IARC Report Links Meat With Increased Risk Of Cancer
Agency Makes No Clear Public Health Recommendation - Confusion Is
Widespread
“The way WHO classifies cancer-causing substances…? Maybe a little
dangerous to your mental health. Because it is really confusing.”
“The messaging isn’t coming off very well, the risk communication
piece.”
These are some of the comments made in the media in response to the
latest report from the International Agency for Research on Cancer (IARC)
reporting on meat and cancer.
The
last time there was similar confusion is when the IARC released its
report on cell phones and brain cancer. This time the issue is
processed meat such as bacon and sausage and red meat such as beef and
pork and their associations with colorectal cancer. The agency appears
to have an ongoing risk communication challenge.
What Are The Findings?
According to IARC, its working group considered more than 800 studies
that investigated associations of more than a dozen types of cancer
with the consumption of red meat or processed meat in many countries
and populations with diverse diets. The most influential evidence came
from large prospective cohort studies conducted over the past 20
years.
The
IARC classified red meat as probably carcinogenic in humans
based on still limited evidence that consumption of red meat
causes cancer in humans and strong mechanistic evidence
supporting a carcinogenic effect mainly for colorectal cancer but also
for pancreatic and prostate cancers.
IARC classified processed meat as carcinogenic based on
sufficient, i.e., convincing, evidence of carcinogenicity in
humans.
Risk Quantified
IARC quantified the risk of eating processed meat by stating the risk
generally increased with the amount of meat consumed and that an
analysis of data from 10 studies estimated that every 50 gram portion
of processed meat (less than two ounces or two slices of bacon) eaten
daily increases the risk of colorectal cancer by approximately 18%.
IARC estimated that if proven to be causal, the risk of colorectal
cancer could increase by about the same amount as for processed meat
(17%) for every 100 gram
portion (3.5
oz) of red meat eaten daily(twice the portion size of processed meat).
According to the Compound Interest website which has published a
helpful infographic about the IARC classifications, when you look at
the actual numbers behind the percentage increase, it makes it a bit
clearer. On average, 64 out of 100,000 people develop colorectal
cancer per year; eating 50 grams of bacon every day would raise your
risk to 72 in 100,000.
Put
another way, the lifetime risk of colorectal cancer is 5% and exposure
of the type IARC identifies could raise that to 6%, according to one
estimate.
Burden of Disease
IARC cited the most recent estimates by the Global Burden of Disease
Project, that an estimated 34,000 cancer deaths per year worldwide can
be attributed to consumption of diets high in processed meat and an
estimated 50,000 attributable to diets high in red meat.
In
seeking to put the risk from meat in perspective, IARC compared the
total deaths per year worldwide for other exposures placed in IARC
category 1. Thus, tobacco smoking causes an estimated 1 million
deaths, alcohol consumption 600,000, and air pollution 200,000. Thus,
exposure to processed and red meat causes close to half the deaths
caused by air pollution (84,000).
Risk Communication
Challenge
The
IARC seeks to provide an objective and strictly evidence-based
assessment of
whether or not an
agent is a cause of cancer. IARC chooses to leave to policymakers the
task of issuing recommendations on what to do about the risk at the
individual and organizational levels.
However, as soon as these risk reports are issued, especially on
exposures that many people use or enjoy such as cell phones and bacon,
the media and the public want to know what they should do.
IARC did point out that there are already many national health
recommendations advising people to limit the intake of processed and
red meat, not because of cancer risk, but because of increased risks
of death from heart disease, diabetes, and other illnesses.
Media And People On
Their Own
The
media and the public were left to grapple with comments about the
report made the media or by outside experts who may have had no role
in the review. Some media equated the risk of red meat to that of
smoking, which was clearly a misleading interpretation of the
findings.
In
the case of processed and red meat, there has been relatively little
questioning by the media or by the experts interviewed about the
validity of the science showing the risk is real. (There have been the
usual assertions epidemiologists have come to expect in
every controversy using
epidemiologic
data informing readers, as one
Canadian doctor
put it
“the warning is based on less
rigorous, ‘observational studies’). Instead most
reports
of this controversy assume the risk is real and are centered on the
question of---so what?
Communication
Challenge
While the IARC did not issue a formal recommendation on this matter,
it did seek to address the question which it knew would be on the
minds of everyone. According to the Q/A accompanying the report, IARC
states “The latest IARC review does not ask people to stop eating
processed meats but indicates that reducing consumption of these
products can reduce the risk of colorectal cancer.” It informs
readers that only next year will a standing group of experts begin
looking at the public health implications of the latest science and
the place of processed meat and red meat within the context of an
overall healthy diet.
One Perspective
In
a blog headlined, "Know Your Risks, but Meat Still Isn’t The Enemy",
Aaron Carroll writes “Let’s be clear. Rational people are
willing to accept small risks of harm to obtain something they value.
The example I always like to use is cars. The No. 1 killer of children
in the United States is, by far, accidents. Every time we put a child
in a car, we are exposing them to the thing most likely to kill them.
We don’t see headlines like “Cars Found to Kill Kids in Record
Numbers!” or “Putting a Child in a Car Increases
Their Risk of
Death by 20 percent!” That’s because we have all recognized that
while cars do increase the risk of a bad outcome, the gains from
driving outweigh the potential and very small absolute risks of death.
The same is true of many things. I like Scotch. I like skiing. I like
the occasional steak. All of these things may increase my absolute
risk of death someday by some very tiny amount, but the daily
happiness and satisfaction I gain from them outweigh those future, and
most likely very small, risks… If you’re consuming multiple portions
of processed meat a day, then you may see some small benefit in the
lifetime risk of cancer by cutting back. But if you’re like most
people I know, enjoying bacon or prosciutto a couple of times a week,
this news most likely doesn’t affect you at all.”
Blog:
https://tinyurl.com/nv8su6b
Infographic on IARC Classifications:
https://tinyurl.com/oken7fz ■
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