General Description
Docosahexaenoic acid (DHA) is an omega-3 oil found primarily in
cold-water fish such as salmon, mackerel, sardines, herring, cod,
tuna, and anchovies. The oil belongs to a class of nutrients known
as essential fatty acids, which are fats that are required for normal
biological functions but cannot be manufactured in the body, and
therefore must be included in the diet. While purified DHA is available
as an individual supplement, the oil is most commonly found in the
form of fish oil capsules, which contain high concentrations of
DHA and another omega-3 essential fatty acid, EPA (eicosapentaenoic
acid). Cod liver is also a rich source of DHA and EPA, along with
the fat-soluble vitamins A and D.
Health Applications
- Cardiovascular health
- Rheumatoid arthritis
- Mental health
- Lupus
- Psoriasis
- Reproductive health
Primary Uses
DHA is involved in numerous vital functions in the human body.
Studies with human newborns and nonhuman primates indicate that
DHA is essential for the normal functional development of the
brain and retina,1 and serious developmental disorders
are associated with DHA deficiency.2-5 DHA is a crucial
component of brain and nerve cells, and DHA deficit has been linked
to depression and learning disabilities.6,7 Research
indicates that DHA may play an important role in reproductive
health, as low DHA levels have been observed in the ejaculate
of infertile men, and the quantity of DHA was correlated with
sperm motility.8 Because the typical "western" diet
provides very little DHA, many nutritionists believe that DHA
supplements could be helpful for many people. Research suggests
that DHA supplements may have therapeutic benefits as well.
Cardiovascular Health
Much of the research conducted on DHA has focused on its potential
to promote cardiovascular health by lowering blood pressure and
altering the serum lipid profile. Numerous animal and human studies
have shown that supplemental fish oil containing DHA and EPA can
reduce blood pressure levels and lower serum triglycerides.9-16
Studies using isolated DHA indicate that it lowers triglycerides,
raises HDL (the "good cholesterol") levels,17,18 and
lowers blood pressure on its own, and may be the primary cardio-protective
component in fish oil.19,20
Rheumatoid Arthritis
Because essential fatty acids are known to play important roles
in inflammatory processes, researchers have been investigating
their potential in the treatment of inflammatory and autoimmune
disorders such as rheumatoid arthritis, lupus, and psoriasis.
Studies indicate that fish oil supplements may improve clinical
symptoms of rheumatoid arthritis,21-24 allowing patients
to decrease painkiller use.24 Fish oil supplements
have been reported to improve symptoms of psoriasis; however,
these effects have not been demonstrated in well-controlled, large-scale
trials.25 While scientists are unsure which compounds
in fish oil are responsible for its therapeutic activity, animal
research suggests that DHA and EPA may work synergistically to
produce antiinflammatory effects.26
Dosage/Toxicity
Dosage recommendations for DHA vary widely with intended application
and form used. A common recommendation for fish oil (typically
2 parts DHA to 3 parts EPA) is 3 grams per day, in divided doses.
For high triglycerides, studies indicate that isolated DHA may
be effective at an intake of 1.25 grams per day.17
DHA has very low toxicity and appears to be well tolerated at
this dosage range. High intakes of fish oil may cause an unpleasant
"fishy burp" in some cases. |
