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(sections
in red italics in the following are quotations from an article on
Robert Cohen's website, www.notmilk.com):
29 January,
2002
Dear Robert,
As you know,
I wrote to you in a personal capacity on 21 December, 2001, pointing
out serious errors in an article you featured on your website. In
my letter, I told you that if you did not respond and take action
to correct certain glaring misstatements and defamatory remarks,
I would make this matter public. Hence, I write this open letter.
I contacted
you 10 weeks ago to provide you with a draft version of the Vegan
Society briefing paper on milk and breast cancer. This briefing
paper is now in official form and is available on www.vegansociety.com/briefings/milkbreastcancer.htm
and www.vegsource.com/articles/walsh_milk_cancer.htm
I was disappointed
to receive no constructive response to either this briefing paper
or my later letter.
I am even more
disappointed that
10 weeks later you are still displaying your article at www.notmilk.com/tomfoolery.html
In this article
you launch a melodramatic attack on the paper by Hjartaker et al
appearing in the September 15 issue of International Journal of
Cancer, accusing the authors of this paper of producing "the
fraudulent study of the century."
You make several
criticisms of the paper to back this up:
1) 317
of the 48,844 women in the study got breast cancer (six- tenths
of one percent), but the study actually began with 57,664 women.
Why were the data from 8820 women eliminated? It turns out that
986 of those women had cancer too (11%). What does that indicate
regarding the entire study?
The authors
were simply following standard good practice by excluding people
whose behaviour and recollection of their diet may have been altered
by related pre-existing disease. In making this criticism you show
ignorance of the basic principles of nutritional epidemiology.
2) Nine
different categories of questions were asked of the 48,844 women
regarding milk and other foods consumed. Only one question was
asked regarding milk consumption as a child:
"How
much milk did you drink as a child each day?"
Even
the authors recognize how poorly they designed this so-called
study. In the discussion section (page 891), they write:
"Our
questionnaire included only a single question on childhood milk
consumption... we do not know how well the question reveals real
differences... although no significant association between childhood
milk consumption and breast cancer incidence was found in our
study, one may speculate on a negative association."
IS
THAT REAL SCIENCE OR REAL BIAS?
It is real science.
The authors did not find a statistically significant effect but
they did find a tendency towards a negative association. They do
not claim anything more than the data justifies.
[For the benefit
of the majority of people, who will not have read the original paper,
I have added some additional explanation of the background to the
next point.
The key table
in the paper was Table 4, which set out the number of cases of breast
cancer according to three categories of long-term milk consumption.
These categories were based on answers to a question about childhood
milk consumption as well as answers to questions on adult milk consumption.
The total number
of women considered was 47,747, and the total number of breast cancer
cases during the study was 311. Taking the authors' figures above
we can work out how many women were in each category.
The risk of
breast cancer for the low-milk consumption group was therefore 42
cases divided by 5,231 women in the category, that is 0.00803. The
risk for the moderate-milk consumption group was 254 cases divided
by 39,057 women in the category, that is 0.0065. The risk for the
high-milk consumption group was 15 cases divided by 3,459 women
in the category, that is 0.0043. The relative risk is calculated
by dividing the risk in each category by the risk in the low-milk
category. For the moderate-milk consumption group this is 0.0065/0.00803
(0.81). For the high-milk consumption group this is 0.0043/0.00803
(0.54).
What you do
below, Robert, is to claim the authors of the study can’t read their
own paper and that the low-milk group has a lower risk of breast
cancer than the other groups. You reach this conclusion by pretending
that half the total group were in the low-milk consumption category
and the other half were in the moderate- and high-milk consumption
categories combined. Based on this, you say that the expected number
of breast cancer cases in the low-milk category was half the total
(156) and the expected number of cases in the other groups combined
was also half the total (155). As there were 42 cases in the low-milk
category and 269 in the moderate- and high-milk consumption categories
combined, this gives your claimed “true” relative risk for moderate
to high-milk consumption of 269/42, that is 6.4 or 640%.
This is nonsense
as there is absolutely no reason to suppose that half the total
group were in the low milk category. This appears a bizarre and
arbitrary assumption on your part.]
3) TABLE
3 reveals the incidence rate ratios of breast cancer according
to milk consumption as a child and as an adult.
Based
upon population statistics supplied by the authors, the expectation
of breast cancers for low-milk consuming females was 156 cases
out of 311. The actual number of cases was only 42.
The
expected number of cases of breast cancer for the moderate- and
high-milk consumption group was 155 cases. The actual number of
cases of breast cancer for the milk drinkers was 269.
In
other words, the authors mis-read their own data.
Women
who drank a lot of milk as children developed more cases of breast
cancer than notmilk users. How much more? A factor of 640%!
This is the
core of your claim that the paper is fraudulent and is an unmitigated
piece of nonsense. You arrived at your figures above by arbitrarily
and incorrectly assuming that half the study population were in
the low-milk consumption group and half were in the medium- and
high-milk consumption groups combined. Based on this fanciful assumption,
one would indeed expect 155.5 cases in the low-milk group based
on the total of 311 cases in the table of age-adjusted cancer incidence.
In my briefing
paper, I reconstructed the number of individuals in each group (using
data in the paper by Hjartaker et al) as 11% low-milk, 82% medium-milk
and 7% high-milk. I then summarised the expected vs observed number
of cases, after adjustment for other risk factors. Your figures
for observed cases in the low-milk group are slightly different
than mine (42 vs 36) as you used the age-adjusted incidence, not
the multivariate-adjusted incidence.
"Only by
using a combined measure of childhood and adult milk intake was
a statistically significant protective association found and this
was only just significant (RR=0.51 "high" milk intake
vs "low" milk intake, with full adjustment for known risk
factors). 11% of the overall group was in the low-milk category.
This category had 36 cases of breast cancer against an expected
29, based on the average risk for the whole group. 7% of the group
was in the high milk category. This category had 13 cases of breast
cancer against an expected 20, based on the average risk. There
was little difference between the age adjusted and fully adjusted
relative risks, indicating that any interactions between milk consumption
and known risk factors, such as age at menarche, did not have a
large effect on the observed risk."
Your claim based
on assuming that 50% of the population studied were in the low-milk
group is nonsense as only 11% of the population were in this category.
You owe the
authors of this study an apology and bring shame on the vegan community
by your arbitrary, nasty and unfounded accusation of fraud.
4) The
authors bring their biases to the discussion by writing (page
892):
"Calcium
intake, however, has previously been investigated with cancer
risk, especially of colon cancer..."
As discussed
in the milk and breast cancer briefing paper -- there is good evidence
for the view that milk consumption does modestly decrease colorectal
cancer risk, though there are much better ways of achieving this
reduction in risk.
Nonsense such
as your "tomfoolery" article brings the vegan community
into disrepute. It sows confusion among vegans seeking to understand
the truth so as to promote veganism effectively.
You do the vegan
community a profound disservice by such behaviour. Vegans - like
everyone else - should be fair. I strongly encourage you to do the
right thing and correct or remove your article and apologise to
those people you unjustly accused of fraud.
If you are prepared
to try to work within the constraints of facts, I would be happy
to help you produce material based on sound science. There is no
need to exaggerate or invent in order to show that the dairy industry,
which causes much animal suffering and environmental damage, is
at best unnecessary for human health and at worst harmful. Distorting
to overstate this case only serves to weaken the credibility of
all vegan advocates, and ultimately to weaken veganism.
yours sincerely,
Stephen Walsh
Robert Cohen's
only reply to Walsh to date:
I
have no idea what you're talking about.
I
do not like your tone, or your agenda.
I
hope that nothing is lost in the translation when I tell you to
go and have carnal relations with yourself.
Robert
Cohen
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