[lizknope]

The cancer arm of the World Health Organization has some serious concerns about some of Americans’ favorite foods. The International Agency for Research on Cancer classifies processed meat as a carcinogen, something that causes cancer. And it classifies red meat as a probable carcinogen, something that probably causes cancer.

https://www.cancer.org/latest-news/hot-dogs-hamburgers-bacon...

[amval]

The cancer arm of the World Health Organization did a disservice to World Health by using such a poor study as an excuse to link cancer and meat consumption, in my opinion. To the point it makes me question if the WHO motives are honest or driven by other reasons (opposition to animal consumption out of ethical reasons or ecological reasons, which are absolutely legit but not health-related).

Some of the reasons why I say this: - It puts consumption of red meat and curated meats under the same category as smoking. According to that study, it increases relative risk of colorrectal cancer by 18%. That puts the average 50yo man from 1.8% to 2.12%[1]. A bit different from the 2.500% increase of lung cancer risk in smokers.

- These studies always have a self-selection bias. In Western countries, people that eat read meat also have worse habits and don't follow other health recommendations. This is a known effect [3], and other studies won't find higher risks associated to meat unless there are other factors (obesity, alcohol consumption) [4]

- Diet was self-reported, which makes results very unreliable.

- Colorrectal cancer and meat consumption are not linked in other countries. It's not the cause in Europe [5] and certainly not in Asia, where the opposite correlation is found [6]. There must be other factors at play.

- "Of 22 members who voted on its conclusions, seven either disagreed or chose to abstain."[7] And yet, the WHO made recommendations based on a single, not particularly conclusive study. Hum...

- Under red meat, it puts things like a sausage or hamburger and a grass-fed filet mignon steak. A strange thing to do, as if processing and quality were not factors to account for.

I could probably continue, but hopefully I made my point.

[1] https://www.ncbi.nlm.nih.gov/pubmed/16338133

[2] https://www.mayoclinic.org/diseases-conditions/cancer/in-dep...

[3] https://link.springer.com/article/10.1007/s11606-010-1609-1

[4] https://www.ncbi.nlm.nih.gov/pubmed/27479196

[5] https://www.ncbi.nlm.nih.gov/pubmed/26143683

[6] http://ajcn.nutrition.org/content/early/2013/07/31/ajcn.113....

[7] https://www.nytimes.com/2015/10/27/health/report-links-some-...

[scythe]

The link between meat consumption and colorectal cancer has been shown to be almost entirely mediated by two primary factors: nitrosamines and transition metals.

Nitrosamines are not naturally present in meat. They are produced when peptides (dietary protein) are heated a lot in the presence of oxygen. Nitrosamines are generally not produced when the protein is intimately mixed with large amounts of carbohydrates, because these act as antioxidants. So the line is "vegetable proteins do not generate nitrosamines", but if you were to extract those proteins into a meat-like product, common sense says that frying this like chicken will generate nitrosamines. The nitrosamines are just generated when organic nitrogen is oxidized to nitrogen dioxide, which reacts with peptides to generate nitrosamines. (Many vegetarian meat substitutes contain a lot more carbohydrate than real meat does. But there is an easy way to mix carbohydrates with your meat; that is left as an exercise to the reader.) (Also, the amino acids lysine and arginine generate more nitrosamines than other amino acids. These tend to be poorly represented in most plant proteins. They are also essential amino acids, and lysine in particular has been the object of serious investigation in the search for "complete" plant proteins.)

Transition metals are naturally present in meat. The most important carcinogenic transition metals are iron and copper. Both iron and copper are carcinogenic. Both iron and copper are necessary nutrients. In fact, iron and copper are two of the most important nutrients available in meat which require some planning to incorporate into a vegetarian diet!

In a very real sense, the same nutrients that would motivate you to eat meat are also the ones which cause it to be correlated with cancer. Red meat is a particularly dense source of iron, so of course it has the strongest correlation with colon cancer. (High iron titers in many vegetables report insoluble iron complexes which are neither nutritive nor carcinogenic. Iron in meat is highly soluble, nutritive and carcinogenic.)

This is not surprising when you consider that cancer is made of the same cells that we are and have (mostly) the same biochemistry that we do. When vegetarians talk about meat causing cancer, they always try to make it sound like God is punishing us for eating animals. Nothing could be further from the case.

But most importantly: the odds ratios are small. So I had a chicken sandwich for lunch.