Body Weight Study explains why eating red meat raises cancer risk
By David Liu Ph.D.
Nov 16, 2008 - 7:32:50 AM
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Editor’s note:
Many
media outlets opt to avoid reporting this study.
We feel this is very important study and many
consumers may find it useful.
Many
epidemiologic studies have associated consumption of meat and milk with
increased risk of cancer, but few provided any explanation why.
We have published part of the report, below
is the complete report on the study.
Red meat, milk boost cancer risk, Aspirin may reduce it
People who use red meat and milk may not want to hear it
that eating these foods increases risk of cancer. But a new study has already found
a mechanism that explains why human consumption of red meat and milk products
increases risk of cancerous tumors.
The study published online this week in advance of print
publication in the Proceedings of the National Academy of Sciences (PNAS) found
a molecule produced after consumption of these foods induces inflammation that
boosts the cancer risk.
The molecule of concern, according to Ajit Varki, M.D., coauthor
of the study, of the University of California, San Diego School of Medicine and
colleagues, was a non-human cellular molecule called N-glycolylneuraminic acid
(Neu5Gc).
Neu5Gc is a type of glycan, a sugary compound, which is
not naturally present in human bodies.
But
this molecule can be incorporated into human tissues as a result of eating red
meat.
When it gets into human tissues,
the body develops anti-Neu5Gc antibodies, an immune response that could lead to
chronic inflammation and boost cancer growth.
"We've shown that tumor tissues contain much more
Neu5Gc than is usually found in normal human tissues," said Varki.
"We therefore surmised that Neu5Gc must somehow benefit tumors."
Chronic inflammation has been known for some time to
actually stimulate cancer, Varki explained. But the researchers wondered why
tumors containing the non-human molecule grew even in the presence of Neu5Gc
antibodies.
"The paradox of Neu5Gc accumulating in human tumors
in the face of circulating antibodies suggested that a low-grade, chronic
inflammation actually facilitated the tumor growth, so we set out to study that
hypothesis," said co-author Nissi M.Varki, M.D. at UCSD.
To test how Neu5Gc affect cancer, the researchers induced
in mice tumors containing Neu5Gc and then administered ant-Neu5Gc antibodies to
one group of mice and left another group mice untreated.
They found in the mice treated with antibodies, which is
equavalent to being treated with ingested red meat and milk, inflammation was
induced and the tumors grew faster compared to mice that were untreated.
In untreated mice, the tumors were less
aggressive.
Prvious studies by other researchers have shown that
humans who take non-steroidal anti-inflammatory drugs (commonly known as
NSAIDs) have a reduced risk of cancer., suggesting that inflammation is
involved in carcinogenesis. But the current study provided one mechanism to
explain why.
To further test if Anti-inflammatory drugs may affect the
effect of Neu5Gc, interestingly the researchers observed the mice treated with
anti-Neu5Gc antibodies and then treated with an NSAID had their tumors reduced
in size.
"Taken together, our data indicate that chronic
inflammation results from interaction of Neu5Gc accumulated in our bodies from
eating red meat with the antibodies that circulate as an immune response to
this non-human molecule – and this may contribute to cancer risk," said
Varki.
The study was supported in part by a grant from the
National Cancer Institute, of the National Institutes of Health.
A study published in Cancer Epidemiology Biomarkers and
Prevention. 2008;17:3098-3107 found that those who ate the most red meat had a
67 percent higher risk of colorectal cancer, regardless of any genetic factors
they may have.
The increased risk was
even greater in those who had specific genes compared to people who did not eat
meat.
So what is the message?
Eating red meat and milk boosts cancer risk. And taking
anti-inflammation drugs reduces the risk.