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Science

No, it is true that meat causes cancer

The WHO's warning that processed meat is cancerous has caused quite a stir - and a counter-reaction. Critics, including a Nobel laureate, say the report is too general and that WHO's health experts are exaggerating.

Get used to it: the World Health Organization is right. Sausages, bacon and other processed meats do indeed cause cancer.

The International Agency for Research on Cancer (IARC), part of the UN's World Health Organization, has evaluated all published studies and data on the subject of meat and cancer, and it has come to the conclusion that processed meat is "carcinogenic" and "causes colorectal cancer."

The same is "probably" true for red meat in general.

On the one hand, this is nothing new, says Rudolf Kaaks, an epidemiologist at the German Cancer Research Center. "Epidemiologists have known for years that those who eat more red and processed meat have a higher risk of cancer," he told DW.

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And yet as the headlines went viral, they provoked a counter-reaction - even from a Nobel laureate.

Harald zur Hausen of the German Cancer Research Center, and a Nobel Prize winner in Medicine in 2008, criticized the results.

"The general statement that red meat and processed meats are the cause for an increased cancer risk require an appeal and more detailed analyses," zur Hausen wrote in a public commentary.

'Science has no emotion'

Zur Hausen himself does research on red meat and its carcinogenic effect. He found that people in Mongolia, Bolivia and Botswana consume high amounts of red meat but still have a low risk of getting cancer.

According to zur Hausen, it is not red meat itself but a specific form of red meat that causes cancer.

"It is becoming more and more evident that meat products of a certain cattle breed bear a higher risk," he wrote.

Zur Haussen claims that a virus inside the meat is the cause of the carcionogenic effect.

Kurt Straif of the IARC, though, tells DW that "zur Hausen's work published on the topic on meat consumption and cancer risk has been considered, but at this time there is no strongly supporting data [for his theory]."

Straif adds that, simply because people in Mongolia and other countries are an exemption to the rule, this is "not an argument against our findings."

The effect is well known in epidemiology, he says, and might be occurring for other reasons - for example, due to a genetic peculiarity in those populations.

'The ultimate answer'

The WHO's IARC regularly publishes evaluations on the cancer risk posed by a substance, a lifestyle choice or an industrial process. These evaluations are called monographs. The program has been running since 1972. Scientists from around the world come together to examine scientific literature to decide if the data support the presumption that something causes cancer.

"I have sat on many committees around the world, I have done cancer research for 35 years - if you want the ultimate answer to something, you go to the IARC monograph program," says Neil Pearce, a professor of epidemiology and biostatistics at the London School of Hygiene & Tropical Medicine.

Pearce tells DW that such criticisms come out every time IARC produces a monograph. "The same happened with smoking, with asbestos and many other things."

Elio Riboli, who directs the School of Public Health at the Imperial College London, adds that the IARC doesn't want to "damn" any food or other life-style choices, since "science has no emotion." If the IARC warns that something causes cancer, it is not to dramatize things, but because the scientific evidence is there.

"The drama," he says, "is that you declare something carcinogenic which is part of our normal life."

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A small risk

So, yes, sausage and bacon have been shown to cause colon cancer. The main question is: How dangerous are these products really?

"Every 50-gram portion of processed meat eaten daily increases the risk of colorectal cancer by 18 percent," the IARC writes in its press release (pdf).

Not everyone, though, might know what that means.

The IARC explains in an accompanying Q&A (pdf) that "about 34,000 cancer deaths per year worldwide are attributable to diets in processed meats."

Altogether not so much, compared to the million or so cancer deaths per year globally due to tobacco smoking. In other words: If you're a smoker, you might have more urgent things to worry about.

The IARC's Straif says admits that "the risk is relatively small," and public health expert Riboli even acknowledges his own personal attachment to processed meats.

"It becomes a personal choice whether you think you don't care about a 20 percent increase in risk of colorectal cancer, or if you do care," he says. "My grandfather was from a region of Parma, and he made prosciutto. I can't give it up completely."

In the end, it is all about a balanced diet. It might not be a good idea to eat these meat products every day. And that is all that the WHO intended to say.

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