A
Vast Range of Applications
by
Morten Bryhn, MD, Ph D
1/31/2001
The acceptance of marine omega-3
fatty acids as beneficial to health is increasing worldwide.
The value of these fatty acids as a supplementary treatment
for patients suffering from certain diseases is also increasingly
accepted. Products containing omega-3 fatty acids are registered
as pharmaceuticals or natural medicines in a number of countries.
In the
early 1970s the Danish doctors Hans Olaf Bang and Jørn
Dyerberg returned from a mission to Greenland reporting
that cardiovascular diseases among the eskimos were extremely
rare. This research opened the eyes of the medical and nutritional
world to the importance of a "new" dietary factor:
marine omega-3 fatty acids.
From mideaval ages In the Nordic countries it has been commmon
knowledge for hundreds of years that fish oil has beneficial
effects on human health. In some coastal areas in Norway,
cod liver oil was regarded as obligatory for pregnant women
as far back as the mideaval ages.
Before
the industrial development made extraction of oil from fish
body possible early this century, the only fish oils available
were those extracted from fish liver. In 1895 P. M. Heyerdahl
in Norway proposed that the healthy principle of cod liver
oil was connected to a polyunsaturated fatty acid. He proposed
to name it "Therapic acid". In the 1950's and
60's professor Notevarp in Norway isolated and described
the fatty acid DHA from fish oil. He was also a pioneer
in indicating the connection between the polyunsaturated
fatty acids and the incidence of cardiovascular diseases.
Since
the discovery of the vitamins early this century, the focus
on the health benefits of cod liver oil has been directed
more towards the vitamins A and D.
Nutritional
recommendations
Dispite the early indications of healthy benefits of omega-3
from fish, it was the work of Bang and Dyerberg that initiated
the "take-off" of omega-3. Since their discovery
of the health benefits of marine omega-3 fatty acids, a
huge amount of research has been carried out.
The
most important omega-3 fatty acids are eicosapentaenoic
acid (EPA) and docosahexaenoic acid (DHA). Up to now clinical
research has resulted in more than 10 000 scientific publications
worldwide, of which more than 3000 are clinical studies.
This research confirms that EPA and DHA are essential fatty
acids that are important for human development and health.While
the recommended daily intake of polyunsaturated omega-3
fatty acids should be in the range of 0.6 - 1 gram, a "normal"
diet in the Western world only satisfies about 10-15 % of
this requirement.
Deficiencies
of essential polyunsaturated fatty acids may cause a wide
range of symptoms, including retarded development in babies
and children, reduced fertility and pathologic changes in
the skin and the retina of the eye. DHA is particularly
important for brain development. A normal adult brain contains
more than 20 g of DHA!
Prophylaxis
and treatment
It is today accepted by the medical society that omega-3
fatty acids lower serum triglyceride and are used as treatment
of hypertriglyceridaemia. Omega-3 also reduces blood pressure
and stabilises the rhythm of the heart. It lends itself
for use both as a prophylaxis and as an adjunct treatment
for cardiovascular disease. Clinical observation shows that
omega-3 fatty acids reduces mortality with 20 % in heart
attack patients and play an important role in preventing
cardiovascular disease.
There
is also growing appreciation for clinical documentation
on the reduction of symptoms in patients suffering from
rheumatoid arthritis. A high dietary intake of marine omega-3
has been linked to a delay in the development of senile
dementia. There have also been reports of positive effects
in patients suffering from depression.
Recent
scientific publications have reported positive effects on
a number of other clinical conditions, including migraine,
heart arrhythmia, mental cognition in adults and attention
deficit/ hyperactivity disorder in children.
Health
supplements: Three product groups
Parallell to the increasing knowledge about omega-3 a large
number of products have been introduced in the market. Most
of these products have been health supplements in the form
of oil in soft gelatin capsules which are sold in food stores,
health stores and pharmacies all over the world.
These
products can be divided into three groups. The most important
ones, at least in volume, are the purified fish oils where
the original chemical composition has been retained.
* The first product that was launched already in the 1970's,
MaxEPA, set some kind of standard for these products. This
is why most of them still contains approximately 18% EPA
and 12% DHA. These products are cheap to produce. On the
other hand they carry with them a large amount of non-essential
fats. The chemical composition of fish oils, the triglyceride
structure where three fatty acids are bound together in
each molecule, limits the content of omega-3 fatty acids
in these products to approximately 30%.
* Higher concentrations are only achieved by some kind of
chemical treatment where the fatty acids are liberated from
the glyceride to single molecules, of which ethyl ester
og free fatty acids are the most common. Concentration by
molecular distillation enables production of products containing
approximately 60% omega-3. Such products, mainly on ethyl
ester form and encapsulated in soft gelatin, are another
important group in the same market.
* The third group consists of products where approximately
60% omega-3 on ethyl ester or free fatty acid form are reconverted
to the original glyceride structure.
Two
pharmaceutical products
In addition to these health supplement product groups come
two highly concentrated products on ethyl ester form that
are approved or in the process of being approved by drug
administration authorities in many countries. The first
of these products was Epadel which has more than 95% concentration
of EPA ethyl ester and is approved and marketed in Japan.
The second product is Omacor, with more than 85% concentration
of EPA and DHA which is being introduced all over the world.
This product is sold in Italy under the brand names "Seacor"
and "Esapent". The application for these drugs
are first of all cardiovascular diseases.
Food
ingredients
Many development projects have been brought about by food
and food ingredient companies over the last 10 years. Such
applications are not easy, because of problems with public
acceptance of fish oil as an additive, and because the addition
of fish oil introduces stability problems with regard to
odour and taste to most food products. One way to avoid
these problems is to add omega-3 to products that have short
shelf-lives. This is done in margarines. Another way is
to convert fish oil to powder by microencapsulation, a technique
that stabilizes the omega-3 fatty acids and makes production
of bread and infant formula possible. Many other examples
of omega-3 added products could be mentioned. But so far
there are no products that can be characterized as highly
successful.
1
million tons of oil
The total fish oil production in the world is in the order
of 1 million tons. Both the composition and the quality
of the oils are very diverse. Only a small fraction of the
available oil lots is suitable for marine omega-3 production.
Fish oil is often a biproduct in fish meal production being
treated in a casual way. Oxidation and hydrolysis often
reduces the quality quite fast during storage. Another issue
is that the fatty acids composition in general and EPA and
DHA content in particular, varies from species to species
and by seasonal and geographical parameters. This is most
cleary demonstrated by the fact that almost all fish oil
with a suitable fatty acid composition comes from the southern
hemisphere, while fish oils from the rich fisheries in the
north are mostly unsuitable. The reason for this is that
the northern oils often have too high contents of long chain
monounsaturated fatty acids, which are not easily removed
by existing techniques. Sourcing of crude oils is therefore
the first step on the way to finished products.
Pollution
It is a regrettable fact that oceans all over the world
are more or less polluted by chlorinated organic pollutant
originating from pesticides and herbicides used in modern
agriculture. These compounds are only slowly biodegradable.
They are fat soluble and therefore extracted from the water
by fats and enriched in fat deposits in fishes. Fortunately,
processes that effectively remove such compounds from fish
oils have been developed.
Oxidation
products
To most people fish oil has a nasty taste. Most grownup
people in Norway will remember the taste of a spoonful of
cod liver oil that were forced into them daily by their
parents as a vitamin supplement. However, new technologies
have emerged that remove almost all the bad taste. These
technologies have mainly been developed and are still being
used for refining vegetable oils. They consist of deacidification
to remove free fatty acids, bleaching to remove colour and
oxidation products, and a final deodorization to get rid
of the nasty taste.
Using
these methods a fish oil product containing 30% EPA and
DHA, will appear as a light yellow clear oil with a bland
taste.
Concentration
processes
The omega-3 fatty acids EPA and DHA have special characters
compared to all other naturally occuring fatty acids in
two ways: they have the longest carbon chain and they are
the most unsaturated. This means that they have the largest
number of double bonds in the chain. Both these properties
are exploited in processes for making products with higher
concentrations of omega-3.
Long
chain fatty acids have lower volatility than short chain
fatty acids thus being separable by distillation. But the
boiling points are high. In order to avoid decomposition
caused by high temperatures, the most common way of distillation
is molecular distillation. This is true even if the separation
is poorer than in ordinary distillation columns. The technique
is characterized by the fact that the evaporation takes
place from a heated thin film and that the distance from
this evaporation zone to the cooled condenser is very short.
In this way temperature strain to the product is minimized.
By molecular distillation it is possible to increase the
omega-3 content from 30 to 60%.
Urea
complexation is a special crystallization technique that
is not yet fully understood. It is based on the fact that
when urea chrystallizes during cooling from a solution of
fatty acids in a suitable solvent, the saturated and monounsaturated
fatty acids are included in the crystals. As a result they
are removed from the solution together with the crystals
by filtration while the polyunsaturated fatty acids remain
in solution. In this way it is possible to remove all saturated
and monounsaturated fatty acids and increase the concentration
of omega-3 fatty acids from a molecular distilled concentrate
from 60 to more than 85%.
New
technologies
New technologies could improve the yields and lower the
costs. They could also simplify the procedures or meet special
demands with regard to concentration or composition.
EPA
ethyl esters with a purity of close to 100% have been produced
by a method based on chromatographic principles. However,
both this process and the making of omega-3 products based
on lipase processes are restrained by relatively high costs.
A third
technique that could be used to concentrate omega-3 fatty
acids is supercritical CO2 extraction. The polarity of fatty
acids varies with chain length and unsaturation and since
the polarity of supercritical CO2 varies with temperature
and pressure it is possible to selectively extract fatty
acids from a mixture in this way. However no such prosess
has been commercialized so far.
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