Putting this in IMHO because though there is factual info out there, a lot of it is confusing and contradictory. I’d like to get your thoughts and opinions on what types of meat and preparation may be better or worse, since anything done to meat other than eating it completely raw and unprepared is essentially processing it.
So bacon and other processed meat is now classified as a class 1 carcinogen, same as tobacco. Bacon I understand because it is so processed, but is it mostly the nitrates/nitrites used to preserve it, is it the smoking and cooking process, or a combo thereof?
And red meat apparently has an iron-based chemical called heme that breaks down during the digestive process into a carcinogenic substance. So even steak tartare, apart from risk of e. coli, is bad for you. But then cooking creates more carcinogens. So that nice tasty sear on a good steak is a killer, right? What about smoking a brisket for 13 hours- how much worse might that be than a quickly seared rare steak (if at all)? How about beef jerky, smoked at low temperatures, or smoked salmon?
NOT planning on turning vegetarian, I just want to be an informed carnivore
it is a scare story that relies on the public’s misunderstanding or relative vs absolute risk.
Is the risk real? probably.
Is it something you need to worry about if you aren’t hoovering down bacon and ham every meal? probably not. This is as good a breakdown as anyand the upshot that, surprise, surprise a diet that doesn’t rely too heavily on red or processed meats is better for you overall but the reverse is not a death sentence.
First the actual question of the op - what is the mechanism? Only speculative answers right now. The solid evidence of increased risk are for “processed meats” defined as meats that have been cured, salted, smoked, or otherwise preserved in some way. The current media flurry regards colon (bowel in the media of late) cancers primarily but the association is also strong for strokes, heart disease, T2DM and more.
Nitrites (and by extension nitrates which the body turns into nitrites) have been a leading contender for the cancer connection. And hemoglobin turns into N-nitroso compounds too so it is double whammy. The theory goes that they cause damage to the cells of the intestinal lining resulting in more turn-over and repair and more chances for various mistakes to then happen. It may also have to do with cooking metho. Processed meats (bacon, sausages, etc.) tend to be cooked at high temperatures and animal protein cooked at high temperature create cancer causing heterocyclic amines and polycyclic aromatic hydrocarbons. That nice char is full of 'em and processed meats even more so. But the process of smoking meats produces many of them too. And there is even speculation that variation of risk exists based on what particular bacteria you have as part of your microbiota. Maybe the preservatives impact the microbiota thus raising the risk? Again, mostly speculative as far as mechanisms go.
The data for the colon cancer increase is pretty dang good. The absolute increase in risk of colon cancer as noted above is not huge … as per Novelty’s cite, something on the order of 10/1000. That’s a 1% increase in the risk of colon cancer. Real and significant but not ginormous. Hence the “it’s a scare story” theme out there, a theme heavily promoted by the Beef Industry.
However.
Don’t forget that colon cancer increase while well established is only one of multiple health risks. Overall, all cause mortality, inclusive not only of cancers but of heart disease, strokes, complications of T2DM, and others? Moresignificant.
To summarize for those who do not want to click - a 10% increase of all cause mortality in the first and in the second the pooled relative risk with an increase of one serving per day was 15% higher.
Controlling for known confounders of course.
So limited consumption seems a reasonable response to me.
Is it the smoking or the nitrates that are carcinogenic? People have been eating smoked and salted meats for millenia; it was the only way to preserve meat. Is there a risk? sure, but probably quite low.
So longer cooking at lower temperatures is better, but not so much smoking at low temperatures, eh? Oh well, not going to stop me from smoking pork shoulders and beef briskets now and then. Or perfectly searing a steak every once in a while, for that matter. I understand that the relative risk isn’t that awfully high.
I may cut down on bacon, mainly because I don’t like the nitrate load in addition to any bad stuff from the cooking process.
A more simplistic, general answer is two things:
[ol]
[li]Meat used to be an expensive delicacy. In the past century and a half it has become a staple. IOW everyone in the developed world eats a lot more of it than ever before.[/li][li]Cancer rates increased dramatically during roughly the same period because after the medical revolution of the late 1800s lifespans nearly doubled. IOW people were now living long enough to develop cancer in their old age whereas before most would have died in their 40s or 50s.[/li][/ol]
Two major things that ‘side-stepped’ natural selection/evolution if you will, both in a very brief period.
