A Red Meat Issue Flames Up

“I am outraged and bewildered,” says Christopher Gardner. The line forms back there, Professor Gardner. Seven – yes, seven – papers in the Annals of Internal Medicine today are whipping up a flaming hot controversy about nutrition guidance broadly and red meat specifically. The bottom line from all these papers? Maybe we need to admit that the evidence for harm to health from red meat is not so hard and fast as some people like to think. Using GRADE criteria, the certainty about the effects of red meat on health is low. Thus, recommendations to eat less red meat for better health are weak.

In other words, there are indeed different and valid ways to look at the issue of red meat in the diet.

Is Nutrition Advice Special?

Harvard’s Frank Hu doesn’t like applying GRADE standards to nutrition advice. “It’s really problematic and inappropriate to use GRADE to evaluate nutrition studies,” he says. One big problem he has with the GRADE system is that it takes randomized, controlled studies to be the gold standard of evidence. Observational data provides weaker evidence. Such thinking is OK for evaluating drugs. But he wrote in 2015 that the standard should be different for nutritional epidemiology:

Some researchers consider RCTs as the be-all and end-all of causal inference. This sentiment may be appropriate in the pharmaceutical industry, but the drug trial paradigm cannot be readily translated for use in the nutritional sciences.

However, it’s worth saying that standards for scientific rigor were not invented by the pharmaceutical industry. The lead on one of these five papers, Bradley Johnston, explains:

Regarding the reaction among some in the nutrition research community … we are sympathetic to the discomfort of acknowledging the low-quality evidence in one’s field. It seems to us, however, that pretending that the rules of evidence differ across fields because the feasibility of definitive studies is not possible in one’s particular field is a poor solution to the problem. We believe it is important to apply common standards for assessing the certainty of evidence across health-care fields.

So What Are We to Think About Red Meat?

The evidence to say that we’re eating more red meat than we should for our own health is weak. However, we do have other reasons to believe that eating less red meat would be a good thing. Red meat is pretty hard on this planet we share. A little red meat probably won’t kill you. But too much of it might indirectly contribute to killing lots of people through climate change.

Regardless of the those facts, opinions and feelings will drive behavior. As one of these five papers point out, some people are really attached to the red meat in their diets. Others have strong passions for avoiding it. No surprises there.

The Need for Objectivity

It’s not easy to be objective about nutrition, but it’s worth a try. We’ve had enough of outrage. Dennis Bier explained this to the New York Times: “The rules of scientific proof are the same for physics as for nutrition.” Nutrition scientists who beg to differ say that these publications will undermine public confidence in their field. Walter Willett says “people will throw up their hands and say nutritional science doesn’t know what it’s talking about.”

Perhaps, though, Willett and others should consider this. Overstating your case is a sure way to undercut your credibility.

Click here, here, here, here, here, here, and here for these five papers. For further reporting, click here, here, here, and here.

Flaming Grill, photograph © Ginny / flickr

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October 1, 2019