Quantifying risk bacon will kill you

You have of course heard the sad news about bacon. As the World Health Organization’s International Agency for Research on Cancer put it last week:

Each 50 gram portion of processed meat eaten daily increases risk of colorectal cancer 18 percent.

How much is 50 grams of processed meat? In bacon terms it’s about two slices. Just to be clear, it isn’t that eating two pieces of bacon will increase your colorectal cancer risk by 18 percent. It’s that eating two pieces of bacon every day for the rest of your life will.

But here’s the important question that isn’t directly addressed: What’s the risk of colorectal cancer to begin with?

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To illustrate how much this can matter: In 1995, the U.K.’s Committee on Safety in Medicines issued a warning that third-generation oral contraceptive pills increased the risk of thrombosis by 100 percent. That meant the risk of getting thrombosis – potentially life-threatening blood clots in the legs or lungs – went from one in 7,000 for women taking second-generation birth-control pills to two in 7,000 for those taking the third-generation variety.

Not a huge risk, then. But a 100 percent risk increase sounds ominous. As psychologist Gerd Gigerenzer describes in his book, “Risk Savvy,” the warning scared many women away from the pill. One result was an estimated 13,000 additional abortions the following year in England and Wales. Another was, ironically, a lot of thrombosis cases – pregnancies and abortions are much more likely to bring on the condition.

Information about relative risk can be misleading, then, unless it’s presented in the context of absolute risk. So what’s the absolute risk of getting colorectal cancer?

Men 60 and younger face almost 5 percent chance of getting colorectal cancer in their lifetimes, and a greater than 2 percent chance of dying from it. For women it’s about 4.5 percent and 1.9 percent, according to the National Cancer Institute.

Let’s say you’re a man, you have about a 5 percent chance of eventually getting colorectal cancer, and you up your bacon consumption by two pieces a day. That increases your cancer risk to almost 6 percent – not a trivial jump.

I like bacon a lot, but I’d rather have a five in 100 chance of getting colorectal cancer than a six in 100 chance. •

Justin Fox is a Bloomberg View columnist.

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