Processed meats as bad as cigarettes: bad reporting on good science

Today, the WHO issued a report that says, in essence, processed meats and red meats are carcinogens. This has been reported in a variety of publications with bombastic headlines such as:

We all know that smoking cigarettes is really bad for you. So a headline such as this makes it seem like if you eat processed meats or red meats, you are as likely to die of colorectal cancer as a cigarette smoker is to die of lung cancer. But is that true?

Well, let’s look at the research. The WHO study referenced by these articles provides the following figures:

• Effect of eating red meat: 17% increased risk of colorectal cancer per 100g per day (average consumption is 50–100g per day)
• Effect of eating processed meat: 18% increased risk of colorectal cancer per 50g per day

That does sound pretty damning, and the figures are statistically significant. But what is the average incidence in the world’s population? The National Cancer Institute says that between 2005 and 2011, the incidence of colorectal cancer was 42.4 per 100,000 men and women.

If you take those figures together, eating an extra 100g of red meat per day and an extra 50g of processed meat per day will increase your risk of getting colorectal cancer from 0.042% to 0.059% (0.042 x 1.17 * 1.18), assuming these figures stack.

How does this compare to smoking cigarettes?

An article published in The Lancet in 2008 based on an NIH-AARP survey shows that lung cancer incidence is 20.3 per 100,000 in non-smoking men and 25.3 per 100,000 in non-smoking women. For people who smoke two packs a day, lung cancer incidence rises to 1,259.2 per 100,000 in men and 1,308.9 per 100,000 in women. This means that a smoking heavily increases your lung cancer incidence from 0.020%/0.025% (men/women) to 1.259%/1.309% (men/women).

This is a much more significant effect than what we see from red meats and processed meats. Put another way, eating more red meat or processed meat increases your risk of colorectal cancer by 17% and 18%, respectively. Heavy smoking increases your risk of lung cancer by more than 5,000% for women and more than 6,000% for men.

There are, of course, hundreds of other studies that would provide different figures, but if you take these scientific publications at face value, it’s clear that the discussion around the effect of red meat and processed meat is overblown. Are they carcinogens? Yes, according to the WHO. But they don’t even come close to comparing to cigarettes. As usual, journalists should be a bit more level-headed when presenting conclusions based on scientific research.

Note: I am not a scientist, and these figures were pulled together after 20 minutes of Googling. It is very possible that my figures are incorrect or that I didn’t pull information from the best source. If you have input on my research, I’m @zs on Twitter; feel free to contact me with suggestions.