Red meat and mortality – this one’s for you.

by Michelle

So, you all saw that headline about red meat being unequivocally Bad For You, right? The headline was super scary – “All red meat is bad for you, new study says” according to the Los Angeles Times.

Very scary, very definite-sounding.

I tried to avoid looking at the study all day, because I knew it would make me angry. I suspected shenanigans from the get-go. Why? Because pretty much nothing in science is ever that unequivocal. Science is, allegedly, the study of material reality – when it’s done well. And material reality is incredibly complex and nuanced, which makes for uncertainty. Bets must always be hedged when observing it.

So I knew that, at the very least, the mainstream media reporting of this study — which might have been a very good study — was oversimplified and sensationalized, as any juicy news story is.

Finally, late last night, I gave into temptation and clicked on the LA Times link, which led me to the abstract of the study. And before I even got into the full-text, by looking at the numbers and methodology reported in the abstract, I was…deeply embarrassed.

This study used a problematic methodology to determine how often people ate red meat – they used a food frequency questionnaire, something I was taught in school should never be used alone to assess a person’s actual food intake. It’s simply not precise enough – it is only a rough guesstimate, and it is vulnerable to faulty memory, to misunderstanding food amounts, and to embarrassment or shame.

Even if you gave a person a food frequency questionnaire every single day for the duration of the study, it would not be great data.

Sadly, this study didn’t even go to that much trouble. The analysis was based on food frequency questionnaires that were only updated once every four years.

I’m going to give you a second to let that sink in.

Once every four years.

Every four years, subjects in the study were given a piece of paper with a bunch of check boxes on it, next to a long list of foods, and asked to check off how often they ate each food over the course of the past four years. Totally accurate, I’m sure — accurate enough to pinpoint with reasonable certainty the type of food each person ate every single day for the 24 years of the study.

Oh wait a second, no. Not at all.

Then, based on this rigorous assessment of each subject’s diet, the researchers managed to find an association between people who reported eating a serving of red meat every single day…

I’ll give you another second.

A serving of red meat Every Single Day…

[Interlude: this is not to say that no one, anywhere eats red meat every single day for 24 years. Plenty of people around the world probably do. But I doubt they represent the larger population from which this study’s subjects were drawn — and even if they did, the results of the data from this study would give them no reason to worry.]

…was associated with a 20% higher risk of dying during the study.

That actually still sounds pretty scary, doesn’t it?

I mean, nobody wants to entertain a 20% higher risk of dropping dead at any moment. Death is the worst bad thing that could ever happen to you, and if avoiding a couple of hamburgers can stave it off, why the hell not?

Yes, it does sound scary — until you point out that the average risk of each person in the study dying, in the first place, was actually very low.

Per person, per year of the study, the risk of dying was less than 1%.

For the people who (allegedly) ate red meat every day, the risk of dying was…also less than 1%.

I’ll give you another second.

The risk of each person dying, per year of the study, was less than 1% — whether or not they ate red meat.

In fact, the risk of people in this study dying was quite a bit lower than the risk of the average person of the same age in the general US population (for year 1994, right in the middle of the study period.)

The subjects would have been between the ages of 44 and 89 years old by the middle of the study, and the risk of an average USian (of roughly this age group) dying in the middle year of the study was 2.5%. (I’m just grabbing rough numbers to make a point here – please don’t mistake for Actual Science.)

Which tells us something important – and probably not that Being In A Study Reduces Your Risk of Death by 67%!!! – it tells us that not only did the people in this study who allegedly ate red meat every single day for 24 years have a lower risk of death than the average person, it tells us that the people in the study don’t represent average people.

You could very well say that not being a predominantly white health professional or nurse is associated with an increased risk of death. Investigating why that is might be a pretty interesting question, no?

But, sadly, it’s not as newsy as saying that red meat will kill you.

Last layer of the onion: this study was not a clinical trial, which means it can only draw correlations between things – it cannot prove causation.

So even if the dietary assessment strategy were sound, even if the population of the study did represent the average person, and even if the difference in risk of death between meat eaters and not-so-much meat eaters was very large, it would only signal the need to do a more rigorous study to get to the bottom of the association, and to find out whether it’s likely that eating more red meat makes you die faster. Nothing more.

This study didn’t prove that red meat was bad, because it didn’t prove anything at all — except that predominantly white health professionals die less often than the average person.

The foundation of nutrition as we know it remains variety. And variety, as we know it, can still include red meat if you like it and are inclined to eat it. I personally wouldn’t suggest eating it every single day for 24 years, but even if you did, this particular study wouldn’t give you a good reason to worry.

Just a note — I don’t want comments to turn into a referendum on red meat. Some people eat it, some people don’t — it’s a judgment call everyone has to make for themselves. Let’s talk instead about how weak observational data shouldn’t be dressed up and paraded around like definitive science.

ETA: Some commenters have pointed to some other critiques of this study, which you may want to take into consideration:

Unpacking the meat data

Red meat is killing us all! Or not…

Will eating red meat kill you?

Also a note to say that I’ve edited this post slightly from the original version. I think I was too mean to the researchers, frankly, and too quick to assume bad faith on their part. My apologies. I will try to be more circumspect in the future.