That’s why I was surprised to read the conclusion from the latest in a long line of red meat studies: The evidence against red meat is actually quite weak and even nonexistent.
What did the study explore when it comes to red meat?
The funniest thing about this latest study is that they had to admit they couldn’t find any strong evidence of a link between unprocessed red meat intake and six health outcomes even though they clearly were hoping to. These are the health outcomes they looked at:
- Colorectal cancer
- Type 2 diabetes
- Ischemic heart disease
- Ischemic stroke
- Hemorrhagic stroke
- Breast cancer
They combined dozens of different cohorts into one massive cohort for each health outcome, drawing on studies from all over the world to extract the data. Other studies have obviously done the same thing, but this one was attempting to do something different: assess the “strength” of the evidence in favor of red meat causing heart disease, cancer, diabetes, and all the other stuff using a new tool called The Burden of Proof. The very first sentence of the abstract establishes that they consider red meat to be a “risk factor.” They’ve already bought into it. Now, they just want to figure out how strong the evidence is.
It turns out that the evidence is very poor. For colorectal cancer, type 2 diabetes, breast cancer, and ischemic heart disease, the evidence of an association with red meat intake is “weak.” For hemorrhagic stroke and ischemic stroke, the evidence is non-existent.
And yet these are the ones everyone always focuses on. Search Pubmed yourself and you’ll see that there are thousands of studies looking for the links between red meat intake and colorectal cancer, diabetes, stroke, breast cancer, and heart disease.
Now, they’re still convinced that red meat is bad. They say that a red meat intake of zero grams per day is probably ideal for health, but there’s not enough evidence to justify actually recommending or prescribing that to people. “We all know” red meat is pretty unhealthy, but we can’t exactly make that an official recommendation… yet. The evidence just isn’t there.
That’s the subtext of the paper.
Lots of pro-meat people were sharing this on social media, very happy that they weren’t able to find any strong evidence against red meat intake. I don’t think it goes far enough. I think it’s still too hard on red meat. “Weak evidence” isn’t accurate. It’s too kind. The evidence is terrible and I suspect, if you considered all the relevant variables, it actually points in the opposite direction: toward benefits.
But you’ll never get that with a typical meta-study.
Drawbacks to meta-studies
You lose granularity when you combine data from hundreds of cohorts from across time and space into one big cohort and try to make connections between red meat intake and various diseases. In nutrition and disease and biology, granularity is everything. The little details matter. It’s not just “red meat intake.” It’s everything else. It’s calcium intake. It’s what kinds of oils are used. It’s carb intake. It’s overall fat intake. It’s bodyweight. It’s whether you’re lifting weights or not. Whether you smoke or drink. It’s ethnicity, culture, and cuisine. It’s the entire food way, not just one single component of a broad diet.
No one in epidemiology is considering all these factors. I don’t quite blame them, as doing so would make an epidemiological paper incredibly unwieldy. Probably wouldn’t work—which is exactly why these papers don’t tell us much at all.
So what’s my issue with this particular paper?
I won’t go through each and every section of the paper. I’ll look at their section on colorectal cancer. The way they characterize it, they “found weak evidence of harmful associations between unprocessed red meat consumption and risk of colorectal cancer” after looking at data from 20 different studies on the subject. Results “varied.” The studies were “inconclusive” and “didn’t agree.” And that’s it?
No, you go deeper. You look at individual studies to understand why they don’t agree.
Why, for instance, did the study they cite in Finnish men find that high intakes of red meat combined with high intakes of dairy are protective against colon cancer? In other words, the people eating more red meat and dairy in this Finnish male cohort had the lowest rates of colorectal cancer. Isn’t that interesting to the authors of this new meta study? Doesn’t it pique their curiosity about the effect of dairy combined with red meat on colon cancer—at least enough to include dairy as one of the variables they controlled for when considering the broader data?
Of course not. The only additional variables they adjusted for were BMI, energy intake, and fruit and vegetable intake. The Finnish data is simply “more data” to be subsumed into the collective cohort.
You also look at studies they didn’t include, studies they couldn’t include—like randomized controlled trials—because they were outside of the study’s scope. Like this one, that finds when you add extra dairy to the diets of living, breathing humans, their colonic environment becomes less carcinogenic. That’s a direct effect. A causal one. And it doesn’t figure into the conclusions of the meta-study at all.
Some might say that’s just one example of something they missed. I say it’s not “just” anything. It’s a huge factor that undermines the and calls the rest of their conclusions into question.
Ignore these studies. They can be interesting for generating hypotheses, but they don’t provide any answers. It comes down to what it always comes down to: what do you personally get out of eating red meat?
Has eating more red meat improved your health, performance, cognitive function, body composition, culinary pleasure, and overall life satisfaction? Or has it worsened it? What else matters?
Thanks for reading, everyone. Take care.