Does Eating Red & Processed Meat Really Affect Your Cancer Risk?
On April 17, 2019, meat eaters worldwide were warned again about the risks associated with eating red and processed meat. The Guardian exclaimed that “even moderate intake of red meat raises cancer risk.” CNN shouted that “eating just one slice of bacon a day [is] linked to a higher risk of colorectal cancer.” And The Telegraph warned that “eating red meat just once a day increases bowel cancer risk by a fifth.” Everyone was so quick to get on board with this story, so eager to send shock waves through the mass media, that no one took the time to point out just how unsurprising and inconclusive this story really is.
If you’re like me and you eat a “dangerously” moderate amount of meat throughout the week, you’re probably wondering how badly the odds are stacked up against you. As a scientist, I usually take whatever I read from a news outlet with a pinch of salt. I try to put sensationalized stories in perspective, not giving them too much thought until I can access the original source. This story, however, really caught my eye because I wanted to know the true extent to which I was rolling the dice with my life.
Statistics are powerful because they can be incredibly deceptive. And when reputable news outlets are throwing numbers in your face, who are you to challenge them? You can’t argue with scientific data.
The original study, published in the International Journal of Epidemiology, found that “people who were consuming red and processed meat four or more times per week, had a 20% increased risk of colorectal cancer compared with those who were consuming red and processed meat less than twice a week.”
On the surface, it may appear as if eating red and processed meat is one of the worst things you can possibly do for your health. However, in studies like these, 20% is a relative statistic, not an absolute value.
Here’s another way to look at the exact same numbers from the study. Of all the participants who ate red and processed meat less than two times a week, 0.40% developed colorectal cancer. Of all the participants who ate red and processed meat more than four times a week, 0.63% developed colorectal cancer. So, between the two population groups, there was a 0.23% difference in the probability of developing colorectal cancer. And, importantly, less than 1% of the “high risk” group developed the disease.
Although the consumption of red and processed meat does statistically increase your risk of developing colorectal cancer, the connection between cause and effect is not as clear as the media would have you believe.
For the sake of comparison, within the same study, colorectal cancer was observed in 0.48% of participants who consumed less than 1 gram of alcohol per day and in 0.68% of participants who consumed more than 16 grams of alcohol per day (two UK standard units of alcohol or less than a pint of regular strength beer). In other words, statistically speaking, drinking a beer every day has a comparable influence on the risk of colorectal cancer to eating red and processed meat four times a week.
To really put these statistics in perspective, let’s compare the effects of eating meat to those of smoking. In Western countries, the risk of developing lung cancer is reported to be between 9.4 and 23.2 times higher in smokers than in non-smokers. So while consuming red and processed meat four times a week may increase your risk of colorectal cancer by about 20%, smoking may increase your risk of lung cancer by somewhere between 840% and 2220%. In this light, the risks of consuming red and processed meat pale in comparison to those of smoking.
Perhaps not surprisingly, there was also some critically relevant information that the media failed to explain. In the original study, the researchers highlighted that “compared with those in the lowest category, participants in the highest category of reported total red-meat intake were slightly older, more likely to be smokers, had a higher BMI and body-fat percentage, had a higher alcohol intake and had lower intakes of fruit, vegetables and fibre.” These lifestyle factors were accounted for statistically in order to determine the level of risk associated with the consumption of red and processed meat.
All things considered, eating red and processed meat is probably not the worst thing you can do to your body. However, this does not mean that it comes without risk, nor does it mean that you should feel free to eat them in excess.
Just how much do we really know about the link between meat and cancer?
A review published in Experimental Biology and Medicine notes that many studies have demonstrated a role for “heme iron” and “heterocyclic amines” in the development of colorectal cancer. While heme iron is found naturally in red meat, heterocyclic amines are produced when it is cooked at a high temperature. Current studies, however, have largely been performed on cells and in animals using “levels of meat or meat components well in excess of those found in human diets” and without the “biologically active protective compounds found in whole foods.” As such, the researchers suggest that it is difficult “to confirm a mechanistic link between the intake of red meat as part of a healthy dietary pattern and colorectal cancer risk.”
That being said, it’s no surprise to me that the highest category of red and processed meat eaters in the latest human study, much like the highest category of drinkers, exhibited the highest rates of colorectal cancer. These population groups, of course, contain all the participants who consume alcohol and meat in excessive quantities — well beyond what is generally recommended as part of a balanced diet.
While nothing is juicier than a story about the one thing you can do to reduce your cancer risk, one day people are going to stop listening to exaggerated media reports. The statistics will no longer mean anything to readers, and health science articles will turn into internet fluff.
The reality is that we don’t have a conclusive answer regarding just how dangerous it is to eat red and processed meat. To err on the side of caution, it’s probably best to not consume it in excess. What is clear from all of this, however, is that the media preys on our fear of cancer. It intentionally overstates findings without putting them in context for readers, and, in doing so, actually makes it more difficult to understand scientific research.