geoff, oh please!

No they didn't say that at all. Here is a direct quote from WCRF:
"There is “convincing” evidence that processed meats, including ham and bacon, increase the risk of colorectal cancer"

Their own quote marks on convincing. I'll point out the word risk.

They go on to say:

"The evidence that red meat is a cause of colorectal cancer is stronger than ever before. People should not eat any more than 500g of red meat a week.
This figure is for cooked meat, and is the equivalent of between 700 and 750g of non-cooked meat."

1, how strong was it before?
2, Who eats 7 quarter pounders worth of red meat a week? Hardly bastions of health. Is it mince or lean beef, charcoaled or otherwise.

The WCRF clearly indicate obesity as the greatest link to cancer, and overconsumption of high energy dense foods like meat products will help one get there.

I too would advise less processed meat.

didn't include this in last post.

"The study from England showed that large amounts of red meat can produce genetic damage to colon cells in just a few weeks, but it does not prove that red meat causes cancer. None of the cells were malignant, and the body has a series of mechanisms to repair damaged DNA."

http://www.health.harvard.edu/fhg/updates/Red-meat-and-colon-cancer.shtml

rojo: The WCRF report does indeed sometimes talk about
red and processed meat increasing cancer risk. This
is because anything which causes cancer increases its
risk. They clearly state that red and processed meat
is a cause of cancer on pages 116,117,121,280,284,382
--- but I may have missed some.

You seem to assume that A can only be said to
cause B if whenever you do A, B follows. This is
simply wrong. Think about me shooting basketball
hoops. I'd miss most of the time, but what do you
say about the ones that score? Was my action the
cause? Absolutely. Did my attempts increase the risk
of a basket? Absolutely. In the case of cancer, there
are multiple links in the DNA damage chain leading to
cancer. Red and processed meat gets you to (at least)
stage 1. This is what makes cancer and antioxidants
tricky. Beta carotene seems to protect a cell from
getting to stage 1, but accelerate its movement
between later stages. There is lab evidence that
other anti-oxidants are similar.

geoff, what does WCRF say are the mechanics that "cause" colorectal cancer, in relation to red meat. Harvard says the nitroso compounds were not causing dna damaged cells to become malignant. Nor do studies suggest that meat causes the polyps that do become cancerous - although compounds derived from meat seems to help them grow once they are established.

So the main risks for colorectal cancer are age, obesity,smoking, sedentary lifestyle, alcohol, low fibre diet and high meat consumption. My question is is it meat alone, or the fact that many other "lifestyle" vices accompany those in a high meat consumption bracket. We have risks A,B,C,D,E,F and G all combined to one extent or another, it's not logical to conclude G is a cause. definately a risk factor, just like driving a car is a risk factor in car accidents.

http://jama.ama-assn.org/cgi/content/abstract/293/2/172?ck=nck

When we look at your basketball analogy we see that while you are shooting hoops 1 in approx 20 is a score (the life time chance of developing colorectal cancer which is about 1 in 20, or 5% of people ) .
Now getting 5% in isn't particularly good shooting for your average basketballer, but then we effectively widen the basket (study focuses on high meat consumption - couple of snags and bacon daily or 750g of red meat/week- quarter pounder/day.)

With a wider net now the scorer has 6.5% (5% increased by 28%- the higher risk of cancer from high meat consumption). Hardly impressive.

What really throws a spanner in the works is scoring without throwing the ball, as vegetarians would do in such a basketball analogy, having a 4% or so chance of developing colorectal cancer.
Maybe a reduced cancer rate for vegetarians is the number of them that eat fish and chicken which are known to reduce risk.

http://cat.inist.fr/?aModele=afficheN&cpsidt=15674139

rojo: In answer to your question, the most important in
a line of about 10 years worth of research is:

http://cancerres.aacrjournals.org/cgi/content/abstract/66/3/1859

This showed red meat didn't just damage DNA, but produced
the "right" kind of damage -- ie. the same as found in
real cancer patients. Were the cells malignant? Of course
not. But denying this evidence because none of the cells
was malignant is like a tobacco company saying, "See,
you had 20 people smoking for a week and not a single one
died! So it isn't causal".

With regard to your claim: "Maybe a reduced cancer rate for
vegetarians is the number of them that eat fish and chicken
which are known to reduce risk." Fish and chicken aren't
"known" to do this at all, even the reference at the link
you cited (yes, I have the full study) didn't say this!

Here is the WCRF assessment regarding fish (you can check
the original which has references to all the studies
involved, p.125):

"Nineteen cohort studies and 55 case-control studies
investigated fish and colorectal cancer. Nine cohort
studies showed decreased risk for the highest intake
group when compared to the lowest, which was statistically
significant in two. Eight studies showed non-significant
increased risk. One study showed no effect on risk and one
study reported that there was no statistically significant
association. Meta-analysis was possible on seven cohort
studies, giving a summary effect estimate of 0.96 (95%
CI 0.92-1.00) per serving/week, with low heterogeneity."

Hardly much evidence for a "known" protective agent!

This shouldn't be surprising, Japanese men have the
highest rate of bowel cancer on the planet and eat plenty
of fish (Japan is 2% of global population and eats 15%
of the fish).

You can't make judgements based on single studies. You can
prove anything with single studies. The WCRF report does
it right --- by assembling all the studies, throwing out
the rubbish and doing the numbers on what is left.

geoff, your study link studies "high (420 g) red meat, vegetarian, and high red meat, high-fiber diets"

Where is the normal red meat consumption? If the high meat-fibre diet has "intermediate" levels, then the normal meat, normal fibre diet can't be that different from vegetarian.

If I can't conclude(and I can't) from a small study that because the cells aren't malignant that cancer is thus not formed in this way, then in my way of thinking one can't conclude that cancer is formed in this way. It would be why "risk" is used instead of "cause". I accept that risk is higher for high meat consumption, but that doesn't say that meat is the cause.

Studies have questioned the risk significance once results were corrected for body mass index, smoking etc. Those with high meat diets presumably are predisposed to obesity through simple calorific intake, less likely to be health conscious with less exercise, less fibre etc etc.
The comparisons invariably look to vegetarians as controls. While some are veg for compassionate reasons others are for their "health", and are not as likely to be obese, smokers or sedentary - and fibre should be no problem. We know that vegetarians aren't immune from colorectal cancer, so meat is not a prerequisite, and the statsitical difference in risk is narrowed greatly by these variables. To the extent that red meat does not cause cancer, but can indeed be a risk factor.

I may have presumptive on the poultry it, unlike fish, may not decrease risk. And I should absolutely not have said "known", sorry genuine error.
http://www.medicalnewstoday.com/articles/26188.php

http://cat.inist.fr/?aModele=afficheN&cpsidt=14842549

http://sciencelinks.jp/j-east/article/200624/000020062406A0986824.php

can't explain the japanese men's risk profile, but just think how bad it could be if they didn't eat so much fish.