The World Health Organization's International Agency for Research on Cancer declared that there is now enough evidence to say that processed meats - bacon, sausage, and other cured delicacies - cause cancer.
In the study where they published their results on Oct. 26, they also said red meat was probably carcinogenic.
Is this a surprise?
For a "long time," she says, "multiple studies have reported the relationship between meat intake and bowel cancer."
And it's true. Researchers have repeatedly reported a connection between processed meat and colorectal cancer (also called bowel cancer) and red meat and the same cancers. A connection to prostate cancer has long been suspected, too.
Bacon ≠ Smoking
But a common reaction so far has been to call bacon "the new smoking:"
Eating bacon is now as bad as smoking! Jesus!!!— Stephen Mulhern (@StephenMulhern) October 26, 2015
This is not the case.
It's true that the WHO's IARC put bacon onto the list of known human carcinogens, along with tobacco, asbestos, and plutonium. Once there is enough evidence that researchers can say, yes, a substance causes cancer, it would be wrong for them not to put it on that list. Alcoholic beverages have been on that list since 2012.
But that doesn't mean that everything on that list is equally dangerous and equally likely to cause cancer. Things are included if we know they can cause cancer, but that doesn't mean they all automatically cause cancer. Exposure to the sun's ultraviolet rays can cause cancer, but doesn't always do so - it depends on dose and other factors.
Eating an additional 50 grams of processed meat a day increases your risk of colorectal cancer by 18%, according to the IARC's report. An increased risk of almost 20% sounds like a lot - and it's definitely something worth paying attention to. But your overall risk of getting these cancers in the first place is still low, so increasing a low number by 20% is less scary.
As Dr. Kurt Straif, Head of the IARC Monographs Programme, put it in a statement: "For an individual, the risk of developing colorectal cancer because of their consumption of processed meat remains small, but this risk increases with the amount of meat consumed."
Cancer Research UK compares what we know about the effects of eating meat to the effects of smoking in this helpful graphic:
Both smoking and eating red or processed meat can cause cancer (probably, in red meat's case), but smoking is responsible for a greater percentage of lung cancers than meat is responsible for colorectal cancers. High meat consumption is just one of many risk factors for colorectal cancer; others include having Crohn's disease, having a family history of cancer, and - surprise - smoking.
To look at the statistics another way, the researchers say that eating processed meats probably causes 34,000 people to die of cancer around the world every year. If red meat causes cancer (and isn't just associated with cancer deaths coincidentally), then it would likely be the cause of an additional 50,000 global cancer deaths every year. Those numbers are significant and they should make anyone who consumes a lot of processed or red meat pause.
But those numbers aren't as bad as others we could look at. Alcohol is responsible for 600,000 cancer deaths every year (including a number of colorectal cancers), and smoking kills one million people each year. Air pollution causes another 200,000 deaths.
So yes, bacon causes cancer, but no, it's not the same as smoking.
As Tom Chivers of BuzzFeed News UK puts it, over your lifetime, the UK's National Health Service calculates your risk of colorectal cancers at 5%. An additional 50g of processed meat a day raises that to 6%.
So can I eat some bacon now?
This isn't meant to absolve or not absolve the consumption of these meats for health reasons (there are other moral considerations for eating industrially produced meat too).
Many interpret these findings to be further confirmation of already-existing health advice: Don't eat too much processed or red meat. Eating these meats every day can quickly put anyone over the amount that's known to significantly increase cancer risk. And that's before considering the other potential health risks of eating large amounts of processed meat, which has also been associated with an increased risk for heart failure in men and women and a higher rate of earlier death from all causes.
Some, like Ahn, who is also a registered dietitian, would say to avoid these meats altogether. "I wouldn't advise eating processed meat," she says. "We have other excellent sources of protein," like chicken, fish, or tofu.
But not everyone goes so far in condemning these meats.
"These findings further support current public health recommendations to limit intake of meat," Dr Christopher Wild, Director of IARC, said in a statement. But he refrained from saying that meat should be avoided altogether, and noted that there are healthy compounds in meat too.
We don't know exactly what causes the increased cancer risk, though the researchers noted that the creation of processed meats often introduces chemical compounds that are carcinogenic. Cooking meat to a charred point also creates carcinogens, according to the report. Ahn is investigating whether gut bacteria make certain people more vulnerable to cancer if they consume red or processed meat.
For now, as always, Michael Pollan's seven-word piece of advice for healthy eating remains relevant: "Eat food. Not too much. Mostly plants."