Scientists have known for years that an unhealthy diet, especially one high in fat and sugar, can cause harmful changes in the brain, leading to cognitive impairment.
Many factors that contribute to cognitive decline, including genetic and socioeconomic factors, are beyond human control. But ongoing research is increasingly showing that poor diet is a risk factor for normal age-related memory loss and increases the risk of developing Alzheimer’s disease.
However, when assessing how some diets may impair brain health as we age, research on the effects of consuming minimally processed and ultra-processed foods is lacking. , has never been seen before.
Two large recent studies suggest that eating ultra-processed foods may exacerbate age-related cognitive decline and increase the risk of developing dementia. In another recent study, consumption of ultra-processed foods was not associated with cognitive decline in people over the age of 60.
More research is needed, but as a neuroscientist studying how diet influences later cognition, these early studies provide a good indication of how basic nutrition affects brain health. I discovered adding a new layer to consider what the impact would be.
Many Ingredients Minimal Nutrition
Ultra-processed foods tend to be lower in nutrients and fiber and higher in sugar, fat, and salt than unprocessed or minimally processed foods.
Examples of ultra-processed foods include sodas, packaged cookies, potato chips, frozen foods, flavored nuts, flavored yogurts, distilled alcoholic beverages, and fast food. Even packaged breads that are high in nutritious whole grains are often considered ultra-processed breads because they contain additives and preservatives.
Looking at it another way, it’s unlikely that the ingredients that make up most of these foods are in your home kitchen.
But don’t confuse ultra-processed foods with processed foods. Processed foods, such as canned vegetables, dried pasta, and frozen fruit, have been processed in some way but retain most of their natural properties.
Research analysis
In a December 2022 study, researchers compared rates of cognitive decline over about eight years between groups of people who consumed varying amounts of ultra-processed foods.
At the start of the study, over 10,000 participants living in Brazil reported their eating habits over the past 12 months. Over the next few years, researchers assessed the participants’ cognitive abilities with standard tests of memory and executive function.
Those who ate a diet high in ultra-processed foods at the start of the study experienced slightly greater cognitive decline than those who ate little or no ultra-processed foods. There was a relatively small difference in the rate of functional decline.
It is not yet clear whether small differences in cognitive decline associated with increased consumption of ultra-processed foods have significant effects at the individual level.
A second study involving approximately 72,000 participants in the UK measured the association between ultra-processed food consumption and dementia. In the group with the highest ultra-processed food intake, about 1 in 120 people were diagnosed with dementia over the decade. The figure was 170 times lower for the group who ate little or no ultra-processed foods.
Studies examining the relationship between health and ultra-processed foods use the NOVA classification, a classification system based on the type and extent of industrial food processing.
Some nutritionists have criticized the NOVA classification for lacking a clear definition of food processing and potentially leading to misclassification. They also found that potential health risks from consuming ultra-processed foods could be explained by low levels of fiber and nutrients and high levels of fat, sugar, and salt in the diet, rather than the amount of processing. I claim.
Many ultra-processed foods are high in additives, preservatives, and colorings, and also have other characteristics of an unhealthy diet, such as low fiber and nutrients. Therefore, it is unclear whether eating more processed foods has any further adverse health effects beyond poor dietary quality.
For example, you can eat hamburgers and fries from fast food chains, but they’re high in fat, sugar, salt, and ultra-processed. You can make the same meal at home, but it may be higher in fat, sugar and salt, but it’s not super processed. More research is needed to determine if one is worse than the other. am.
good food for the brain
Even in the absence of processes leading to dementia, the aging brain undergoes biochemical and structural changes associated with cognitive deterioration.
However, for adults over the age of 55, a healthier diet may increase the chances of maintaining better brain function. In particular, the Mediterranean and ketogenic diets are associated with improved cognitive performance in older adults.
The Mediterranean diet emphasizes plant foods and healthy fats such as olive oil, seeds and nuts. A ketogenic diet is high-fat, low-carb, and the main source of fiber is vegetables. Both diets minimize or eliminate sugar consumption.
Our study and that of others show that both diets can reverse some of these changes and improve cognitive function — presumably by reducing harmful inflammation.
Inflammation is a normal immune response to injury and infection, but chronic inflammation can be detrimental to the brain. Studies show that excess sugar and fat can contribute to chronic inflammation, and ultra-processed foods can also exacerbate harmful inflammation.
Another way diet and ultra-processed foods impact brain health is through the gut-brain axis, the communication that occurs between the brain and the gut microbiome, or microbial community that inhabits the gut. am.
The gut microbiome not only aids in digestion, but also influences the immune system and produces hormones and neurotransmitters that are important for brain function.
Studies have shown that ketogenic and Mediterranean diets alter the microbial composition of the gut in ways that are beneficial to humans. It is also associated with changes in the type and amount of microorganisms.
uncertainty
It is difficult to disentangle the specific effects of individual foods on the human body. One reason is that it is problematic to closely control and study people’s diets over time. Moreover, the most reliable type of study for establishing causality, randomized controlled trials are expensive to conduct.
So far, most nutrition studies, including these two, have only shown correlations between ultra-processed food consumption and health. , and many other variables that can affect cognitive function.
This is where lab-based research using animals can be very helpful. Rats show similar cognitive decline as humans as they age. It is easy to control the diet and activity level of rodents in the laboratory. It also reduces study time, as rats transition from middle-aged to old in a matter of months.
Animal laboratory studies make it possible to determine whether ultra-processed foods play an important role in the development of cognitive impairment and dementia in humans. As the world’s population ages and the number of older people with dementia increases, this knowledge will not come quickly.
Sara N. Burke, Associate Professor of Neurobiology and Cognitive Aging, University of Florida
This article is republished from The Conversation under a Creative Commons license. Please read the original article.
