New Research Indicates Link Between Ultraprocessed Foods and Depression—Here’s What a Psychiatrist Has to Say

Daniel Lieberman

Written by Daniel Z. Lieberman, MD

Updated 10/13/2023

When you pull into a drive-through or pop a frozen dinner into the microwave, odds are you’re not looking for a balanced meal that’s going to nourish your body. You just want to be satiated, whether that means satisfying a specific craving or just eating whatever’s closest. But what if those prepackaged, wallet-conscious choices had an outsized effect on your body and your brain?

A new study published in JAMA Open Network confirms researchers’ long-held suspicions that consuming high amounts of ultraprocessed foods doesn’t just worsen existing physical and mental health conditions.

The study, which tracked the eating habits and mental health of more than 31,000 respondents over 14 years, found that people who habitually consumed 9 or more servings of ultraprocessed foods were more likely to develop depression over the course of that multiyear research period. 

The study began before many respondents reported any depressive symptoms, and it showed that they were 50% more likely to develop depression than those who consumed the least amount of “ultraprocessed grain foods, sweet snacks, ready-to-eat meals, fats and sauces, ultraprocessed dairy products, savory snacks, processed meat, beverages, and artificial sweeteners.”

So does that mean you have to put down the fries forever if you want to stay on top of your mental health? Not exactly. We checked in with Dr. Daniel Z. Lieberman, Clinical Professor of Psychiatry and Behavioral Sciences at George Washington University and SVP of Mental Health at Hims and Hers, to get some more insights about what exactly the study found and how to incorporate this knowledge into our daily lives.

Dr. Lieberman: We can define highly processed foods as those that contain high levels of fat, added sugars, and salt. You know the famous Lay's potato chips saying “betcha can't eat just one” — that's the truth. And that's not an accident. They're engineered so that you can't eat just one. Sugar, salt, and fat are what is going to do it. 

These foods are intentionally made to bypass the satiety circuits in our brains telling us that we've had enough. You can eat an apple, and you'll probably be satisfied and you won't need another apple. But if you have a piece of chocolate, you'll never be satisfied.

You could keep eating until either you feel guilty about it or you start to feel sick. But you will likely never say, “OK, that's enough.” That’s because ultraprocessed foods create addictive behavior patterns in our bodies.

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The question of what is addictive is a controversial one in psychiatry. There's no controversy about chemicals—cocaine, alcohol, nicotine, those are obviously addictive. But when you get into other things, particularly behavioral things, it becomes more problematic. And one thing the psychiatric community is very sensitive to is over-pathologizing ordinary behavior. We don't want to do that. 

It might make sense here to step back and ask ourselves, “Well, what is an addiction? And I think that it would be characterized by two things: compulsive use, inability to voluntarily make the decision not to engage in the behavior anymore, accompanied by negative consequences.

So what about food? In some ways, it doesn't make sense. We all need food, right? So does that mean we're all addicted? No, it does not.

What it means is that companies—and coincidentally, companies that used to sell cigarettes, so these are companies that know a great deal about how to make it so that their customers cannot stop being customers—they have found ways to process food so that they stimulate the centers of the brain that are responsible for addictions and compulsive behaviors. And these are specifically areas of the brain that are rich in the brain chemical dopamine.

Dopamine is a neurotransmitter, a brain chemical, that signals reward. It signals that something is going to be evolutionarily favorable for us. In general, this is survival things like eating and drinking, it’s sex, and it's also winning competitions. And that can be as simple as having your boss pat you on the back and say, “Hey, great job yesterday,” or could be scoring the winning goal in your soccer game. 

So things that are addictive, like cocaine, alcohol, and nicotine, artificially hit dopamine. And because we've got a direct chemical stimulation, what we get is a stronger dopamine signal than natural behaviors.

So if you come home at night, and you're a good father, that makes you feel good about yourself, and you'll get some dopamine. If you come home at night and do a line of cocaine, you are gonna get far more dopamine.

So these processed foods, also known as highly palatable foods, produce a lot more dopamine than the kinds of foods our evolutionary ancestors ate. And as a result, our brains are not equipped to handle these foods any more than they're equipped to handle cocaine.

In some ways, a serving is arbitrary. Food companies were trying to game the system in the past by making their so-called servings unrealistically small, so that they could claim low calories, low fat, low sugars. The FDA cracked down on that, and they said, you have to make it more realistic

But nevertheless, if you buy a package of food, in many cases, the average person is going to think, “Oh, this package is one serving.” But if you look on that nutrition facts box, it may say three or four.

So you know, I recently was in the airport, and I grabbed a fairly healthy snack, a medium-sized bag of trail mix, and I ate it. And then I felt a little sick, so I looked at it, and I had just consumed four servings. So there's no a priori definition of what a serving is.

It makes consumers misinterpret the nutrition guidelines on the box, so that they may be getting two, three, or four times as many calories as they think they are. And you know, the general recommendation is that you shouldn't eat these kinds of processed foods out of the package.

You should put them on a plate, because since they're stimulating these dopamine centers, you're not going to get satiety. You're not going to know when to stop, so you need to put a serving on a plate. And when the plate is done, you're done—in theory. 

And I do that. I try to avoid these processed foods, but I do like chips once in a while. And when my serving is finished, I usually go to the bag and pour myself out another serving. Because it's tough to resist. 

We don’t fully know, but there are a lot of possibilities. Let’s start with sugar. When you consume high levels of sugar, you get the “sugar high.” And that feels nice. But what it does is it stimulates the release of a very large amount of insulin into your bloodstream.

And what insulin does is take the sugar out of the bloodstream into the cells. And since a high sugar level results in high insulin release, all the sugar’s gone, and you get a crash. And I think that that whipsaw effect of going up and down, up and down, is potentially a risk factor for depression. So that's one. 

Another one is that these foods really don't have a whole lot of nutrition in them. They might have added vitamins and minerals. But added vitamins and minerals don’t do the same thing as getting them from natural foods. They're not absorbed in the body as well. 

A third reason, which I think is the most interesting right now, is that it may bring about something called “dysbiosis.” And that means that it leads to a negative balance of microbes in the gut.

We are learning more and more about the gut-brain connection, and it is incredibly powerful. An unhealthy diet causes unwelcome microbes in the gut, and these cause problems that are then transmitted up to the brain and lead to depression.

Many people who eat artificial sweeteners are doing it because they want to lose weight. But ironically, we can get energy from different sources. And if you're trying to lose weight, the source you want to get energy from is stored fat.

Ironically, artificial sweeteners block that metabolic pathway. So if you're consuming artificial sweeteners, you can't burn your fat. 

The other issue is that they trick your brain. Artificial sweeteners are often called non-nutritive sweeteners, meaning there's no nutrition in them. The tongue leads the brain to expect its favorite nutrition, sugar, and it gets nothing.

And that's a recipe for disaster—it essentially enrages your brain, and it says, Alright, you better go out and get some sugar. And so you just eat more and more, and you make your brain more and more unsatisfied.

I'd like to focus on the word “mindful.” Mindful means experiencing the present with all of your senses, not having your mind wander to other things, not being distracted, but really experiencing what you are doing in the present moment. 

When people consume hyperpalatable foods, they're generally not doing it mindfully. Oftentimes, they're watching TV, or they're on the internet, and they may not even realize that they're putting food into their mouth.

Maybe the bag may be empty, and they're like, “How on earth could it be empty? It was full a second ago.” And they have really no recollection of eating all of it. If we actually pay attention and experience what we're doing, it changes the equation. 

There's a wonderful quotation from Winnie the Pooh. Christopher Robin asks Winnie the Pooh, “What do you like best to do in the world, Pooh?” And Pooh is about to say “eating honey.” But then he stops. And he realizes that there's a moment just before he starts eating honey that is better than eating the honey itself. But he didn't know what it was called.

Well, now we do know what it's called. It's called dopamine. Dopamine is released with expectation.

And so maybe for us it's like, “I'm gonna have chips,” but I start eating the chips and I'm not really getting the pleasure out of it that I anticipated. But I don't notice because I'm not paying attention. I'm watching TV, I'm watching my computer, I'm thinking about something else. And so by consuming food mindfully, we can get a sense.

Is this really giving me what I expected? Is it worth it? But if you pay attention, and if it's not giving you the pleasure you expected, stop. But you can only do that if you're eating mindfully.

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I would say the easiest way in is to start with breakfast and lunch. 

If you're looking for substitutes to processed foods, I think the number one most important thing needs to be that they're highly accessible. Grapes are a great example—you can just grab grapes, they're sweet, they're delicious, and they require no preparation.

Berries are really good, as are baby carrots, because you can just grab the bag and start eating. Maybe a loaf of multi-whole-grain bread or small rolls—things that are just very, very easy to grab. What you do not want to do is consume highly processed foods that are labeled as “healthy.”

Dinner is more challenging. And maybe it's unrealistic to say to people don’t make something instant, don’t do takeout. But breakfast and lunch are doable. And if you start there, you may notice that you kind of feel better, your mood is better, you have more energy, you feel lighter. And that might help create some motivation for working on dinner.

This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment. Learn more about our editorial standards here.

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