Do scientists hate hot dogs? Do they want to ban bacon? A recent study sponsored by the World Health Organization finds a statistical link between the consumption of red meat and processed meat with cancer, but the data are open to interpretation.
By now you have probably seen the fear-baiting headlines about the World Health Organization study that allegedly found that eating red meat and processed meat causes cancer. Reporters all over the planet have been telling us that eating meat is more deadly than smoking cigarettes. Millions of people have serious questions about the safety eating meat. Even paleo dieters are concerned that their bacon-friendly, meat-based diets could have unexpected long-term consequences. Before we get too far into the discussion of the study, however, it's important to understand some basic definitions, at least as the World Health Organization used them.
What Did the World Health Organization Study of Red Meat and Processed Meat and Cancer Risk Really Say?
If you live in the United States, you may have heard the advertising slogan, "Pork, the other white meat." In terms of health, however, pork is red meat, as are beef, veal, pork, lamb, mutton, horse, and goat meat. Any muscle meat taken from a mammal is "red" meat, because they all contain heme- iron. This is the kind of iron that is also found in blood. It occurs even in hallal and kosher meat. This kind of iron is more easily absorbed by the body. Because iron "rusts," it generates free radicals that have major health effects.
Processed meat is red meat that has been treated by curing or smoking. Processing red meat makes it tastier and more easily digestible, as billions of bacon lovers can attest. The downside of processing is that it causes the formation of carcinogenic chemicals, including N-nitroso-compounds (NOC) and polycyclic aromatic hydrocarbons (PAH). These chemicals are concentrated when processed meat is pan-fried.
In countries around the world, from 2 percent to 100 percent of the population regularly eats red meat. In most of the world, red meat consumption averages about 50 to 100 grams (1 to 3 ounces) per person per day. Americans on average eat about 200 grams of red meat per day, and Argentinians more than that. About 65 percent of the world's population eat some processed meat every day, often as a breakfast food.
The World Health Organization selected 800 studies of the relationship between meat-eating and cancer, but the data you see in the news reports was based just on studies of the relationship of eating meat with one particular form of the disease, colorectal cancer. Moreover, the review panel selected only the "best" studies. Even in these groups of 29 studies of the relationship of red meat consumption and colorectal cancer and 27 studies about the relationship of processed meat consumption and colorectal cancer, half of the results found no association. (Of course, choosing different studies gives different final results.) After the review panel chose the studies, they merged the data sets to conclude:
- Eating 100 grams of red meat a day increases the lifetime risk of colorectal cancer by 17 percent. (Actually, there is a "confidence interval" in the data analysis. The increased risk could be as low as 1 percent or as high as 31 percent.)
- Eating 50 grams of red meat a day increases the lifetime risk of colorectal cancer by 18 percent. (Again, there is a confidence interval in the data analysis. They increased risk could be as low as 10 percent or as high as 28 percent.)
Putting the Results of the Cancer Risk Study in Perspective
A 17 percent risk of cancer is nothing to ignore. However, this meta-analysis did not find that eating red meat raises the risk of colorectal cancer to 17 percent and eating processed meat raises the risk of colorectal cancer to 18 percent. The study found that, in a very large population, eating red or processed meats raises risk of colorectal cancer by 17 or 18 percent, respectively.
If you don't have a family member who has had colon or rectal cancer, your lifetime risk of developing either disease is 1.8 percent. Increasing that lifetime risk by 18 percent gives you a lifetime risk of the disease of 2.1 percent. It adds 0.3% additional risk of the disease, not 17 or 18 percent. If colorectal cancer runs in your family, your risk is higher, but not very much higher. Two cases in the family raises individual risk to 7 percent. Eating bacon, hot dogs, and barbecue raises that risk to 8 percent.