Bell Shaped Curve
Remarkable British Medical Journal Paper shows Vitamin A Limits Vitamin D
by John Cannell, MD
Vitamin D Council) 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
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
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 highest levels.
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.
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
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 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 et al. 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
that the young to make an equivalent amount of vitamin D.
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 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 et al. 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.
Let"s look at Dr. Pamela Goodwin"s study from the University of Toronto that
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
Goodwin PJ et al. 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? 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
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
Ng K et al. Clin Oncol. 2008 Jun 20;26(18):2984-91. Circulating
25-hydroxyvitamin D levels and survival in patients with colorectal cancer.
J Clin Oncol. 2008 Jun 20;26(18):2984-91.
Tretli S et al. 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.
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 Cannell, MD
Vitamin D Council
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