How junk food affects the brain

Ultra-processed foods are said to fuel anxiety, depression and neurodegenerative diseases. A lot is still unclear - but there is more and more data

Ready meals, fast food and sweets are almost always highly processed products. They are suspected of being addictive – and causing long-term damage to the brain.

Cornflakes for breakfast, a fast food burger for lunch and, because things have to be quick, a ready-made pizza for the evening. Your daily diet won't always look like this, but if you're being honest, you'll probably find some breakfast cereals, frozen meals, snack bars, packaged sweets and more on your diet. It is precisely these highly processed foods that are suspected of triggering anxiety, depression and neurodegenerative diseases - and the more often you consume highly processed foods, the more so.

Not to mention health consequences such as Diabetes, cardiovascular diseases, Obesity or various types of cancer, as several studies show.

But what makes these foods so questionable? And how can you protect yourself from the consequences of consumption? After all, they are often practical and some taste good too. Much is still unclear, researchers are looking for answers to essential questions. But knowledge about the influence of food on health is constantly increasing.

From natural to highly processed

Back in 2009, Brazilian researchers developed a four-stage scale that divides foods into unprocessed, minimally processed, processed and highly processed. Examples of unprocessed foods include fruit, vegetables, grains, rice, legumes and dairy products. These foods are minimally processed if they have been chopped, pressed or refined, such as starch, oils, vinegar or sugar. Processed is everything that is baked, smoked, cured, preserved or fermented, such as bread, jams, spreads, preserves, beer or wine. Highly processed or ultra-processed are almost all industrially produced foods, such as cereals, snack bars or ready-made frozen meals.

"Highly processed foods contain ingredients that you wouldn't use in recipes at home. Corn syrup, for example, hydrogenated oils, protein isolates or chemical additives such as artificial flavors, sweeteners, emulsifiers and preservatives," explains Eurídice Martínez Steele, who researches food processing at the University of Sao Paulo in Brazil and helped develop the scale. The classification system is now used by most nutrition researchers.

Highly processed foods include the majority of packaged foods that are increasingly found on supermarket shelves. They are also increasingly being consumed by all social groups.

The British doctor and professor at University College London Chris van Tulleken emphasizes in STANDARD interview that foods are often made with the cheapest possible ingredients and, due to their composition, are more addictive than alcohol or nicotine. It is not yet clear why this is. But it must be due to the special composition with flavors, emulsifiers and more, which are tailored to the fact that people want more and more from a product.

Finished products and the psyche

But addiction is not just an issue; the psyche is also influenced by it. This is what a study from 2022 says: shown to over 10,000 adult participants in the United States. The more often they consumed highly processed foods, the more likely they were to experience anxiety and depression. "Those who covered at least 60 percent of their calorie intake with highly processed foods had significantly more days on which they felt mentally bad," says study author Eric M. Hecht from the University of Miami Miller School of Medicine. This is not proof of a causal connection, but there is almost certainly a connection.

A Brazilian study, which was completed in 2022, also provides corresponding information Hints. Almost 11,000 adults were accompanied over a decade. It found that high consumption of highly processed foods is linked to poorer cognitive function. Those affected were less able to remember things, learn new things or solve problems.

Study author Natalia Gomes Goncalves from the University of São Paulo Medical School says: "With increasing age, there is a natural decline in these abilities. But in people who consumed more than 20 percent of their calorie intake from convenience foods and the like, this cognitive decline accelerated by 28 percent.

However, a healthy diet may be able to offset these harmful effects. The Brazilian researchers tested whether the MIND diet, which is rich in Whole grains, green leafy vegetables, legumes, nuts, berries, fish, chicken and olive oil reduce the risk of dementia from highly processed foods - and found that they do this to a large extent. "Those who followed the MIND diet but still ate convenience foods did not experience cognitive decline," says Goncalves.

Little knowledge about impact

But why do highly processed foods have this effect? This is not clear, as the specialist journal “Nature” writes. Many high-quality randomized studies show the positive effect of a nutrient-rich diet on depression. "But we still don't fully understand the impact processed foods have on mental health," said Melissa Lane, who works at the Food & Mood Center at Deakin University in Australia conducts research.

The intestinal microbiome is likely to play an important role. Several studies are now investigating the connection between bacterial flora in the intestine, brain and mental health. The microbiome benefits above all from a diet rich in fiber, such as DER STANDARD here reported. However, highly processed foods usually contain very little fiber. These are mainly found in whole grains, vegetables, fruits, legumes, seeds and nuts. The bacteria need them to produce short-chain fatty acids, which are important for brain functions.

We know that people with depression and other mental health disorders have a less diverse gut microbiome and fewer short-chain fatty acids. Chemical additives in highly processed foods can also affect the intestinal flora," reports Wolfgang Marx, President of the International Society for Nutritional Psychiatry Research and Senior Research Fellow at Deakin University. "New findings, particularly from animal experiments, also indicate that isolated nutrients such as fructose, additives such as artificial sweeteners or emulsifiers can have a negative impact on the microbiome. And human data is now also available."

Sugar leads to inflammation

However, a less diverse microbiome in the gut and a diet high in sugar can increase chronic inflammation - which in turn is linked to mental and physical problems. The interaction of increased inflammation levels and the brain could drive depression. So diet affects mood, but mood also affects diet. If you are stressed, anxious or feeling depressed, you are more likely to choose foods with a lot of fat, sugar and chemical additives.

So it makes sense to reduce highly processed foods in your diet. But how do you recognize these? It's best to read the ingredient list. The rule of thumb is: the longer it is and the more incomprehensible things there are, the more highly processed the product is. A second rule of thumb is: If an ingredient cannot be found in private pantries, then it is better not to eat it. But that doesn't mean you can't eat processed foods at all. Canned beans, frozen vegetables or canned fish, for example, can be part of a healthy diet. The only important thing is that you would also use the other ingredients, such as herbs, salt or oil, at home.

Pia Kruckenhauser, Standard from August 3, 2023