A recent study in the Journal of the American Medical Association (JAMA) Neurology found that “a higher percentage of daily energy from ultra-processed foods was associated with cognitive decline during 8 years of follow-up.” With 10,775 participants, the results of this high-quality study cannot be ignored.
Diets high in UPFs have already shown clear links to increased rates of cardiovascular disease, metabolic syndrome, obesity, and all-cause mortality. This study, however, is unique because it is one of the first to show a clear link between ultra-processed foods (UPFs) and cognitive decline.
As part of the study, participants filled out a survey detailing their eating habits in a given year. Researchers then divided reported food intake into three categories: unprocessed food, processed food, and UPFs. Fruits, grains, fish, or milk were considered unprocessed foods, and canned fruit, artisanal cheese, and cured meat were considered processed foods. UPFs were defined as processed food with added flavors, colors, or sweeteners – basically anything in the snack aisle at a supermarket.
The researchers used these survey results to calculate the amount of daily energy that participants were getting from UPFs. Participants were divided into four groups based on the percentage of energy intake from UPFs. The lowest consumption level group got up to 19.9% of their daily energy from UPFs, and the highest consumption level group got up to 72.7% of their energy from UPFs.
To assess cognitive change over time, participants took several standardized tests that focused on memory, executive function, and global cognition. Executive function is defined as the mental processes that enable us to plan, focus, and exercise self-control. Global cognition includes attention, language fluency, and visuospatial ability. As one can imagine, a decline in any of these areas would be devastating to daily function.
Participants took cognitive tests approximately every three years to compare the rate of cognitive decline between the study groups. The results of these tests are striking. Participants who got more than 19.9% of their energy from UPFs experienced a 25% faster executive function decline than those in the 19.9% or less group. Furthermore, those getting more than 19.9% of their energy from UFPs had a 28% faster global cognitive decline.
From these results, it is clear that diets high in UPFs can have detrimental effects on cognition. But what is it about high UPF diets that is causing this cognitive decline?
Many causes have been suggested. Theories from microvascular lesions to systemic inflammation have been proposed and may, or may not, play a role. While further investigation into the cellular cause of this cognitive decline is warranted, it is noteworthy that the results of this study support Dr. Chris Palmer’s theory of Brain Energy. Dr. Palmer’s theory suggests that mental disorders are metabolic disorders of the brain.
In his new book, Dr. Palmer outlines that “dietary factors are directly linked to mitochondrial function, metabolic health, and mental health.” As mentioned above, diets high in UPFs have already been linked to increased rates of metabolic syndrome and obesity. In line with the Brain Energy theory, then, it makes sense that foods which cause metabolic dysregulation in the body would cause dysfunction in the brain as well.
Dr. Palmer notes in Brain Energy that unhealthy diets full of highly processed junk foods can lead to a number of problems with metabolism and mitochondria. Take insulin resistance, for example. Long term exposure to diets that cause high blood glucose levels can cause insulin resistance. Mitochondrial biogenesis is then directly inhibited by insulin resistance, decreasing energy availability. Although the mechanism that caused the cognitive decline in the current study is not known, the Brain Energy theory offers a very plausible answer: a metabolic disorder of the brain.
All that said, it is important to look at the positives that come out of studies like these. Yes, a diet high in UPFs carries an increased risk of cardiovascular disease, all-cause mortality, and cognitive decline. But by simply lowering consumption of UPFs, one can remove that increase in risk from the equation. As Dr. Palmer says in his book, “diet plays a powerful role in metabolism and mitochondrial health.” Changes to diet can improve metabolism and mitochondrial health, an encouraging message to take from Brain Energy as we strive to live healthy and meaningful lives.
Disclaimer: This article is for educational purposes only and is not medical advice. You should consult with your healthcare provider before starting any treatments for any medical conditions.
Colin is cofounder and CEO of MediKnow International, a medical education company. He is also a contributing author on multiple studies in healthcare and neuroscience. Colin is completing his final year of medical school and is pursuing a residency in psychiatry. He is passionate about researching novel therapies and understanding the underlying cause of mental health disorders.