Potatoes Aren’t Killing You

It’s more complicated than a few fucking fries

They’re terrifrying

Someone who enjoys the occasional fried potato could be forgiven for becoming convinced that they were going to abruptly die because of their evil habit. It could be because potatoes are basically Satan’s version of a light snack, but it’s more likely that they’ve read any one of hundreds of news headlines decrying the evils of our favorite calorific snack:

Put the french fries down: Eating fried potatoes doubles risk of death, study says — Washington Times

Eating fried potatoes linked to higher risk of death, study says — CNN

Study: Eating fried potatoes linked to higher risk of death — Fox

It seems like a lot of news outlets have become convinced that eating fried potatoes is not just a moderately unhealthy food choice, it’s going to double your risk of death.

That’s pretty scary.

And, as usual, wildly misleading.

The Big Scary Study

As ever, there is a Big Scary Study behind all of this media noise. The Big Scary Study is a wonderful phenomenon whereby the media take a piece of pretty everyday research — say, fried potatoes aren’t super healthy — and turn it into something that you and I can walk about in harrowed whispers over our MacDonald’s drive-thru lunch.

Suffice to say, it’s rarely as simple as all that.

The Big Scary Study in question was recently published in the American Journal of Clinical Nutrition, and is a large-scale analysis of data from North Americans*.

Basically, the researchers wanted to know whether eating potatoes was bad for you. Now, we know that eating a lot of calorie-dense food is bad for you. There’s no question. You get fatter, you get more diseased, you may die. But these researchers wanted to know whether specifically potatoes were bad for you, excluding all else.

Well, excluding as much as possible.

So they looked at 4,400 people, divided them by the amount of potatoes they ate, and used some cool statistics to see if people who ate more potatoes were more likely to die.

If you’ve seen any of the headlines above, I’m sure you can guess what they found. Doom, gloom and mayhem, with potatoes carrying no increased risk of death regardless of the amount consumed.

Sorry, did I say doom, gloom and mayhem? I meant nothing at all.

The study showed that, in general, there was no increased risk of death for people who ate more potatoes.

What the researchers did find is that, if they analyzed only the consumption of fried potatoes, that there was an increased relative risk of about 2x.

You may notice that they used relative risk, something that I’ve previously written about quite a lot. Basically, it’s a bit misleading, because it significantly overstates what that risk actually means. In this sample, the number of people who died overall was about 5.4%, and whilst it’s pretty difficult to calculate the absolute risk of dying for people who ate lots of fried potatoes without access to the study data, it looks like that 200% increase in relative risk equates to about a 2% increase in absolute risk.

To put it another way, every year about 2% more people who ate loads of fries died than people who ate virtually none.

Sounds a bit less scary when I put it like that, doesn’t it?

Media Monstrosities

So, the risk was tiny. People are still dying from eating fries, right?

Well, not exactly.

The first thing that virtually every media outlet ignored is that, to have a higher risk of death, you have to eat a lot of fries. The increased risk was only apparent in people who ate fried potatoes twice (or more) a week.

It’s also worth noting that, for such a big study, the results had some fairly wide confidence intervals. A confidence interval is basically a statistical measure of doubt; we calculate that the answer is probably one number, but almost certainly lies between a bigger interval. If the confidence interval crosses 1, it means that the results were not statistically significant.

If you have a look at this table from the study, you’ll notice that the technically significant confidence intervals are still veering pretty close to 1. Now, this may just mean that we need a bigger study, but since this study was pretty huge it’s also not unlikely that this effect was more down to statistical chance, or potentially another variable, than it was to fries.

Also important was that this study was observational. This means that any associations that were noticed in the study are not necessarily causally linked; basically that it could have been something other than fries causing all of those deaths. It could’ve been due to wealth — rich people are generally healthier than poor people — or other dietary factors — people who eat fries eat lots of other unhealthy things that can cause them to die.

And worst of all?

The researchers said all of this in the damn study.

Paywalls And Tears Of Sadness

This is one case where I actually don’t blame the reporters who wrote the silly stories about how fried potatoes are going to murder you in your sleep. It might be pretty easy to Google a study, but it’s not always easy to access it.

To read this particular nugget of academic wisdom, you’d actually have to subscribe to the American Journal of Clinical Nutrition for several hundred dollars a year, or pay $25 just to read it**.

It’s not always that easy to check the facts.

And to be fair, a lot of news articles did say (buried at the bottom of the piece) that the study was observational in nature, which was good. They failed to mention that the authors called for more research before drawing any definitive conclusions from their study, which was less good.

In fact, since the study demonstrated that potatoes were not themselves linked to more deaths, it’s almost certain that the increased mortality was down to something to do with the frying process.

In other words, fried food is bad for you.

Which comes as a surprise to literally no one in the world.

Headlines, Deadlines

The media madness was clearly unfounded. The fried potato epidemic is a minor risk that could probably be explained by statistical chance or potentially something like general dietary habits.

If the media outlets had been honest about it, they probably would’ve come up with a headline like this:

New Study Suggests That Frying Food Is Unhealthy

Which, of course, is not that interesting.

Real science rarely is.

Fries aren’t healthy. They are loaded with fat, salt, and carbs, and eating loads of them is almost certainly not a good idea.

However, you could say the same about virtually any fried food. It’s not that fried potatoes are bad for you, it’s that frying things is bad for you. If you started eating fried bread (yes, it’s a thing), you’d probably get pretty unhealthy pretty quick.

The best advice I could give you? Eat food, not too much, mostly plants.

Eat the occasional deep-fried thing, because it’s delicious, but don’t make it an everyday occurrence.

For more specific advice, see a dietitian. They can tell you far more than I ever could about you and your diet.

If you liked the scienc-y ranting, click on the little green heart below to let me know — it’ll make my smile today just that bit more genuine :) You can also follow me here on medium, on twitter, or on facebook. If you didn’t enjoy, I’d love to know why in the comments, or @ me on twitter!

*The study itself is behind a paywall, so if you want to read it you’ll either have to have access by paying lots of money, being a member of an institution that pays lots of money, or be a nefarious criminal and use scihub. Which I would never advise. Because it’s criminal.

**Or steal it with something like scihub like a common scientist***.

***Sorry, I meant criminal.