart, blood vessels, lungs, nerves, etc.
It also helps in reducing associated fever, skin
rashes and fatigue.
• Prevent Cancer :
Now cancer has become most
dangerous disease. In every year a huge
number of people die from various types of
cancer like kidney, colon, pancreas etc. Several
in vitro
and animal experiments have clearly
shown that the long-chain ω-3 polyunsaturated
fatty acids (PUFAs), EPA and DHA, the main
components of fish oil, help inhibit the
promotion and progression of cancer. Their
beneficial effect is particularly pronounced in
hormone-dependent cancers such as breast
and prostate cancer. Following are the steps
how cancer is prevented:
1. They suppress the synthesis of pro-
inflammatory eicosanoids from arachidonic
acid and thus produce an overall anti-
inflammatory effect.
2. They positively affect gene expression or the
activities of signal transduction molecules
involved in the control of cell growth,
differentiation apoptosis, angiogenesis and
metastasis.
3. They suppress excessive production of
nitrogen oxide (NO) during chronic
inflammation and thereby help prevent DNA
damage and impaired DNA repair.
4. They decrease estrogen production and thus
reduce the estrogen- stimulated growth of
hormone- dependent cancer cells.

Vol. 30, No. 3, 2009 203
5. Fish oils improve insulin sensitivity and cell
membrane fluidity and may help prevent
metastasis through these effects.
Other studies have shown that a daily
EPA + DHA intake in excess of 2.3 grams
decreases the production of superoxide, a
potent cancer promoter. Besides fish oil lowers
the risk of colon cancer by lowering the COX-
2 enzyme level, whose over expression leads
colon cancer.
Chemotherapy and other conventional
medical treatments have proven ineffective in
improving quality of life and survival of patients
with end stage cancer. Now Greek medical
researchers report that fish oil supplementation
markedly increases the survival time for cancer
patients with generalized malignancy.
Supplementation with dietary ω-3
polyunsaturated fatty acids, specifically fish oils
with an antioxidant such as vitamin E may
offer significant palliative support to cancer
patients with end stage metastatic disease.
• Inflammation:
Fish oil has anti inflammatory
properties; therefore, it is effective in reducing
inflammation in blood and tissues. Regular
consumption of fish oil supplements, tablets,
pills and capsules is helpful to those suffering
from chronic inflammatory diseases. Fish oil
is effective in treating gastrointestinal
disorders, sprue, short bowel syndrome and
inflammatory bowel disease (IBD) including
Crohn’s Disease and ulcerative colitis, which
are typical disorders of the intestine. Patients
suffering from Crohn’s disease find it difficult
to absorb vitamins, fats and essential
supplements. Fish oil supplements are an
effective diet for such patients. In ulcerative
colitis, fish oil prevents the accumulation of
leukotriene on the colon. It should be noted
that the anti inflammatory properties of fish
oil are limited to reducing inflammation. Fish
oil provides little effect in preventing
inflammation. Research is also being
conducted to enhance the anti-inflammatory
action of fish oil by addition of other dietary
supplements and drugs.
• Arthritis: Fish oil is useful in treating
arthritis, rheumatism (Sales
et al
., 2008)
Raynaud’s symptoms and similar conditions.
In case of osteoarthritis, fish oil can be helpful
in reducing the impact of enzymes that destroy
cartilages. ω-3 fatty acid suppresses the
production of inflammatory eicosanoids. So
they are able to reduce pain.
• Mental disorder: Brain contains
phospholipids, sphingolipids, gangliosides
and cholesterol. These are involved in the
structure and function of cell membranes in
the brain. The glycerophospholipids in the
brain contain a high proportion of
polyunsaturated fatty acids (PUFA). This is
derived from linoleic acid and alpha-linolenic
acid. The main PUFA in the brain are
docosahexaenoic acid (DHA), alpha-linolenic
acid, and arachidonic acid and
docosatetraenoic acid.DHA is derived from ω-
3 fatty acids. Experimental studies in animals
have shown that diets lacking ω-3 PUFA lead to
substantial disturbances in neural function
(Sinclair
et .al
., 2007).This neural dysfunction
can be restored by the inclusion of ω-3 PUFA in
the diet. In the past 10 years there has been an
emerging interest in treating neuropsychological
disorders (depression and schizophrenia) with
ù-3 PUFA. Due to the presence of ω-3 fatty
acids, fish oil is good for relieving depression,
sadness, anxiety, restlessness, mental fatigue,
stress, decreased sexual desire, suicidal
tendencies and other nervous disorders. Fatty
acids are effective in treating Alzheimer’s disease.
Since fish oil is one of the best sources of essential
fatty acids including EPA and DHA, it helps in
Alzheimer disease.
• Asthma: Asthma involves an inflammation
of the airway (pharynx, larynx and lungs).
Epidemiological studies have shown that
populations with a high intake of fish oils have

204 AGRICUTURAL REVIEWS
a lower incidence of inflammatory diseases
such as asthma. Asthma is an increasingly
common affliction in the Western world. It is
estimated that between 20 and 25 per cent of
all children suffer from one or more symptoms
of asthma at some point. Dietary intake of
polyunsaturated fatty acids (PUFAs) may be
effective in reducing asthma symptoms in
many patients. Dietary supplementation with
fish oils or other enriched sources of ω-3
PUFAs may be a viable therapy for asthma.
• Eye Disorder: It is well known that fish oil
is good for its ability to improve vision. One of
the most common degenerative eye diseases
is macular degeneration. It also helps in
avoiding age related macular degeneration.
DHA in fish oil may be the most important
nutrient when it comes to continued eye health,
as a person ages. ω-3 fatty acids are a major
component of the retina. DHA is very
important as it accounts for 60% of the fatty
acids in the retina.
• Pregnancy: Fish oil is very useful for
pregnant women as DHA present in it helps
in the development of the eyes and brain of
the baby. It helps in avoiding premature births,
low weight at birth, and miscarriage. It is also
believed that women who do not have a
sufficient intake of EPA and DHA in their diet
suffer from depression after birth as there is
transfer of some amount of brain mass from
the mother to the child in the last stages of
pregnancy. Low birth weight can be avoided
by consuming proper amount of fish oil at the
time of pregnancy. There is some evidence that
insufficient intake of ω-3 fatty acids may
increase risk of premature birth and low birth
weight.
Fish oil and Vitamin:
Fish oil, especially the one obtained
from liver such as the cod liver oil, is a rich
source of Vitamin A and Vitamin D. However,
excessive dosage of such oils can lead to
hypervitaminosis, accumulation of excessive
vitamins in the body, which can cause side
effects.
Interrelationship between Vitamin E
and Fish oil:
• Fish oil is extremely susceptible to oxidation
the moment it is extracted from the fish and
will go rancid very quickly if preventive
measures are not taken. Taking an inferior
fish oil that has started to become rancid can
increase the number of free radicals roaming
about in the body, counteracting any health
benefits from the fish oil itself. In order to
protect the oil from becoming rancid, good fish
oil must contain a powerful fat soluble
antioxidant such as tocopherol (vitamin E) to
protect it and keep it fresh both within the
capsule and the body (Sau
et al
.,2004 and
Paul
et al
., 2004).
• Excessive dosage of fish oil leads to reduction
of Vitamin E in the human body. This loss of
Vitamin E should be supplemented with
external Vitamin E supplements.
• The combination of fish oil and vitamin E
can have added benefit in the treatment of
many cancers and heart diseases, than if they
are used individually.
Source and requirement:
Although taking fish oil supplements
gives many health benefits to the body, wrong
dosage of such can also have harmful effects.
The American Heart Association recommends
the consumption of 1g of fish oil daily,
preferably by eating fish, for patients with
coronary heart disease. Optimal dosage relates
to body weight.
Almost all the polyunsaturated fat in
the human diet is from EFA. ω-3 and ω-6 fatty
acids are derrived from alpha linolenic acids.
The richest source of very long chain ω-3 fatty
acids are fish oil and various oily fish.The
various types of fish which can be a good
source of fish oil are mackerel, rainbow trout,
lake trout, halibut, herring, sea bass etc. Besides
this many cyprinid spices like silver carp,

Vol. 30, No. 3, 2009 205
grass carp and common carp exhibit higher
levels of essential fatty acids, particularly ω-3
PUFA ( Steffens and Wirth,1997). Summary
requirement fatty acids are given below.
CONCLUSION
Fish oil has a number of beneficial
effects. Fish oil is an excellent and usually
uncontaminated source of EPA and DHA,
which the body uses to make the”calming” ω-
3 fatty acids and keep the brain and heart
healthy. The favorable effect of ω-3 fatty acids
on cardiovascular health is most consistently
related to the use of fish oil. Fish and fish oil
supplements should be recognized as a
potential treatment choice in persons with
known cardiovascular disease. Eating a
modest amount of fish oil ensures a direct
supply of EPA and DHA. So in conclusion we
must say that fish oil is highly beneficial
Consumption of 1.0g fish oil daily will help the
human being to combat the coronary heart
disease. Fish oil supplements are generally
safe. But the processing and packaging of the
fish oil is very crucial. There must be a balance
between intake of ω-3 and ω-6 fatty acids. It
can be concluded that fish oil give us healthy
life. Health professionals need to educate
peoples about benefits, side effects, dose,
duration, and drug-drug interactions to
maximize therapy and to extract the maximum
benefit from fish oil.
Population Recommendation
Patients with Choronarry heart disease They should Consume 1 g of EPA+DHA per day, preferably from
oily fish. EPA+DHA supplements could be considered in consultation
with the physician.
Patients needing triglyceride lowering Two to four grams of EPA+DHA per day provided as capsules under
a physician’s advice.
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