Whoa, it’s been an awful long time since I had a french fry. Must be why I’m depressed.

Articles about nutrition are among the least interesting science articles I read. I’d like to care more, nutrition is important and affects our lives significantly, but so many of them look like this:

A research team in Hangzhou, China, found that frequent consumption of fried foods, especially fried potatoes, was linked with a 12% higher risk of anxiety and 7% higher risk of depression than in people who didn’t eat fried foods.

They fit into a simple template. We fished up a small statistical correlation of simple cause A to complex behavioral/physiological phenomenon B. It’s annoying because they don’t have a mechanistic explanation, only a correlation, and their result is the product of a huge amount of work.

The study evaluated 140,728 people over 11.3 years. After excluding participants diagnosed with depression within the first two years, a total of 8,294 cases of anxiety and 12,735 cases of depression were found in those that consumed fried food, while specifically fried potatoes were found to have a 2% increase in risk of depression over fried white meat.

The study had also found that the participants consuming more than one serving of fried food regularly were more likely to be younger men.

One hundred forty thousand subjects over 11 years! And all they have to show for it is that feeble increase in likelihood that young men who eat fried foods are somewhat more depressed and anxious. Oh, how surprising. Have they considered that cheap fried fast food might be what people who are depressed and anxious might choose to eat? Or worse, might have limited choices in what they can eat?

Instead, let’s look to animal models, specifically zebrafish. These researchers do some impressively detailed, thorough analyses of zebrafish behavior after they add up to 0.5mM acrylamide to their tanks. The fish didn’t like it.

In the new study, the researchers suggest that acrylamide, a chemical formed during the frying process, especially in fried potatoes, is to blame for the higher risk of anxiety and depression.

In a separate paper referenced in the new study, the researchers exposed zebrafish to the chemical, finding that long-term exposure had caused the fish to dwell in dark zones within the tank, a common sign of a higher anxiety level in the fish.

The zebrafish had also displayed a reduced ability to explore their tanks and socialize, as they did not swim closely with other zebrafish, even though zebrafish are known to form schools with their species.

I worked with zebrafish for many years and am familiar with their behavior. They are flighty and sensitive; it’s easy to provoke changes in behavior. They’re like people in that regard. Throwing software at detailed video analyses of their behavior might generate tons of numbers and lots of graphs, but I fail to see what we learn from it, beyond that short summary: they didn’t like acrylamide.

Behavioral profiles of zebrafish by the long-term exposure to acrylamide in the novel object exploration test and the social preference test. (A) Representative swimming trajectories of zebrafish in the control group and three acrylamide exposure groups (0 mM wide type, 0.125 mM, 0.25 mM, and 0.5 mM). A novel object for zebrafish was placed in the left part (Zone 1) and the right part was Zone 2. (B) Heatmap visualization of zebrafish trajectories in the novel object exploration test. (C) Duration time spent in Zone 1 or Zone 2 of total time (%). (D) Distance traveled in Zone 1 or Zone 2 of total distance (%). (E) Representative swimming trajectories of zebrafish in different groups (0 mM wide type, 0.125 mM, 0.25 mM, and 0.5 mM). (F) Radar chart of 12 behavioral parameters of zebrafish in different groups (0 mM wide type, 0.125 mM, 0.25 mM, and 0.5 mM). a, duration; b, distance; c, average velocity (cm/s); d, accelerated speed; e, average entry time duration (s); f, turning angle (°); g, turning angle (°)/time; h, activity; i, rapid move ratio; j, normal move ratio; k, freezing time ratio (s); l, freezing time duration (s). (G) Heatmap visualization of zebrafish trajectories in the social preference test. (H) Duration time spent in the left or right chamber of total time (%). (I) Distance traveled in the left or right chamber of total distance (%). (J) Traversing times between the left and right chambers. (K) Numbers of crossing the middle line. (L) Hierarchical clustering of zebrafish in the social preference test. All the histograms were present with mean ± SEM, while all behavioral parameter data were analyzed by the two-way ANOVA followed by multiple comparisons or the one-way ANOVA followed by the Turkey post hoc test. The level of significance was defined as *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001; #P < 0.05, ##P < 0.01, ###P < 0.001, ####P < 0.0001 (* indicates significance between different groups and # indicates significance between different regions within the same group).

Yep, I believe it. Stress zebrafish by dosing their tank with a strange small molecule, and stressed zebrafish are stressed. They proved it, I’m satisfied. I am more than satisfied, I must concur: they have quantified to a remarkable degree that zebrafish are stressed by the presence of one component of french fried potatoes in their tanks. That’s total overkill.

I would just ask, do you think fast food workers are stressed by the omnipresent smell of fried foods in their clothes, their hair, the air they breathe? Does that suggest that you have identified the specific biological agent that causes anxiety and depression? No, it does not.

I respect the amount of work that went into the analysis, and think that every bit of knowledge we gain from research is worthwhile. But is it “run to CNN and let the world know that french fries cause depression” level of worthwhile? Is it even “publish in PNAS” worthwhile? OMG, is it “16 authors!” worthwhile?

Anli Wang, Xuzhi Wan, Pan Zhuang, Wei Jia, Yang Ao, Xiaohui Liu, Yimei Tian, Li Zhu, Yingyu Huang, Jianxin Yao, Binjie Wang, Yuanzhao Wu, Zhongshi Xu, Jiye Wang, Weixuan Yao, Jingjing Jiao, and Yu Zhang (2023) High fried food consumption impacts anxiety and depression due to lipid metabolism disturbance and neuroinflammation. PNAS 120(18) e2221097120.


  1. says

    I recently made the mistake of skipping lunch and snacking late 9in the afternoon on one of those inedible burgers with pink slime patties and special sauce. It was so bad I threw half of it into the bin. I was left with the “do you want fries with that?” offering and yes I was bloody depressed and hungry so I guess the researchers are right.

  2. René says

    Thank you very much for this. I just started a very nasty diet in preparation for a gastro & coloscopy

  3. says

    The paper’s title claims “due to lipid metabolism disturbance and neuroinflammation.” Did they in fact support that conclusion?

    Reading the paper the authors write that they started with the observation of how acrylamides are known to do shit to our biochemistry and hypothesized from that observation that they should observe greater depression among people who eat fried food. They say they accounted for confounding variables (e.g. income, gender, stuff like that). I didn’t check their work, but that’s what I’d be looking at in peer review.

    It could still be a case of p-hacking. Did they preregister their hypothesis?

    I get why PZ is dismissive of papers like this, and, like him, I’m impressed with the work that went into this. However, I’d say that a conclusion that might seem obvious in retrospective doesn’t mean that it shouldn’t be checked out.

  4. wzrd1 says

    If you torture P enough, it’ll give you any answer that you want.

    As for acrylamide and zebrafish, OK, if I’m ever a zebrafish, I’ll avoid fried potato water, it’ll make me anxious after clogging up my frigging gills.
    Interestingly, I had fish and chips for lunch, don’t feel 2% anxious or depressed, guess my P needs torturing.

    It took a bit, bud I decided on dinner. Made a gallon of pasta sauce last night, a gallon of chicken and barley stew the other night. I’ll do the stew for lunches and the sauce to night, trying out that lentil pasta a neighbor gave me to try. Hopefully, it retains at least some of the lentil flavor profile.

  5. DanDare says

    People on the street will now go about saying “they” have proven fries make you depressed and anxious.

    This is “them” at work.

  6. chrislawson says

    Nope, I can’t respect the amount of work put into this paper given the authors’ misrepresentation of their own study. As Helge has pointed out, the authors claim to have demonstrated causation. To quote their Significance section: ‘We demonstrated that long-term exposure to acrylamide induces anxiety- and depressive-like behaviors via oxidative stress-mediated neuroinflammation, and unravel the underlying mechanism that PPAR signaling pathway mediates acrylamide-induced lipid metabolism disorder in brain.’ Not one part of that sentence is true, and everything about mechanism isn’t their own work (I can let that last point go due to possible language barriers, but not for the editors).

    Their chosen methodology is incapable of demonstrating causality, incapable of demonstrating the biochemical effects of fried food consumption, incapable of isolating acrylamide as a signficant causal agent, and incapable of demonstrating that studies in zebrafish and mice are directly applicable to humans.

    Regarding that the zebrafish acrylamide study (a good study, btw, that was mapping out a research model and does not exaggerate the signficance of its findings): They used concentrations of acrylamide of up to 100 mg/L that the fish were swimming in from early embryonic stages. (There was also a 300 mg/L exposure group with zero surviving embryos, so not included in the datasets). Cooked high-carb foods contain up to 4 mg/kg acrylamide and acrylamide and its nasty metabolites have half lives of 2-25 hours in humans. So, a back-of-napkin conservative estimated equivalent of swimming in 100 mg/L of the stuff: the average human contains about 40 L of water, so that would be 4000 mg of acrylamide. Given a half-life of 25 hours, that means a human would need to ingest about ~ 3840 mg per day. At 4 mg/kg and assuming 100% absorption, that’s 960 kg of chips a day.*

    This is rank intellectual dishonesty intended to drive up metrics, the academic version of clickbait, and it is a mark against PNAS’s editorial team that they published this paper in its current wording.

    *Please note that none of this is intended to diminish the importance of diet on health, including mental health, or the dangers of acrylamide. Just because this zebrafish study used very high doses to establish the best levels for future toxicology studies, as one would expect from a toxicology paper, does not mean that lower doses of acrylamide can be assumed safe. I’m just putting into perspective the claims of this PNAS paper and reinforcing the importance of careful interpretation of toxicology studies. And all of this could have been avoided with some simple rewording such as ‘we found an association which could indicate an important public health effect, possibly mediated by acrylamide given recent research findings; however this study cannot show causation.’

  7. rockwhisperer says

    Wow. This just seems like almost-woo. There are a whole lot of variables about life that are really, really hard to quantify, in people who might or might not be eating fried foods. I have a hard time figuring out how you could even manage control and affected groups for the time needed to really study this. My extended family who are fried food fans live different lives, in different parts of the US, from those who avoid fried foods.

    Because I have been on one diet or another my entire life, with little ultimate success, I don’t fry foods in my kitchen. Once a year, at most, I might cover the periphery of the cooktop in aluminum foil and grill steaks in a grill pan. Once an effing year. I hate, hate, hate cleaning up grease, so a powerful craving is behind the effort. Since I switched from sautéing onions (turned out they were triggering my IBS) to adding low-FODMAP onion-derived powder to my soups, I simply don’t cook anything with oil on the stovetop. I do oven-roast potato wedges tossed with olive oil and my family’s favorite, Southwest-inspired, dry seasoning. They nosh away while I steam a red potato in the microwave and top it with a heaping teaspoon of lowfat sour cream. (I, a lifelong Californian, am the granddaughter of Minnesota farmers and Wisconsin immigrants from rural Norway. Life completely without sour cream (and yogurt and cheese) is not worth contemplating. I have even found a Wisconsin dairy that will ship me three or four years’ worth of brick cheese in one winter, and it gets progressively better, the longer it lives in the back of my refrigerator.)

    My husband and I rarely eat out, and never fried foods. At worst, I have a delivery service show up with our favorite burritos, but that happens rarely. Our housemate eats out more often, but usually healthy food. I’m a healthy, good cook, and like to feed my family well, which includes our housemate. We are carnivorous but focus on low-fat animal proteins and lots of vegan, pulse-based soups. Rice, quinoa, and barley are often on the menu, seasoned with some terrific dry seasonings I’ve discovered by exploring online. (Mind you, I live in a diverse city with lots of local markets carrying seasonings from around the world, but I can barely walk. Makes shopping in person a challenge.) Fresh veggies.

    I feel for my fellow USians who live in relative food deserts, and that is an issue in parts of California.

    The thing is, my knees have all but given out, my weight is a continuing problem, and I have had severe asthma since teen-hood. But Husband and I are almost to retirement age, and yet our cardiovascular systems are in good shape. I can’t believe my cooking philosophy, established in the early 1980s, hasn’t contributed to that.

  8. chrislawson says

    Whoops. Forgot to account for the half in half-life. It should only be 480 kg of chips a day.

  9. rockwhisperer says

    @ 12 chuckonpiggott, If you review the menu carefully, Taco Bell has some not-terrible food. I’ve indulged on long road trips when the alternative was a burger place; white meat chicken fragments, a quarter-ounce or so of cheese, and some flavoring in a not-fried flour tortilla, times 2 or 3, isn’t the most healthful lunch but won’t kill you.

    But to address the substance of your post, as someone who suffers from chronic depression, I assert that it leads to all kinds of bad choices, including food choices.

    I am going on 64. The opportunities freely available to my husband and me, as university graduates, are much rarer now. Those available to CC grads are even more elusive. Deities help kids who aren’t classroom learners and can’t connect with opportunities in the trades; they are completely screwed. [Political rant not happening here and now.]

    The thing is, even I, daughter of middle-class, supportive parents, have struggled with depression my entire life. Parents quite understandably didn’t pick up on it, and my first 12 years of post-university employment involved security clearances. I was warned that the Powers That Be frowned on clearance holders seeking mental health support. I have no idea if that was really true, or if that is the case today, even if it was then, but I had invested my all in my engineering work and wasn’t about to lose that. I left that job a burned-out wreck, and only in my early 30’s finally got mental health support.

    Life is a challenge, and the US makes it more than it ought to be for most young adults. Kids whose brain chemistry has betrayed them, like mine did to me, are struggling even harder. So, Taco Bell aside, your observation is spot on.

  10. wzrd1 says

    @11, well there we have it!
    ‘We demonstrated that long-term exposure to acrylamide induces anxiety- and depressive-like behaviors via oxidative stress-mediated neuroinflammation…”
    So, oxygen is linked to neuroinflammation. Eliminate the oxygen, inflammation disappears, QED!
    Just as valid a “finding” and one can trivially find all manner of linkage in the research on oxidative stress and inflammation.
    No inflammation or stress without oxygen, as inflammation or stress tend to be a tad difficult when dead.

    rockwhisperer, that was true for security clearance holders, seek mental health care guidance, endanger one’s clearance. After the government took enough heat over suicides, that changed, largely due to military influence and research, as well as VA research condemning such idiotic views and now, one’s clearance is no longer endangered if one seeks professional mental health care guidance.
    That said, it’s a relatively recent change and there was some brief resistance that was stepped on heavily by Congressional pressure.
    As an aside, our granddaughter suffered from depression. Her first mental health provider jumped straight to antidepressants and therapies that were unsuccessful and another provider performed testing that revealed hypothyroidism. Once treated, her depression symptoms vanished. Such is the current state of the US mental health care system, with only a part following fully evidence guided approaches.

  11. Michael Noone says

    Have they explored the possibility of causation running the other direction?

    Surely people (or Zebra finches) who are anxious and/or depressed are also more likely to eat a higher fat diet. It should be the task of the authors to demonstrate the direction of causation not assume it.

  12. Colin J says

    Everyone seems to be ignoring the most important part of this study. Sure, eating fried food makes you more likely to be depressed. But it also makes it more likely to be a young man.

    As an old man, I’m all for it. Fountain of youth!

  13. fergl says

    Sorry for the diversion but just reading the morning news here in the Uk. “Donald Trump rape accuser takes the stand”. Thats down in 14th spot behind such things as “Cheese sandwich price raised by a third”. Just another Trump story that we’ve got used to seemingly.

  14. StevoR says

    @ ^ fergl : problem is how “normalised” & even expected Trump’s antics have become.


    Make me person #111 here to note the likely inverse causation versus co-relattion here given fries ae comfort food for many and easy and cheap.

  15. KG says

    I ate chips (“french fries”) for the first time in ages last night and sure enough, felt somewhat anxious this morning. Now this could be because my indulgence in the chips resulted from spending an hour drinking wine in a very crowded bar (a few of us repaired there after a meeting planning the destruction of the monarchy), maybe the biggest risk of catching Covid I’ve deliberately taken in the course of the pandemic. But surely much more likely that it was the acrylamide!

  16. Louis says

    “…maybe predict human behaviours…study was done IN THE MOUSE*!”

    *Or in this case, the fish.


  17. says

    I’m almost surprised nobody is trying to use “fish become distressed in the presence of a chemical which is found in chips” as Proof of God™ …..

    Seriously, what is so hard for some people to grasp from behind their walls of privilege? Some of us simply aren’t interested in living forever, working our butts off every day watching this above us in the pyramid get rich, while all we wind up with are enough scars to disqualify us from any “best preserved corpse in the cemetery” award. Smoking a cigarette (or something stronger), drinking alcohol, eating fried foods — we know all these things that make life a little more bearable could kill us, but doing any of them and surviving feels like cheating death, at least in a tiny way. And not surviving doesn’t even seem like much of a hardship.

    It’s exactly the same as me wanting my one sweetie now; not because I have not learned to delay my gratification or any such pretentious BX, but because I’ve already been on the receiving end of too many broken promises to trust you to come up with two sweeties later, and I’d prefer one in the belly, thank you very much.