Cod Liver Oil - Number One Superfood
By Krispin Sullivan, CN
Cod liver oil is very good for you, more than you ever knew.
Research studies ranging from 1918-2001 give cod liver oil an A+ rating. This
marvelous golden oil contains large amounts of elongated omega-3 fatty acids,
preformed vitamin A and the sunlight vitamin D, essential nutrients that are
hard to obtain in sufficient amounts in the modern diet. Samples may also
naturally contain small amounts of the important bone - and blood-maintainer
There is hardly a disease in the books that does not respond well
to treatment that includes cod liver oil, and not just infectious diseases but
also chronic modern diseases like heart disease and cancer. Cod liver oil
provides vitamin D that helps build strong bones in children and helps prevent
osteoporosis in adults. The fatty acids in cod liver oil are also very
important for the development of the brain and nervous system. "If you
want to prevent learning disabilities in your children," said David
Horrobin, distinguished medical and biochemical researcher, "feed them cod
Cod liver oil contains more vitamin A and more vitamin D per unit
weight than any other common food. One hundred grams of regular cod liver oil
provides 100,000 IU of vitamin A, almost three times more than beef liver, the
next richest source; and 10,000 IU vitamin D, almost four times more than lard,
the next richest source. Of course, cod liver oil is only consumed in small
amounts, but even a tablespoon (about 15 grams) provides well over the
recommended daily allowance for both nutrients.
In addition, cod liver oil contains 7 percent each of the
elongated omega-3 fatty acids EPA and DHA. EPA is the precursor of important prostaglandins, localized tissue
hormones that help the body deal with inflammation; and DHA is extremely
important for the development and function of the brain and nervous system. So
it's no surprise that in numerous studies cod liver oil has proven to be a
powerhouse in fighting disease.
GOOD FOR WHAT AILS YOU
Cod liver oil greatly improves heart function to prevent heart
disease and to treat it even in advanced stages, after a heart attack and after
heart surgery. Cod liver oil alters the linings of the arteries in such a way
as to improve healing after damage. This is attributed to the omega-3 fatty
acids but vitamin A, D and K all have important roles to play in facilitating
mineral absorption, improving muscle function and supporting elasticity of the
blood vessels. The inflammation-reducing prostaglandins made from EPA help
mediate the inflammatory response in the arteries. In other studies the
heart-protective effect was associated with changes in the muscle response to
serotonin, increasing the heart's ability to "relax." In a study with
rats, treatment with cod liver oil actually caused artery-blocking atheromas to
become smaller and blood vessel diameter to enlarge. Weston Price noted that
heart attack deaths increased during periods when the vitamin A content of the
diet was low. Cod liver oil can provide vitamin A on a continuous basis
throughout the year.
Many of the conditions addressed by cod liver oil are considered
related under the title Syndrome X. These include obesity, hypertension,
insulin resistance, adult onset diabetes and stroke. Evidence is accumulating
that these diseases of civilization are the result of high levels of omega-6
fatty acids and low levels of omega-3 fatty acids along with deficiencies of
fat-soluble vitamins. We may be paying a very high price for our rejection of
parental wisdom to take our cod liver oil.
In numerous studies, the elongated omega-3 fats found in cod liver
oil have been shown to improve brain function, memory, stress response, immune
response, allergies, asthma, learning and behavioral disorders, including
bipolar syndrome and manic-depression.
Cod liver oil is most famous for contributing to bone health,
preventing and reversing rickets in children and osteomalacia in adults. Before the
discovery of cod liver oil as a source of vitamin D, many children suffered
greatly with deformed bones. Osteoporosis responds to vitamin D and to cod
liver oil. Sufficient elongated omega-3 oils found in cod liver oil are one of
the keys to keeping and rebuilding bone. In women, higher levels of vitamin D
from cod liver oil improve bone mineral density.
Two of the symptoms of low levels of vitamin D are bone pain and
muscle pain. This may manifest as pain in the legs, muscle weakness and
difficulty climbing stairs. Numerous studies have shown improvement in muscle
pain, muscle strength and bone pain scores with cod liver oil.
Cod liver oil is effective in treating arthritis as well.
Researchers funded by Great Britain's Arthritis Research Campaign found that
the elongated omega-3 fatty acids in cod liver oil reduce both pain and damage
in inflamed joints.
Pregnant women using cod liver oil have infants with a lower risk
for juvenile type 1 diabetes. 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 fatty acid profile in breast milk to promote
optimal brain development and also increases levels of vitamin A to prevent
infections. Interestingly, cod liver oil does not provide increased vitamin D
in breast milk.
Cod liver oil given to infants after birth and during the first
year had no protective effect against type 1 diabetes but it nevertheless is an
important source of nutrients for optimal infant health. In more than forty
trials, vitamin A has been shown to reduce morbidity and mortality of children.
Cod liver oil was the supplement of choice in many of these trials. Books on
feeding infants published in the 1930s and 1940s routinely recommended cod
liver oil, starting with 1 teaspoon at the age of three weeks. It was Dr. Spock
who threw this wisdom out the window by recommending vaccinations instead of
the powerful nutritional support of cod liver oil. Few modern books on infant
care mention the importance of the fat-soluble nutrients in this wonderful
As for treating diabetes in adults, cod liver oil has been used in
a number of trials with both insulin-dependent and non-insulin-dependent
diabetes. In both conditions cod liver oil improved glucose response and other
markers of the disease. Vitamin A in cod liver oil helps promote healing and
protects the retina, both problem areas in the diabetic patient.
Cod liver oil has lowered blood pressure induced by
stress-elevated levels of cortisol. Cod liver oil given
to rats reduced intraocular pressure suggesting a use in prevention and
treatment of glaucoma. Vitamin D in cod liver oil promotes absorption of
calcium and magnesium, thereby lowering blood pressure.
Colitis responds more effectively to the type of omega-3 fatty
acids in cod liver oil than to medication. Cod liver oil should be the first
protocol for this condition as well as irritable bowel syndrome and Crohn's
Topically applied, cod liver oil contributes to faster wound
healing and improvement in skin quality. An excellent treatment for diaper rash
and other skin conditions is cod liver oil mixed with zinc oxide. And cod liver
oil taken orally helps maintain soft skin and minimize wrinkles.
And what about cancer? All the nutrients in cod liver oil help
prevent cancer. Vitamin A has been part of every successful alternative cancer
therapy so far. In a study in China, use of cod liver oil was found to be
protective against childhood leukemia. In a study of Norwegian men and women,
consumption of cod liver oil was found to protect against lung cancer.
Eating fish will not provide the levels of nutrients that are
found in cod liver oil. Even in heavy fish-eating populations, the addition of
cod liver oil improves health. And taking fish oils is not the same as taking
cod liver liver oil. One tablespoon of regular cod liver oil and one-half
tablespoon of high-vitamin cod liver oil provide the amount of elongated
omega-3 fatty acids found in twelve 1,000 mg fish oil capsules.
As for vitamin D, body oils of fish can be good sources as long as
you are willing to eat a lot of them. One-half pound of fatty herring or
sardines gives a dose of vitamin D equal to that of about one tablespoon of cod
liver oil. But salmon oil has one-fifth the potency of cod liver oil.
One concern about taking cod liver oil is the presence of
contaminants - heavy metals (such as
mercury, cadmium and lead), PCBs and so forth. Fortunately, consumers need not
worry when it comes to cod liver oil. All cod liver oils in the US must be
tested according to protocols of the Association of Analytical Communities (AOAC)
and approved free of detectable levels of 32 contaminants before they can be
imported into this country. Furthermore, mercury is water soluble. It may be
present in the flesh of fish, but it is not present in the oil.
Another concern is rancidity. Cod liver oil can become rancid if
improperly handled. In a 1988 study, peroxide values (indicating rancidity)
ranged from a low of 2 to a high of 44.7. Nevertheless, properly handled cod
liver oil is relatively stable. It contains 21 percent saturated fatty acids
and 57 percent monounsaturated fatty acids, which provide stability. The fishy
smell of cod liver oil is due to the presence of small amounts of fish protein
and is not a sign of rancidity. To ensure that your cod liver oil is fresh,
avoid buying the large economy size or the end-of-season sale item. Buy cod
liver oil in small dark bottles and keep them in a cool dark place. Cod liver
oil need not be refrigerated after opening if it is used up quickly - within two months.
Virtually all cod liver oil imported into the US comes from
Norway, and while all of it is safe, there are different grades, depending on
vitamin levels. The lighter oil from the "top of the barrel" has a
lower molecular weight, goes rancid more quickly and has lower levels of
vitamins, while the heavier oil, which sinks, is richer in vitamins. The
heavier oil is what Dr. Price referred to as high-vitamin cod liver oil. It
contains double the amounts of vitamin A and D as regular cod liver oil.
Virtually all cod liver oil imported into the US is the lighter, "top of
the barrel" variety. The Norwegians keep the best for themselves!
Whenever taking cod liver oil, remember the findings of Dr. Price. He noted
that he did not get good results from cod liver oil unless he gave it
concurrently with high-vitamin butter. Just why this is so is a matter of
speculation, but we do know that the very unsaturated fatty acids found in cod
liver oil cannot be effectively assimilated and stored in the tissues without
the presence of adequate saturated fatty acids, the kind that would be provided
by butter. This means that even regular butter would help support cod liver oil
therapy; but Price found that the combination of cod liver oil with
high-vitamin butter, from cows eating rapidly growing green grass, was nothing
short of miraculous, reversing tooth decay and bringing patients back from the
brink of death.
I do not find it hard to take Carlson's cod liver oil on a spoon,
but for many, the big challenge is how to get this oily substance down. One
technique is to add cod liver oil to a small amount of water or fresh juice,
stir and then quickly send it down the hatch. If you can't bring yourself to
take cod liver oil on a spoon or in water, then use the capsules. For babies
and small children, use an eye dropper.
OLD RESEARCH BROUGHT TO LIGHT
In researching this article, I had the great fortune to stumble
upon a book published in the 1930s?it is truly exciting to come upon material found and lost and
found again. Ultraviolet Light and Vitamin D in Nutrition, by Katharine Blunt
and Ruth Cowan, published by the University of Chicago, contains fascinating
material, including a chapter on the research of Mrs. May Mellanby published in
1918 in The Lancet II, page 767.
The book describes the work of scientists E. M. Honeywell, A. F.
Hess and C. E. Bills (after which the Bills's Scale for determining
antirachitic value for vitamin D is named) who studied all aspects of fish oil
potency, production and seasonal distribution. Early in their research they
discovered that oil extracted from cod when the fish were fat in the summer
contained much lower amounts of vitamin D. Summer oil scored 100 on the Bills
scale but winter oil scored above 1,000 and some oils scored 20,000. Their
conclusion: "For a fish of a given size, antirachitic potency varies
inversely with the amount of fat or oil in the liver." In other words, the
less oil in the fish, the more concentrated it was.
In one fascinating study, they found that fish kept in darkened
aquariums and fed on trimmed raw veal muscle had the same amount of vitamin D
as free-swimming fish exposed to sunlight. So how the fish obtain vitamin D
remains a mystery. Perhaps they are able to extract it from microscopic
plankton and algae. It is important to note that the amount of vitamin A in cod
liver oil does not have any consistent relation with the amount of vitamin D.
In numerous samples, oils rich in vitamin A were poor in vitamin D, and oils
rich in vitamin D were poor in vitamin A. According to the book, in 1922 the US
imported about 1.8 million gallons of cod oil and cod liver oil. By 1927 this
amount grew to almost 5 million gallons based on data from the Bureau of
Foreign and Domestic Commerce of the United States Department of Commerce. Cod
oil is rancid oil used in the tanning industry, not for human consumption. The
figures don't distinguish the difference, but most of the increase was in the
edible cod liver oil due to research showing its benefit in preventing rickets.
According to the Commerce Yearbook of 1928, "Medicinal oil production has
increased greatly, and the advance in its price has lessened the supply of
common cod oil for tanning."
In 2000, America imported only about one tenth that amount (less
than half a million gallons), indicating a huge decline in use.
In 1930, when the book was compiled, the technology was just being
developed to determine vitamin D potency. The accepted value as of August 31,
1929 was " one rat unit of vitamin D," defined as "that amount
of vitamin D which, when uniformly distributed into the standard vitamin D
deficient diet-ration, will produce a narrow and continuous line of calcium
deposits on the metaphyses of the distal end of the radii and ulnae of standard
rachitic rats." "Potent cod liver oil" is defined as that
containing one of these rat units per 0.75 mg. The International Units started
out as rat units!
Testing of 18 oils in use at that time showed great variations in
potency. Luckily today we have methods of standardization and much better
methods of transportation and storage to improve the amount of vitamin D and
freshness of our cod liver oil.
In 1929, researchers tested a variety of foods for vitamin D
content and found the second most potent source of vitamin D was egg yolk. The
book describes studies in which Hess both cured and prevented rickets in rats
by giving them egg yolks. He also gave prophylactic treatment to 12 infants to
forestall development of rickets in the winter months, which his experience had
taught him to expect in the great majority of bottle-fed infants. He gave them
one egg yolk added to their regular formula starting in December. None of the
12 developed rickets in March as expected and, unlike prior years, blood
phosphates remained stable at summer values.
About this same time, Johns Hopkins University investigators cured
seven African-American children of rickets, in most cases severe, by adding one
or two eggs daily to their diet of milk and cereal.
Like the vitamin D in cod liver oil, the amount of vitamin D in
egg yolks also varies. Researchers in Kansas looked at four groups of hens: one
group got sunlight in the yard plus 30 minutes under a quartz mercury vapor
lamp producing UV-B light; another got sunlight through glass plus 30 minutes
under the lamp; the third group got sunlight alone; and the fourth group got
sunlight under glass alone. Eggs from hens under glass produced rickets in
rats. Those with considerable UV-B prevented rickets completely and those with
less (no lamp) caused the development of slight rickets. Only the sunlight plus
lamp completely prevented rickets, showing that the natural UV-B in Kansas did
not provide sufficient light for optimal vitamin D. Giving cod liver oil to the
chickens had the same effect as exposure to UV-B light. Cod liver oil as two
percent of the ration increased levels of vitamin D in the egg yolks fivefold.
The surprising conclusion is that chickens should either be given sunlamp
treatment or cod liver oil. Poultrymen and consumers alike need to recognize
that the axiom "an egg is an egg" is a mistaken one. Rather, "an
inadequate ration may yield impoverished eggs as well as animals." The
authors suggest that eggs be graded by vitamin content. What a concept! Too bad
no one listened. What would they think of our so-called "organic"
eggs from hens raised in barns, never exposed to light and given
MEET MRS. MELLANBY
The most fascinating part of this little book is the chapter
describing the experiments done in England by a Mrs. May Mellanby. Her husband,
Dr. E. Mellanby, was the author of over 400 studies and the first to control
rickets with diet. Cod liver oil had been used for centuries as a remedy but
the specific application to rickets was first demonstrated by Dr. Mellanby.
(Control of rickets using UV-B light was demonstrated almost simultaneously by
investigators at Columbia and Johns Hopkins University in 1921.) In his
research into rickets in dogs, he discovered the mineral-blocking effect of
phytic acid in grains and legumes. Dr. Mellanby demonstrated that diets
containing high levels of cereals, especially oatmeal, and lacking vitamin D,
are the most effective producers of rickets. If vitamin D is inadequate there
is poor tooth development, but Mrs. Mellanby then went on to prove that no
matter how much cereal is fed, if vitamin D is adequate tooth formation is
normal. Mrs. Mellanby believed that as cereals increase in the diet, vitamin D
must also be increased to offset their anti-calcifying effects - think of the implications of this
research on today's baby-feeding habits, where infants are given cereals as
their first food but denied egg yolks until they are one year old!
Mrs. Mellanby also determined that vitamin D must be present from
conception in order for proper tooth formation to occur. If vitamin D is absent
during the early gestational period, the enamel cannot form properly, and it
cannot be repaired by giving vitamin D later.
In her initial studies Mrs. Mellanby used dogs as the source of
data but she later examined more than one thousand "baby" teeth from
children. She divided these teeth into four categories?normal, hypoplastic (slightly
underdeveloped), moderately underdeveloped and grossly underdeveloped. Only
149, or about 14 percent, of the total 1,036 were sound. About one-quarter were
slightly underdeveloped, but nearly two-thirds were moderately or grossly
It is more difficult to examine teeth in place, but of 266 adult
teeth examined by Mrs. Mellanby, not one was sound. The teeth were extracted
only for purposes of straightening the teeth, which means that they were
erupting in a jaw that was underdeveloped. Thus, children with narrow faces
most likely have underdeveloped teeth. Tooth structure and later decay are
directly related. Prevention of cavities must start in the womb.
A final plum from this most fruitful book regards secondary
dentine. Secondary dentine, a less well-organized form of tubular dentine, is
produced throughout life as a patching material where cavities have begun,
where the overlying enamel has been worn away, and within the pulp chamber as
part of the aging process. Sometimes when cavities occur, production of secondary
dentine can "heal" the decayed spot or rebuild portions of the tooth
that have worn away. If vitamin D is adequate, secondary dentine will be well
calcified. If vitamin D is lacking, dentine will be of poor quality or not
present at all.
There is some evidence that the mineralization of dentine may
depend on calcium derived from saliva rather than blood; in other words, it is
deposited from the exterior rather than the interior of the tooth. The book
describes studies by Dr. C. L. Pattison who, working with Mrs. Mellanby,
determined that the calcium content of saliva doubled or even tripled when the
diet contained adequate vitamin D from cod liver oil.
Now that I have told you all this good news about cod liver oil, I
need to comment on the research surrounding its possible toxicity.
Over-elevated serum levels of vitamin D are a possibility if you combine summer
or southern sun and cod liver oil. So if you are spending a lot of time out in
the sun during the summer months, it's probably best to cut back on the dose.
If you are unsure, you should test your blood levels of vitamin D.
Cod liver oil is no longer recommended in Great Britain and in the
US pregnant women are advised to avoid most vitamin A and vitamin A-containing
foods, including cod liver oil. Both countries have adopted this policy because
of the recognized teratogenicity (may cause birth defects) of retinoic acid, a
synthetic form of vitamin A. But low vitamin A also causes birth defects. In
the developing countries, such as Brazil, Pakistan and India, vitamin A
deficiency is widespread, afflicting millions. A 1992 survey of the US
population determined that 50 percent of Americans consume 19 percent or less
of the Recommended Daily Allowance (RDA) or 400 IU.
The original study showing birth defects associated with intake of
mostly synthetic vitamin A exceeding 5,000 IU daily was published November 23,
1995 in the New England Journal of Medicine. 46 Other studies showing an
association of birth defects with vitamin A concerned topical creams containing
vitamin A derivatives such as Accutane, or extremely high doses of A used in
A later study, less well publicized, from the National Institute
of Child Health and Human Development (NICHD), found no association with birth
defects in women who took up to 10,000 IU of vitamin A during pregnancy.
Because few women took more than 10,000 IU, researchers could not determine
whether higher doses were a problem. Later Mills and others continued their
research and determined that after serum testing and determining safe serum
levels, women taking 30,000 IU of preformed vitamin A from animal foods (not
beta-carotene) daily had the same blood levels of A as healthy pregnant women
in the first trimester who had healthy babies. The conclusion is that a dosage
over 30,000 IU vitamin A daily may be teratogenic for a certain few, but
anything up to that amount is safe.
Thus if you are or may become pregnant, limit cod liver oil intake
to not more than a total vitamin A value of 30,000 IU. If using my favorite
brand, Carlson Labs cod liver oil, that would equal the amount of vitamin A
found in 12 teaspoons or 4 tablespoons, more than anyone would ever take. If
using high-vitamin cod liver oil, the limit would be 2 tablespoons. Two
tablespoons of regular cod liver oil provide 15,000 IU vitamin A, 2600 IU
vitamin D and 6 grams of mixed omega-3 fatty acids, safe for pregnancy and good
for mom and baby.
There is one situation in which high levels of vitamin A are not
recommended and that is the condition of certain types of liver disease in
which there is altered vitamin A metabolism. This is frequently the case with
alcoholism. Alcoholics should not take high doses (not more than 1-1.5
tablespoons of regular cod liver oil) and what they do take should be
accompanied by zinc supplements. The enzymes needed for vitamin A metabolism in
the liver are zinc dependent.
The most likely culprits for production of birth defects in humans
are topical and oral vitamin A analogs, not cod liver oil. Researchers have
criticized the original 1995 study, from which governmental policy has been
derived, for overstating the negative effect. Only 1.4 percent took supplements
exceeding 10,000 IU a day, not a large enough sample from which to draw
conclusions. However, it is important to never combine cod liver oil or vitamin
A from supplements with oral or topical medications for acne or other skin
disorders treated with retinoic acid derivatives.
If you sunbathe regularly and have found that your vitamin D
levels are within the normal range, do not use cod liver oil unless you are
willing to test and retest to determine that your blood levels of vitamin D
have not gone too high. We do not know enough to say whether or not sunbathing
and cod liver oil work synergistically or antagonistically. If you decide to
get lots of sun and also use cod liver oil, please send me your vitamin D tests
for my continued research. Cod liver oil use is safe in most of the US and all
of Canada in winter but it should not be combined with other sources of vitamin
D without careful testing and monitoring.
We all need to take cod liver oil (and eat plenty of good butter).
For growing children, and for almost every disease condition, cod liver oil is
the number one superfood, the supplement of choice.
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have been evaluated by the FDA. These products are not intended to diagnose,
treat, cure or prevent any disease. As always, consult your physician before
taking any and all supplements. LifeSource Vitamins. Individual results may
Disclaimer: All the information contained throughout this website is based upon the
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team at LifeSource Vitamins whose relentless research and studies have been
ongoing on since 1992. Other articles
and information are based on the opinions of the authors, who retains the
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