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* EPA: eicosapentaenoic acid; DHA: docosahexaenoic
acid
Why are omega-3 fatty acids healthful?
Once they are consumed, omega-3 fatty acids are avidly absorbed
by different tissues and incorporated mainly into cell membranes.
There, they affect the metabolic activities carried out in the cells,
sometimes restraining activity, other times facilitating certain
functions. For example, these long-chain omega-3 fatty acids are
incorporated into the retina of the eye where they affect visual
function. In the brain, they affect neurodevelopment and function.
In the heart, they influence electrical activity so that abnormal
heart rhythms are discouraged. No other fatty acids have been shown
to have such effects. Our understanding of omega-3 metabolism is
advancing rapidly and revealing an enormous array of functions positively
influenced by these fatty acids.
Are all omega-3 fatty acids the same?
No. Fish contain mainly EPA and DHA omega-3s. Some plants and seeds
contain another omega-3 fatty acid, alpha-linolenic acid or ALA.
This particular fatty acid is the omega-3 found in walnuts, flax
seed and oil, canola oil and to a lesser extent, soybean oil. ALA
is shorter, has fewer missing hydrogens, and behaves differently
in the body from EPA and DHA. Most ALA is oxidized or "burned"
before it can affect metabolic activity.
ALA is healthful and has been favorably linked to heart health.
However, it does not have all the functions of EPA and DHA, particularly
in maternal and infant nutrition. For neurodevelopment and other
activities, ALA needs to be converted to EPA and DHA. The human
body can perform this conversion, but it does so very inefficiently.
In adults, the conversion to DHA may be less than 5 percent. Under
the best circumstances, consuming large amounts of ALA yields only
small amounts of EPA and DHA. Thus, the easiest and most effective
way to obtain the health benefits of omega-3s is to get them already
preformed - in Pacific troll-caught albacore and other fatty fish.
Omega-3 Fatty Acids and Cardiovascular
Health
Fish oil omega-3 fatty acids have been shown to improve heart health
in the following ways:
· Reduce the chance of sudden cardiac death.
Almost half of all cardiac deaths in the U.S. - about a quarter
of a million each year - are attributable to sudden cardiac death.
· Reduce the chance of having a first heart attack.
People at high risk of having a heart attack may reduce their chance
of a first myocardial infarction (heart attack) by consuming fish
oil omega-3s regularly.
· Reduce the risk of stroke. Several studies
have shown that people who consume fish regularly are less likely
to have a stroke.
· Lower blood triglycerides (fats). Many
people, especially those with type 2 or non-insulin dependent diabetes
mellitus, have high triglycerides, which significantly increases
the risk of heart disease. Regular consumption of fish oil omega-3s
lowers blood triglyceride levels, especially in people whose triglycerides
are above normal levels.
· May increase high-density lipoprotein levels,
the so-called "good" cholesterol that reduces the risk
of heart disease. This favorable change often occurs in people with
high triglycerides or type 2 diabetes, where the risk of heart disease
is increased three times or more.
· Reduce the likelihood of blood clots forming in
arteries. Blood clots can be fatal. Fish oil omega-3 fatty
acids make platelet clumping less likely and reduce the activity
or production of several substances that promote clot formation.
They may encourage the production of substances that promote the
breakdown of clots, as well.
· Improve vascular function. The cells lining
the blood vessels are called endothelial cells. They produce substances
that maintain blood fluidity and vessel wall muscle tone. Fish oil
omega-3 fatty acids inhibit excessive endothelial cell activity
that could lead to a heart attack. Omega-3s encourage blood vessel
wall relaxation, which improves blood flow and reduces pressure.
· Reduce inflammation. Fish oil omega-3 fatty
acids discourage the development of inflammation in blood vessels
that frequently accompanies heart disease. Inflammatory conditions
stimulate the production of substances involved in clot formation
and make artery disease worse. Inflammation increases the risk of
heart failure.
· May stabilize atherosclerotic plaques.
Recent findings suggest that fish oil omega-3s may increase the
stability of atherosclerotic plaques making them less likely to
rupture and cause a heart attack.
· Modestly reduce blood pressure. High blood
pressure greatly increases the risk of heart disease and stroke.
Consuming fish oil omega-3s is associated with small but beneficial
reductions in blood pressure.
Maternal and Infant Health
Fish oil omega-3 fatty acids are essential for healthy fetal and
infant development. During pregnancy, the developing baby obtains
omega-3 fatty acids from the mother. After birth, the infant must
obtain them from breast milk or formula supplemented with essential
fatty acids. In early human development, fish oil omega-3 fatty
acids are beneficial for:
· Healthy infant visual function. The photoreceptor
cells in the retina of the eye have large amounts of DHA, which
is involved in visual function. Infants whose diets contain fish
oil omega-3 fatty acids have improved visual scores on a number
of measures of visual acuity when compared with infants not receiving
them.
· Improved infant neurodevelopment. Several
tests of motor skills, learning behavior, language development,
and mental function in infants and children have shown that infants
consuming fish oil omega-3 fatty acids from breast milk or supplemented
formula have higher developmental measures than those not receiving
them. In several studies, infants consuming omega-3s exhibited a
more mature type of neurodevelopment than those of the same age
who did not have omega-3 fatty acids. It is not certain whether
the findings in infancy carry over into childhood and adulthood.
· Reduced risk of premature and underweight births.
Consuming omega-3s - particularly DHA* - in pregnancy, especially
in the last trimester, reduces the risk of premature and underweight
babies. Studies have shown that babies of mothers who consumed DHA
in the last trimester were heavier than those of mothers not fed
DHA. Gestation time is also prolonged and this reduces the risk
of prematurity.
· Important in pregnancy. In the last three
months of pregnancy, the fetus avidly takes up omega-3 fatty acids
from the mother's circulation. These fatty acids are incorporated
into brain, eye, and other tissues. Because the mother's diet and
body stores are the only source of these essential nutrients, pregnant
women are wise to consume fatty fish regularly.
· Important in lactation. In the first six
months of life, infants depend on breast milk or infant formula
for all or most of their nutrition. Nursing women can ensure their
infants receive essential fatty acids by eating fatty fish regularly,
at least once a week. These dietary omega-3s are transferred to
breast milk, so the infant will obtain them.
· Low birthweight and premature infants. Underweight
and "preemie" babies are at increased risk of receiving
too little omega-3 fatty acids during gestation. When a baby is
born early, it has less time to acquire these vital fatty acids
from its mother. Thus, it is especially important for these infants
to receive all essential fatty acids, including omega-3 fatty acids,
to ensure healthy development. Human milk and fatty acid supplemented
formula will supply the necessary omega-3s.
Improvements in Clinical Conditions*
* Note: always check with your doctor before taking any substances
to alleviate any clinical conditions. These statements are provided
only for information and are not intended to treat, cure, prevent,
or mitigate any existing health conditions.
Omega-3 fatty acids in fish oils have beneficial
effects on the symptoms of several health conditions that involve
the immune and inflammatory system, intestinal tract, and brain.
They appear to have important benefits in type 2 or non-insulin
dependent diabetes.
Type 2 Diabetes Mellitus
· Type 2 diabetes greatly increases the risk of cardiovascular
disease and heart attack. However, diabetics who consume fatty fish
regularly - once or more per week - are less likely to incur a first
heart attack. Mortality from heart disease is also significantly
lower among diabetics who do compared with those who do not eat
fish.
· Sugar and fat metabolism are impaired in type 2 diabetes.
Blood triglyceride (fat) levels are increased while high-density
lipoprotein (HDL) levels - the "good cholesterol" - are
reduced. Regular consumption of fatty fish or omega-3 fatty acids
significantly lowers triglycerides and often raises HDL levels,
thereby diminishing the risk of heart disease.
· Omega-3s improve blood circulation, reduce the tendency
of blood to clot, improve vascular (blood vessel) function in several
ways that reduce the risk of heart disease, and slightly lower blood
pressure. These changes favor heart health.
Inflammatory Conditions
· Omega-3s in fish dampen the production of inflammatory
substances produced in rheumatoid arthritis, psoriasis, asthma,
and some skin conditions. They also stimulate the production of
substances the counteract inflammation. The result is often an improvement
in the symptoms of these conditions, e.g., less soreness or itching,
easier breathing, and less swelling. Omega-3s may need to be consumed
over a long period before improvements appear.
Crohn's Disease, Ulcerative Colitis
· These serious intestinal diseases have strong inflammatory
responses that may become less severe with the regular consumption
of omega-3s from fish. Omega-3s tend to reduce the severity of the
symptoms, but do not cure these conditions.
Mental Function
· Emerging evidence suggests that the regular consumption
of omega-3s from fish may be beneficial in reducing the severity
of several mental conditions such as Alzheimer's disease, depression,
and bipolar disorder. In children, improvements with the consumption
of omega-3s have been reported in attention deficit hyperactivity
disorder and dyslexia. Caution is warranted because data are inconsistent
and do not permit firm conclusions.
Written by Joyce A. Nettleton, DSc, RD, ScienceVoice
Consulting, Denver, CO.
© American Fishermen's Research Foundation, 2003
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