It wasn’t that long ago that researchers were issuing dire warnings that eating bacon and other processed meats will kill you.
Now the headlines are telling us that chowing down on red meat – including bacon – is fine and dandy. Just keep doing what you’re doing and it won’t really affect your risk of cancer, heart disease or diabetes.
If there is something to conclude from this seeming about-face, it’s that we should take most nutritional research with a grain of salt. (Wait, is salt good or bad for us this week?)
The fact is nutritional research is an inexact science. It’s pretty well impossible to say how good or how bad any foodstuff, let alone a single nutritional component, is for our health.
Earlier this week, the Annals of Internal Medicine published a series of five research papers, including dietary recommendations crafted by a team led by Bradley Johnston, an epidemiologist at Dalhousie University in Halifax. In a series of meta-analyses – combining many published studies and interpreting them – they concluded that there was really no compelling evidence that reducing meat consumption would confer health benefits.
They noted that the average person in North America eats about 4.5 servings of meat weekly. According to the new analysis, if everyone reduced that to one serving a week, we would see between one and six fewer heart attacks per 1,000 population, but there would be no impact on cardiovascular mortality. Similarly, if everyone cut three servings of meat a week from their diet, there would be seven fewer cases of cancer but, again, there would be no reduction in cancer deaths.
The publication was greeted by howls of outrage from many nutritional researchers and groups such as the American Heart Association.
They argue that reduced meat consumption has a significant impact on disease rates on a broader population level, even though it does not make a huge difference on an individual level. In other words, there are no downsides to reducing your intake of meat.
Another criticism of the research is that it compared only different levels of meat consumption; it did not look at the benefits of vegetarianism or veganism. Nor did it consider what people eat when they don’t eat meat. If you replace your daily burger with fries and cookies, that is very different than replacing it with carrots and quinoa.
Further, the new studies did not consider the negative environmental effects or ethical aspects of meat consumption.
The reality is that the long-standing recommendations from heart, cancer and diabetes groups to eat less meat and the new recommendations to stay the course are based on more or less the same evidence. And that evidence is flawed and flimsy.
The authors of the new research argue that nutritional researchers overstate the risks of meat consumption on individuals’ health. The critics of the new research argue that understates the impact of meat consumption on the overall health of the population and the planet.
They’re probably both right.
In other words, it’s the interpretation of the evidence that is at issue. The point that people need to to keep in mind is that this fight isn’t about how much meat you should eat, it’s about how nutrition studies should be conducted and interpreted.
The purists – such as the authors of these studies – want only the highest-quality evidence, long-term randomized clinical trials that carefully monitor dietary patterns over time. But those are almost impossible to do. So most research is observational, asking people what they eat and looking for patterns in outcomes. But that data is imperfect at best.
It’s also a debate about how we should measure and communicate risk.
When someone says to you that reducing meat consumption could cut your risk of cancer by 1.8 per cent, or that eating more red meat raises your risk of a heart attack by 18 per cent (these are just random examples), what does that mean to you?
That depends on a lot of things, many of them immeasurable.
Ultimately, we probably shouldn’t be making any firm recommendations to individuals based on the nutritional data we have.
But people want guidance. So here’s the best nutritional advice you will ever get, courtesy of Michael Pollan: “Eat food. Not too much. Mostly plants.”
As for the rest, let the nutritional scientists madly argue about methods and pay them no mind.
Our Morning Update and Evening Update newsletters are written by Globe editors, giving you a concise summary of the day’s most important headlines. Sign up today.