Do bacon and red meat cause cancer? Evidence and answers.

Will Eating Bacon Really Give You Cancer? Answers to Your Burning Questions.

Will Eating Bacon Really Give You Cancer? Answers to Your Burning Questions.

Health and medicine explained.
Oct. 26 2015 4:40 PM

Does Bacon Cause Cancer?

You can’t always eat what you want.

Bacon.
Fear the sizzle.

Photo by Michael E. Allen/A Sharp Photo/Thinkstock

In 2012, two cheeky nutritionists decided to pick some common cookbook ingredients at random and see which ones had been linked to cancer. The results were revealing: Possible cancer-causers included flour, coffee, butter, sugar, salt, tomatoes, onions, lemon, celery, carrot, parsley, lobster, veal, cinnamon, and mustard. The paper’s title, “Is everything we eat associated with cancer?,” neatly conveyed its authors’ sigh of exasperation—one that is emphatically shared by the American public at large. We’re sick of being told how all the things we love will probably lead to chronic disease, cancer, and ultimately, death. So it was especially annoying to read this morning’s headlines: Our bacon is killing us.

After reviewing a slew of studies finding a connection between meat-eating and cancer, the World Health Organization has announced that processed meats cause cancer, and red meat probably does, too. In the most definitive assertion the organization has made on the connection between eating meat and cancer, bacon is now considered a carcinogen in the same category as cigarettes, asbestos, and alcohol. The organization reached this conclusion after 22 scientists from the International Agency for Research on Cancer assessed the best available scientific evidence, and the full report was published Monday in the journal the Lancet Oncology. But is eating a slice of bacon really akin to smoking a cancer stick? Let’s take a step back and approach some of the questions raised by these findings calmly and rationally.

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Are you f*@$ing kidding me?

Unfortunately, no. Studies have long shown that red meat was associated with cancer. A recent review of more than 22 studies in the Archives of Medical Science found that red meat intake was associated with colon and potentially rectal cancer, two forms of cancer that are likely a byproduct of our meat-rich Western diets. In 2012 a study published in JAMA Internal Medicine reviewed the cause of death in more than 121,000 people and found that eating both processed and unprocessed red meat increased the risk of death by cancer, spawning similarly alarmist headlines (e.g., “Death By Bacon? Study Finds Eating Meat Is Risky”). That same year, a study in the British Journal of Cancer reviewed more than 6,000 pancreatic cancer cases to find that eating large amounts of processed meat was a major factor. So, yes, eating lots of meat does cause cancer.

OK. But, like, the bad kind of cancer?

Yes, the bad kind. Specifically, eating red meat is associated with colorectal cancers—the second most lethal form of cancer in the United States, causing nearly 50,000 deaths a year. (The WHO report also found a weaker association for pancreatic and prostate cancer.) The report concluded that for every daily 50-gram portion of processed meat—that’s about one sausage link or two small strips of bacon—your risk of colorectal cancer increases by 18 percent. If that sounds absurdly high, consider that past studies have been in that range as well. According to the meta-analysis, eating more than 120 grams of red meat a day elevates the risk of colorectal cancer by about 29 percent. (An 8-ounce steak, for reference, weighs about 225 grams.) An Australian study recently found that 18 percent of colorectal cancers in Australia in 2010 were attributable to eating red or processed meat.

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How do the researchers know that red or processed meat was the culprit?

The truth is, it’s difficult to tell. Most studies compare cancer rates in those who eat red meat frequently with cancer rates in those who eat very little meat. But of course, eating red meat is associated with a host of other factors. For instance, a Western diet rich in red meat may be lacking in dietary fiber, fish, fruits and vegetables, and other crucial foods or nutrients that may reduce the risk of cancer. Moreover, eating more than 120 grams of meat a day—the number used in many studies—suggests you have an unusual diet and probably other not-so-healthy lifestyle habits as well. That might help explain why eating more than 120 grams of meat a day is linked not only to colorectal cancer but to lung cancer, pancreatic cancer, and breast cancer. Researchers try to account for other variables when they do their analyses, but dietary data are notoriously noisy.

How do red meat and processed meat cause cancer?

I was worried you were going to ask that. There are three frequently proposed factors. According to the meta-analysis, red meat can lead to a build-up of acidic bile in the colon, which can make cells more susceptible to mutation and ultimately malignant transformation. Fat from red meat may also increase the development of hormone-related cancers such as breast and prostate cancer. Processed meat comes with its own risks. Industrial processing methods may create potentially carcinogenic compounds, and “high-temperature cooking by pan-frying, grilling, or barbecuing generally produces the highest amounts of these chemicals,” the report states—which means that you might want to keep an eye not just on how processed the meat you buy is but on how you process it once it reaches your kitchen.

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How processed does the meat need to be? Is ham in the same category as bacon?

According to the WHO report, “Processed meat refers to meat that has been transformed through salting, curing, fermentation, smoking, or other processes to enhance flavor or improve preservation. Most processed meats contain pork or beef, but processed meats may also contain other red meats, poultry, offal, or meat by-products such as blood. Examples of processed meat include hot dogs (frankfurters), ham, sausages, corned beef, and biltong or beef jerky as well as canned meat and meat-based preparations and sauces.” The study did not address processed fish or chicken; however, if the risk is inherent in the cooking method, then some of the risks could be the same.

I can’t stop eating bacon. What can I do?

You might want to stop eating it so often. “The frequency of red meat consumption rather than total amount of consumed meat is associated with a higher risk of colorectal carcinogenesis,” reads the meta-analysis. The strongest cancer association stems from cases of eating red meat more than once daily—which is a lot. Additionally, physical exercise has been shown to help prevent colon and rectal cancer (though evidence is stronger for the colon than the rectum). Getting enough fiber is also “undoubtedly a protective factor,” according to the review, meaning you should eat more fruits and vegetables. The review also suggests that calcium intake might help prevent the build-up of bile. Finally, some studies have linked a vegetarian diet to lower rates of many kinds of cancers. At the very least, try eating veggie bacon—it’s actually really good!

Rachel E. Gross is the science web editor at Smithsonian.