Red meat and cancer

Amtmann

This was reported recently in the Irish Times:

The [American Institute for Cancer] has distilled the learning from thousands of studies on the subject of diet, weight, physical activity and cancer into the following recommendations: be physically active for at least 30 minutes a day; eat more of a variety of fruit and vegetables as well as whole grains and beans; avoid sugary drinks; limit the consumption of salty and processed foods and red meat; limit alcoholic drinks to two for men and one for women each day; be as lean as possible without becoming underweight; do not use supplements to protect against cancer; mothers should breastfeed exclusively for up to six months, and, after treatment, cancer survivors should follow the recommendations for cancer prevention.

That's me screwed on the red meat front. Can any of the regulars here write a little of what they know about the link between red meat and cancer? How conclusive is the research?

Sapsorrow

The link seems to exist in some observational studies (hypothesis forming studies that can't prove cause and effect), but I don't know that is does in any more conclusive types like intervention studies or whether those observational studies that did find an association had controlled for variables or distinguished between cooking methods and meat types or not. The largest observational study ever conducted (The China Study) didn't find a correlation between meat consumption and cancer when all relevant variables were accounted for in the statistical analysis.

People are often of the opinion that there is a link between nitrate consumption (used as a preservative in processed meats especially bacon) and cancer but then I've read some interesting stuff lately by Stephan Guyenett that fairly blows that theory out of the water: http://wholehealthsource.blogspot.com/2010/06/nitrate-protective-factor-in-leafy.html

There may also be a link between ferrous iron (which red meat is a great source of) lingering in the gut and the initiation of redox reactions that can cause oxidative damage to very delicate epithelial cells in the gut, so if you are chronically constipated and consuming masses of iron from supplements and/or red meat, you may be at increased risk as a result. This can easily be prevented by eating plenty of fibre, antioxidant rich fruit and veg and drinking lots of water.

In my opinion, the only really strong link between meat consumption and cancer risk comes from fried, charred/burnt and barbequed meats. When meat is cooked certain amino acids are converted to heterocyclic amines (carcinogens) at extremely high temperatures. This doesn't happen with boiled/stewed meats or meats that are protected with tin foil etc so I don't really consider it something to worry about unless someone is primarily eating fried meats.

EDIT: Meant to mention also, with those sort of public health warnings, you have to remember that they are making a very broad statement with the aim of making it as easy as possible for everyday folk with no knowledge of nutrition to understand. They also try not to give instructions that are too complicated or unrealistic for everyday people to adopt because you get a higher rate of compliance (and so, theoretically reduction in disease risk) that way.

It's much logical for them to make a short, concise statement like 'minimise all red meat consumption to reduce cancer risk' because it's much easier for people to take direction from such a simple statement. To go into detail about different cooking methods, fibre intake etc. etc. would only cause confusion for most people.

Nutritional guidelines are for this reason usually fairly inaccurate and far from ideal goals to aim for, but if followed will offer some improvement for the vast majority of people who eat a SAD diet and are the target of these sorts of campaigns.

Amtmann

Sapsorrow wrote: »

It's much logical for them to make a short, concise statement like 'minimise all red meat consumption to reduce cancer risk' because it's much easier for people to take direction from such a simple statement. To go into detail about different cooking methods, fibre intake etc. etc. would only cause confusion for most people.

I can see the rationale for these broad statements. But I think they should give people more credit. I'm a smart guy; but when I read that a spokesperson from a seemingly eminent organisation says that red meat should be minimised because it might cause cancer, I think "Jesus, that's scary". I find your explanation far more beneficial. I don't have a science background, but I understand everything you've written and find it far more helpful than blanket statements that raise anxiety in people about their grilled sirloin and roast beef.

Khannie

No mention of poultry or fish there. Does it reasonably follow that I can eat as much of those as I want?

The lean thing is interesting too. I remember watching a TV show about a guy years ago who was living on a severely calorie restricted diet (around 1500 calories per day) because he thought it would lengthen his life (there have been successful studies of that nature with rats iirc).

Sapsorrow

Heterocyclic amines will form in any muscle meat cooked over 400C (I think, it's a long time since I studied this stuff) so charred chicken etc would still not be an ideal thing to eat too regularly.

I don't think anyone disagrees that fish is anything other than very good for you, although it might be wise to avoid fish higher up on the the food chain that can be more concentrated sources of heavy metals. It's probably a good idea to go for sardines, mackerel etc over tuna, but that has nothing to do with colon cancer particularly.