- This article is about the fish extract, for the traditional
Newfoundland song, see "Cod Liver
Oil ".
Cod liver oil is a
nutritional supplement derived from
liver of cod fish. It has high levels of
the
omega-3 fatty acids,
EPA and
DHA, and very high levels of
vitamin A and
vitamin D.
It is widely taken to ease the symptoms of
arthritis as well as other health benefits. It was
once commonly given to
children, because
the high levels of vitamin D in cod liver oil have been shown to
prevent
rickets .
Characteristics
Depending on the quality of the oil, the
flavor and
aroma range from a
mild
sardine-like flavor, to an intense odor
of fish and oil. High quality cod liver oil is a pale-yellow, thin,
oily liquid, having a slightly fishy and bland taste. Manufacturers
sometimes add flavorings, such as citrus or mint essence, to cod
liver oil to make it more palatable.
Manufacture
Traditionally manufactured by filling a wooden barrel with fresh
cod livers and seawater and allowing the mixture to ferment for up
to a year before removing the oil. Modern cod liver oil is made by
cooking the whole cod body
tissues
of fatty
fish during the manufacture of
fish meal.
Therapeutic uses
Cod liver oil is widely taken to ease the pain and joint stiffness
associated with
arthritis, but has also
been clinically proven to have a positive effect on heart, bone,
and brain, as well as helping to nourish skin, hair, and
nails.
Cod liver oil and
fish oil are similar, but
cod liver oil has much higher levels of vitamins A and D. Many
adults do not meet the RDA for Vitamin D.Reginster JY. The high
prevalence of inadequate serum vitamin D levels and implications
for bone health. 2005. Curr Med Res Opin 21:579-586.
DOI:
10.1185/030079905X41435 PMID
15899107Calvo MS, Whiting SJ, Barton CN. Vitamin D
fortification in the United States and Canada: current status and
data needs. 2004. Am J Clin Nutr 80:1710S-1716S.
PMID
15585792 full text (free)Peterlik M, Cross HS. Vitamin D and
calcium deficits predispose for multiple chronic diseases. 2005.
Eur J Clin Invest 35:290-304.
DOI:
10.1111/j.1365-2362.2005.01487.x PMID
15860041
Cod liver oil is effective in treatment of household burns because
of its high vitamin content , often leaving no burn-related
blister.
Cod liver oil may be an effective complementary measure for
long-term treatment of
multiple
sclerosis.
Use of cod liver oil during pregnancy is associated with lower risk
of
Type I diabetes in the
offspring.Stene LC, Ulriksen J, Magnus P, et al. Use of cod liver
oil during pregnancy associated with lower risk of Type I diabetes
in the offspring. 2000. Diabetologia 43:1093-1098.
DOI:
10.1007/s001250051499 PMID 11043854
full-text (free) This effect was found only in
mothers taking cod liver oil, not in mothers taking multivitamin
supplements. Cod liver oil taken by nursing mothers improves the
breast milk by increasing the amount of fatty acids, which promotes
brain development, and the amount of vitamin A, which helps prevent
infections, but the level of vitamin D is unchanged.
A Norwegian study of more than 68,000 women reported that female
cancer patients who took daily cod-liver oil supplements had
significantly reduced mortality (25% for all cancers, 45% for lung
cancer) compared to women who did not take such supplements.
Adverse effects
Because cod liver oil has a very high level of Vitamin A, it is
possible to exceed the
Recommended Dietary Allowance
(RDA) of vitamin A. Vitamin A accumulates in body fat, and can
reach harmful levels sufficient to cause
hypervitaminosis A. Pregnant women may
want to consider consulting a doctor when taking cod liver oil
because of the high amount of natural forms of Vitamin A (
Retinol). High doses of synthetic Vitamin A
(
Retinoids) have been shown to cause birth
defects.
The risks of hypervitaminosis and of exposure to environmental
toxins such as
mercury,
polychlorinated biphenyls,
dioxins, and other
contaminants, are reduced when purification processes are applied
to produce refined fish-oil products, which consequently contain
raised levels of omega-3 fatty acids, such as
EPA and
DHA.
A high intake of cod liver oil by pregnant women is associated with
a nearly five-fold increased risk of
gestational hypertension, although
this study did not control for mercury, which can be present in
harmful amounts in fish and which is another cause of
hypertension.
Some urge caution when taking cod liver oil and other fish-based
supplements since they may contain elevated levels of toxins such
as
mercury and
PCBs found in fish. Some supplement
companies regularly test cod liver oil for purity, while others do
not. Consumerlab.com tested 44 fish and cod liver oil supplements
and found that all were free of detectable levels of mercury.
Other uses
In
Newfoundland
, cod liver oil was sometimes used as the liquid
base for traditional red ochre paint, the
coating of choice for use on outbuildings and work buildings
associated with the cod fishery.
Vikings used cod liver oil as a lubricant to
allow the transport of ships across land—the oil was smeared across
logs, which acted as rollers beneath the hull of the ship. Cod
liver oil also formed part of the Viking diet.
See also
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