Red Meat and Cancer

I personally like looking at the "Paleo" take on diet, because it can give us a good idea on what kind of food works for humans. But one of the controversies about this kind of diet, is the role of "red meat". Most of the people on TV or in books talking about the "Paleo Diet" stress lots of good beef from free range ruminants. Yet the research has often stressed that "red meat" isn't good for people, and might be implicated in cancer and heart disease.

Recently, the idea that "saturated fat" is the problem has been somewhat discredited. But lately there has been another study that is interesting:

A Large Prospective Study of Meat Consumption and Colorectal Cancer Risk: An Investigation of Potential Mechanisms Underlying this Association

This study actually broke down the types of meat being consumed, and how much. Their conclusions are that yes, there is an association between colon cancer and red meat. They broke down the risks based on three mutagens: high heat cooking, nitrates/nitrates, and heme iron. White meat was not associated with increased risk of colon cancer. This is interesting, because white meat is often cooked at high heat also?

More than 2,700 diagnoses of colon cancer or rectal cancer were made among participants of this study during its 7-year duration. The conclusion was clear: diets highest in red meat and processed meat were associated with a 24% and 16% higher risk, respectively, for developing these types of cancer compared to diets lowest in these types of meat.  The people with diets lowest in red meat ate an average of 9g per 1,000 calories–or, about 0.6oz of red meat per day assuming a 2,000 calorie per day diet.  Conversely, the people with diets highest in red meat ate an average of 66.5g per 1,000 calories–or, about 4.7 oz red meat per day assuming a 2,000 calorie per day diet.  Furthermore, as red or processed meat intake increased from the lowest levels of intake to higher levels of intake, colorectal cancer risk increased as well.
The researchers found no link between white meat consumption and an elevated cancer risk, possibly due to a difference in total iron content. In looking at dietary impact, it is important to distinguish between the heme iron found in meat, and non-heme iron, which comes primarily from fortified cereals, fruit juice, vegetables, beans and grains. The non-heme iron has not been linked with cancer.

http://www.fyiliving.com/diet/why-red-meat-may-cause-colorectal-cancer/

Anyway, if the association with cancer is mainly due to the heme iron, this explains some of the Paleo paradox. First, our ancestors rarely, if ever, relied on large ruminant meat for most meals. Taking down a big strong, horned, non-domestic 1,000 lb animal, using spears, isn't something you do every day. They DID do it, amazingly enough, though possibly the Neanderthals did it better. Most existing non-technological cultures though, eat large ruminants occasionally, but gathered a large variety of fish, insects, small mammals, reptiles, and birds for protein on a daily basis. Oddly enough, it seems that eating fish and poultry isn't associated with raising iron levels like beef is, even though they do contain a fair bit of iron.

But even if our typical caveman did manage to eat Aurochs every night, said caveman also had parasites. Hookworm was (and is) everywhere people go barefoot and don't have indoor plumbing. Hookworm removes iron from the gut rather nicely. This might explain why red meat wasn't associated with cancer in the China study either: rural Chinese are probably more likely to have parasites.

This study doesn't go into the neu5gc issue, which is an important one I think. Also, I think the issue with "processed meat" might not be the nitrates, but with other preservatives in those foods, which increase iron absorption. If that were the case, then chicken-sausage wouldn't have the same problems as beef-sausage.

So what does this say for modern people trying to follow a Paleo diet? I think the emphasis on those nice manly steaks is a bit misplaced. The healthiest cultures seem to be the ones eating more fish and eggs, not ruminant meat. However, if the issue is mainly heme iron, then people who are eating a lot of this kind of meat maybe should get hookworm, or else be sure to eat iron-blocking foods with the meat.