As predicted last week, the World Health Organisation (WHO) has classified processed meat as "carcinogenic to humans".

The decision is based on the findings of 22 experts from 10 countries working with WHO's cancer tentacle the International Agency for Research on Cancer (IARC).

Having reviewed the "accumulated scientific literature", they concluded there was "sufficient evidence in humans that the consumption of processed meat causes colorectal cancer", as the press release (PDF) puts it.

Quite how great the danger is depends on how much processed meat you eat. While a person's "risk of developing colorectal cancer because of their consumption of processed meat remains small", the experts have calculated that "each 50 gram portion of processed meat eaten daily increases the risk of colorectal cancer by 18%".

This "Group 1" rating places processed meat with alcohol, asbestos, arsenic and cigarettes. IARC has also classified red meat as "probably carcinogenic to humans" (Group 2A). This is based on "limited evidence that the consumption of red meat causes cancer in humans and strong mechanistic evidence supporting a carcinogenic effect".

IARC director Dr Christopher Wild concluded: "These findings further support current public health recommendations to limit intake of meat. At the same time, red meat has nutritional value."

"Therefore," he continued, "these results are important in enabling governments and international regulatory agencies to conduct risk assessments, in order to balance the risks and benefits of eating red meat and processed meat and to provide the best possible dietary recommendations."

The meat industry is, unsurprisingly, most upset with the idea that its product could be detrimental to health. Dr Betsy Booren, of the North American Meat Institute, said recently: "If they determine that red and processed meat causes cancer – and I think they will – that moniker will stick. It could take decades and billions of dollars to change that."

In response to today's announcement, Dr Booren launched an all-out attack on the IARC. She said: "It was clear sitting in the IARC meeting that many of the panelists were aiming for a specific result despite old, weak, inconsistent, self-reported intake data. They tortured the data to ensure a specific outcome.

"Red and processed meat are among 940 agents reviewed by IARC and found to pose some level of theoretical 'hazard'. Only one substance, a chemical in yoga pants, has been declared by IARC not to cause cancer."

Having worked up a good head of steam, Booren mocked: "IARC says you can enjoy your yoga class, but don’t breathe air (Class I carcinogen), sit near a sun-filled window (Class I), apply aloe vera (Class 2B) if you get a sunburn, drink wine or coffee (Class I and Class 2B), or eat grilled food (Class 2A). And if you are a hairdresser or do shiftwork (both Class 2A), you should seek a new career." ®