Wellll was it natural vit A, or synthetic. That's
the question. People have been using Cod Liver oil
for centuries, and liver is chock full of the
stuff. Vit A is required by the body for eyesight
and the synthesis of T3 from the T4 thyroid
hormone. I'be never heard of a case of toxicity
from eating liver or natural A from Cod liver oil,
but I have for synthetic Vit A.
I also read a paper somewhere refuting the
painting of natural vit A with the same brush as
synthetic vit A.
Annie
Control your destiny or somebody else will.~Jack Welsh
Pat wrote:
This Vitamin D Council newsletter was interesting, concerning vitamin A and cod liver oil. http://www.vitamindcouncil.org/newsletter/vitamin-d-vitamin-a-and-cancer.shtml
I'll try to copy and paste, but it might be too long.
The Vitamin D NewsletterFebruary 2010
Vitamin D, Vitamin A, and Cancer
A Remarkable Paper
A few weeks ago, the British Medical Journal published a
remarkable paper, remarkable that it studied more than 500,000 subjects, remarkable that it had 56 (fifty-six) authors, remarkable that it
confirmed low vitamin D levels obtained in the past are a risk
factor for developing colon cancer in the future. However, the most
remarkable part of the paper is that the 46 scientists minimized the
true significance of their own research. They found that vitamin A, even in relatively low amounts, appears
to thwart vitamin D's association with reduced rates of colon cancer. Jenab M, et al. Association
between pre-diagnostic circulating vitamin D concentration and risk of
colorectal cancer in European populations:a nested case-control study. BMJ 2010;340:b5500.
This is a prospective nested case-controlled study, which means it
uses subject's vitamin D blood samples obtained and frozen in the past
and then reviews their medical records into the future to see who gets
colon cancer, comparing the study subjects to similar members of the
group that did not get the illness. Dr. Mazda Jenab and his 45
colleagues from the International Agency for Research on Cancer
confirmed that low vitamin D levels are a risk for colon cancer in a
dose response manner; those with the highest levels were about twice as
less likely to develop colon cancer compared to those with the lowest
levels.
Vitamin A and the U-shaped Curve
However, hidden on page eight is one sentence and a small table,
which shows that the benefits of vitamin D are almost entirely negated
in those with the highest vitamin A intake. And the retinol intake did not have to be that high in these older adults to begin to negate vitamin D's effects, about 3,000 IU/day. Remember, young autistic
children often take 3,500 IU of retinol a day in their powdered multivitamins, which doesn't count any additional vitamin A given in high, single doses.
Pancreatic Cancer
This is the largest study to date showing vitamin A blocks vitamin
D's effect and explains some of the anomalies in other papers on vitamin D and cancer. For example, Dr. Rachael
Stolzenberg-Solomon of the NIH conducted two similar studies on pancreatic cancer, with startling
different results. Her first paper showed high vitamin D levels tripled
the subsequent risk of pancreatic cancer, her second paper showed no
effect. The difference, the first was conducted in a cod liver oil
country, Finland, the second in the United States. Stolzenberg-Solomon RZ, et al. A prospective nested case-control study of vitamin D status and pancreatic cancer risk in male smokers. Cancer Res. 2006 Oct
15;66(20):10213–9. Stolzenberg-Solomon RZ, et al. Serum vitamin D and risk of pancreatic cancer in the prostate,
lung, colorectal, and ovarian screening trial. Cancer Res. 2009 Feb 15;69(4):1439–47.
Prostate Cancer
Prostate cancer is another
good example. Ten similar studies have been conducted on vitamin D blood levels and the risk of subsequent prostate cancer. Dr. Lu Yin of the
German Cancer Research Center reviewed them in detail. Eight of the
studies found no relationship but two studies found a U shaped curve,
that is, an increased risk of prostate cancer at both lower and higher
vitamin D levels. You guessed it; both of these studies were from Nordic countries where cod liver oil consumption is rampant. Yin L, Raum E, Haug U, Arndt V,
Brenner H. Meta-analysis of longitudinal studies: Serum vitamin D and prostate cancer risk. Cancer Epidemiol. 2009
Dec;33(6):435–45.
So why is there no relationship between vitamin D levels and the
future risk of prostate cancer? All the subjects had their vitamin D
levels checked in the late 1980s or 1990s, well into the sun-scare but
before the vitamin D revolution.
So how did these older people get high levels of vitamin D back then? Multivitamins? No, they only contained a meaningless 400 IU. Vitamin D
supplements? No, they were not widely available back then and only
contained a meaningless 200 to 400 IU of vitamin D if available.
Sunshine? Maybe, but I doubt it. Studies have shown that the elderly
were the first to abide by sun-avoidance advice; anyway, the elderly
lose the ability to make vitamin D from sunshine; it takes the elderly
up to ten times more time in the sun than the young to make an
equivalent amount of vitamin D.
Cod Liver Oil and Retinol
However, the elderly of many countries, not just Nordic countries,
were raised on cod liver oil and I suspect that a sizable number of
Americans continue to take cod liver oil as they age. While cod liver
oil from the 1980s and 90s had higher amounts of vitamin D than does
modern cod liver oil, it still had toxic amounts of vitamin A. I suspect if authors of the above ten studies had controlled for cod liver oil
intake, they would have found that high retinol intake was blocking the
cancer-preventing effects of vitamin D.
I say this because one author has controlled for retinol intake and
the pre-cancerous condition, colon adenomas. Dr. Kyungwon Oh, of the
Korea Centers for Disease Control and Prevention, working with Harvard epidemiologists, found that high retinol intake
completely thwarted the beneficial effects of vitamin D, stating, "a
higher retinol intake, approximately > 4,800 IU/day, appears to counter the
beneficial effect of vitamin D . . ." In other words, exactly what the British Medical Journal paper found with colon cancer. Oh K, Willett WC, Wu K, Fuchs CS,
Giovannucci EL. Calcium and vitamin D intakes in relation to
risk of distal colorectal adenoma in women. Am J Epidemiol.
2007 May 15;165(10):1178–86.
Breast Cancer
Let's look at Dr. Pamela Goodwin's study from the University of
Toronto that studied breast cancer survival. This a very different
study as it looked at vitamin D levels obtained after the diagnosis of
breast cancer and subsequent survival in 535 Toronto women between 1989
and 1996. Vitamin D levels ranged from 3 ng/mL to 70 ng/mL. The women with the lowest levels were
about twice as likely to die and to suffer distant cancer recurrence
compared those with the highest levels. Ten year survival was 85% for
those in the upper one-third of vitamin D levels compared to 74% in the
lower one-third. However, the data suggested a U shaped curve for the
women with levels above 40 ng/mL, that is, a higher risk of dying, but it was
not statistically significant. Goodwin PJ, Ennis M, Pritchard KI,
Koo J, Hood N. Prognostic effects of 25-hydroxyvitamin D levels
in early breast cancer. J Clin Oncol. 2009 Aug
10;27(23):3757–63.
Again, let's ask where women would get levels above 40 ng/mL in
Toronto between 1989 and 1996? Sunshine? We know the answer is no as the authors found no seasonal variation in 25(OH)D levels in the 535 women, even in the women with the highest levels. So where did blood levels of 40–70 ng/mL come from in the early 1990s?
Vitamin D supplements were not widely available in the early 1990s,
and only contained meaningless doses when available. As sunshine was
ruled out, they could only have gotten it from cod liver oil. I have
emailed Dr. Pamela Goodwin, lead author, asking how hard it would be to
see if cod liver oil use was asked about in the dietary questionnaire
and if she could control for cod liver oil intake. She did find retinol
intake was associated with higher vitamin D levels but I am particularly interested in cod liver oil intake in women with vitamin D levels above 40 ng/mL.
It's not just in breast cancer that vitamin D levels appear to have a treatment effect; it's in lung, prostate and colon cancer as well.
Again, these are studies of people diagnosed with cancer to see if high
vitamin D levels at the time of diagnosis are associated with improved
survival; that is, do high vitamin D levels have a treatment effect?
Those With Highest Vitamin D Levels Live Longer
On average, those with the highest vitamin D levels at time of
diagnosis lived 2 or 3 times longer. One has to ask how high vitamin D
levels are associated with greatly improved survival once you get cancer but a higher risk of getting cancer in the first place. That requires
some gymnastic thinking and acrobatic basic science. Zhou W, et al. Circulating 25-hydroxyvitamin D levels predict survival in early-stage
non-small-cell lung cancer patients. J Clin Oncol. 2007 Feb
10;25(5):479–85. Ng K, et al. Circulating 25-hydroxyvitamin d levels and survival in patients with colorectal
cancer. J Clin Oncol. 2008 Jun 20;26(18):2984–91. Tretli S, Hernes E, Berg JP, Hestvik UE, Robsahm TE. Association between serum 25(OH)D and death
from prostate cancer. Br J Cancer. 2009 Feb 10;100(3):450–4.
Remember, studies of vitamin D levels and subsequent risk of cancer
are only one type of epidemiological study. Studies of latitude and
cancer are quite clear, the less sunshine the higher the cancer risk.
Studies of dietary vitamin D intake and cancer are also mostly
supportive but such studies are limited by the tiny doses people get in
their diets.
Avoid Retinol and Cod Liver Oil
So it is not just autistic children that are being harmed by vitamin A. Avoid cod liver oil like the poison it is and check your
multivitamins. Life Extension Foundation just reformulated their
multivitamin to contain only 500 IU of preformed retinol. And, I am
happy to report that Purity Products, which markets my vitamin D, has no preformed retinol at all in any of their multivitamins, only beta-carotene. Purity has also stopped selling cod
liver oil. Now, if only Carlson, Solgar, Nature's Way, and other
companies would stop selling cod liver oil and stop selling their
concentrated vitamin A supplements to a country whose problem is
widespread sub-clinical vitamin A toxicity, I'd be a happier
agitator.
John Jacob Cannell MD Executive Director
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