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.
Ten Points To Take Away From The Study Of Red Meat, Processed Meat, And Cancer
The World Health Organization data show that the relationship between eating red or processed meat and colorectal cancer is significant, but not very large. This is often the case with studies that involve tens of thousands or hundreds of thousands of people. The study does not find that paleo is poisonous or that ham harms.
Moreover, the data in these studies was not accumulated by scientific studies, but from food frequency questionnaires. Researchers asked random respondents to guess what they had eaten over the last twelve months. These kinds of studies are notoriously inaccurate (and studies of studies have found that they are.) People forget what they ate. They make up menus to sound better, and millions of people are enamored of bacon, whether or not they really eat it all time.
The studies didn't assess a difference between a stopping at Burger King for a triple whopper to eat in front of the TV and eating a small steak when you get in from the gym.
It's not wonder that the scientists had to cherry-pick the data (or refine their inclusion parameters) to get significant results, and even when they did, about half of the studies did not find a relationship between eating red or processed meat and colorectal cancer. Hundreds of other kinds of cancer were not even mentioned.
That doesn't mean that there are absolutely no reasons to believe there could be a relationship between meat consumption and cancer. Here are the three main links between meat and cancer.
- Curing and smoking meat create n-nitroso-compounds and polycyclic aromatic hydrocarbons, respectively. Both are known carcinogens.
- Nitrate-cured meats (such as bacon, ham, and sausage) contain chemicals that become nitrosamines in the colon itself. The heme- iron in meat accelerates this process. Even "kosher" and "hallal" bacon products (made with chevron or beef) form nitrosamines.
- High-temperature cooking of meat forms carcinogens. Sautéing, searing, grilling, and caramelization of red meat creates heterocyclic amines in the broiler and polycyclic aromatic hydrocarbons over open flame. The hotter and longer the cooking method, the more carcinogenic the resulting meat. Well-done meat is more carcinogenic than rare or medium-rare meat.
However, there are many things you can do to make the meat you eat safer.
- Marinating red meat (especially in cherry juice, but also in spices, garlic, onions, citrus, wine, honey, or vinegar) reduces the formation of carcinogens during cooking.
- Cooking in liquid (steaming, braising, slow-cooking) meats reduces the formation of cancer-causing compounds. Cooking in the marinade reduces the formation of carcinogens even more.
- Cooking in a pressure cooker reduces exposure to oxygen and accelerates the cooking process, reducing formation of carcinogens.
- Eating high-fiber foods reduces contact of carcinogens with the lining of the digestive tract.
- Eating resistant starches (sticky white rice, cold boiled potatoes, plantain, sweet potatoes) reduces contact of carcinogens with the digestive tract.
- The more red meat you eat, the more vegetables you should eat. Green vegetables provide both fiber and antioxidants that reduce the formation of cancer-inducing chemicals.
- Eat nuts and seeds, for the reason explained below.
- Maintain your probiotic health. Friendly, probiotic bacteria convert the linolenic acid in nuts and seeds into butyric acid, whic protects against colon cancer.
- Eat identifiable meat. If you can't tell what cut of meat it is by looking at it, it's probably over-processed.
- Cook gently. Slow-cooked meats, not overdone, preferably rare, are always the most gut-healthy meat choice.
Sources & Links
- Bouvard V, Loomis D, Guyton KZ, Grosse Y, Ghissassi FE, Benbrahim-Tallaa L, Guha N, Mattock H, Straif K
- International Agency for Research on Cancer Monograph Working Group. Carcinogenicity of consumption of red and processed meat Lancet Oncol. 2015 Oct 23. pii: S1470-2045(15)00444-1. doi: 10.1016/S1470-2045(15)00444-1. [Epub ahead of print] PMID: 26514947.
- Photo courtesy of honor photo bar: www.flickr.com/photos/honorphotobar/9589239266/
- Photo courtesy of cookbookman17: https://www.flickr.com/photos/cookbookman/6175755733/