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Cod Liver Oil Update
Dear Members,
We are obliged to issue another official statement on cod liver oil
after the November bulletin of the Vitamin D Council, which contains
"an unprecedented warning about the ingestion of cod liver oil
and resultant vitamin A toxicity."
The warning accompanies a report on a review article co-authored by
Dr. John Cannell, head of the Vitamin D Council, and fifteen other researchers,
entitled "Cod Liver Oil, Vitamin A Toxicity, Frequent Respiratory
Infections, and the Vitamin D Deficiency Epidemic" in the November
issue of Annals of Otology, Rhinology and Laryngology.
NO Proof that Vitamin A is Toxic
Most of this paper is a review of studies showing the benefits of
vitamin D in protecting against various illnesses, including respiratory
infection. THIS PAPER DOES NOT PRESENT ANY INFORMATION WHATSOEVER INDICATING
THAT COD LIVER OIL IS TOXIC, and, in fact, admits that vitamin A can
significantly reduce the incidence of acute lower respiratory tract
infections in Third World children.
A portion of the review article is an attempt to explain why a 2004
study providing 600 to 700 IU of vitamin D and 3,500 IU of vitamin A
in the form of cod liver oil and a multivitamin failed to meaningfully
reduce upper respiratory tract infections when studies from the 1930s
found that cod liver oil could reduce the incidence of these infections
by 30 to 50 percent. The authors of the recent commentary suggested
that the older studies were more effective because cod liver oil in
the 1930s contained much more vitamin D. They suggested that modern
cod liver oil is low in vitamin D because the deodorization process
removes the vitamin while manufacturers fortify the oil with only a
fraction of the original amount. As an example, they cited cod liver
oil made by Nordic Naturals,
advertised as containing only "naturally occurring vitamins A and
D," which has only 3 to 60 IU of vitamin D per tablespoon but between
150 and 12,000 times as much vitamin A.
This conclusion is essentially the same as the conclusion reached by
the Weston A. Price Foundation and the research of Chris Masterjohn;
we have continually pointed out that vitamins A and D work together
and that without vitamin D, vitamin A can be ineffective or even toxic.
We do not recommend Nordic Naturals regular cod liver oil or any brand
of cod liver oil that is low in vitamin D. But it is completely inappropriate
to conclude from this 2004 study that cod liver oil is toxic because
of its vitamin A content. Similar reviews could be put together showing
the benefits of vitamin A and cod liver oil in numerous studies, including
the studies from the 1930s. Obviously the solution is to use the type
of cod
liver oil that people took in the 1930s, which did not have most of
the vitamin D removed by modern processing techniques.
Our recommendations for cod liver oil brands can be found at westonaprice.org/basicnutrition/cod-liver-oil-menu.html
Vitamin A Does Not Antagonize Vitamin D
The Vitamin D Council report claims that the vitamin A in cod liver
oil is excessive and antagonizes vitamin D by inhibiting the binding
of its active form to DNA and thus preventing its ability to regulate
the expression of vitamin D-responsive genes.
Vitamins A and D are both precursors to active hormones that regulate
the expression of genes. The body possesses certain enzymes that convert
each of these in a two-step process to their active forms: vitamin A
is converted to retinal and then to active retinoic acid while vitamin
D is converted to calcidiol and then to active calcitriol. While directly
consuming either retinoic acid or calcitriol would be unnatural, consuming
vitamins A and D, together, as in cod liver oil, is perfectly natural.
The enzymes involved in these conversions are responsible for producing
incredibly powerful hormones and are therefore highly regulated.
In order for vitamin D to activate the expression of its target genes,
it must bind to the vitamin D receptor (VDR) and then combine with the
retinoid X receptor (RXR), which is activated by a particular form of
vitamin A called 9-cis retinoic acid. RESEARCHERS FROM SPAIN RECENTLY
SHOWED THAT VITAMIN D CAN ONLY EFFECTIVELY ACTIVATE TARGET GENES WHEN
ITS PARTNER RECEPTOR IS ACTIVATED BY VITAMIN A.
In the ABSENCE OF VITAMIN A, molecules called "corepressors"
bind to the VDR/RXR complex and PREVENT vitamin D from functioning.
The molecular biology of 9-cis¬ retinoic acid, however, is extremely
complex, and this has led to some confusion. The RXR and its activator
9-cis retinoic acid partner up not only with the vitamin D receptor,
but also with the receptors for steroid hormones, thyroid hormone, and
most other nuclear receptors. In fact, if enough 9-cis retinoic acid
is present, RXRs will even partner up with themselves. Ordinarily, this
versatile form of vitamin A is gradually derived in small amounts from
the larger pool of all-trans retinoic acid as needed. When scientists
add
large amounts of 9-cis retinoic acid to isolated cells, then, it may
cause effects that smaller amounts naturally produced in the cell would
not cause.
Researchers have shown, for example, that 9-cis retinoic acid interferes
with the ability of vitamin D to stimulate the production of osteocalcin,
a vitamin K-dependent protein involved in organizing the mineralized
matrix of bone. This may have been because the excessive amount of 9-cis
retinoic acid caused RXRs to pair up with themselves and thereby made
these receptors unavailable to vitamin D. When scientists incubate cells
with activated vitamin D and all-trans retinoic acid, ordinarily the
source of 9¬-cis retinoic acid in the cell, the two hormones stimulate
the production of osteocalcin with remarkable synergy.
More information on the interactions between vitamins A and D can be
found
in these articles:
http://www.westonaprice.org/basicnutrition/vitamin-k2.html
http://westonaprice.org/basicnutrition/vitamina-osteo.html
http://westonaprice.org/basicnutrition/vitamin-d-safety.html
The Spanish research demonstrating the necessity of 9-cis¬ retinoic
acid for the functioning of the vitamin D receptor can be found here:
http://www.ncbi.nlm.nih.gov/pubmed/16936639?
http://mcb.asm.org/cgi/content/full/28/11/3817?
Plant Foods are Not a Good Source of Vitamin A
In the December Vitamin D Council newsletter, Dr. Cannell further
claims that consuming preformed vitamin A is "unnatural" and
that the body highly regulates the conversion of carotenoids found in
vegetables to vitamin A as needed. However, the enzymes that convert
carotenoids to vitamin A are less critically maintained because they
are unneeded when preformed vitamin A is provided in the diet-as it
usually is. They are therefore, like the enzymes that convert essential
fatty acids in plant oils to their elongated and desaturated forms,
subject to variations in genetics, circumstantial health, and dietary
and environmental influences.
Many factors can interfere with the conversion of carotenoids into
vitamin A including thyroid problems, liver problems, diabetes and genetics.
Babies and children convert carotenes very poorly if at all.
The statement that preformed vitamin A is unnatural is ludicrous in
the light of what we know about traditional diets. The chief source
of calories in the traditional Inuit diet, for example, is seal oil,
which Weston Price found to be higher in vitamin A than cod liver oil.
Fish heads, extremely rich in vitamin A, are a staple in the Japanese
diet. Many cultures consume liver, often in high amounts-yet the authors
of the review paper imply that liver is toxic. Tell that to the Frenchman
enjoying his foie gras, the Englishman consuming liver and onions, or
the South Sea Islander who submits to great danger to obtain shark liver
for men and women, in order to ensure healthy children. The truth is
that pre-formed vitamin A is more plentiful in traditional foods than
vitamin D, yet politically correct nutrition insists that we must obtain
vitamin A through the laborious process of converting carotenes.
More information on the conversion of carotenoids to vitamin A can
be found in these articles:
http://www.westonaprice.org/basicnutrition/vitaminasaga.html
(see the
section "Vitamin A Vagary").
http://westonaprice.org/basicnutrition/vitamina-osteo.html#carotenesnotad
Cod Liver Oil in Pregnancy
The Annals paper does not cite any studies showing toxic effects from
cod liver oil, but Dr. Cannell cites one study in his December newsletter
associating intake of cod liver oil with hypertensive disorders during
pregnancy. Users of cod liver oil in this study had about twice the
intake of vitamins A and D as non-users and eight times the intake of
long-chain omega-3 fatty acids. The study found the most robust association
with long-chain omega-3 fatty acids, which were associated with lower
risk between 0.1 and 0.9 grams per day and higher risk above 0.9 grams
per day. The authors suggested that the association with high
blood pressure might be related to oxidative stress caused by a high
intake of polyunsaturated fatty acids.
The abstract of the study can be found here:
http://www.ncbi.nlm.nih.gov/pubmed/16487202?
The new Annals article offers nothing new to incriminate cod liver
oil. It provides a well-written argument that vitamin D intakes need
to be higher and incriminates only highly processed modern cod liver
oils that have inadequate amounts of this critical nutrient. We recommend
only high-vitamin cod liver oils that provide abundant vitamins A and
D without an excess of polyunsaturated fatty acids.
The Cod Liver Oil Public Health Initiative
As we pointed out in our last update on cod liver oil, during the
first half of the century, cod liver oil was the focus of a worldwide
health initiative. Parents were urged to give cod liver oil to their
children by doctors, by government officials, by teachers and principals
in schools, and even by their ministers in churches. A large portion
of adults in America born before the Second World War received cod liver
oil as children and this practice contributed to a high level of health,
intelligence and physical development in those lucky enough to receive
it. In many European countries, children received a daily ration of
cod liver oil, especially during the war years. In the UK, for example,
the government issued cod liver oil to all growing children until the
early 1950s.
What has led to the demise of this obviously beneficial practice? Cod
liver oil is a food; it can't be patented, it can't be created in a
laboratory; it can't create millions for the drug companies. So interest
in this wonderful superfood has naturally waned. But if you are basing
your dietary habits on the principles of healthy nutritional diets,
don't hesitate to include cod liver oil-our recommended brands of cod
liver oil--as a healthy and natural food source of critical vitamins
so lacking in modern diets.
Sally Fallon, President
The Weston A. Price Foundation
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