Mexico City.- Approximately 60 percent of the calories in the American diet come from highly processed foods. We have known for decades that eating these packaged products, such as some breakfast cereals, soda bars, frozen foods and practically all packaged sweets, among many other things, are related to unwanted health outcomes, such as a greater risk of diabetes , obesity and even cancer. But more recent studies have revealed another important disadvantage of these delicious and always convenient foods: they also seem to have a significant impact on our minds.
Research over the last ten years has shown that the more ultra-processed foods a person eats, the greater the chances of feeling depressed and anxious. Some studies have suggested a link between eating ultra-processed foods and a greater risk of cognitive impairment.
How insidious are these foods and how can you avoid mental consequences? The scientists are still working on the answers, but this is what we know right now.
What qualifies as an ultra-processed food?
In 2009, Brazilian researchers classified foods on a scale of four parts, from unprocessed and minimally processed (such as fruits, vegetables, rice and harine) to processed (salt, butter, sugar, dairy products, some canned foods and meat and fish smoked)) and ultra-processed. “The ultra-processed foods include ingredients that are rarely used in homemade recipes, such as high fructose maize syrup, hydrogenated oil, protein isolates and chemical additives” such as colors, artificial flavors, sweeteners, emulsifiers and preservatives, says Eurídice Martínez Steele, food processing researcher at the University of Sao Paulo, Brazil. This classification system is now widely used by nutrition researchers.
The ultra-processed foods constitute the majority of packaged foods that are found in the frozen food stores in grocery stores and on the menu of fast-food restaurants: 70 percent of the packaged foods sold in the United States are considered ultra-processed. More and more healthy foods are shifting towards people’s diets and are widely consumed by all socioeconomic groups.
“Ultra-processed foods are carefully formulated to be as appetizing and satisfying as they are almost addictive,” says doctor Eric M. Hecht, epidemiologist at the Schmidt Medical School at Florida Atlantic University. “The problem is that in order for products to sell better and better, manufacturers make them less and less like real food”.
What effect do ultra-processed foods have on mental health?
Recent research has shown a link between highly processed foods and low mood. In a 2022 study of more than 10,000 adults in the United States, the more the participants ate, the more likely it was that they reported mild depression or feelings of anxiety. “There is a significant increase in mentally unhealthy days for those who consume 60 percent or more of their calories in ultra-processed foods”, says doctor Hecht, author of the study. “This is not a causality test, but we can say that there seems to be an association”.
A new investigation has also found a connection between high consumption of these foods and cognitive deterioration. A 2022 study that followed nearly 11,000 Brazilian adults for a decade found a correlation between eating ultra-processed foods and poorer cognitive function (the ability to learn, remember, reason and solve problems). “If we have a natural decrease in these abilities with age, we have seen that this decrease has accelerated to a 28 percent in people who consume more than 20 percent of their calories in ultra-processed foods”, says Natalia Gomes Goncalves, professor of the University of São Paulo and lead author of the study.
It is possible that eating a healthy diet compensates for the harmful effects of eating ultra-processed foods. Brazilian researchers discovered that following a healthy diet, such as the MIND diet, which is rich in whole grains, green leaf vegetables, legumes, nuts, berries, fish, chicken and olive oil, greatly reduces the risk of dementia associated with the consumption of ultra-processed foods. Those who followed the MIND diet, but ate ultra-processed foods, “did not see an association between the consumption of these foods and cognitive impairment”, says Goncalves, and added that researchers also do not know how safe it is to eat ultra-processed foods .
Why can ultra-processed foods have this effect?
It’s not clear. “Many high-quality randomized studies have demonstrated the beneficial effect of a nutrient-rich diet on depression, but we still do not fully understand the role of food processing in mental health”, says Melissa Lane, Food & Mood researcher, from the University of Deakin in Australia. However, there are some clues.
Much of the research has focused on how poor intestinal health could affect the brain. Diets rich in ultra-processed foods tend to be low in fiber, which is found mainly in foods of vegetable origin such as whole grains, fruits, vegetables, nuts and seeds. Fiber helps feed the good bacteria in the intestine. Fiber is also necessary for the production of short-chain fatty acids, the substances that are produced when they break down in the digestive system and that play an important role in brain function, says Wolfgang Marx, president of the International Society for Research en Psiquiatría Nutricional and a researcher at the University of Deakin. “We know that people with depression and other mental disorders have a less diverse composition of intestinal bacteria and less short-chain fatty acids”.
Chemical additives in ultra-processed foods can also have an impact on intestinal flora. “The emerging evidence, mainly from animal studies, but also some human data, suggests that isolated nutrients (such as fructose), additives such as artificial sweeteners (such as aspartame and saccharin) or emulsifiers (such as carboxymethylcellulose and el polisorbato-80) can negatively influence the intestine”, says Dr. Marx.
Poor diversity of the intestinal microbiota, as well as a diet high in sugar, can contribute to chronic inflammation, which has been linked to a number of mental and physical problems, says Doctor Lane. “It is believed that the interactions between the increase in inflammation and the brain drive the development of depression”, he says. It is also worth considering the possibility that the link between highly processed foods and mental health works in both directions. “The diet influences the state of mind, but the opposite is also true”, says doctor Frank Hu, professor of nutrition and epidemiology at Harvard. “When you are stressed, anxious or depressed, you tend to eat unhealthy foods, in particular ultra-processed foods that have a high content of sugar, grease and chemical additives”. How to recognize ultra-processed foods
The best way to identify ultra-processed foods is to read the product labels. “A long list of ingredients, and especially one that includes ingredients you would never use in home cooking”, are clues that the food is ultra-processed, says Whitney Linsenmeyer, assistant professor of nutrition at the University of Saint Louis in Missouri and voice of the Academy of Nutrition and Dietetics. The chemical names, the unpronounceable words and everything that is little likely to be found in a kitchen cabinet are just signs that a food is in the ultra-processed category.
However, you can use precooked foods to facilitate cooking without resorting to ultra-processed foods. Products such as canned fried beans, frozen vegetables, precooked brown rice or canned fish are abbreviated ingredients that fit well within the scope of a healthy diet, as long as there are no industrial elements in the list of ingredients. “If the added ingredients are the ones you would use yourself, such as herbs, spices, salt or cooking oil”, says doctor Linsenmeyer, “this is an indication that food, even if processed, is not intrinsically bad for you”.
