DHA is a long
chain omega-3 polyunsaturated fatty
acid derived from the tissues of
oily fish and marine mammals.
As far as dietary sources are
concerned, the location of highest concentration
seems to be within the the livers of fish.
Otherwise, DHA is
widely available through the
ingestion of various nutritional supplements.
DHA is a potent inhibitor of the
many
inflammatory processes taking place
regularly in the body; competing with arachidonic acid in
the cyclooxygenase and lipoxygenase
inflammatory pathways. [1]
These enzymatic pathways are chiefly
responsible for the many adverse
symptoms resulting from
inflammation. In fact, these
two pathways are targeted by several
prescription drugs. Drugs like
aspirin and the newer
Cox-inhibitors work to eliminate the
symptoms associated with these
inflammatory processes.
DHA is readily
converted into eicosapentaenoic
acid, another essential
polyunsaturated fatty acid in
humans. [2]
The term ‘essential fatty acid'
relates to the fact that these are a
grouping of fats that are necessary
for human health; their synthesis is
minimal in the body and, therefore,
must be obtained from diet to insure
proper biochemical functioning. DHA and other
long chain polyunsaturated fatty
acids comprise nearly one-third of
the fatty material in brain tissue. DHA has been shown to not only be a
major component of brain tissue, but
affects neurologic and eye
development to such an extent that
is has recently been included in
commercial baby formulas. [3]
Receiving inadequate amounts of this
nutrient has been linked to impaired
cognitive function, visual
disturbances, and attention-deficit
hyperactivity disorder (ADHD) in
children.
Although widely
available in purified form as a
supplement, DHA is found in
nearly all forms of seafood, most
notably cold water fish.
Popular cold water
fishes include; salmon, herring,
sardines, halibut, bluefish, tuna,
and mackerel. In fact, the colder
the environment from which the fish
is found, the higher its content of DHA. This is important to keep in
mind as farm raised fish (including
those listed above) are typically
very low in DHA and other omega-3
fatty acids. They are not
feed algae, nor do they live in an
extremely cold environments like wild fish. Sea algae provides
some of the precursor material for
fatty acid development in fish.
Other animal
sources of DHA include eggs and
organ meats. While these foods do
contain some DHA, they are
considered a
less than optimal source, especially when comparing
relative quantities to those found
in fish sources.
Vegetable sources
of DHA include flax seed, soy, and canola
oils. Although other oils (e.g. borage and
evening primrose) contain only
minimal
amounts of DHA that are ineffective
at fulfilling daily requirements,
they do still provide a
healthy source of essential fatty
acids. Seeds and nuts
contain another type of fatty acid,
known as alpha-linolenic acid, and
the body can convert this fatty acid into DHA
if needed.
DHA, included
with eicosapentaenoic acid (EPA),
comprise what are known as essential
fatty acids (EFAs). DHA is
incorporated into the human brain
quite rapidly during the third
trimester of pregnancy and during
the course of early postnatal
development (0-6 months). [4] DHA plays a
highly important role in brain
function and is thought to
contribute to proper structural
development, neurologic development,
and synaptic membrane development. [5]
Additional research
shows that DHA exerts a positive
effect on retinal function and
development, visual function,
learning ability, and memory. [6] Further evidence for the importance
of DHA in human development is its
presence in breast milk; children
that are fed solitarily with DHA-devoid
formulas have lower levels of DHA in
the brain and throughout the body. Clinical studies are ongoing to
determine what effect this may have
on one's neurologic development and
future health outcome.
DHA has
beneficial effects in cardiovascular
disease; supplementation with DHA
results in elevated HDL (the "good"
cholesterol) and reduces serum triglyderides. [7] It also, however, elevates LDL
cholesterol (the "bad" cholesterol)
and particle size, but does not
appear to elevate total
cholesterol. [8]
DHA exerts slight effects on blood
viscosity by increasing the ability
of red blood cells to deform, which
allows them to travel with greater
ease through narrow spaces (thus
decreasing potential clots in
narrowed arteries). [9]
DHA as a
supplement has been shown to
decrease stress-related aggression. [10]
This is being studied in people with
developmental disorders. When given
to premature infants, DHA was shown
to improve visual function,
and decrease the severity of
movement disorders in children with dyspraxia, a specific type of
physical movement disabilty. [11,
12] Supplementation
with DHA seems to improve the
development of neurologic
structures, as this fatty acid is
incorporated into the grey matter of
the brain - 1/3 of which is comprised
of long chain polyunsaturated fatty
acids. [13]
Diets rich in DHA may
decrease mortality in people with
coronary artery disease as well. [14] This is thought to be due to DHA's
positive effects on blood lipid
profiles.
There is no
established RDA for DHA. It
is typically supplied in combination
with other polyunsaturated fatty
acids, such as eicosapentaenoic
acid (EPA). The majority of research
suggests 1 - 3 grams of DHA per day;
most fish oil supplements contain
roughly 12% DHA (in combination with
EPA). 5 grams of
supplemental fish oil will yield
approximately 72 - 312 milligrams of
DHA -
0.32%. DHA is also a common
ingredient in
infant formulas. [15]
|
DHA
Deficiencies
and Toxicities |
DHA Deficiency
Diets that contain no
cold water marine animal sources may
be low in DHA. Likewise, diets low
in animal foods and seeds or nuts
may be further depleted. Researchers
believe that pregnancy may deplete DHA stores in women, setting them up
for deficiency toward the end of
pregnancy. [16]
As mentioned, nfants that are not breast fed have
lower amounts of DHA in their bodies
than those that are. This may have
a negative effect on neurological
development.
DHA Toxicities
DHA Side
Effects:
Taken in large
amounts, DHA may cause nausea and
gas. Side effects specific to DHA
are extremely rare, but often occur after consumption of
combination fish
oils (EPA and DHA). Side effects reported include, increased bleeding time
and risk of bleeding, nose bleeding,
loose stools, and fishy taste when
combination products are ingested. [17-19]
DHA Interactions:
DHA is not thought to
cause interaction
with any foods. Although DHA itself
does not affect blood clotting
status, when
taken in combination with other fish
oils (i.e. EPA) a concern arises.
Caution should also be used
when supplementing with herbs that affect
platelet function. [20,
21] These
include, but are not limited to; garlic, ginger, ginkgo, red clover,
angelica, dong quai, and turmeric.
DHA
Drug Interactions:
Combined with EPA,
DHA may increase the risk of blood
thinning when taken with
an anticoagulant or antiplatelet drugs,
including aspirin. In
addition,
because DHA may theoretically lower blood
pressure, caution should be used
when combining it with high blood
pressure medicines; as it may have
an additive effect. [22,
23]
Lab
Test Interactions:
DHA may change lipid
profiles. HDL may be elevated, and
LDL concentration and particle size
may be increased in patients with
already high cholesterol levels. [24]
DHA can also raise
triglyceride levels in people with
elevated cholesterol levels as well.
The following table lists various
products that contain a safe and
reliable source of DHA:
|
Manufacturer |
Ingredient |
Amount |
US RDA |
Learn More |
|
NSI |
DHA From Fish Oils |
275 mg |
-- |
Click Here
 |
|
GNC |
Fish Body Oils |
1000mg |
-- |
Click Here
 |
|
Natrol |
DHA |
100 mg |
-- |
Click Here
 |
