When the International Agency for Research on Cancer (IARC) issued a comprehensive review of the research last month linking red and processed meats to increased colorectal cancer risk, the news received a lot of media coverage. Their conclusions were similar to AICR’s reports. and we heard from many people indignant about, and dismissive of, the findings.
“EVERYTHING causes cancer if you listen to the ‘experts’,” wrote one of the hundreds of commenters who weighed in on AICR’s Facebook page. This response was common.
The day after the IARC report was released, the authors of a study in the journal Obesity claimed their work confirmed that sugar, irrespective of its high-calorie nature, was itself a “toxic” substance. One week later, an article in the British newspaper The Telegraph reported on results from a paper published months before, which showed that heating some vegetable oils to very high temperatures produced compounds that may be linked to cancer risk.
There will be more stories reported in the press about foods and their links to poor health outcomes, such as cancer. And the more it happens, the more people find themselves confused and overwhelmed. “If EVERYTHING causes cancer,” they think, “why bother eating a healthy diet at all?”
The Factors That Do Increase Cancer Risk
Such frustration is understandable. But in a time when new studies on cancer links make news weekly, it’s easy to lose sight of the clear and consistent evidence: many common cancers have their roots in lifestyle factors.
The conclusion that diets can play a role in lowering or increasing cancer risk, such as eating too much processed and red meats, is clear because of the sheer weight of evidence behind it. The consistency with which these data point to a causative relationship lead us to conclude that certain foods and other factors play an important role in cancer risk.
That kind of consistency, observed across multiple independent, well-designed studies, simply does not exist for sugar, or vegetable oils, or other dietary factors that so often get featured in headlines. In most cases, these findings are plucked from single studies, not from reports that set out to collectively and systematically examine the totality of evidence.
What the Evidence Shows
Tobacco use and overexposure to ultraviolet rays are known to be causes of cancers. Aside from not smoking or using tobacco products, research shows that excess body fat is the single largest preventable cause of US cancers.
Eating a healthy diet – high in fruits, vegetables, whole grains and other plant foods and low in red meats – and regular physical activity also reduce cancer risk.
AICR estimates that approximately one-third of the most common cancers can be prevented by staying a healthy weight, eating healthy and being active.
It is possible that one day, enough studies will confirm the results seen in some of these studies highlighted in the press and this will inform our cancer prevention recommendations. But it’s also possible that studies will not be able to reproduce these results, or demonstrate with any degree of certainty that they play a role in human cancer.
When it comes to breaking news, a healthy skepticism will help distinguish responsible science reporting from the “shocking-breakthrough”/”everything-you-thought-you-knew-was-wrong” clickbait. These stories can engender a deep distrust of many scientific findings, even those that are recognized by the scientific community as strong and convincing. And that is unfortunate, because this distrust can turn into the frustration and apathy that’s causing many Americans to mistakenly conclude that everything causes cancer.