A valid meat message, slightly overcooked
WHO did a poor job of explaining what risk-ranking system really means
For the first 18 years of my life, I was raised as a vegetarian. My father was convinced of the perils of red meat after my paternal grandmother died on the operating table from latestage colon cancer. While my father would no doubt be pleased by the news last week that a panel convened by the World Health Organization (WHO) declared processed meats a cause of colorectal cancer — and red meat a probable one — I’m not convinced.
By no means am I a staunch defender of red meat. It has a greater impact on the environment than any other food in our diet: An estimated 20 per cent of all greenhouse gases are attributable to raising animals for food. A vast majority of the meat we consume comes from factory farms, where animals are fattened with hormones and antibiotics and routinely subjected to inhumane conditions that breed disease. These are all compelling reasons to cut back on meat consumption — and part of the reason, even though I’m no longer a strict vegetarian, I rarely eat red meat.
But does bacon cause cancer, as the WHO seemed to assert last week? That’s not a risk I worry about.
The main problem with the public health messages put out by WHO is that the agency did a poor job of explaining what its risk-ranking system really means. By most accounts, it’s arcane and confuses even some scientists. That’s because it’s based only on the strength of the overall research, not on the actual danger of a specific product.
A result is that the agency has created a hodgepodge of probable and possible carcinogens that borders on the ridiculous: pickled vegetables, coffee, cellphones, frying, working as a barber (think hair dye) and now red meat. As for bacon? The agency listed it alongside cigarettes, alcohol, as- bestos, plutonium and salted fish. Of the more than 900 potential carcinogens WHO has evaluated since 1971, it has determined that only one — a nylon-manufacturing chemical found in drinking-water supplies — is “probably not” carcinogenic.
Even the most strident anti-meat crusader knows that eating bacon is not as risky as smoking or asbestos exposure. Smoking raises a person’s lifetime risk of developing lung cancer by a staggering 2,500 per cent. Meanwhile, two daily strips of bacon, based on the associations identified by the WHO, would translate to about a 6-per-cent lifetime risk for colon cancer, up from the 5-per-cent risk for people who don’t enjoy bacon or other processed meats.
But that’s not the message that came across.
We do know that eating a lot of processed meat or red meat is associated with higher cancer risk; the WHO report cited 800 studies documenting the association. But that’s a long way from cause and effect. It may simply be the so-called healthy user bias, the idea that people who eat lots of bacon are more likely to engage in risky behaviours (such as smoking or a sedentary lifestyle) that lead to cancer; and that non-meateaters exhibit other healthful virtues (such as exercise or eating vegetables) that protect them.
Untangling the effect of red meat from all these other risk factors is extremely difficult. And relying too heavily on relatively small associations to draw conclusions can lead health authorities down the wrong path.
It was a lesson learned after years of recommending that women take menopause hormones to protect their hearts, a finding based on observational studies that showed women who took hormones had fewer heart attacks. But when a large government study actually compared hormone use to a placebo, the result was the precise opposite of what the observational data had suggested. Women who took hormones had a higher risk of heart attack.
Other examples abound. Observational studies have suggested that a high intake of beta-carotene and vitamins B, C and E could protect against death from heart disease. Clinical trials showed they did not. Fibre and folic acid seemed to protect against colorectal cancer in observational studies; clinical trials indicated they did not.
John Ioannidis, the chairman of disease prevention at Stanford Uni- versity, published a paper in 2012 titled “Is Everything We Eat Associated With Cancer?” He and a co-author scoured the medical literature and found many foods — among them eggs, coffee, and even carrots and tomatoes — that had been linked to both an increased and a decreased risk of cancer in various studies.
Ioannidis said his normal inclination would be to dismiss the meat-and-cancer link “as one of these 500 foods that have studies all over the place.” But in this case the link, while relatively tiny, he said, is consistent across many studies.
“We could be wrong,” he added. “But my best interpretation is that there’s probably something there.”
His co-author, Jonathan Schoenfeld, an assistant professor of radiation oncology at Harvard Medical School, offered the analogy of driving a car in the rain, which makes you significantly more likely to get into a car accident.
“That doesn’t mean you shouldn’t drive when it’s raining,” he said. “It means it might not make sense to speed in the rain — or to be one of the highest consumers of processed meat.”
Perhaps the single most important measure you can take to protect yourself from colorectal cancer, experts say, is to get a screening between the ages of 50 and 75. But only 58 per cent of people in that age range do so.
“There’s nothing wrong with the concept of reducing your intake of red and processed meat,” said Amy Elmaleh, director of Colon Cancer Canada, an advocacy group. “But there’s a better conversation to have about screening, which is a huge opportunity to prevent colon cancer.”
Because of my family history, I plan to have a colorectal cancer screening sooner than people of average risk. I have an older brother who is almost 40. I haven’t asked him about his intake of bacon. But last week I sent him a text message reminding him to get screened.
“I’ll make sure I get checked out,” he responded. “Thank you.”