5 Reasons To Toss The Junk Food: The Truth About Ultra-Processed Foods (UPFs) and Brain Health By Dr. Annie Fenn

By Annie Fenn, MD

We all know junk food is not good for us. Now, thanks to several recent large-scale studies, we can quantify exactly how bad these foods are for brain health. Some processed foods are easy to spot—things like soda, energy drinks, potato chips, and candy. Others are more tricky. They may seem healthy (microwave popcorn and roasted nuts come to mind) but firmly belong in the trash.

What is it about UPFs that erode our brain health? 

I’ll share 5 emerging concepts about how these foods impact the brain. Then, I’ll walk you through how to spot the worst culprits and rid your home of these brain-harming foods.

More than an occasional indulgence

Here’s an astounding statistic: UPFs now account for more than half of calories consumed in the U.S., Canada, and the U.K. The evidence is mounting that eating these foods increases the risk of heart disease, diabetes, obesity, and dementia, including Alzheimer’s. 

5 ways ultra-processed foods are bad for brain health:

1. UPFs make anxiety and depression worse. It’s been known since 2017 when the SMILES trial came out that following a Mediterranean-style diet helps those living with anxiety and depression get better. Now, we have data to say that UPFs make these mental health challenges worse. In this study of over 10,000 participants, those who consumed the most UPFs were more likely to be anxious and suffer mild depression. And this one from Italy found that the more UPFs a young adult consumes, the more likely they are to experience depression. That may be because a junk food diet is deficient in essential brain health nutrients like DHA and EPA, B-complex vitamins, and fiber while fueling neuroinflammation with sugar and unhealthy fats.
2. Removing UPFs from the diet reduces dementia risk. This large-scale study of more than 72,000 participants looked at the impact of UPFs on cognitive health. The authors asked the question: what happens when you cut back on 10% of the UPFs? Well, if you replace those junk foods with an equivalent proportion of unprocessed or minimally processed foods, dementia risk goes down by 19%.  
3. Junk food impacts thinking skills. Another study of over 15,000 people found a linear relationship between UPFs and cognitive decline. Those who consumed UPFs in the top quartile of the group showed a 28% faster rate of cognitive decline. This was especially evident for executive function skills, or the ability to finish complex tasks expeditiously. Junk food eaters had a 25% faster rate of executive function decline.  
4. UPFs are bad for the gut microbiome. When the trillions of microbiota that live in your gut encounter the ingredients in junk food, they see them as foreign and mount an inflammatory response. Poor gut health spills over into the brain and fuels the neuroinflammation that creates an environment that accelerates Alzheimer’s.
5. Junk food choices reduce adherence to a Mediterranean diet. As this study shows, less brain-healthy foods make it onto the plate when the diet also includes UPFs like fast food and pastries. As many studies have shown, close adherence to a Medi-style dietary pattern, like the MIND diet, is a powerful tool to prevent Alzheimer’s.

How to tell if a food is an UPF

An UPF is at the most extreme end of the processed food spectrum. It will sport a long ingredient list of additives, binders, and chemicals, but little or no recognizable food. 

Not every packaged food deserves to be called ultra-processed. Some are actually smart additions to a brain healthy diet. The NOVA classification (see the picture), details the difference between an UPF (like instant noodle soup) and one that is unprocessed or minimally processed (like pasta and frozen fruit). I like to think of minimally processed foods like canned beans and frozen vegetables as “conveniently healthy.” They provide brain health nutrients (like the omega-3’s in a can of salmon) while speeding up meal preparation. 

Here’s how I cleaned out my mom’s pantry when she was diagnosed with dementia

Last time I told you that cleaning out my mother’s pantry was the first thing I did when she was diagnosed with mild cognitive impairment. Some of the worst foods I found were marketed to appear healthy, yet would qualify as NOVA class 4. These included microwave popcorn (made with hydrogenated oils), boxed granola and granola bars, flavored roasted nuts, packaged bran muffins, breakfast cereal, gummy fruit snacks, sweetened oatmeal, pretzels, and Nutella.

Processed dairy and meats are proven brain-harming foods. I tossed the packaged “cheese” balls, cream cheese, sweetened and flavored yogurt and plant milk, and whipped “cream” toppings. The tub of margarine was replaced by a small stick of grass-fed butter, and I replaced her long-expired olive oil with a fresh good-quality one. I tossed all the processed meats (lunch meat, hot dogs, salami), too. 

In the pantry, I replaced her collection of vegetable and seed oils (safflower, sunflower, grapeseed) with one bottle of good-quality avocado oil. Out went the packaged sweets (muffins, cookies, cake mix) and the frozen processed food (chicken pot pies, TV dinners, pizza).

Finally, I tackled the drinks. My mom had a daily Diet Coke habit, an addiction that proved hard to break. (We weaned her off this over several weeks so as not to induce caffeine withdrawal headaches.) She was also fond of ready-made sweet tea in a bottle, also requiring a slow wean. Since my mom was already diagnosed with dementia, drinking alcohol was off the table. My siblings and I watered down her wine until she wasn’t drinking at all. 

Finding healthy swaps is key

I won’t sugarcoat it; this was a tough time. My mother was attached to many of these foods and resistant to change. Once these food products were out of the home, however, it only took a few weeks for them to fade away in her memories. Plus, I made sure to find healthier swaps that she liked: Triscuits for Cheez-its, herbal tea (like Celestial Seasons Bengal Tea) for sweet tea, plain Greek yogurt with a drizzle of honey for sweetened and flavored ones, raw nuts and seeds for roasted salted ones, and flavored sparkling water for diet soda. 

Don’t wait until you or your loved one has dementia to purge UPFs

It’s been 10 years since the big pantry clean-out. My biggest regret is waiting until my mother had dementia to purge these foods from her home. A steady diet of UPFs is a known factor in accelerating dementia; this pantry sweep should have happened years ago. But I am happy to report that my mother transitioned well to eating very close to the MIND diet guidelines. Junk food habits can linger for decades, apparently: she continued to ask for a Diet Coke each afternoon. Redirection to a healthier choice is easier when there are plenty of tasty brain-healthy choices instead.

What about the occasional cheat meal of ultra-processed food?

I’ve long maintained that eating for brain health is not about being perfect. No one is expected to adhere to the guidelines 100% of the time. Progress over perfection, not perfection, is the goal. (I wrote about that here.) So what is the impact of cheating every once in a while? 

According to the 2021 UK Biobank study of nearly 500,000 participants, even small amounts of processed meat can have a large negative impact on brain health. Consuming as little as 25 grams of processed meat per day (about one slice of bacon) was associated with a 44% increased risk of developing dementia overall, and a 52% increased risk of Alzheimer’s disease specifically, compared to those who did not consume processed meat.

Interestingly, the study suggested that higher consumption of unprocessed red meat (such as beef, lamb, or pork) was associated with a 19% lower risk of dementia.

If you end up eating some junk food, try not to dwell on it. Make sure your next meal is a brain healthy one. Here’s the good news: once you shift your diet to include mostly healthy food, junk food cravings lessen. Eating a brain-healthy Mediterranean or MIND diet can reduce the risk of developing Alzheimer’s or another dementia by at least half. Not only that, studies show that eating this way helps people think more clearly and remember better. 

DR. ANNIE FENN is a physician, chef, and author of The Brain Health Kitchen: Preventing Alzheimer’s Through Food (Artisan 2023), a science-based cookbook and care manual for the brain. She founded the Brain Health Kitchen, the only cooking school of its kind focused exclusively on helping people prevent cognitive decline through food and lifestyle. 

Dr. Fenn hosts Brain Health Retreats in Italy, Mexico, and Costa Rica. She writes Brain Health Kitchen, a twice-weekly newsletter on Substack to a large community of food-loving brain health enthusiasts where she provides cooking classes, in-depth lifestyle guides, and recipes. Dr. Fenn is an adjunct faculty member at the University of Cincinnati and Harvard University where she lectures young adults and medical students about brain health. Dr. Fenn lives in Jackson, Wyoming where she enjoys skiing, cycling, foraging for mushrooms and berries, and exploring the Teton mountains with her husband and dogs.