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Scientists have known for years that unhealthy diets – particularly those that are high in fat and sugar – may cause detrimental changes to the brain and lead to cognitive impairment.
Many factors that contribute to cognitive decline are out of a person’s control, such as genetics and socioeconomic factors. But ongoing research increasingly indicates that a poor diet is a risk factor for memory impairments during normal aging and increases the risk of developing Alzheimer’s disease. But when evaluating how some diets may erode brain health as we age, research on the effects of consuming minimally processed versus ultraprocessed foods has been scant – that is, until now.
Two recent large-scale studies suggest that eating ultraprocessed foods may exacerbate age-related cognitive decline and increase the risk of developing dementia. In contrast, another recent study reported that ultraprocessed food consumption was not associated with worse cognition in people over 60.
Although more research is needed, as a neuroscientist who researches how diet can influence cognition later in life, I find that these early studies add a new layer for considering how fundamental nutrition is to brain health.
Ultraprocessed foods tend to be lower in nutrients and fiber and higher in sugar, fat, and salt compared to unprocessed or minimally processed foods. Some examples of ultraprocessed foods include soda, packaged cookies, chips, frozen meals, flavored nuts, flavored yogurt, distilled alcoholic beverages, and fast foods. Even packaged bread, including those high in nutritious whole grains, qualify as ultraprocessed in many cases because of the additives and preservatives they contain.
Another way to look at it: You are not likely to find the ingredients that make up most of these foods in your home kitchen. But don’t confuse ultraprocessed with processed foods, which still retain most of their natural characteristics, although they’ve undergone some form of processing – like canned vegetables, dried pasta, or frozen fruit.
In a December 2022 study, researchers compared the rate of cognitive decline over approximately eight years between groups of people that consumed different amounts of ultraprocessed foods.
At the beginning of the study, over 10,000 participants living in Brazil reported their dietary habits from the previous 12 months. Then, for the ensuing years, the researchers evaluated the cognitive performance of the participants with standard tests of memory and executive function.
Those who ate a diet containing more ultraprocessed foods at the start of the study showed a slightly more cognitive decline compared with those that ate little to no ultraprocessed foods. This was a relatively modest difference in the rate of cognitive decline between experimental groups. It is not yet clear if the small difference in cognitive decline associated with higher consumption of ultraprocessed foods will have a meaningful effect on the level of an individual person.
