It’s what every examination of the science of diet and health requires. For too long, authorities have demonized specific foods in an attempt to explain poor health outcomes, or anointed the latest “superfood” a panacea against disease.
That’s more or less the gist of a new article in the New York Times, “Red Meat is Not The Enemy.” The author suggests that experts historically “cherry-pick” data from individual studies to single out one nutrient or food in an attempt to determine its role in human health.
The Totality of Evidence
We agree that this can be a problem, and a misleading one. And that’s precisely why, at the American Institute for Cancer Research, when we perform our ongoing analyses of the global evidence on the connections between cancer risk and lifestyle (read: diet, weight, physical activity), we do so using systematic literature reviews and meta-analyses. (We call it the Continuous Update Project, or CUP.)
Every systematic literature review in the CUP is conducted using a pre-established protocol — meaning that before when we go looking for studies to include in our analyses, we establish a strict set of criteria. If a study meets that criteria, it’s included; if it doesn’t, it’s left out.
This rigorous, comprehensive and transparent process is precisely the opposite of cherry picking. It allows us to consider a huge volume of new data alongside the findings of previous studies, and collectively weigh the totality of evidence.
And when it comes specifically to red meat consumption and colorectal cancer risk, that accumulated evidence is objectively clear and convincing: diets high in red meat (more than 18 ounces (cooked) per week) are a cause of colorectal cancer. And even smaller amounts of processed meat, eaten regularly, increase colorectal cancer risk as well.
(You can read the full World Cancer Research Fund International Colorectal Cancer CUP report, as well as the full systematic literature review and the protocol behind it, here.
What About RCTs?
It’s true that few randomized controlled trials (RCTs) are part of the CUP; this is for a very simple reason alluded to by the NYT writer: RCTs are ideally suited to studying the effects of individual agents (a drug, a dietary supplement) in subjects over a short time period. With something as complex and ever-changing as the human diet, and a disease like cancer that can decades to form, they cannot provide a clear picture.
That clear picture only emerges by looking at all of the relevant data from across the globe, gathered by different scientists using different study designs. When we see consistency across these many different scientific investigations, we can feel confident that a given link exists.
And one such link is the link between red meat and cancer.
We agree with the writer that when it comes to red meat, and in fact to many other specific foods, it’s easy to lose focus on the bigger picture. Again and again we see that it’s your overall lifestyle — your usual pattern of diet and physical activity — that counts.
One of AICR’s 10 Recommendations for Cancer Prevention is to limit red meat and avoid processed meat. But it’s only a part of the cancer-protective lifestyle those 10 Recommendations outline. Our advice on red and processed meat isn’t an attempt to demonize them, but to provide Americans with the best advice that emerges from the totality of the scientific evidence.
Which is to say: context.