A story of heart disease, cancer, and the fascinating complexity of scientific evidence
There’s something almost mythical in a perfect steak. While it seems like a very simple thing to do — throw a bit of meat on the grill, cook until done — there’s an art to getting steak right that takes the humble hunk of cow from a boring dish into a masterpiece of culinary skill.
There are few things better than a really well-cooked piece of red meat.
The problem is that the deliciousness of red meat has long been considered to be outweighed by its side-effects. Study after study has found that red meat is associated with poor health for any number of reasons — it may cause cancer, it’s associated with heart disease, and it could even cause diabetes. These findings have led to many guidelines recommending people eat a bit less red meat to improve their health.
But now, according to headlines from across the world, all of that has changed. A controversial new study has proven that actually there’s no evidence that eating red meat is bad for us, and that we can go ahead and gorge on steak and burgers once again.
On the other hand, headlines have hit out saying that this new research is nonsense, and that it could be deadly if people start eating more meat. This seems like a contradiction — either red meat is or isn’t good for us, surely?
The answer, as you might have guessed, is very complicated, but it boils down to a simple fact: nutrition science is far harder than most people assume.
The new study that everyone is talking about is actually more than one piece of research — researchers from across the world came together and conducted a series of 5 systematic reviews of the evidence, looking at the effects of red meat on a wide variety of health issues.
Without going too deeply into the findings — you can read the full recommendations here — the argument from the researchers was fairly simple: there is currently no good evidence that red meat is harmful to health, so the most evidence-based guideline is not to tell people to eat either more or less red meat. There is some evidence that red meat consumption might be harmful, but it’s not strong enough to justify telling people to change their dietary habits.
Basically, keep doing whatever you are currently doing, because we simply don’t know if it’s harmful or not.
This has been met by predictable outcry from all the other scientists who have spent decades developing guidelines that say that red meat is bad for you so you should eat less of it.
Why do these new studies contradict established research? The basic answer has more to do with interpretation than anything else.
The reason that this new research differs so markedly from previous recommendations is largely to do with what a systematic review is and what it does. Essentially, these studies are a type of research where people comb through all of the publications on a single topic, and bring them together to form the most robust perspective on a subject. For example, you might look at every study of a medication for diabetes and conclude that it works very well even though individual trials aren’t convincing. If you conduct multiple systematic reviews on the same topic in a short space of time, there’ll be a lot of crossover in your results — there are only so many studies on each topic, after all.
The problem is that systematic reviews are, inherently, somewhat about interpretation. We can do everything in our power to control for our own biases — which in this case the researchers appear to have done — but ultimately reviews of research are always going to have some elements of bias in them.
What this means is that you always have to read systematic reviews very carefully to see what was done and how reasonable the conclusions are based on the methodology. In this case, the biggest difference between the new studies and past research seems to boil down to one argument: whether the evidence is solid enough to form conclusions*.
What do I mean by that? Well, it’s important to look at the exact language of the research. The scientists have not said that red meat isn’t harmful — what they’ve said is that the current level of evidence is not sufficient to make recommendations about red meat consumption either way. Previous research has drawn different conclusions from essentially the same data — remember, they are reviewing the same studies that other systematic reviews were looking at!
So the main difference comes from interpretation, rather than the evidence itself. The new studies argue that, since the evidence we have is relatively sparse, we can’t tell people what to do based on the research. Previous studies have instead said that we have enough evidence to know that red meat — particularly if it’s processed — probably causes harm, and since there are definitely alternatives that don’t carry the same risks we should tell people to switch to those instead.
It’s a very subtle point — no one is saying that red meat is definitely harmless, and they’re certainly not saying that it’s good for your health. The argument really boils down to how confident we can be when we say that red meat is bad for your health.
Which brings us neatly back to nutrition science.
Everyone wants a take-home. We want a simple, easy phrase that can sum up a scientific question like “is red meat a horrible cancer-causing nightmare?” without too many long words and confusing qualifications.
For everyone who wants a simple answer, here’s my take:
Nutrition science is fiendishly complicated, and we’ll probably never know definitively whether red meat is good or bad for your health.
The simple take-home message from this research is that there is no simple take-home message. There are certainly signals of risk that suggest that red meat probably contributes to things like cardiovascular disease and cancer, but these risks are likely to be quite small and, in the scheme of things, not very meaningful to your life.
And while there is some experimental evidence on the topic, it’s basically impossible to run the kind of trial that would definitively prove that red meat was good or bad. Realistically, this would involve randomizing then feeding meat/no meat to thousands of people for decades which is a) unethical and b) impractical in the extreme.
Short of an interested billionaire with a passion for controlled science who isn’t afraid to spend most of their money, we probably aren’t going to get an answer any time soon.
The real message from this study seems to be that a variety of eating patterns are probably fine for your health. If you want to eat red meat, that is probably not that harmful. If you want to cut it out entirely, you’re probably totally justified also.
If you’re worried about your health, speak to a registered professional about it: ideally, a dietitian or doctor. They do fancy degrees and years of training to give you the best personalized advice around.
Just don’t worry too much about red meat.
The science is probably more complicated than you’ve been told.
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*Note: this is not the only difference. There were some decisions made in the recent studies that are very questionable, but to discuss these I’d need another few thousand words and hours of your time. For the sake of simplicity, we’ll assume that the science was robust, even though that’s a question open to debate!